JP2010240257A - X-ray computer tomography device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-Ray computer tomography device in which the movement of organs and the flow of an imaging agent by breathing are observed relating to a body axial direction during continuous scan or intermittent scan. <P>SOLUTION: The X-Ray computer tomography device includes: an X-Ray tube 101; a multiarray type X-Ray detector 103; a supporting mechanism 102 rotatably supporting the X-Ray type and the multiarray type X-Ray detector; a recording section 112 recording a plurality of projecting data detected by the multiarray X-Ray detector; a perspective image forming section 121 selectively reading the projecting data set collected when the X-Ray tube is located in a specific angle from the recording section parallel with the continuous rotation of the X-Ray tube and the multiarray type X-Ray detector and instantly forming the perspective image data; a display section 116 instantly displaying the formed perspective image data sets parallel with the continuous rotation of the X-Ray tube and the multiarray type X-Ray detector; and a reconstituting section 114 reconstituting 3D image data based on plurality of projecting data sets. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an X-ray computed tomography apparatus equipped with a multi-row type surface detector (also referred to as an area detector) capable of imaging a wide range at a time.

  In recent years, an X-ray computed tomography apparatus equipped with an area detector of 320 columns or the like has appeared, and a wide area can be imaged at one time by one rotation. In addition, there is a function of displaying an image of a certain cross section in real time in a continuous scan for photographing many rotations continuously and observing the passage of time.

  In addition, there is a function called Real Prep (Patent Document 1), which creates a cross-sectional image continuously in real time during continuous rotation scanning, and measures the change in CT value of the contrast agent in the specified region of interest. Then, the degree of staining of the contrast medium is observed.

  Further, the invention of Patent Document 2 is to create a fluoroscopic image with an X-ray computed tomography apparatus of a surface detector, and the detector of the X-ray computed tomography apparatus is arranged in an arc shape. A method of correcting and generating the generated distortion for the projection data is shown. This is used by switching between the CT imaging mode and the fluoroscopic imaging mode.

  An X-ray computed tomography device with an area detector such as 320 rows has appeared, and it has become possible to image a wide area at once with one rotation, but it is possible to observe in real time with respect to the body axis direction during continuous scanning imaging I can't.

JP-A-10-127621 JP 2005-103088 A

  An object of the present invention is to realize, in an X-ray computed tomography apparatus, observing the movement of an organ due to respiration, the flow of a contrast agent, and the like in the body axis direction during continuous scanning or intermittent scanning.

  An aspect of the present invention includes an X-ray tube that generates X-rays, a multi-row X-ray detector that detects X-rays transmitted through a subject, the X-ray tube and the multi-row X-ray detector, A support mechanism that rotatably supports a storage unit, a storage unit that stores a plurality of projection data sets detected by the multi-row X-ray detector, and a continuation of the X-ray tube and the multi-row X-ray detector. In parallel with the target rotation, a perspective image creation unit that selectively reads out a projection data set collected when the X-ray tube is positioned at a specific angle from the storage unit and instantly creates perspective image data; In parallel with the continuous rotation of the X-ray tube and the multi-row X-ray detector, a display unit that instantly displays the created fluoroscopic image data, and 3 based on the plurality of projection data sets. An X-ray computer comprising a reconstruction unit for reconstructing dimensional image data To provide a tomography apparatus.

  According to the present invention, in an X-ray computed tomography apparatus, it is possible to observe the movement of an organ due to respiration, the flow of a contrast agent, and the like in the body axis direction during continuous scan imaging.

