CN113437098A - CT flat panel detector and CT machine - Google Patents

CT flat panel detector and CT machine Download PDF

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Publication number
CN113437098A
CN113437098A CN202011040640.7A CN202011040640A CN113437098A CN 113437098 A CN113437098 A CN 113437098A CN 202011040640 A CN202011040640 A CN 202011040640A CN 113437098 A CN113437098 A CN 113437098A
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flat panel
panel detector
reading
tft
time
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刘洪斌
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14643—Photodiode arrays; MOS imagers
    • H01L27/14658—X-ray, gamma-ray or corpuscular radiation imagers
    • H01L27/14663—Indirect radiation imagers, e.g. using luminescent members
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]
    • A61B6/032—Transmission computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
    • A61B6/4233—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using matrix detectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14609—Pixel-elements with integrated switching, control, storage or amplification elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14609—Pixel-elements with integrated switching, control, storage or amplification elements
    • H01L27/14612—Pixel-elements with integrated switching, control, storage or amplification elements involving a transistor

Abstract

The invention provides a CT flat panel detector, each array element is provided with an independent post-stage operational amplifier and an independent analog-to-digital converter, and each array element is scanned simultaneously in a row unit to obtain a projection matrix of a section where each row is located. The invention also provides a CT machine. By increasing the size of the flat panel detector, the CT machine can obtain the requirement of each section image of one part by scanning for one circle or half circle without spiral scanning; by improving the internal circuit of the acquisition unit, the circuit structure meets the requirement of CT scanning, and better image quality under respective conditions is obtained; the substrate adopts a double-sided technology, so that the signal-to-noise ratio is improved; the scanning frequency is reduced by reducing the array element number of each row; by means of the ray pulse control technology of the CT machine or by removing the reading TFT in the array element and transferring the functions of the reading TFT to the peripheral circuit, the requirement of the CT machine on the mobility of the thin film transistor of the detector is reduced, and the CT flat panel detector can be practically applied.

Description

CT flat panel detector and CT machine
Technical Field
The invention relates to the technical field of CT equipment, in particular to a CT flat panel detector and a CT machine.
Background
The detector structure of the detector is that detectors in a row of rows are distributed side by side (a photoelectric conversion circuit and an analog-to-digital conversion circuit corresponding to the detectors are arranged below the detectors), the row number is developed to the current 128 rows of mainstream (individual 256 rows or 320 rows) from the initial single row, and the number of effective detection array elements in each row is less than 900.
The existing CT machine detector and the CT machine thereof have the following objective defects:
1. the number of rows of detectors is limited, so that the scanning range of 360-degree rotary scanning is narrow (the current longitudinally widest detector is 160mm, which basically can meet the requirement of single-circle scanning of a small part but cannot meet the requirement of single-circle scanning of a large part), one part can be completed only by multi-circle spiral scanning, and a bed moves during scanning, so that motion artifacts are easily formed;
2. spiral scanning is needed, an image scanned by 360 degrees is not a real transverse section, but a section image which has a certain layer thickness and is not on the same section, although the current 256 rows can achieve the 625um layer thickness (the minimum is 400um), the image is not an isometric image; interlayer spacing exists, and although the current 256 rows can also give an interlayer gap image with the thickness of 625um (the thinnest 400um) through an algorithm, the image is not a real image; there is also a possibility of missed detection of the initial microscopic lesions;
3. the scanning time is long, and the dose of the patient to be irradiated is also large. Because of the need of multi-circle scanning, the time is longer, and the dosage of the radiation irradiation received by the patient is increased;
4. the spatial resolution is low and the reconstructed image pixels are not high. The highest resolution is less than 24Lp/cm and the reconstructed image pixels are typically 512 x 512 or 1024 x 1024.
In view of the above drawbacks of the conventional CT machine detectors, many manufacturers try to apply flat panel detectors to CT machines. However, the flat panel detector applied to the CT machine has the following problems:
1. the medical flat panel detector for DR and DSA in the market at present has a unilateral size of 17 inches (about 43cm) at most, which can completely meet the use requirement, but if the medical flat panel detector is applied to a flat panel CT machine, the size is too small, and the abdomen and the chest cannot be taken into a scanning range in the transverse direction;
2. the circuit structure of the existing flat panel detector is designed for obtaining a frame image with the same shape as the detector, and can not be applied to a CT machine which requires tomography in a row unit;
3. the existing flat panel detector has too many array elements in each row and too high required scanning frequency, so that the CT machine has too high requirement on the mobility of the flat panel detector, and the frequency of the flat panel detector and the mobility of a thin film transistor are generally low in reality and cannot meet the requirement of the CT machine;
4. the number of array elements of each row of the current flat panel detector is too large, so that the number of channels of the detector (the channel of the current CT refers to a peripheral circuit part of each acquisition unit and is used for amplifying and performing analog-to-digital conversion on data acquired by each array element; the channel in the design has the same meaning as the channel, and the detector with reading signals designed in the peripheral circuit can also comprise circuits such as a reading field effect tube, a resetting field effect tube or an amplifying field effect tube) is too large, and the cost of the detector is too high.
Disclosure of Invention
The invention aims to provide a CT flat panel detector and a CT machine, which overcome the defects of the existing CT machine and solve the technical problem that the existing flat panel detector is applied to the CT machine.
In order to solve the above technical problems, the present invention provides a CT flat panel detector (which is called a flat panel detector for CT machine in the single context of the present design, and is sometimes directly called as a flat panel detector), comprising an X-ray imaging sensor and a peripheral circuit, wherein the X-ray imaging sensor is composed of a plurality of rows and columns of pixel matrices, each unit in the pixel matrices is called an array element, all the array elements are integrated on a substrate, and the peripheral circuit comprises a back-stage operational amplifier, an analog-to-digital converter and a buffer; the upper surface of the pixel matrix is also provided with a scintillator layer so as to convert X rays into visible light and transmit the visible light to the photodiode for photoelectric conversion; each array element in the pixel matrix comprises a photodiode, and the photodiode is used for converting an acquired optical signal into an electric signal; each array element in the pixel matrix is provided with a data output port, data of each array element is independently output to a respective independent post-stage operational amplifier and an analog-to-digital converter through the data output port, and a data acquisition and processing unit which is composed of a single array element and a post-stage operational amplifier and an analog-to-digital converter in a peripheral circuit (a detector for reading signals designed in the peripheral circuit can also comprise a reading field effect tube, a resetting field effect tube or an amplifying field effect tube and the like) is called as an acquisition unit; the control signal of each acquisition unit comprises a reading signal with a switching function and used for controlling data reading and a reset signal with a resetting function, the effective potential time of the reading signal is called reading time, the effective potential time of the reset signal is called resetting time, the reading signals of all the acquisition units on the CT flat panel detector are mutually connected, so that all the acquisition units on the CT flat panel detector are controlled by the same reading signal to read data simultaneously, and the reset signals of all the acquisition units on the CT flat panel detector are mutually connected, so that all the acquisition units on the CT flat panel detector are controlled by the same reset signal to reset simultaneously; the CT flat panel detector scans in each row unit, wherein each array element needs to acquire data at the same time to obtain a group of projection matrixes, each row scans at least one circle or at least half circle to obtain a projection matrix of a section, an image of the section is reconstructed by software calculation, the array elements in different rows need to scan at the same time to obtain projection matrixes of different sections, and the CT flat panel detector scans at least one circle or at least half circle to obtain images of each section corresponding to each row.
As a further optional scheme of the CT flat panel detector, a structure of the flat panel detector is that a reading signal and a reset signal of each acquisition unit are directly input into an array element, each array element in the pixel matrix further includes a reset TFT, a reading TFT and at least one amplification TFT, the reset TFT is controlled by the reset signal to reset data, the reading TFT is controlled by the reading signal to control output of the data, the amplification TFT is used for amplifying an electrical signal of the photodiode, and the reading TFT is disposed behind the amplification TFT; the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
As a further optional scheme of the CT flat panel detector, a structure of the flat panel detector is that a reading signal and a reset signal of each acquisition unit are directly input into an array element, each array element in the pixel matrix further includes a reset TFT and at least one amplification TFT, the reset TFT is controlled by the reset signal to reset data, a power supply of the reset TFT is called a reset power supply, and all the reset TFTs on the CT flat panel detector share the same reset power supply; the amplifying TFT is used for amplifying the electric signal of the photodiode; the TFT for amplification in each array element is controlled by a reading signal, and controls the output of data while amplifying the electric signal generated by the photodiode; the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
As a further optional scheme of the CT flat panel detector, a structure of the flat panel detector is that a reading signal and a reset signal of each acquisition unit are directly input into an array element, each array element in the pixel matrix further includes a reset TFT, a reading TFT, and at least one amplification TFT, the reset TFT is used for resetting an electrical signal of the photodiode, the reading TFT is controlled by the reading signal to control output of data, the amplification TFT is used for amplifying the electrical signal of the photodiode, and the reading TFT is disposed before the amplification TFT; the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
As a further optional scheme of the CT flat panel detector, a structure of the flat panel detector is that a reading signal of each acquisition unit is input to the outside of an array element, and data output is controlled by using a field effect tube for reading in a peripheral circuit, each array element in the pixel matrix further includes a TFT for reset and at least one TFT for amplification, the TFT for reset is used to reset an electrical signal of the photodiode, and the TFT for amplification is used to amplify the electrical signal of the photodiode; the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
As a further alternative of the CT flat panel detector, a structure of the flat panel detector is that a reading signal of each acquisition unit is directly input into an array element, each array element in the pixel matrix further includes a reset TFT and a reading TFT, the reset TFT is used for resetting an electrical signal of the photodiode, and the reading TFT is controlled by the reading signal to control output of data.
As a further alternative of the CT flat panel detector, a structure of the flat panel detector is that a reading signal of each acquisition unit is directly input to the outside of an array element, and a field effect transistor for reading in a peripheral circuit is used to control the output of data, and each array element in the pixel matrix further includes a TFT for resetting, where the TFT for resetting is used to reset an electrical signal of the photodiode.
As a further alternative of the CT flat panel detector, a structure of the flat panel detector is that a reading signal and a reset signal of each acquisition unit are both input outside the array element, a field effect tube for reading in a peripheral circuit is used to control output of data, and a field effect tube for resetting in the peripheral circuit is used to reset the photodiode.
As a further alternative of the CT flat panel detector, the post-operational amplifier can adopt an inverting amplifier or a homotropic amplifier.
As a further optional scheme of the CT flat panel detector, a substrate (generally, a glass substrate) of the CT flat panel detector adopts a double-sided technology, one side of the substrate is used for loading a pixel matrix (a TFT/photodiode is attached to the substrate and is the same as that of an existing flat panel detector), the other side of the substrate is used for loading a post-stage operational amplifier and an analog-to-digital converter in a peripheral circuit (which may further include a field effect tube for reading, a field effect tube for resetting, and a field effect tube for reading, which move an internal function of an array element to the peripheral circuit), and a conductive pin is embedded in a position corresponding to each array element in the substrate to transmit data of each array element to the peripheral circuit such as the respective post-stage operational amplifier for processing.
As a further optional scheme of the CT flat panel detector, under the low pixel requirement, when the CT machine adopts a 2K projection matrix value, the number of array elements in each row in the CT flat panel detector is 1097-; when the CT machine adopts a 4K projection matrix value, the number of each row of array elements in the CT flat panel detector is 1552 and 1716; when the CT machine adopts an 8K projection matrix value, the number of each row of array elements in the CT flat panel detector is 2195-2427; when the CT machine adopts a 16K projection matrix value, the number of each row of array elements in the CT flat panel detector is 3105 and 3432.