It is a figure which shows the structure of the X-ray computed tomography apparatus which concerns on embodiment of this invention. It is a perspective view of the area detector of FIG. It is a flowchart which shows the scanning operation | movement procedure in the continuous exposure mode by this embodiment. It is a figure which shows the continuous rotation of FIG. It is a figure which shows the fluoroscopic image preparation display operation performed in parallel with the collection of the projection data by the continuous exposure mode of this embodiment. It is a figure which compares the fluoroscopic image imaging | photography with the area detector of this embodiment compared with the scanogram imaging | photography with the conventional single detector. It is a figure which shows the data collection by the area detector of this embodiment. It is a figure which shows the process which produces a fluoroscopic image using all the channels of the area detector of this embodiment. It is a flowchart which shows the scanning operation | movement procedure of the intermittent irradiation mode by this embodiment. It is a figure which shows the perspective image preparation display operation performed in parallel with intermittent collection of the projection data by the intermittent exposure mode of this embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The outline of the present embodiment is as follows.
(1) During continuous scanning imaging, a fluoroscopic image is created using projection data at an arbitrary angle (for example, zero degree (top position) or the like). In this case, scanning is a single piece of image data, here a set of projection data (one unit) necessary to reconstruct three-dimensional image data (volume data) (one unit of projection data is projected). Collecting projection data while the X-ray tube rotates around the subject through a range of 360 ° or 180 ° + fan angle is defined as a unit operation. Continuous scanning refers to an operation that continuously repeats scanning with continuous rotation of the X-ray tube.

  The fluoroscopic image is created in the same way as the scanogram creation. This is due to the influence of the X-ray detectors arranged in an arc shape, and there is distortion, but the image is approximate to the planar image (perspective image) by the X-ray diagnostic apparatus. Become. However, the image is sufficient for observation in the direction of the body axis, particularly for observation of organ movement due to respiration and the like, and the flow of contrast medium. These fluoroscopic images are immediately created and displayed one after another at a specific angle for each rotation in parallel with the continuous rotation. Of course, the distortion correction processing or the like may be performed by converting the projection data from the arrangement on the arc to the arrangement on the plane.

(2) Further, by creating a difference image using the fluoroscopic images of each rotation, an image of only (or close to) the contrast agent can be created, and an image in which the flow of the contrast agent can be easily observed can be obtained. Regarding the difference, a method of taking the difference between the first image and the current image, a method of accumulating the difference from the immediately preceding image, and the like can be considered.

(3) Means for taking an image in the intermittent mode, in which the irradiation is performed only at an arbitrary angle while rotating, and the continuous imaging is performed while looking at the contrast timing while observing the image created from the projection data. Prepare.

  By providing such a feature, it becomes possible to observe the movement in the body axis direction, particularly the movement of the organ due to respiration, the flow of the contrast agent, and the like at intervals of rotation during continuous scan imaging. In the intermittent mode, exposure can be reduced.

  The X-ray computed tomography apparatus according to the present invention will be described below in detail with reference to the drawings. In the X-ray computed tomography system, ROTATE / ROTATE-TYPE, in which an X-ray tube and an X-ray detector are combined as one body, rotates around the subject, and a large number of detection elements arrayed in a ring shape are fixed. There are various types such as STATIONARY / ROTATE-TYPE in which only the X-ray tube rotates around the subject, and the present invention can be applied to any type. Here, it is described as ROTATE / ROTATE-TYPE. Further, in order to reconstruct image data, projection data for one rotation around the subject and 360 ° is required, and projection data for 180 ° + fan angle is also required in the half scan method. The present invention can be applied to any reconstruction method. Here, the 360 ° method will be described as an example. In addition, the mechanism for converting incident X-rays into electric charges is based on an indirect conversion type in which X-rays are converted into light by a phosphor such as a scintillator and the light is further converted into electric charges by a photoelectric conversion element such as a photodiode. The generation of electron-hole pairs in a semiconductor such as selenium and the transfer to the electrodes, that is, the direct conversion type utilizing a photoconductive phenomenon, are the mainstream. Any of these methods may be adopted as the detection element. Further, in recent years, so-called multi-tube type X-ray CT apparatuses in which a plurality of pairs of X-ray tubes and X-ray detectors are mounted on a rotating ring have been commercialized, and peripheral technologies have been developed. The present invention can be applied to both a conventional single-tube X-ray CT apparatus and a multi-tube X-ray CT apparatus. Here, a single tube type will be described.

  FIG. 1 is a diagram showing a configuration of an X-ray computed tomography apparatus according to the present embodiment. The gantry 100 accommodates a rotation support mechanism 102. The rotation support mechanism 102 includes a rotation ring and a ring support mechanism that rotatably supports the rotation ring about the rotation axis Z. An X-ray tube 101 is mounted on the rotating ring. The X-ray tube 101 radiates X-rays from the focal point upon receiving application of tube voltage and supply of tube current from the high voltage generator 109 via the slip ring 108. A collimator unit 111 is attached to the X-ray emission window of the X-ray tube 101. The collimator unit 111 limits the X-rays from the X-ray tube 101 to a quadrangle. The X-ray bundle is formed into a pyramid shape by the collimator unit 111.