Correspondingly, the invention also provides a CT machine consisting of the CT flat panel detector, wherein a ray emitter of the CT machine adopts a ray pulse control mode, the ray emission of the ray emitter is controlled by a ray pulse signal, the frequency of the ray pulse signal is the same as the scanning frequency of the CT flat panel detector, the ray emitter emits rays when the ray pulse signal is at an effective potential, the ray emitter does not emit rays when the ray pulse signal is at a non-effective potential, and the time for emitting rays is equal to the time for not emitting rays; the data acquisition of the CT flat panel detector is synchronous with the ray emission of the ray emitter of the CT machine, the data acquisition time is called as sampling time, the sampling time is equal to the ray emission time, the CT flat panel detector adopts interval scanning, and acquires data once at intervals (ideally, acquires data once at intervals of one array element width, namely acquires data once when the outermost array element on each row rotates by one array element width), while does not acquire data within the next rotation time with the same width, and performs reading and data resetting by using the time of not acquiring data; the CT machine adopts a 360-degree scanning mode; when the pixel is low, the CT machine scans a circle to obtain each section image, the ray pulse signal for controlling the ray emitter to emit the ray, the reading signal and the reset signal of the CT flat panel detector need to adopt an inverse technology, and the signals need to be subjected to 180-degree phase shift in phase after the ray emitter and the CT flat panel detector rotate and scan for half time (namely after the ray emitter and the CT flat panel detector rotate and scan for 180 degrees); when the pixel is high, the CT machine scans two circles to obtain each section image in advance when the scanning bed does not move, the ray pulse signal for controlling the ray emitter to emit the ray, the reading signal of the CT flat panel detector and the reset signal all need to adopt an inversion technology, and besides the inversion technology under the repeated low pixel mode, the inversion technology can also adopt the phase shift of 180 degrees on the phase of the signal when the first circle is scanned and the phase of the signal when the second circle is scanned.
Correspondingly, the invention also provides a CT machine consisting of the CT flat panel detector, wherein the CT machine adopts the working mode of a ray emitter of the existing CT machine, namely the ray emitter continuously emits rays when the CT flat panel detector reads, and a photodiode of the CT flat panel detector continuously performs photoelectric conversion; when the pixel is low, the CT machine can adopt a 180-degree scanning mode; when the pixel is high, the CT machine adopts a 360-degree scanning mode; when the pixel is low, when the CT machine adopts 360-degree scanning, the CT machine can be designed to scan the first half and the second half of the rotary scanning by adopting rays with two different energies so as to obtain two images with the same section under two different energies.
As a further alternative to the above two CT machines, for the above CT machine (whether the CT machine is in a radiation pulse mode or in an existing radiation emitter operation mode) which is composed of the CT flat panel detector with the amplifying TFT before the reading TFT (or the peripheral circuit reading field effect tube), the reset time of each array element of the CT flat panel detector can be scheduled within the reading time, and the reset time is scheduled at the end of the reading time.
When the CT flat panel detector is applied to a CT machine, the CT flat panel detector at least has the following advantages:
on the basis of the existing DSA medical dynamic flat panel detector technology, various improvements are made to the circuit structure according to the CT scanning principle, so that the requirements of CT tomography can be met. The data of each array element is independently output to the respective post-stage operational amplifier and the analog-to-digital converter, reading signals of all the acquisition units are mutually connected, and the whole detector can simultaneously acquire data and perform caching in a row unit, so that the flat panel detector can meet the requirements that a CT machine scans a circle or a half circle to obtain a section image, and the whole detector scans a circle or a half circle to obtain each section image of a part. The substrate adopts a double-sided technology, so that data in an array element matrix can be conveniently transmitted to a peripheral circuit such as a rear-stage operational amplifier for processing, the transmission distance is shortened as much as possible, the transmission loss of signals is greatly reduced, the signal to noise ratio is greatly improved (the possibility is provided for shifting all functions of a reset TFT, a reading TFT and an amplifying TFT out to the peripheral circuit. The layered design greatly improves the fill factor. For the CT machine adopting a ray pulse control mode, a ray emitter adopts a pulse control technology, and the ray emitter does not emit rays and has no trailing phenomenon when a CT flat panel detector reads; the data during reading is exactly the determined quantity for acquiring the width of an array element, is complete and non-missing projection data, eliminates the loss of image data of the detector in the reset time under the working mode of the existing ray emitter, and also eliminates the image data in the total transit time lost due to the delay of a TFT during reading; acquiring data once every other array element width; by using the 180-degree phase reversal technology, the data of the array element widths which are not acquired during reading in the scanning of the first 180 degrees are supplemented back by the later 180 degrees, so that a complete image is obtained by scanning a circle; meanwhile, the requirement of the CT machine on the scanning frequency of the flat panel detector can be reduced by half. Under the radiation pulse control mode, the reading time is prolonged to the maximum extent, so that the requirement on the mobility of the thin film transistor of the flat panel detector is greatly reduced (by about 5 times). For the CT machine adopting the working mode of the existing ray emitter, the ray emitter continuously emits rays when a flat panel detector collects and reads, and the CT machine can obtain each section image of a part by scanning at 180 degrees when pixels are low, so that in the CT machine rotating in a slip ring mode, the scanning time can be shortened, and the scanning of the parts such as the heart and the like with high requirements on the scanning speed is facilitated; when 360-degree scanning is adopted, rays with two different energies can be used for scanning at the front 180 degrees and the rear 180 degrees, and a CT machine with more enhanced functions is developed; the CT machine can be made into a C-shaped arm structure (but the scanning speed is very slow because the rotating speed of the C-shaped arm is not high), and the CT image requirement in DSA (digital subtraction angiography) operation is met; when the pixel is high, the CT machine adopts a 360-degree scanning mode, and can obtain image pixels which are twice as large as those of a 180-degree scanning mode. By reducing the number of array elements of each row of the detector, the scanning frequency is reduced, so that the requirement of the CT machine on the mobility of the flat panel detector is reduced, and the manufacturing cost of the detector is reduced. The flat panel detector has the possibility of being practically applied to the CT machine through the design.
The improved flat panel detector is applied to a CT (computed tomography) machine to replace the existing CT detector, the CT flat panel detector has a length (the human shoulder width direction is usually 26 inches) larger than that of a flat panel detector for DSA (digital signal processor), has a width (the human height direction is usually 26 inches) larger than that of the existing CT detector, and can cover a single part of a human body (four limbs can be excluded), so that the single part of the CT machine only needs to be scanned for 360 degrees or 180 degrees (the four limbs can be excluded) without spiral scanning, and the scanning time is greatly shortened (from the original 3-5 seconds to 0.3-0.5 seconds); the scanning part can be positioned by using the positioning lamp, and the scanning of a positioning sheet is not needed, so that the time is saved and the irradiation of a patient is reduced; the front and back movement of the examination table is not needed during the scanning period, so that the motion artifact can be effectively reduced; greatly reduces the irradiated dose of the patient (about 1/10 of the original dose); the spatial resolution (improved by more than 2 times), the pixel (improved by 2-8 times) and the number of longitudinal scanning layers are greatly improved (the number of rows is the same as that of the detector), the scanning is gapless, fine focuses can be found, and the omission is avoided; the overall working efficiency is at least doubled; the using amount of the ray emitter is greatly reduced, the service life can be prolonged by 3-5 times, and good economic benefits are achieved.
Simultaneously, the function of current CT machine can be promoted by a wide margin to cooperation software:
1. clearer and richer fault images in any direction. Due to the fact that abundant three-dimensional voxel data can be obtained, the cross-sectional images with extremely high pixels in any direction can be obtained, including the inclined plane cross-sectional images with any angles, the cross-sectional images with any interested non-plane can also be obtained, and the images are clearer; the scanning frame does not need to be inclined to scan cervical vertebra, lumbar vertebra and other parts; when the film is displayed, the image quality is higher, the layers are richer, and the film can be seen from any angle and is not limited to the longitudinal direction and the transverse direction.
2. The perspective three-dimensional image is more real and clearer. The three-dimensional image which is more real than the existing CT can be given through software, a clearer semitransparent three-dimensional image (referred to as perspective three-dimensional imaging, but more suggested to be spatial four-dimensional imaging, because the image in a box can be seen) can be obtained, the four-dimensional image of the same tissue and the interior of the tissue in a scanning part can be rotatably observed when the window width and the window position are not changed, the four-dimensional image of different tissues can be observed by changing the window width and the window position, and the body structure and the lesion position can be really seen through at one eye; and the pathological tissues and the pathological blocks thereof can be separated independently for three-dimensional and four-dimensional display. Has great significance for more intuitively mastering the disease condition of a clinician, more easily knowing the disease condition of the family members of the patient, facilitating communication between doctors and patients, teaching work and the like.
3. More accurate positioning function. Due to the fact that real three-dimensional data of smaller voxels exist, more accurate positioning can be achieved clinically, a fine operation scheme can be made, and the flat-panel CT can be introduced into an operating room for accurate minimally invasive operations through subsequent development and applied to an operation navigation system and robot operations.
Drawings
FIG. 1 is a circuit diagram of a pixel matrix of a conventional amorphous silicon flat panel detector;
FIG. 2 is a circuit diagram of an acquisition unit in a conventional amorphous silicon flat panel detector for DR;
FIG. 3 is a block diagram of the CT flat panel detector of the present invention;
FIG. 4 is a circuit diagram of an acquisition unit with an amplifying TFT before a reading TFT;
FIG. 5 is a circuit diagram of a pixel matrix before a reading TFT for an enlarging TFT;
FIG. 6 is a circuit diagram of an acquisition unit that shares the same TFT with the amplification and readout circuitry;
FIG. 7 is a circuit diagram of a pixel matrix with enlarged and read-out common TFT;
FIG. 8 is a circuit diagram of an acquisition unit with an amplifying TFT after a reading TFT;
fig. 9 is a pixel matrix circuit diagram of an enlarging TFT after a reading TFT;
FIG. 10 is a circuit diagram of an acquisition unit with reading signals in a peripheral circuit and an array element having an amplifying TFT;
FIG. 11 is a circuit diagram of a pixel matrix with read signals in peripheral circuits and amplifying TFTs in array elements;
FIG. 12 is a circuit diagram of an acquisition unit with a reading signal in an array element but without an amplifying TFT;
FIG. 13 is a circuit diagram of a pixel matrix with read signals in the array elements but without the amplifying TFTs;
FIG. 14 is a circuit diagram of an acquisition unit in which the read signal is in a peripheral circuit and no TFT for amplification is provided in the array element;
FIG. 15 is a circuit diagram of a pixel matrix in which the readout signal is in the peripheral circuit and no TFT for amplification is provided in the array element;
FIG. 16 is a circuit diagram of an acquisition unit with both read and reset signals in peripheral circuitry;
FIG. 17 is a circuit diagram of a pixel matrix with read and reset signals in peripheral circuits;
FIG. 18 is a timing diagram of CT machine data acquisition with a ray pulse control mode during the reset time within the reading time;
FIG. 19 is a timing diagram of CT machine data acquisition with reset time within reading time using existing ray control;
FIG. 20 is a timing diagram of CT machine data acquisition with a reset time after a read time using a radial pulse control scheme;
FIG. 21 is a timing diagram of CT machine data acquisition with reset time after read time using a conventional ray control scheme;
FIG. 22 is a timing diagram of CT machine data acquisition with a ray pulse control scheme after the reset time is read, the transition time of a TFT for amplification is delayed by the conversion start request time;
FIG. 23 is a timing diagram of data acquisition for a CT machine using a conventional ray control scheme, wherein the reset time is after the read time, and the transition time of an amplifying TFT is delayed by the conversion start request time;
FIG. 24 is a timing diagram showing data acquisition of a CT machine using a ray pulse control method in which the reset time is after the read time, the conversion start request time is delayed by the transition time of a field effect tube for amplifying a peripheral circuit;
FIG. 25 is a timing diagram showing data acquisition of a CT machine using a conventional ray control method, in which a reset time is set after a read time, a conversion start request time is delayed by a transition time of a field effect transistor for amplifying a peripheral circuit;
description of reference numerals:
the inverted open triangles in fig. 5, 7, 9, 11, 13, 15 and 17 represent the data output interfaces of the array elements; in fig. 2, 4, 6, 8, 10, 12, 14 and 16, the left side of the dotted line is the internal circuit of the array element, and the right side of the dotted line is the external circuit of the array element; vPDDenotes a bias power supply, VDDDenotes bias power supply, VREADRepresenting a reading signal, VGRSTRepresents a reset signal, VRSTIndicating reset of electricitySource, VCNVSTIndicating a transition initiation request signal.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. For those skilled in the art, under the premise of not making creative work, other related drawings can be obtained according to the drawings, and for those skilled in the circuit knowledge, the specific circuit diagram of the whole detector can be easily designed according to the drawings, and for those skilled in the art and professional companies, the actual CT flat panel detector and the corresponding CT machine thereof can be easily manufactured according to the design idea.