  An X-ray tube 101 and an X-ray detector (referred to as an area detector) 103 called a two-dimensional array type or a multi-row type are mounted on the rotating ring. The area detector 103 is attached at a position and an angle facing the X-ray tube 101 across the rotation axis Z. As shown in FIG. 2, the area detector 103 has a plurality of X-ray detection elements. In the following description, it is assumed that a single X-ray detection element constitutes a single channel. The plurality of channels are two-dimensional in two directions: a direction parallel to the rotation axis Z (slice direction) and an arc direction (channel direction) that is orthogonal to the rotation axis Z and gently curves around the X-ray focal point. Arranged. The area detector 103 having such a two-dimensional detection element arrangement may be configured by arranging a plurality of detection elements arranged in a line in the channel direction in the slice direction. It may be configured by arranging a plurality of modules arranged in a × N matrix. In imaging or scanning, a subject is inserted into a cylindrical imaging area between the X-ray tube 101 and the area detector 103.

  A data acquisition circuit 104 generally called DAS (Data Acquisition System) is connected to the output of the area detector 103. The data acquisition circuit 104 includes an IV converter that converts a current signal of each channel of the area detector 103 into a voltage, and an integrator that periodically integrates the voltage signal in synchronization with an X-ray irradiation cycle. An amplifier that amplifies the output signal of the integrator and an analog / digital converter that converts the output signal of the preamplifier into a digital signal are provided for each channel.

  Data (pure raw data) output from the data collection circuit 104 is transmitted to the preprocessing device 106 via the non-contact data transmission device 105 using magnetic transmission / reception or optical transmission / reception. The preprocessing device 106 performs preprocessing on the pure raw data. Preprocessing includes, for example, sensitivity non-uniformity correction processing between channels, X-ray strong absorber, processing for correcting an extremely low signal strength drop or signal drop mainly due to a metal part, and the like. The data immediately before reconstruction processing output from the pre-processing device 106 (referred to as raw data or projection data, here referred to as projection data) is associated with data representing a view angle when data is collected. And stored in a projection data storage unit 112 having a magnetic disk, a magneto-optical disk, or a semiconductor memory.

  The projection data is a set of data values according to the intensity of the X-rays transmitted through the subject. Here, for convenience of explanation, all the viewing angles collected at the same time in one shot for each viewpoint are the same. A set of projection data across channels is called a projection data set. Further, the view angle represents each position on the circular orbit around which the X-ray tube 101 circulates around the rotation center axis Z as an angle in a range of 360 ° with the top position of the rotation orbit being zero °. is there.

  The reconstruction processing unit 114 is based on projection data within a range of 360 ° or 180 ° + fan angle of view angle, for example, an image of a substantially cylindrical reconstruction range set in advance according to the extended Feldkamp reconstruction method, for example. Reconstruct data (volume data). The display device 116 creates and displays an arbitrary cross section and a three-dimensional rendering image based on the image data.

  The perspective image creation unit 121 creates perspective image data by selectively reading out the projection data set collected when the X-ray tube 101 is positioned at a specific angle from the projection data set stored in the projection data storage unit 112. To do. The perspective image creation unit 121 may create data of a single perspective image from a single projection data set related to a specific angle, or a minute angle range centered on the specific angle, for example, a 3 ° range. Data of a single perspective image may be created by simple addition or weighted addition of a plurality of projection data sets including, for example, 3 to 5 projection data sets. In the weighted addition process, it is preferable to give a maximum weight to the projection data set corresponding to a specific angle, and to reduce the weight as the distance (angle difference) from the specific angle increases.

  In the continuous exposure mode of the present embodiment, the fluoroscopic image data creating process by the fluoroscopic image creating unit 121 is a scan for acquiring a projection data set with continuous rotation of the X-ray tube 101 and the area detector 103. Are repeated immediately during a continuous scanning operation. The specific angle is designated by the operator via the operation unit 115.