In the description of the present invention, it should be understood that the term "peripheral circuit" refers to a circuit outside the internal structure of the array element, including the following operational amplifiers, analog-to-digital converters, various power supplies, buffers, and other circuits, which are all components of the detector, and is only for convenience of describing the present invention and simplifying the description, but not referring to a circuit outside the detector. The TFT is a thin film transistor, and comprises a photodiode inside an array element, a field effect tube for switching, a field effect tube for amplification and the like; the TFT in the present design refers specifically to a field effect transistor for switching, a field effect transistor for amplification, and the like in a thin film transistor, except for a photodiode, where the field effect transistor for switching includes a field effect transistor for reading and a field effect transistor for resetting.
It should be noted that the present invention does not relate to the specific manufacturing process and material of the CT flat panel detector (except for the substrate double-sided technology, the processes and materials mentioned elsewhere are only proposed and are not specified or limited by the present invention), and does not include the peripheral circuit design except for the acquisition unit, the design of the acquisition unit circuit is limited only (but does not include the specific design of the post-stage operational amplifier and the analog-to-digital conversion circuit), and the flat panel detector is applied to the CT machines of two different radiation emitter working modes, and particularly, a CT machine adopting the radiation pulse control technology is designed, but the present invention does not limit the specific implementation mode of the radiation pulse control (the implementation mode in the embodiment is only an example, and does not represent the limitation of the implementation mode), and only requires the function of the radiation pulse control.
Since the maximum single side of the flat panel detector for the existing DSA is only 17 inches, the flat panel detector needs to be enlarged in size to be used for the CT machine. In order to meet the requirement that only one circle of scanning is needed for a single part (except for four limbs) in the human body height direction while the scanning in the human body shoulder width direction is met, the length of a CT flat panel detector (which is called as a flat panel detector for CT machine for short and is sometimes directly called as a flat panel detector in the single context of the design) can be 25-34 inches, and the width of the CT flat panel detector is 25-34 inches, but the CT flat panel detector is not limited to the dimension, and preferably 26 × 26 inches. The above dimensions are those of the flat panel detector. But is preferably designed as an arc so that the radiation can be incident on the detector elements at a normal angle, where the dimension is the length of the chord on which the arc is located.
As shown in fig. 1 and 2, the conventional flat panel detector is an X-ray imaging sensor composed of millions of pixels, each of which is composed of a photosensor, a signal storage device and a switching device, and is used for generating, storing and reading out signals; the array elements on each row are mutually connected through row lines and are used for outputting reading signal control data, but the row lines of different rows are independent; the array elements on each column are connected with each other through a column readout line, the column readout line is used as a data output port, the data output of all the array elements on each column shares the column readout line and shares the subsequent post-stage amplifying circuit and analog-to-digital conversion circuit, and the readout lines of different columns and the subsequent post-stage amplifying circuit and analog-to-digital conversion circuit are independent respectively.
Current TFT/photodiode matrices are typically scanned row by row from top to bottom. The top-down progressive scanning scheme of the current TFT/photodiode matrix and the above-described circuit configuration are designed for obtaining a photographic image in DR photography or a video image in DSA.
The CT machine requires that a row of detectors are arranged in a row unit, each row of detectors is equivalent to one row of the existing CT detectors, each array element (also called as pixel) needs to acquire data at the same time to obtain a group of projection matrixes, a circle or a half circle is rotated to obtain a projection matrix of a section, and an image of the section is reconstructed by software calculation; the detector array elements in different rows need to be scanned simultaneously to obtain projection matrixes of different sections, and images of different sections are obtained. Therefore, there is a need for improvements to existing detector circuits: the data of each array element is independently output to a post-stage operational amplifier and an analog-to-digital converter which are independent; the reading signals of all the acquisition units are mutually connected and controlled by the same reading signal, and data are read simultaneously; progressive scanning is modified to scan in units of lines and each array element is scanned simultaneously per line, buffered in units of lines (see fig. 3).
In fig. 3, since the inside of the acquisition unit may have different designs, a block diagram is shown, and specific circuits designed for two different ways and different design ideas that the reading signal is designed inside or outside the array element are shown in fig. 4, 6, 8, 10, 12, 14 and 16, and in fig. 5, 7, 9, 11, 13, 15 and 17, which are circuit diagrams of a single acquisition unit.
In fig. 3, each acquisition unit includes an array element, a post-stage operational amplifier and an analog-to-digital converter (ADC); each array element in the pixel matrix comprises 1 photodiode, and other elements such as a reset TFT, an amplification TFT, a reading TFT and the like can be included according to different designs. A bias voltage is required to accelerate the photodiode current, but is not generally set separately, and a reset power supply of a reset TFT or a reset field effect transistor in a peripheral circuit may be used to charge the photodiode junction capacitance to provide a bias voltage, as all embodiments in the present design do not set a dedicated bias voltage. All array elements are interconnected in bias voltage sharing the same bias voltage supply (designated V in the figures)PD) (ii) a The amplifying TFT is used for amplifying data photoelectrically converted by the photodiode, and the drain power supply thereof is called biasSource (labeled V in the figures)DD) The bias power supplies of all the array elements are connected with each other and share the same bias power supply (the use of more than 2 bias power supplies is not excluded in the CT detector with more than 2 amplifying TFTs in a single array element).
In fig. 3, all TFTs in each array element may be structurally designed one (or several) layers below the photodiode layer, also called a layered design, to increase the fill factor. Because there are a plurality of TFT in every array element in this design, if according to the horizontal layout structure in the coplanar of photodiode/TFT commonly used, can obviously reduce the pixel and survey the area, make the fill factor receive the influence to bring very big influence to image quality. For this reason, a new process is required: the influence of the fill factor on the image quality is completely solved by a method of designing the photodiodes/TFTs hierarchically, for example, one layer above is used for the photodiodes and the TFTs are arranged in the next layer (or layers) below, so that the fill factor approaches 100%.
In fig. 3, each acquisition unit further includes two control signals, a reading signal and a reset signal, which may be located inside the array element or in a peripheral circuit of the array element according to two different designs of the reading signal inside or outside the array element; the reading signals of all the acquisition units are mutually connected, so that the data of each acquisition unit is controlled by the same reading signal, and the data are read simultaneously; reset signals for all acquisition units (marked V in the figures)GRST) Interconnected, reset power supply (marked V in the figures) of all acquisition unitsRSTRequires VRST﹥VPD) The data acquisition units are connected with each other and share the same reset power supply, so that the data of each acquisition unit is controlled by the same reset signal and reset simultaneously.
In fig. 3, the control signals of each acquisition unit also include a conversion start request signal of the analog-to-digital converter, denoted V in the figuresCNVSTAs control of the start of analog-to-digital conversion; the time for sending out the request is called the conversion start request time, and is generally arranged after the reading time and requested immediately (except for special description, the same is true in the following embodiments), and the conversion start request time is required to be more than or equal to that of the later-stage operational amplifierThe sum of the transit time and the transit time of the analog-to-digital converter.
The photodiodes of fig. 4-17 are designed for cathode output, and in other embodiments may be modified for photodiode anode output.
All the later-stage operational amplifiers of the following embodiments employ inverting amplifiers or homotropic amplifiers. In the existing flat panel detector, the later-stage operational amplifier is an integral amplifier. In the present design, in order to simplify the circuit structure, ensure the accuracy of data and facilitate the arrangement of time sequence, the CT flat panel detectors of the embodiments all propose to use an inverting amplifier or a homonymous amplifier. This is because: the CT flat panel detector with the TFT for amplification in the array element stores data by using the junction capacitance of the photodiode, because of the field effect transistor attribute of the TFT for amplification, the input loop resistance is very large and is approximately open-circuit, current is hardly required from a signal source, the voltage on the junction capacitance of the photodiode is hardly reduced in the whole reading process, and only the voltage is increased along with the increase of time on the basis of the voltage at the beginning of reading due to the increase of real-time data, so that the data output to a later-stage operational amplifier in reading at each moment is the accumulated value of the data collected by the previous photodiode, and integration is not needed when the data reaches the later-stage operational amplifier; for the CT flat panel detector without the TFT for amplification in the array element, the field effect tube for amplification is added in the peripheral circuit to achieve the purpose. Of course, it is not excluded to use integrating amplifiers in other embodiments.
The substrate of the CT flat panel detector adopts a double-sided technology, one side of the substrate is used for loading a TFT/photodiode (the TFT/photodiode is attached to the substrate and is the same as the existing flat panel detector), the other side of the substrate is used for loading a post operational amplifier and an analog-to-digital converter in a peripheral circuit (a field effect tube for reading, a field effect tube for resetting and a field effect tube for reading which can also move the internal functions of an array element to the peripheral circuit outwards) (which are conventionally called as a channel in the existing CT machine, and other peripheral circuits such as a buffer, various control signals and a power supply need to be additionally designed on the channel), and a conductive pin is embedded in the corresponding position of each array element in the substrate so as to transmit the data of each array element to the peripheral circuits such as the respective post operational amplifier for processing. Each array element corresponds to one channel, no available channel IC may exist at present, the channel IC needs to be specially customized according to the size and the shape of the whole detector, and for a detector without intervals between rows, if a single channel forms one IC, the size of the channel IC on the plane of the substrate is required to be not larger than that of each array element (the height direction is not limited by the size); if an IC is composed of a plurality of (or all) channels in each row, it is required that the size of the channel IC in the plane of the substrate cannot exceed the assembly of the sizes of the array elements composed of the channel IC (the height direction is not limited by this). Meanwhile, the number of channels is large, so that the manufacturing cost is high.
The CT detector in the design also has a buffer which is not shown in all the figures, and the buffer temporarily stores the scanning data of each line of the detector by line unit and finally transmits the scanning data to an operation table computer.
The CT flat panel detector can be made of various materials, and because the CT machine has high requirements on the mobility of the detector transistor, the conventional amorphous silicon can not meet the requirements at present, and high-mobility materials such as an Oxide thin film transistor (Oxide TFT) or a low-temperature polycrystalline silicon thin film transistor (Poly-Si TFT) can be used to meet the requirements of the CT machine on the mobility of the flat panel detector thin film transistor. The DSA plate commonly used at present is amorphous silicon, and the mobility of the amorphous silicon is low (0.5-1 cm)2V.s)), the readout time per row of the TFT (a-Si TFT) readout circuit prepared therefrom is about 1ms, which limits its application to high frame rate X-ray flat panel detectors, and therefore, it is necessary to introduce TFTs with high mobility to achieve high frame rate detection. The mainstream high mobility thin film transistor is an oxide thin film transistor (which can reach 15-50 cm)2V.s) and low temperature polysilicon thin film transistors (up to 100 cm)2V.s) two types. The limited mobility of the thin film transistor is the most fundamental factor that makes the flat panel detector not applicable to CT machine.
Because the more array elements of each row of the detector, the higher the requirement on the scanning frequency of the detector, if the matrix is designed according to the matrix width of the existing flat panel detector, each row of the CT flat panel detector has higher requirement on the scanning frequency of the detectorThe number of array elements in the row will reach about 4000 or more, and the required scanning frequency of the detector is too high when the detector is applied to a CT machine (taking a 4205 array element detector as an example, one circle of scanning is performed in 0.3 second under a radiation pulse control mode, or a half circle of scanning is performed in 0.3 second under a radiation working mode of the existing CT machine, which are both required to reach about 22017Hz, the mobility of the TFT of the flat panel CT detector in fig. 4 is required to be not less than 276.3cm under the working mode of the existing radiation emitter2V.s)), which puts high demands on the TFT mobility of the flat panel detector, and is difficult to implement. At the moment, the scanning frequency of the detector can be reduced by reducing the number of array elements of each row, the requirement of the CT machine on the mobility of the flat panel detector is reduced, the number of channels is reduced, and the manufacturing cost of the detector is reduced. It should be noted that, in the present design, the calculation of each mobility is based on the premise that the mobilities of the TFTs in the array element are the same (the materials are the same), the calculation is based on the approximate value that the transit time of the TFT for amplification is equal to 1.5 times of the transit time of the TFT for reading, the transit time of the TFT for reading is equal to the transit time of the TFT for reset, and the minimum TFT mobility value required by the calculation is only an approximate value, and a large error exists, and is only used for reference.
Therefore, the number of array elements of the flat panel detector needs to be redesigned, and the scanning frequency is reduced by a method of reducing the number of array elements (the following pixels and data of the scanning frequency are obtained by controlling and scanning one circle or scanning half circle in the existing mode by ray pulse under low pixel requirement): 1. when the CT machine adopts 2K projection matrix values, the number of each row of array elements in the CT flat panel detector is about 1155, and the CT flat panel detector is allowed to float within the range of +/-5%; 1K (1024 x 1024) of reconstructed image pixels can be obtained; the required flat panel detector scan frequency (equal to the readout frequency) is about 1814Hz for 1 second complete one revolution (one revolution in the case of a radiation pulse, one half revolution in the case of a conventional radiation emitter operating, the "one revolution" mentioned in the rest of this paragraph is the same and not repeated), about 3628Hz for 0.5 second complete one revolution, about 6048Hz for 0.3 second complete one revolution, the above frequency varies with the floating number of the array elements and is also allowed to float within ± 5%. 2. When 4K projection matrix values are adopted, the number of each row of array elements can be designed to be about 1634, and the floating is allowed within the range of +/-5%; a reconstructed image pixel of 2K (1448 × 1448) can be obtained; the required flat panel detector scan frequency is approximately 2565Hz for a single sweep in 1 second, 5133Hz for a single sweep in 0.5 second, and 8556Hz for a single sweep in 0.3 second, which varies with the number of array elements floating and is also allowed to float within ± 5%. 3. When 8K projection matrix values are adopted, the number of array elements of each row can be designed to be about 2311, and the floating is allowed within the range of +/-5%; a reconstructed image pixel of 4K (2048 × 2048) can be obtained; the required flat panel detector scan frequency is about 3630Hz for a single sweep in 1 second, about 7260Hz for a single sweep in 0.5 second, and about 12100Hz for a single sweep in 0.3 second, which varies with the number of array elements floating and is also allowed to float within 5%. 4. When 16K projection matrix values are adopted, the number of each row of array elements can be designed to be about 3268, and the array elements are allowed to float within the range of +/-5%; a reconstructed image pixel of 8K (2896 and 2896) can be obtained; the required flat panel detector scan frequency is about 5132Hz for a single sweep in 1 second, about 10267Hz for a single sweep in 0.5 second, and about 17112Hz for a single sweep in 0.3 second, which varies with the number of array elements floating and is also allowed to float within ± 5%. The size of the array elements of the CT flat panel detector is different along with the difference of the whole size of the flat panel detector, but the array elements are uniformly arranged without gaps; and the rows of the whole detector are arranged uniformly and without gaps (if the number of rows of the detector is reduced for reducing the cost of the detector, the rows can have gaps).
The above modifications are basically common to all embodiments except for the specific description, and the above modifications will not be described repeatedly in the following embodiments in order to save the weaving. Through the technical improvement, the following common technical effects can be achieved: the size of the CT scanner can meet the requirement that a CT machine can obtain a tomographic image of a part by scanning for one circle or half circle, when the CT scanner is applied to the CT machine, spiral scanning is not needed any more (if the number of rows of detectors is reduced for reducing the cost of the detectors, spiral scanning is needed), the scanning time is greatly reduced, the irradiation dose of a patient is greatly reduced (about one tenth of that of the existing CT machine), gapless scanning is realized, and missing detection is avoided; the data of each array element is independently output to a respective post-stage operational amplifier and an analog-to-digital converter, reading signals of all the acquisition units are mutually connected and simultaneously acquire data, and the data are cached in a row unit, so that the circuit structure meets the requirements that each row scans for one circle or a half circle to obtain a section image, and the whole detector scans for one circle or a half circle to obtain each section image of one part; the material meets the requirements of CT scanning on the mobility of the detector thin film transistor; the substrate adopts a double-sided technology, so that data in the array element matrix can be conveniently transmitted to peripheral circuits such as a post operational amplifier and the like for processing, the transmission distance is shortened as much as possible, the transmission loss of signals is greatly reduced, the interference is reduced, the signal-to-noise ratio is greatly improved, and the dosage requirement on rays is greatly reduced; the layered design greatly improves the filling factor; the number of detector array elements is reduced, the requirement of the CT machine on the mobility of the flat panel detector is reduced, and the number of channels is reduced, so that the cost of the detector is reduced. The above technical effects are common effects of all embodiments, and are not repeated in the following embodiments in order to save the weaving.
The above is a common technique for all embodiments in the present design, and the invention points are as follows: the data of each array element is independently output to a respective post operational amplifier and an analog-to-digital converter, and reading signals of all the acquisition units are mutually connected and simultaneously acquire data and are cached in a row unit; the substrate adopts a double-sided technology; the array element number of each row of the flat panel detector which needs to be designed for obtaining various CT image pixels is determined, and the scanning frequency is reduced by reducing the array element number so as to adapt to the mobility of the flat panel detector made of the existing material and reduce the detector cost.
The present invention will be described in further detail with reference to specific examples.
Example 1
As shown in fig. 4 and 5, in the present embodiment, the CT flat panel detector utilizes the junction capacitance of the photodiode itself to store the acquired data, and the reading signal is added to the inside of the array element; each array element comprises 1 reading TFT, 1 amplifying TFT and 1 resetting TFT besides 1 photodiode; the reading TFT is used for controlling data output, and its control signalThe numbers are called reading signals (marked as V in the figures)READ) (ii) a The reset TFT is used for resetting data, and its control signal is called a reset signal (denoted as V in the drawings)GRST) The power supply of which is called reset power supply (marked as V in the figures)RST) (ii) a The reading TFT is arranged behind the amplifying TFT; in this embodiment, the subsequent operational amplifier is an inverting amplifier or a homonymous amplifier. The circuit diagram of a single acquisition unit of the CT flat panel detector of this embodiment is shown in fig. 4, and the corresponding structure diagram of the pixel matrix circuit is shown in fig. 5, which is a current type, and can also be designed as a voltage type (since the voltage amplification type needs to add resistance to the drain, the temperature inside the array element matrix will be increased, and the dark current of the photodiode will be increased, which is not generally recommended. The application conditions are that the CT machine adopts a ray emitter pulse control mode: when the CT flat panel detector collects the radiation, the ray emitter emits the ray; the ray emitter does not emit rays when the CT flat panel detector reads and resets. The CT machine is required to adopt a 360-degree scanning mode.
In this embodiment, the radiation emission of the radiation emitter of the flat panel CT machine adopts a pulse modulation (or gate control) technique. The ray emitter (generally referred to as "bulb") of this embodiment adopts grid control, changes the commonly used diode structure of the bulb into a triode, and controls the ray emission of the bulb by applying a sufficiently high negative voltage to the grid and controlling the negative voltage through a ray pulse signal, and controlling the cathode electron current in a switch state (in other embodiments, the pulse control method can also theoretically realize the pulse control of the ray in addition to the above implementation method, and the pulse square wave characteristic is more ideal and the frequency is higher, but the current of the carbon nanotube cold cathode bulb is relatively lower at present, so that the current is temporarily difficult to meet the requirement, and the improvement of the current is still needed. The computer of the operation desk can calculate the scanning frequency of the detector according to the selected scanning condition, the computer of the operation desk provides a square wave pulse signal with the same width of a high-low potential time axis at the frequency, the signal is called a ray pulse control signal, meanwhile, a negative voltage power supply is added in a circuit (in order to reduce the voltage of the negative voltage power supply, the cathode of the bulb tube is suggested to be grounded, the realization mode of the negative voltage power supply is not limited), the ray pulse control signal is correspondingly converted and is used for controlling the negative voltage power supply to generate a negative voltage (about several kilovolts) which is enough to cut off the electron current of the cathode of the bulb tube and has the same frequency, and the negative voltage is provided for the grid of the bulb tube, so that the pulse control of ray emission is realized. The ray pulse control signal sent by the computer on the operation table is used for controlling the output of the ray, and the time width of the emitted ray is equal to the time width of the non-emitted ray. The computer of the operation desk sends various control signals required by the CT flat panel detector, including reading signals, reset signals, conversion starting request signals and the like, while sending ray pulse control signals, and sends the control signals to the CT flat panel detector in a wireless mode. The frequencies of the reading signal, the resetting signal, the conversion starting request signal and the like of the CT flat panel detector are the same as the frequency of the ray pulse signal and are the scanning frequency of the CT flat panel detector. The CT flat panel detector under the control of ray pulse adopts interval scanning to acquire data once every other array element width, namely, the data is acquired once when the outermost array element on each row rotates by one array element width, and the data is not acquired in the rotating time of the next array element width, and the reading and data resetting are carried out by utilizing the time of not acquiring the data; when the ray emitter emits rays, the CT flat panel detector collects data, the time for collecting the data is called as sampling time, and the sampling time is equal to the ray emitting time.
The scanning frequency of the CT flat panel detector is controlled by a projection matrix value and scanning time required by the scanning condition of a computer on an operation table, the computer automatically provides a square wave pulse signal (namely a ray pulse control signal of a ray emitter) according to the scanning frequency, the width of the square wave pulse signal can be equal to that of a high-low potential time shaft, the phase inversion can also be carried out after 180-degree scanning, and the scanning frequency is set by software in the computer. The calculation formula of the scanning frequency of the CT flat panel detector is as follows: and X is Y/Z/T, wherein X is the scanning frequency of the CT flat panel detector, Y is the projection matrix value required to be achieved, Z is the array element number of each row of the flat panel detector, and T is the time for scanning 360 degrees. In order to obtain an ideal image effect, a CT machine under a radiation pulse control mode needs to satisfy a calculation formula X ═ Z/(2T) at the same time.
In other embodiments, the reset time of the CT flat panel detector is generally set after the read time, which is also the way all CT flat panel detectors in the present design can take. At this time, in the ray pulse control mode, the sum of the reading time and the reset time is equal to the sampling time.
However, due to the delay characteristics of the reset TFT, the amplifying TFT and the reading TFT (the algorithm of the delay time is t)TR＝L2/(uV)，tTRFor the transit time of the TFT, u is mobility, L is semiconductor thickness, and V is voltage), for a CT machine composed of a CT flat panel detector in which the TFT for amplification precedes the TFT for reading (or a field effect tube for reading of peripheral circuits), the reset time of the CT flat panel detector can be set within the reading time (for the reason see example 2), and the reset time is arranged at the end of the reading time (whether the CT machine is a radiation pulse control type or a non-radiation pulse control type, the reset time can be set within the reading time). At this time, in the ray pulse control mode, the reading time is equal to the sampling time. In this way, the design can prolong the reading time to the maximum extent so as to reduce the limit of the mobility of the CT flat panel detector to the CT machine.
The timing control of the embodiment: the reading time needs to be longer than the sum of the transit times of the amplifying TFT and the reading TFT, the reading time is equal to the sampling time, the resetting time needs to be longer than the transit time of the resetting TFT, and the resetting time is arranged within the reading time. The timing control diagram of the present embodiment is shown in fig. 18. It should be noted that, because the high-frequency part of the radiation emission has a very high frequency, it is directly replaced by a straight line in the figure, and is not expressed in a high-frequency form (the same below); meanwhile, the high potential time lengths of the various signals in the figure are only approximate values and only represent the respective approximate time lengths and the corresponding sequential logic relations (therefore, the time lengths of the same signals are originally different in other different embodiments, but are also described in the same figure, which only represents that the time lengths of the same signals are identical in time logic, and not that the time sequences of the two different embodiments are completely identical in the time lengths of the respective signals).
The CT machine of the present embodiment employs a 360 ° scanning mode.
Under the requirement of low pixel, the image of a section can be obtained by only scanning one circle. In order to ensure that the flat-panel CT machine uniformly obtains the projection of each axial line of the slice during 360 ° scanning, when the flat-panel detector rotates to 180 °, the radiation pulse control signal of the radiation emitter and various control signals of the flat-panel detector (including the reading signal, the reset signal and the conversion start request signal) are respectively inverted (180 ° phase shift from the first 180 ° phase of the rotational scanning) to obtain the projection data of the axial line missed because the radiation emitter does not emit the radiation and the flat-panel detector does not collect during reading of the flat-panel detector within the first 180 ° scanning range, otherwise, the scanning of the later 180 ° is likely to be the axial line (the axial lines overlap, but the data is different).