  The fluoroscopic image correcting unit 122 corrects the fluoroscopic image created by the fluoroscopic image creating unit 121 to an image approximate to a fluoroscopic image taken by parallel X-rays. The difference processing unit 123 generates a difference image by subtracting two perspective images having different collection times. Typically, the difference image is generated by subtracting the fluoroscopic image collected before injection of the contrast medium or before flowing into the imaging region and the latest fluoroscopic image. In addition, a difference image is generated by subtracting the latest fluoroscopic image and the fluoroscopic image collected immediately before the difference and accumulating the difference values after the injection of the contrast agent.

  The comparison unit 124 compares the pixel value at the specific position or the average pixel value of the specific region of the created fluoroscopic image data or difference image data with a predetermined threshold value. This specific position or specific area is designated by the operator via the operation unit 115. The message generator 125 stores message data in advance. The message data is, for example, voice or image data related to a message that “the contrast medium has flowed into the region of interest”. The message generator 125 sends message data to the display device 116 or a speaker (not shown) when the pixel value of the specific position or the average pixel value of the specific region of the fluoroscopic image data or the difference image data reaches a predetermined threshold value in the comparison unit 124. In addition to outputting, a predetermined control signal is output. When this control signal is output, when the intermittent exposure mode is selected under the control of the host controller 110, the X-rays are switched from intermittent exposure to continuous exposure.

  The intermittent exposure mode and the continuous exposure mode are selected and designated in advance by the operator via the operation unit 115.

  FIG. 3 shows an operation procedure in the continuous irradiation mode. First, an arbitrary angle (specific angle α °) for creating a projection image is designated in advance by the operator via the operation unit 115 before starting rotation (S11). The specific angle α ° is typically designated as zero °, which is the uppermost position of the rotation trajectory of the X-ray tube 101. At the same time, the continuous exposure mode is selected by the operator via the operation unit 115. Thereafter, when the operator presses the continuous scan trigger button via the operation unit 115, the driving of the rotation support mechanism 102 by the gantry driving unit 107 is started under the control of the host controller 110. Thereby, as shown in FIG. 4, the continuous rotation of the rotating ring with the X-ray tube 101 and the area detector 103 is started (S12). When the rotation speed of the rotating ring reaches a constant speed, the tube voltage is continuously applied to the X-ray tube 101 by the high voltage generator 109 and the filament current is continuously supplied under the control of the host controller 110. Is started. Thereby, continuous X-ray irradiation from the X-ray tube 101 and continuous irradiation to the subject are started (S13). At the same time, collection of projection data sets is started via the area detector 103 (S14). The collection of the projection data set is repeated at almost constant angles, and stored in the projection data storage unit 112 one after another. Each projection data set is associated with data relating to the angle (view angle) of the X-ray tube 101 at the time of acquisition.

  As shown in FIG. 5, in the perspective image creation unit 121, in parallel with the continuous scan, a specific angle (α °) is obtained from a plurality of projection data sets stored in the projection data storage unit 112 as shown in FIG. ) Is selectively read out (S15), and based on the read out projection data set, as shown in FIG. 7, through the interpolation process and the coordinate conversion process to the XY coordinate system, the perspective projection is performed. Image data is created and displayed on the display device 116 (S16). If necessary, the fluoroscopic image correction unit 122 corrects the fluoroscopic image created by the fluoroscopic image creation unit 121 to an image approximate to a fluoroscopic image taken with parallel X-rays as shown in FIG. And displayed on the display device 116. The selective reading of these projection data sets and the creation and display processing of the fluoroscopic image data are immediately performed in parallel with the continuous scanning.

  The created fluoroscopic image data is differentiated with other fluoroscopic image data having different collection times by the difference processing unit 123. Typically, the difference image is generated by subtracting the fluoroscopic image collected before injection of the contrast agent or before flowing into the imaging region and the latest fluoroscopic image. Note that a difference image may be generated by subtracting the latest fluoroscopic image and the fluoroscopic image collected immediately before the difference and accumulating the difference value after injection of the contrast medium. The difference image data is sent to the comparison unit 124, and the pixel value at the specific position of the difference image data or the average pixel value of the specific region is compared with a predetermined threshold (S17). When the pixel value at the specific position of the difference image data or the pixel value average of the specific region reaches a predetermined threshold value, the message data is output from the message generator 125 to the display device 116 or a speaker (not shown). Is displayed, and the sound is output (S18).