In this embodiment, under the high pixel requirement, two scanning cycles are required to obtain an image of a section. At this time, the 180-degree inversion technology under the condition of the above low pixels can be repeated; a 360 degree phase inversion technique may also be used, i.e. the first turn is scanned without phase inversion and the second turn is scanned with a 180 phase shift relative to all the control signals above the first turn. A high pixel scan can achieve twice as many pixels as a low pixel scan, but the scan time will be doubled.
In the embodiment, under the low pixel requirement, the CT flat panel detector adopts 8K projection matrix values, and the number of array elements in each row can be designed to 2311, which allows the array elements to float within a range of ± 5%; the reconstruction image pixel of 4K can be obtained, the scanning frequency of the flat panel detector is required to complete one circle of scanning in 0.3 second, the scanning frequency is about 12100Hz, the scanning frequency is equivalent to about 82.6us of each acquisition and reading period, the time allocated to the reading of the detector is about 41.3us (the sum of the transition time of the TFT for amplification and the TFT for reading is required to be less than the time), and the mobility of the thin film transistor is required to be not less than 30.3cm2V.s (in terms of mobility, 0.5-1 cm)2/(V.s) amorphous siliconRead time in a detector with reading TFT was 1ms versus the calculated approximate value and was measured at 0.5cm2V.s read time 1ms as a reference, and calculated as an approximate value where the transit time of the amplifying TFT is 1.5 times the transit time of the reading TFT, this error is large; the range of the data itself of the referred amorphous silicon is large, if 1cm2V.s. as reference, the resulting mobility value will be doubled; and the difference between the semiconductor thickness and the voltage is not considered, so the result can only provide a reference. Similarly, the mobility values mentioned in the following are advanced by 2311 array elements to obtain 8K projection matrix values, which are also 0.5cm2V.s amorphous silicon readout time 1ms is an approximate value for reference, all for reference). The required flat panel detector scanning frequency is about 7260Hz when completing one circle of scanning in 0.5 second, and the mobility of the thin film transistor is required to be not less than 18.2cm2V.s. If the detector TFT has a mobility of 100cm2V.s.the shortest scan time theoretically available for a CT machine is 0.091 seconds (theoretically minimum, actually needed to be greater than this value, and considering mobility alone, without considering whether the rest of the CT machine can meet the conditions or not).
The CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the above CT flat panel detector:
the reading signal is added into the array element, the junction capacitance of the photodiode is used for storing data, the reading signal is amplified by the TFT and then is output under the control of the reading signal, so that the output signal intensity is stronger, and the signal to noise ratio is improved. And an inverting amplifier or a homodromous amplifier is adopted, so that the accuracy of data is ensured. The pulse control technology is adopted for a ray emitter of the CT machine, the ray emitter does not emit rays when a flat panel detector reads, no trailing phenomenon exists, data cannot be lost, the sampling time is equal to the reading time, the data during reading is just the determined quantity for acquiring the width of an array element, and for single data, the data is complete and non-missing projection data; the application of 180-degree phase reversal technology ensures that a complete image is obtained by scanning a circle; meanwhile, the requirement of the CT machine on the scanning frequency of the flat panel detector can be reduced by half; and the reading time is prolonged to the maximum extent, so that the requirement on the mobility of the flat-panel detector thin film transistor is greatly reduced (by about 5 times compared with the embodiment 2).
The disadvantage of this embodiment is that the cost of the radiation emitter of the CT machine will increase, as well as the cost of the modification of the radiation pulse control technique.
In addition to the above common points of invention, the present design has the following points in the present embodiment: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the reset time is scheduled within the reading time; the pulse control technology of the ray emitter of the CT machine is designed in a matching way (the technology can be applied to all CT detectors).
Example 2
In this embodiment, with the CT flat panel detector in embodiment 1, a circuit diagram of each acquisition unit is shown in fig. 4, and a structure diagram of a corresponding pixel matrix circuit is shown in fig. 5. Here, the structure thereof will not be described repeatedly.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: because the ray emitter continuously emits rays when reading, the photodiode continuously collects data, and the reading time is required to be as short as possible for image quality (the reading time is required to be less than or equal to 10% of the reading period, the smaller the reading time is, the better the reading time is, but the smaller the requirement on the mobility of the thin film transistor of the detector is, the time of one reading period is equal to the time of the outermost array element of the detector rotating by the width of one array element and changing along with the scanning frequency in the CT machine adopting the working mode of the existing ray emitter). Since the transit time of the reading TFT is substantially equal to the transit time of the resetting TFT (assuming that the reset voltage is the same as the reading voltage), the reset time can be arranged within the reading time (at the end of the reading time) for the detector in which the amplifying TFT precedes the reading TFT (or the field effect transistor for reading in the peripheral circuit), and the reset data of the photodiode needs to pass through the amplifying TFT to reach the reading TFT under the action of the reset voltage signal, and the reading TFT is turned off at this time, so that the reset data does not enter the post-processing circuit, and normal image data is not affected. If the reset time is arranged after the reading time, due to the time delay of the TFT, when the reading is completed, the newly acquired data within the total transit time (the total transit time is equal to the sum of the transit times of the amplifying TFT and the reading TFT in the embodiment) does not reach the operational amplifier at the later stage, the data will be cleared by the subsequent reset signal, and the data within the reset time is also lost, that is, the lost data will be the newly acquired data within the time of the sum of the total transit time and the reset time; if the reset time is arranged within the reading time, the loss in the reset time is put within the reading time, and the loss is only newly acquired data within the total transit time, so that the loss is reduced (other embodiments have the same reason and are not explained below); on the other hand, on the premise of losing the same data volume, the reading time can be maximized, so that the requirement of the CT machine on the mobility of the flat panel detector is reduced. In this embodiment, the reading time is required to be longer than the total transit time, the reset time is longer than the transit time of the reset TFT, the reset time is arranged within the reading time, and the reading time is 10% or less of the reading period. The timing chart of this embodiment is shown in fig. 19.
When the image pixel requirement is low, the CT machine composed of the CT flat panel detector in the embodiment can adopt a 180 ° scanning mode. At the moment, the scanning time can be reduced by half under the same scanning frequency, which is beneficial to the scanning of heart and the like with high requirements on time; or the scanning frequency can be reduced by half in the same time, which is beneficial to reducing the requirement of the CT machine on the mobility of the flat panel detector (considered in design). When 360-degree scanning is adopted, the CT machine can be designed to be scanned by adopting rays with two different energies at the front 180-degree angle and the back 180-degree angle of the same ray emitter, so that 2 images with the same section under two different energies are obtained, and the CT machine with more enhanced functions is developed. For an application with low requirement on scanning speed (such as a DSA/CT integrated machine), the CT machine adopting the detector of the embodiment can be provided with a C-shaped arm structure, but the scanning speed is low because the rotating speed of the C-shaped arm is slow.
When the image pixel requirement is high, the CT machine composed of the CT flat panel detector in this embodiment can adopt a 360 ° scanning mode, and can obtain pixels twice as many as the 180 ° scanning. In this case, either the scanning time needs to be doubled, or the scanning frequency of the detector needs to be doubled within the same time, which doubles the requirement for the mobility of the detector (which needs to be considered in the design).
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
the reading signal is added into the array element, the junction capacitance of the photodiode is used for storing data, the reading signal is amplified by the TFT and then is output under the control of the reading signal, so that the output signal intensity is stronger, and the signal to noise ratio is improved. And an inverting amplifier or a homodromous amplifier is adopted, so that the accuracy of data is ensured. The CT machine adopting the detector can adopt a 180-degree scanning mode, can reduce half of scanning time under the same scanning frequency, and is beneficial to scanning of heart and the like with high requirements on time; or the scanning frequency can be reduced by half in the same time, which is beneficial to reducing the requirement of the CT machine on the mobility of the flat panel detector. For the application with low requirement on the scanning speed, the scanning frame can be made into various C-shaped arm structures, so that the manufacturing cost of the CT machine is reduced, various mobile use requirements can be met, and the CT machine and the DSA/CT machine can be made into mobile CT and DSA integrated machines; when 360-degree scanning is adopted under the requirement of low pixel, the function of the CT machine can be greatly improved by the double-energy ray scanning technology.
A disadvantage of this embodiment is that newly acquired data in the total transit time (and also the data in the reset time) is lost. However, the greatest disadvantage is that the reading time is required to be too short, the requirements on the mobility of the flat panel detector are too high: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when the scanning is completed in 0.3 second and a half-circle, and the mobility of the thin film transistor is required to be not less than 151.3cm2V.s, conventional materialsThe quality can not meet the requirements, and only the appearance of high-mobility materials after waiting; the required scanning frequency of the flat panel detector is about 7260Hz when the scanning is completed in 0.5 second and the mobility of the thin film transistor is not less than 90.8cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest half-cycle time for scanning that can be theoretically used by CT machines is about 0.454 seconds, requiring a scanning frequency of about 8000 Hz.
In addition to the above common points of invention, the present design has the following points in the present embodiment: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the reset time is scheduled within the reading time; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
Example 3
As shown in fig. 6 and 7, in the present embodiment, the junction capacitance of the photodiode itself is used to store the collected data; each array element in the pixel matrix comprises 1 photodiode, 1 reset TFT for resetting data, a control signal of the reset TFT is called a reset signal, a power supply of the reset TFT is called a reset power supply, and all the array elements share the same reset power supply; the reading signal of the CT flat panel detector is input into the amplifying TFT in the array element, so that the amplifying TFT performs amplification processing and controls the output of data. In this embodiment, the subsequent operational amplifier is an inverting amplifier or a homonymous amplifier.
The radiation emitter of the CT machine of this embodiment adopts the radiation pulse control method of embodiment 1, and the operation principle will not be described repeatedly.
The timing control of the embodiment: the reading time needs to be longer than the transit time of the amplifying TFT, the resetting time needs to be longer than the transit time of the resetting TFT, the resetting time is arranged after the reading time, and the sum of the reading time and the resetting time is equal to the sampling time. The timing control diagram is shown in fig. 20.
In this embodiment, when the pixel requirement is low, the requirement for the mobility of the flat panel detector is as follows: taking 2311 array elements to obtain 8K projection matrix values as an example, the required flat panel detector scanning frequency is 0.The mobility of the thin film transistor is required to be not less than 18.2cm when one circle of scanning is finished in 3 seconds and is about 12100Hz2V.s); the required flat panel detector scanning frequency is about 7260Hz when completing one circle of scanning in 0.5 second, and the mobility of the thin film transistor is required to be not less than 10.9cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest scanning time that can be used by a CT machine is theoretically 0.054 seconds, and the scanning frequency is required to be about 66667Hz (difficult to achieve).
Under high pixel requirements, two passes of scanning are also required, similar to example 1 and will not be repeated.
The flat panel detector and the CT machine thereof have the following technical effects besides the common technical effect of the CT flat panel detector:
because the TFT for reading in the array element is removed, the function of the array element is combined with the TFT for amplification, and the TFT for amplification is used for controlling the output of data, the number of the TFT is reduced, the transit time during reading is reduced, and the requirement of a CT (computed tomography) machine on the mobility of a thin film transistor of a flat panel detector is reduced (by about 40 percent compared with embodiment 1); the pixel detection area is increased for a detector with a planar transverse layout, so that the filling factor of the detector is increased (the effect is not achieved for a layered layout in the design); the internal structure of the array element is simplified, and the manufacturing cost is reduced; the remaining effects related to the ray pulse control are the same as those of embodiment 1 and are not repeated.
The invention in this embodiment is as follows: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; a ray pulse control technology.
Example 4
In this embodiment, with the CT flat panel detector in embodiment 3, a circuit diagram of each acquisition unit is shown in fig. 6, and a structure diagram of a corresponding pixel matrix circuit is shown in fig. 7. Here, the structure thereof will not be described repeatedly.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: in this embodiment, the reading time is required to be longer than the transition time of the amplifying TFT, the reset time is longer than the transition time of the resetting TFT, and the reset time is arranged after the reading time, and the sum of the reading time and the reset time should be 10% or less of the reading period. The timing chart of this embodiment is shown in fig. 21.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when the scanning is completed in 0.3 second and a half-circle, and the mobility of the thin film transistor is required to be not less than 90.8cm2V.s); the required scanning frequency of the flat panel detector is about 7260Hz when the scanning is completed in 0.5 second and the mobility of the thin film transistor is not less than 54.5cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest half-cycle time for scanning that can be theoretically used by a CT machine is about 0.272 seconds, requiring a scanning frequency of about 13333 Hz.
When the image pixel requirement is low, the CT machine composed of the CT flat panel detector in the embodiment can adopt a 180 ° scanning mode. When 360-degree scanning is adopted, the CT machine can be designed to be scanned by adopting rays with two different energies at the front 180-degree angle and the back 180-degree angle of the same ray emitter, so that 2 images with the same section under two different energies are obtained, and the CT machine with more enhanced functions is developed.
When the image pixel requirement is high, the CT machine composed of the CT flat panel detector in this embodiment can adopt a 360 ° scanning mode, and can obtain pixels twice as many as the 180 ° scanning. In this case, either the scanning time needs to be doubled, or the scanning frequency of the detector needs to be doubled within the same time, which doubles the requirement for the mobility of the detector (which needs to be considered in the design).
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
the reading TFT in the array element is removed, the functions of the array element are combined to the amplifying TFT, and the amplifying TFT is used for controlling the output of data, so that the number of the TFTs is reduced, the reading speed is improved relative to the structure with the reading TFT in the array element, and the limitation of the mobility of the thin film transistor on the application of the CT machine is reduced (by about 40 percent compared with embodiment 2); the transition time of the reading TFT is not available, so that the data loss caused by the time delay in the reading time is reduced; only a photodiode, a TFT for amplification and a TFT for resetting are needed in an array element, and the pixel detection area of the detector with the planar transverse layout is increased, so that the filling factor of the detector is increased (the effect is not achieved in the layered layout in the design); the internal structure of the array element is simplified, and the manufacturing cost is reduced. The remaining effects associated with the 180 degree scan are the same as in example 2 and are not repeated.
This embodiment has a disadvantage that newly acquired data in the transit time of the amplifying TFT and the transit time of the resetting TFT is lost.
In addition to the above common points of invention, the present design has the following points in the present embodiment: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
Example 5
As shown in fig. 8 and 9, in the present embodiment, the junction capacitance of the photodiode itself is used to store the collected data; the structure of the detector is that a reading signal of each acquisition unit is directly input into an array element, each array element in a pixel matrix comprises 1 photodiode, a reset TFT, a reading TFT and an amplification TFT, the reset TFT is used for resetting an electric signal of the photodiode, the reading TFT is controlled by the reading signal to control the output of data, the amplification TFT is used for amplifying the electric signal of the photodiode, and the reading TFT is arranged in front of the amplification TFT; in this embodiment, the subsequent operational amplifier is an inverting amplifier or a homonymous amplifier.
The radiation emitter of the CT machine of this embodiment adopts the radiation pulse control method of embodiment 1, and the operation principle will not be described repeatedly.
The timing control of the embodiment: the reading time needs to be larger than the transition time of the reading TFT, the resetting time needs to be larger than the transition time of the resetting TFT, the resetting time is arranged after the reading time, and the sum of the reading time and the resetting time is equal to the sampling time; the switching start request time needs to be delayed by the transit time of one amplifying TFT after the reading time. The timing control diagram is shown in fig. 22.
In this embodiment, when the pixel requirement is low, the requirement for the mobility of the flat panel detector is as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when one circle of scanning is finished in 0.3 second, and the mobility of the thin film transistor is required to be not less than 24.2cm2V.s); the required flat panel detector scanning frequency is about 7260Hz when completing one circle of scanning in 0.5 second, and the mobility of the thin film transistor is required to be not less than 14.6cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest scanning round time that can be used by a CT machine is theoretically 0.073 seconds, requiring a scanning frequency of about 50000Hz, which is difficult to achieve.
Under high pixel requirements, two passes of scanning are also required, similar to example 1 and will not be repeated.
The flat panel detector and the CT machine thereof have the following technical effects besides the common technical effect of the CT flat panel detector:
by designing the reading TFT in the array element before the amplifying TFT, the total transit time is reduced compared with that of the embodiment 1, but the reset time can only be set after the reading time, so that the total transit time is reduced a little, and the requirement of the CT machine on the mobility of the flat-panel detector thin-film transistor is reduced by about 20% (compared with the embodiment 1); the remaining effects related to the ray pulse control are the same as those of embodiment 1 and are not repeated.
The invention in this embodiment is as follows: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; a ray pulse control technology.
Example 6
In this embodiment, with the CT flat panel detector in embodiment 5, a circuit diagram of each acquisition unit is shown in fig. 8, and a structure diagram of a corresponding pixel matrix circuit is shown in fig. 9. Here, the structure thereof will not be described repeatedly.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: in this embodiment, the reading time requirement is greater than the transition time of the reading TFT, the reset time is greater than the transition time of the resetting TFT, the reset time is arranged after the reading time, and the sum of the reading time and the reset time is required to be less than or equal to 10% of the reading period; the switching start request time needs to be delayed by the transit time of one amplifying TFT after the reading time. The timing chart of this embodiment is shown in fig. 23.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when the scanning is completed in 0.3 second and a half-circle, and the mobility of the thin film transistor is required to be not less than 121cm2V.s); the required scanning frequency of the flat panel detector is about 7260Hz when the scanning is completed in 0.5 second and the mobility of the thin film transistor is not less than 72.6cm2V.s. If the detector TFT has a mobility of 100cm2The shortest scanning half-circle time which can be adopted by the CT machine is about 0.363 seconds theoretically by taking low-temperature polycrystalline silicon (V.s) as a material, and the scanning frequency is required to be about 10000 Hz.
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
by designing the reading TFT in the array element before the amplifying TFT, the total transit time is reduced compared with that of the embodiment 2, but the reset time can only be set after the reading time, so that the total transit time is reduced a little, and the requirement of the CT machine on the mobility of the flat-panel detector thin-film transistor is reduced by about 20% (compared with the embodiment 2); the effects associated with the remaining low pixel 180 degree scan and high pixel 360 degree scan are the same as in embodiment 2 and will not be repeated.
This embodiment has the disadvantage of losing the newly acquired data in the transit time and reset time of the reading TFT.
In addition to the above common points of invention, the present design has the following points in the present embodiment: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
Example 7
As shown in fig. 10 and 11, in the present embodiment, the junction capacitance of the photodiode itself is used to store the collected data; the structure of the flat panel detector is that a reading signal of each acquisition unit is input to the outside of an array element, the output of data is controlled by using a field effect tube for reading in a peripheral circuit, each array element in the pixel matrix comprises 1 photodiode, a TFT for resetting and a TFT for amplifying, the TFT for resetting is used for resetting an electric signal of the photodiode, and the TFT for amplifying is used for amplifying the electric signal of the photodiode; the later operational amplifier adopts an inverting amplifier or a homodromous amplifier.
The radiation emitter of the CT machine of this embodiment adopts the radiation pulse control method of embodiment 1, and the operation principle will not be described repeatedly.
The timing control of the embodiment: the reading time needs to be longer than the sum of the transit time of the amplifying TFT and the transit time of the reading field effect tube in the peripheral circuit, the resetting time needs to be longer than the transit time of the resetting TFT, the resetting time is arranged within the reading time (at the end of the reading time), and the reading time is equal to the sampling time. The timing control diagram is shown in fig. 18.
In this embodiment, when the pixel requirement is low, the requirement for the mobility of the flat panel detector is as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when one circle of scanning is completed in 0.3 second, and the mobility of the thin film transistor is required to be not less than 18.4cm2V.s); the required flat panel detector scanning frequency is about 7260Hz when completing one circle of scanning in 0.5 second, and the mobility of the thin film transistor is required to be not less than 11cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest scanning round time that can be used by CT machine is 0.058 seconds theoretically, requiring a scanning frequency of about 62500Hz (difficult to achieve).
Under high pixel requirements, two passes of scanning are also required, similar to example 1 and will not be repeated.
The flat panel detector and the CT machine thereof have the following technical effects besides the common technical effect of the CT flat panel detector:
by arranging the reading signal outside the array element and controlling the reading by using the field effect tube in the peripheral circuit, compared with embodiment 1, the transition time of the TFT for reading is reduced, so that the total transition time (equal to the sum of the transition time of the TFT for amplifying and the transition time of the field effect tube for reading in the peripheral circuit) is reduced, and the requirement of the CT machine on the mobility of the flat-panel detector thin film transistor is reduced (by about 40% compared with embodiment 1); the remaining effects related to the ray pulse control are the same as those of embodiment 1 and are not repeated.
The invention in this embodiment is as follows: reading is designed outside the array element by using a TFT; the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the reset time is scheduled within the reading time; a ray pulse control technology.
Example 8
In this embodiment, with the CT flat panel detector in embodiment 7, a circuit diagram of each acquisition unit is shown in fig. 10, and a structure diagram of a corresponding pixel matrix circuit is shown in fig. 11. Here, the structure thereof will not be described repeatedly.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: in this embodiment, the reading time needs to be longer than the sum of the transition time of the amplifying TFT and the transition time of the reading field effect transistor in the peripheral circuit, the resetting time needs to be longer than the transition time of the resetting TFT, the resetting time is arranged within the reading time (at the end of the reading time), and the reading time needs to be equal to or shorter than 10% of the reading period. The timing control diagram is shown in fig. 19.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when the scanning is completed in 0.3 second and a half-circle, and the mobility of the thin film transistor is required to be not less than 96.7cm2V.s); the required scanning frequency of the flat panel detector is about 7260Hz when the scanning is completed in 0.5 second and the mobility of the thin film transistor is not less than 56.5cm2V.s. If the detector TFT has a mobility of 100cm2V.s low temperature polysilicon is the material, theoretically the shortest scanning half-cycle time that can be used by the CT machine is about 0.29 seconds, requiring a scanning frequency of about 12500 Hz.
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
by arranging the reading signal outside the array element and controlling the reading by using the field effect tube in the peripheral circuit, compared with the embodiment 2, the transition time of the TFT for reading is reduced, so that the total transition time (equal to the sum of the transition time of the TFT for amplifying and the transition time of the field effect tube for reading in the peripheral circuit) is reduced, and the requirement of the CT machine on the mobility of the flat-panel detector thin film transistor is reduced (about 37% lower compared with the embodiment 2); the effects associated with the remaining low pixel 180 degree scan and high pixel 360 degree scan are the same as in embodiment 2 and will not be repeated.
This embodiment has a disadvantage in that newly acquired data in the transit time of the TFT for amplification and the transit time of the field effect tube for reading in the peripheral circuit are lost.
In addition to the above common points of invention, the present design has the following points in the present embodiment: reading is designed outside the array element by using a TFT; the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the reset time is scheduled within the reading time; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
Example 9
As shown in fig. 12 and 13, in the present embodiment, the junction capacitance of the photodiode itself is used to store the collected data; the flat panel detector is structurally characterized in that a reading signal of each acquisition unit is directly input into an array element, each array element in the pixel matrix comprises 1 photodiode, a reset TFT and a reading TFT, the reset TFT is used for resetting an electric signal of the photodiode, and the reading TFT is controlled by the reading signal to control data output; a field effect tube for amplification is arranged in front of the rear operational amplifier, and the rear operational amplifier adopts an inverting amplifier or a homodromous amplifier.
The radiation emitter of the CT machine of this embodiment adopts the radiation pulse control method of embodiment 1, and the operation principle will not be described repeatedly.
The timing control of the embodiment: the reading time needs to be longer than the transition time of the reading TFT, the resetting time needs to be longer than the transition time of the resetting TFT, the resetting time is arranged after the reading time, the sum of the reading time and the resetting time is equal to the sampling time, and the switching start request time needs to be delayed by the transition time of a field effect tube for amplifying a peripheral circuit after the reading time. The timing control diagram is shown in fig. 24.
In this embodiment, when the pixel requirement is low, the requirement for the mobility of the flat panel detector is as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when one circle of scanning is finished in 0.3 second, and the mobility of the thin film transistor is required to be not less than 24.2cm2V.s); the required flat panel detector scanning frequency is about 7260Hz when completing one circle of scanning in 0.5 second, and the mobility of the thin film transistor is required to be not less than 14.6cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest scanning round time that can be used by a CT machine is theoretically 0.073 seconds, requiring a scanning frequency of about 50000Hz, which is difficult to achieve.
Under high pixel requirements, two passes of scanning are also required, similar to example 1 and will not be repeated.
The flat panel detector and the CT machine thereof have the following technical effects besides the common technical effect of the CT flat panel detector:
by reducing the TFT for amplification in the array element, the total transit time is reduced, so that the requirement of the CT machine on the mobility of the flat-panel detector thin film transistor is reduced (by about 20 percent compared with embodiment 1); the remaining effects related to the ray pulse control are the same as those of embodiment 1 and are not repeated.
The invention in this embodiment is as follows: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; a field effect tube for amplification is arranged in front of the rear operational amplifier; a ray pulse control technology.
Example 10
In this embodiment, with the CT flat panel detector in embodiment 9, a circuit diagram of each acquisition unit is shown in fig. 12, and a structure diagram of a corresponding pixel matrix circuit is shown in fig. 13. Here, the structure thereof will not be described repeatedly.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: in this embodiment, the reading time needs to be longer than the transition time of the reading TFT, the resetting time needs to be longer than the transition time of the resetting TFT, the resetting time is arranged after the reading time, the sum of the reading time and the resetting time needs to be less than or equal to 10% of the reading period, and the switching start request time needs to be delayed by the transition time of a field effect transistor for amplifying the peripheral circuit after the reading time. The timing control diagram is shown in fig. 25.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when the scanning is completed in 0.3 second and a half-circle, and the mobility of the thin film transistor is required to be not less than 121.1cm2V.s); the required scanning frequency of the flat panel detector is about 7260Hz when the scanning is completed in 0.5 second and the mobility of the thin film transistor is not less than 72.6cm2V.s. If the detector TFT has a mobility of 100cm2The shortest scanning half-circle time which can be adopted by the CT machine is about 0.363 seconds theoretically by taking low-temperature polycrystalline silicon (V.s) as a material, and the scanning frequency is required to be about 10000 Hz.
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
by reducing the TFT for amplification in the array element, the total transit time is reduced, so that the requirement of the CT machine on the mobility of the flat-panel detector thin film transistor is reduced (by about 20 percent compared with embodiment 2); the effects associated with the remaining low pixel 180 degree scan and high pixel 360 degree scan are the same as in embodiment 2 and will not be repeated.
This embodiment has a disadvantage in that newly acquired data in the transit time of the reading TFT and the transit time of the resetting TFT is lost.
In addition to the above common points of invention, the present design has the following points in the present embodiment: the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; a field effect tube for amplification is arranged in front of the rear operational amplifier; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
Example 11
As shown in fig. 14 and fig. 15, in this embodiment, the flat panel detector is configured such that the reading signal of each acquisition unit is directly input to the outside of an array element, and the output of data is controlled by using a field effect transistor for reading in a peripheral circuit, each array element in the pixel matrix includes, in addition to 1 photodiode, a TFT for resetting an electrical signal of the photodiode; an amplifying field effect tube (which can be before or after the reading field effect tube, and in this embodiment before the reading field effect tube) is arranged in front of the later stage operational amplifier, and the later stage operational amplifier adopts an inverting amplifier or a homonymous amplifier.
The radiation emitter of the CT machine of this embodiment adopts the radiation pulse control method of embodiment 1, and the operation principle will not be described repeatedly.
The timing control of the embodiment: the reading time needs to be longer than the sum of the transit times of the field effect tube for amplification and the field effect tube for reading in the peripheral circuit, the resetting time needs to be longer than the transit time of the TFT for resetting, the resetting time is arranged after the reading time, and the sum of the reading time and the resetting time is equal to the sampling time. The timing control diagram is shown in fig. 20.
In this embodiment, when the pixel requirement is low, the requirement for the mobility of the flat panel detector is as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when one circle of scanning is finished in 0.3 second, and the mobility of the thin film transistor is required to be not less than 12.3cm2V.s); the required flat panel detector scanning frequency is about 7260Hz when completing one circle of scanning in 0.5 second, and the mobility of the thin film transistor is required to be not less than 7.3cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest scan round time that can be theoretically used by CT machines is 0.04 seconds, requiring a scan frequency of about 90909Hz (difficult to achieve).
Under high pixel requirements, two passes of scanning are also required, similar to example 1 and will not be repeated.
The flat panel detector and the CT machine thereof have the following technical effects besides the common technical effect of the CT flat panel detector:
by arranging the reading signal outside the array element and controlling the reading by using the field effect tube in the peripheral circuit, compared with embodiment 1, the transit time of the reading TFT and the amplifying TFT is reduced, so that the total transit time (equal to the sum of the transit time of the amplifying field effect tube in the peripheral circuit and the transit time of the reading field effect tube in the peripheral circuit) is reduced, and the requirement of the CT machine on the mobility of the flat-panel detector thin film transistor is reduced (by about 60% compared with embodiment 1); the remaining effects related to the ray pulse control are the same as those of embodiment 1 and are not repeated.
The invention in this embodiment is as follows: the reading signal is designed to be outside the array element; a field effect tube for amplification is arranged in front of the rear operational amplifier; the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; a ray pulse control technology.
Example 12
In this embodiment, with the CT flat panel detector in embodiment 11, a circuit diagram of each acquisition unit is shown in fig. 14, and a structure diagram of a corresponding pixel matrix circuit is shown in fig. 15. Here, the structure thereof will not be described repeatedly.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: in this embodiment, the reading time needs to be longer than the sum of the transit times of the field effect transistor for amplification and the field effect transistor for reading in the peripheral circuit, the resetting time needs to be longer than the transit time of the TFT for resetting, and the resetting time is arranged after the reading time, and the sum of the reading time and the resetting time needs to be less than or equal to 10% of the reading period. The timing control diagram is shown in fig. 21.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: taking 2311 array elements to obtain an 8K projection matrix value as an example, the required scanning frequency of the flat panel detector is about 12100Hz when the scanning is completed in 0.3 second and a half-circle, and the mobility of the thin film transistor is required to be not less than 64.5cm2V.s); the required scanning frequency of the flat panel detector is about 7260Hz when the scanning is completed in 0.5 second and the mobility of the thin film transistor is not less than 37.7cm2V.s. If the detector TFT has a mobility of 100cm2V.s, the shortest half-cycle time for scanning that can be theoretically used by a CT machine is 0.2 seconds, requiring a scanning frequency of about 18182 Hz.
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
by arranging the reading signal outside the array element and controlling the reading by using the field effect tube in the peripheral circuit, compared with embodiment 2, the transit time of the reading TFT and the amplifying TFT is reduced, so that the total transit time (equal to the sum of the transit time of the amplifying field effect tube in the peripheral circuit and the transit time of the reading field effect tube in the peripheral circuit) is reduced, and the requirement of the CT machine on the mobility of the flat-panel detector thin film transistor is reduced (by about 60% compared with embodiment 2); the effects associated with the remaining low pixel 180 degree scan and high pixel 360 degree scan are the same as in embodiment 2 and will not be repeated.
The disadvantages of this embodiment are: the newly acquired data is lost in the time of the sum of the reset time, the transit time of the field effect tube for amplification in the peripheral circuit and the transit time of the field effect tube for reading.
In addition to the above common points of invention, the present design has the following points in the present embodiment: the reading signal is designed outside the array element; a field effect tube for amplification is arranged in front of the rear operational amplifier; the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
Example 13
As shown in fig. 16 and 17, in this embodiment, the flat panel detector has an array element including only a photodiode, and no reset TFT, amplification TFT, and reading TFT, signals collected by the photodiode are directly output outside the array element, reading signals and reset signals of each collecting unit are input outside the array element, data output is controlled by using a reading field effect transistor in the peripheral circuit, and the photodiode is reset by using a reset field effect transistor in the peripheral circuit; an amplifying field effect tube (which can be before or after the reading field effect tube, and in this embodiment before the reading field effect tube) is arranged in front of the later stage operational amplifier, and the later stage operational amplifier adopts an inverting amplifier or a homonymous amplifier.
The radiation emitter of the CT machine of this embodiment adopts the radiation pulse control method of embodiment 1, and the operation principle will not be described repeatedly.
The timing control of the embodiment: the reading time needs to be longer than that of the otherThe sum of the transit time of the field effect tube for amplification and the transit time of the field effect tube for reading in the peripheral circuit, the reset time needs to be longer than that of the field effect tube for reset in the peripheral circuit, because the mobility of the field effect tube in the peripheral circuit is very high (usually 1000 cm)2V.s) or more, the transit time is very small (if at 1000 cm)2V.s) of about 0.5us, the reset time of the present embodiment may be sufficiently small (about 0.5us) that the reset time is scheduled within the reading time (at the end of the reading time). But since the reset time is rather short and arranged after the reading time has little effect, in this embodiment the reset time is arranged within or after the reading time), the reading time is equal to the sampling time. The timing control diagram is shown in fig. 18.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: because the array element is not provided with a reset TFT, an amplifying TFT and a reading TFT, the limitation of the mobility of a thin film transistor of the flat panel detector on a CT machine is completely eliminated. For example, when 2311 array elements obtain an 8K projection matrix value, the required scanning frequency of the flat panel detector is 12100Hz when the half-turn scanning is completed in 0.3 second; the required flat panel detector scan frequency is approximately 7260Hz at 0.5 seconds to complete a half-turn scan.
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
reading signals are arranged outside the array elements, the field effect transistors in the peripheral circuit are used for controlling the reading, the reset TFT, the amplifying TFT and the reading TFT are not arranged in the array elements, the limitation of the mobility of the thin film transistor of the flat panel detector on the CT machine is completely eliminated, the flat panel detector is not limited by the material of the TFT, the flat panel detector enters a high-speed reading era, and the CT machine becomes a 'eye' and can see through a measured object by aiming at one eye; the remaining effects related to the ray pulse control are the same as those of embodiment 1 and are not repeated.
In this embodiment, since the acquired signals are directly output without being amplified in the array element, the problem of low signal-to-noise ratio may exist for the conventional detector that transmits data to the post-processor through a cable. In the design, due to the application of the double-sided technology of the detector substrate, the loss and possible interference of the transmission distance to the signals are overcome, and in addition, the acquired signals are stored on the junction capacitor of the photodiode and are output when being read, so that the influence on the signal-to-noise ratio is small, and the problem is well solved.
In addition to the above common points of invention, the present design has the following points in the present embodiment: only a photodiode is arranged in the array element; the reading signal and the reset signal are both designed outside the array element; resetting the photodiode by using a reset field effect tube in a peripheral circuit; a field effect tube for amplification is arranged in front of the rear operational amplifier; the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; a ray pulse control technology.
Example 14
As shown in fig. 16 and 17, in this embodiment, the flat panel detector has an array element including only a photodiode, and no reset TFT, amplification TFT, and reading TFT, signals collected by the photodiode are directly output outside the array element, reading signals and reset signals of each collecting unit are input outside the array element, data output is controlled by using a reading field effect transistor in the peripheral circuit, and the photodiode is reset by using a reset field effect transistor in the peripheral circuit; an amplifying field effect tube (which can be before or after the reading field effect tube, and in this embodiment before the reading field effect tube) is arranged in front of the later stage operational amplifier, and the later stage operational amplifier adopts an inverting amplifier or a homonymous amplifier.
The application conditions of the CT flat panel detector in the embodiment are that the CT machine adopting the working mode of the existing ray emitter: when the CT flat panel detector collects and reads, the ray emitter continuously emits rays.
The timing control of the embodiment: the reading time needs to be longer than the sum of the transit time of the field effect tube for amplification in the peripheral circuit and the transit time of the field effect tube for reading, and the resetting time needs to be longer than the transit time of the field effect tube for resetting in the peripheral circuit, because the mobility of the field effect tube in the peripheral circuit is very high (usually 1000 cm)2/(V.s) Above), their transit times are very small (say at 1000 cm)2V.s) of about 0.5us, the reading time (about 1us) and the reset time of this embodiment can be sufficiently small (about 0.5us), the reset time being arranged within the reading time (at the end of the reading time). But since the reset time is rather short and arranged after the reading time has little effect, in this embodiment the reset time is arranged within or after the reading time), the reading time requirement is less than or equal to 10% of the reading period. The timing control diagram is shown in fig. 19.
In this embodiment, the requirements for the mobility of the flat panel detector are as follows: because the array element is not provided with a reset TFT, an amplifying TFT and a reading TFT, the limitation of the mobility of a thin film transistor of the flat panel detector on a CT machine is completely eliminated. For example, when 2311 array elements obtain an 8K projection matrix value, the required scanning frequency of the flat panel detector is 12100Hz when the half-turn scanning is completed in 0.3 second; the required flat panel detector scan frequency is approximately 7260Hz at 0.5 seconds to complete a half-turn scan.
The flat panel CT machine using the flat panel detector in this embodiment has the following technical effects besides the technical effect of the common property of the CT flat panel detector:
reading signals are arranged outside the array elements, the field effect transistors in the peripheral circuit are used for controlling the reading, the reset TFT, the amplifying TFT and the reading TFT are not arranged in the array elements, the limitation of the mobility of the thin film transistor of the flat panel detector on the CT machine is completely eliminated, the flat panel detector is not limited by the material of the TFT, the flat panel detector enters a high-speed reading era, and the CT machine becomes a 'eye' and can see through a measured object by aiming at one eye; the reading time and the resetting time are both very small, so that the loss of data is greatly reduced; the effects associated with the remaining low pixel 180 degree scan and high pixel 360 degree scan are the same as in embodiment 2 and will not be repeated.
The disadvantage of this embodiment is that the newly acquired data in the transit time of the field effect tube for amplification and the transit time of the field effect tube for reading are lost, but the loss is very small because the time is very short. Therefore, the CT machine composed of the flat panel detector of this embodiment does not need to adopt the radiation pulse control method, because the very small loss is somewhat irrevocable compared with the huge cost of the radiation pulse control. In the embodiment, the acquired signals are directly output without being amplified in the array elements, and the problem of low signal-to-noise ratio exists in the traditional detector for transmitting data to a post processor through a cable.
In addition to the above common points of invention, the present design has the following points in the present embodiment: only a photodiode is arranged in the array element; the reading signal and the reset signal are both designed outside the array element; resetting the photodiode by using a reset field effect tube in a peripheral circuit; a field effect tube for amplification is arranged in front of the rear operational amplifier; the later-stage operational amplifier adopts an inverting amplifier or a homodromous amplifier; the front 180 degrees and the back 180 degrees adopt rays with two different energies for scanning, and a plurality of new functions of the CT machine can be developed.
By combining the effects and the disadvantages of the above embodiments, the CT machine adopting the ray pulse control mode is obviously superior to the CT machine adopting the existing ray working mode no matter what kind of CT flat panel detector: the requirement of the flat panel detector on the mobility of the thin film transistor is greatly reduced (except for example 13, the limitation of the flat panel detector on the CT machine due to the mobility of the thin film transistor is completely eliminated by the detector structure); so that the metal oxide thin film transistor can be applied to a CT flat panel detector; data loss in the transit time is avoided, and image quality is improved. Of course, if the practical application of example 14 proves its feasibility, it is not necessary to use the radiation pulse control technique of example 13 in terms of economic efficiency.
It should be noted that, the design is originally designed for a hospital CT machine, but due to the technical universality, the design can also be applied to the field of medical instruments such as PET-CT, and the technology can also be applied to other industries, such as CT machines in industry, animal inspection, customs and other industries, and the technology is protected.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims (15)

1. A CT flat panel detector is characterized by comprising an X-ray imaging sensor and a peripheral circuit, wherein the X-ray imaging sensor consists of a pixel matrix with a plurality of rows and columns, each unit in the pixel matrix is called an array element, all the array elements are integrated on a substrate, and the peripheral circuit comprises a rear-stage operational amplifier, an analog-to-digital converter and a buffer;
the upper surface of the pixel matrix is also provided with a scintillator layer so as to convert X rays into visible light and transmit the visible light to the photodiode for photoelectric conversion;
each array element in the pixel matrix comprises a photodiode, and the photodiode is used for converting an acquired optical signal into an electric signal;
each array element in the pixel matrix is provided with a data output port, data of each array element is independently output to a rear-stage operational amplifier and an analog-to-digital converter which are independent respectively through the data output port, and a data acquisition and processing unit composed of the single array element and the rear-stage operational amplifier and the analog-to-digital converter in a peripheral circuit of the single array element is called as an acquisition unit;
the control signal of each acquisition unit comprises a reading signal with a switching function and used for controlling data reading and a reset signal with a resetting function, the reading signals of all the acquisition units on the CT flat panel detector are mutually connected, so that all the acquisition units on the CT flat panel detector are controlled by the same reading signal to simultaneously read data, and the reset signals of all the acquisition units on the CT flat panel detector are mutually connected, so that all the acquisition units on the CT flat panel detector are controlled by the same reset signal to simultaneously reset;
the CT flat panel detector scans in each row unit, wherein each array element needs to acquire data at the same time to obtain a group of projection matrixes, each row scans at least one circle or at least half circle to obtain a projection matrix of a section, an image of the section is reconstructed by software calculation, the array elements in different rows need to scan at the same time to obtain projection matrixes of different sections, and the CT flat panel detector scans at least one circle or at least half circle to obtain images of each section corresponding to each row.
2. The CT flat panel detector as claimed in claim 1, wherein the reading signal and the reset signal of each acquisition unit are directly inputted into the array element, each array element in the pixel matrix further comprises a reset TFT, a reading TFT and at least one amplifying TFT, the reset TFT is used for resetting the electric signal of the photodiode, the reading TFT is controlled by the reading signal to control the output of data, the amplifying TFT is used for amplifying the electric signal of the photodiode, and the reading TFT is arranged behind the amplifying TFT;
the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
3. The CT flat panel detector as claimed in claim 1, wherein the reading signal and the reset signal of each acquisition unit are directly inputted into the array element, each array element in the pixel matrix further comprises a reset TFT and at least one amplifying TFT, the reset TFT is used for resetting the electrical signal of the photodiode, and the amplifying TFT is used for amplifying the electrical signal of the photodiode;
the TFT for amplification in each array element is controlled by a reading signal, and controls the output of data while amplifying the electric signal generated by the photodiode;
the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
4. The CT flat panel detector as claimed in claim 1, wherein the reading signal and the reset signal of each acquisition unit are directly inputted into the array element, each array element in the pixel matrix further comprises a reset TFT, a reading TFT and at least one amplifying TFT, the reset TFT is used for resetting the electric signal of the photodiode, the reading TFT is controlled by the reading signal to control the output of data, the amplifying TFT is used for amplifying the electric signal of the photodiode, and the reading TFT is arranged before the amplifying TFT;
the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
5. The CT flat panel detector as claimed in claim 1, wherein the reading signal of each acquisition unit is inputted to the outside of the array element, the reading in the peripheral circuit is used to control the output of data by using a field effect transistor, each array element in the pixel matrix further comprises a reset TFT and at least one amplifying TFT, the reset TFT is used to reset the electrical signal of the photodiode, and the amplifying TFT is used to amplify the electrical signal of the photodiode;
the CT flat panel detector utilizes the junction capacitance of the photodiode to store collected data.
6. The CT flat-panel detector as claimed in claim 1, wherein the reading signal of each acquisition unit is directly inputted into the array element, each array element in the pixel matrix further comprises a reset TFT and a reading TFT, the reset TFT is used for resetting the electric signal of the photodiode, and the reading TFT is controlled by the reading signal to control the output of data.
7. The CT flat panel detector of claim 1, wherein the reading signal of each acquisition unit is inputted to the outside of the array element, the output of the data is controlled by a field effect transistor using the reading in the peripheral circuit, and each array element in the pixel matrix further comprises a reset TFT for resetting the electric signal of the photodiode.
8. The CT flat panel detector of claim 1, wherein the reading signal and the reset signal of each acquisition unit are input outside the array element, the reading field effect tube in the peripheral circuit is used for controlling the output of data, and the reset field effect tube in the peripheral circuit is used for resetting the photodiode in the array element.
9. The CT flat-panel detector of any one of claims 1-8, characterized in that the operational amplifier of the back stage can be an inverting amplifier or a homonymous amplifier.
10. The CT flat-panel detector as claimed in any one of claims 1-8, wherein the substrate of the CT flat-panel detector adopts a double-sided technology, one side is used for loading the pixel matrix, the other side is used for loading the post-stage operational amplifier, analog-to-digital converter and the like in the peripheral circuit, and the substrate is embedded with a conductive pin at the corresponding position of each array element so as to transmit the data of each array element to the respective peripheral circuit such as the post-stage operational amplifier for processing.
11. CT flat-panel detector according to any of claims 1-8, characterized in that at low pixel requirements,
when the CT machine adopts a 2K projection matrix value, the number of each row of array elements in the CT flat panel detector is 1097 and 1213;
when the CT machine adopts a 4K projection matrix value, the number of each row of array elements in the CT flat panel detector is 1552 and 1716;
when the CT machine adopts an 8K projection matrix value, the number of each row of array elements in the CT flat panel detector is 2195-2427;
when the CT machine adopts a 16K projection matrix value, the number of each row of array elements in the CT flat panel detector is 3105 and 3432.
12. A CT machine comprising the CT flat panel detector according to any one of claims 1 to 8, wherein the radiation emitter of the CT machine adopts a radiation pulse control mode, the radiation emission of the radiation emitter is controlled by a radiation pulse signal, the frequency of the radiation pulse signal is the same as the scanning frequency of the CT flat panel detector, the radiation emitter emits radiation when the radiation pulse signal is at an active potential, the radiation emitter does not emit radiation when the radiation pulse signal is at an inactive potential, and the time of emitting radiation is equal to the time of not emitting radiation;
the data acquisition of the CT flat panel detector is synchronous with the ray emission of the ray emitter of the CT machine, the time for acquiring the data is called sampling time, the sampling time is equal to the time for ray emission, the CT flat panel detector adopts interval scanning, data is acquired once every other width, data is not acquired in the next rotating time with the same width, and the reading and data resetting are carried out by utilizing the time for not acquiring the data;
the CT machine adopts a 360-degree scanning mode;
when the pixel is low, the CT machine scans a circle to obtain each section image, the ray pulse signal for controlling the ray emitter to emit the ray, the reading signal and the reset signal of the CT flat panel detector need to adopt an inverse technology, and the signals need to be subjected to 180-degree phase shift in phase after the ray emitter and the CT flat panel detector rotate and scan for half time;
when the pixel is high, the CT machine scans two circles to obtain each section image in advance when the scanning bed does not move, the ray pulse signal for controlling the ray emitter to emit the ray, the reading signal of the CT flat panel detector and the reset signal all need to adopt an inversion technology, and besides the inversion technology under the repeated low pixel mode, the inversion technology can also adopt the phase shift of 180 degrees on the phase of the signal when the first circle is scanned and the phase of the signal when the second circle is scanned.
13. The CT machine according to claim 12, wherein when the detector of claim 2 or 5 is used as the CT flat panel detector, the reset time of each array element of the CT flat panel detector is arranged within the reading time, and the reset time is arranged at the end of the reading time.
14. A CT machine comprising the CT flat panel detector according to claims 1-8, wherein the CT machine is further capable of operating with the radiation emitter of the existing CT machine, that is, the radiation emitter continuously emits radiation when the CT flat panel detector reads, and the photodiode of the CT flat panel detector continuously performs photoelectric conversion;
when the pixel is low, the CT machine can adopt a 180-degree scanning mode;
when the pixel is high, the CT machine adopts a 360-degree scanning mode;
when the pixel is low, the CT machine adopts 360-degree scanning, and the CT machine can be designed to scan the first half and the second half of the rotary scanning by adopting rays with two different energies so as to obtain two images with the same section under two different energies.
15. The CT machine according to claim 14, wherein when the detector of claim 2 or 5 is used as the CT flat panel detector, the reset time of each array element of the CT flat panel detector is arranged within the reading time, and the reset time is arranged at the end of the reading time.
CN202011040640.7A 2020-02-18 2020-09-28 CT flat panel detector and CT machine Pending CN113437098A (en)

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CN202010098603 2020-02-18
CN2020102370719 2020-03-30
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CN2020102587398 2020-04-03

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114305481A (en) * 2022-03-08 2022-04-12 北京信远志成科技发展有限公司 Oral cavity X-ray imaging device and system for spaceflight

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114305481A (en) * 2022-03-08 2022-04-12 北京信远志成科技发展有限公司 Oral cavity X-ray imaging device and system for spaceflight
CN114305481B (en) * 2022-03-08 2022-06-14 中国人民解放军总医院第七医学中心 Oral cavity X-ray imaging device and system for spaceflight

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