  The operations in steps S14 to S18 are repeated until the scheduled scan time or the scheduled rotation speed has elapsed (S19). After completion of the continuous scan for collecting projection data, a plurality of three-dimensional image data are reconstructed by the reconstruction processing unit 114 based on a plurality of projection data sets collected by the continuous scan (S20).

  FIG. 9 shows an operation procedure in the intermittent irradiation mode. FIG. 10 shows a fluoroscopic image creation / display operation performed in parallel with intermittent collection of projection data in the intermittent exposure mode.

  First, a threshold for a pixel value that shifts from an intermittent scan to a continuous scan and a target position of the continuous scan together with an arbitrary angle (specific angle α °) for creating a projection image via the operation unit 115 Is designated in advance before the start of rotation (S21). Thereafter, when the operator presses the intermittent scan trigger button via the operation unit 115, the rotation of the rotation support mechanism 102 by the gantry driving unit 107 is started under the control of the host controller 110. Thereby, the continuous rotation of the rotating ring with the X-ray tube 101 and the area detector 103 is started (S22). When the X-ray tube 101 passes a specific angle α ° within the rotation speed of the rotating ring (S23), the tube voltage to the X-ray tube 101 by the high voltage generator 109 is controlled under the control of the host controller 110. Short time application (pulse voltage application) and filament current supply (pulse current supply) for a short time (S24). As a result, short-time pulse X-ray irradiation from the X-ray tube 101 and short-time irradiation to the subject are performed (S24). A projection data set is collected via the area detector 103 in synchronization with the X-ray irradiation (S25). In the perspective image creation unit 121, in parallel with the continuous rotation, based on the projection data set of the specific angle α ° stored in the projection data storage unit 112, the perspective image is obtained by interpolation processing and coordinate conversion processing to the XY coordinate system. Data is created and displayed on the display device 116 (S26). The selective reading of these projection data sets and the creation and display processing of the fluoroscopic image data are performed immediately in parallel with the continuous rotation.

  In the intermittent exposure mode as well, as in the continuous exposure mode, the fluoroscopic image creation unit 121 outputs a pulse with a duration corresponding to the passing time in a minute angle range centered on a specific angle, for example, a 3 ° range. A single fluoroscopic image data may be created by irradiating the subject with X-rays and performing simple addition or weighted addition of a plurality of projection data sets, for example, 3 to 5 projection data sets therebetween.

  The created fluoroscopic image data is differentiated with other fluoroscopic image data having different collection times by the difference processing unit 123. Typically, the difference image is generated by subtracting the fluoroscopic image collected before injection of the contrast agent or before flowing into the imaging region and the latest fluoroscopic image. In the comparison unit 124, the pixel value at the specific position of the difference image data or the pixel value average of the specific region is calculated (S27) and compared with a predetermined threshold value (S28).

  The operations of Steps S22 to S27 are repeated until the pixel value at the specific position of the difference image data or the pixel value average of the specific region reaches a predetermined threshold (S28).

  When the pixel value at the specific position of the difference image data or the pixel value average of the specific area reaches a predetermined threshold value, the top plate on which the subject not shown is moved is moved according to the continuous scan position specified in S21, and the message Data is output from the message generator 125 to the display device 116 or a speaker (not shown), a message “Contrast medium has flowed into the region of interest” is displayed, and the sound is output. In step S29, an intermittent scan with intermittent X-ray exposure and data collection is shifted to a continuous scan with continuous X-ray exposure and data collection (S29).

  The continuous scan ends when the scheduled scan time or the scheduled number of rotations has elapsed (S30). After the scan is completed, a plurality of three-dimensional image data are reconstructed by the reconstruction processing unit 114 based on a plurality of projection data sets collected by continuous scanning.

  As described above, according to the present embodiment, it is possible to realize the movement of the organ due to respiration, the flow of the contrast agent, and the like in the body axis direction during the continuous scan or the intermittent scan.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Furthermore, the above embodiment includes various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, some constituent requirements may be deleted from all the constituent requirements shown in the embodiment.

  INDUSTRIAL APPLICABILITY The present invention can be used in a field in an X-ray computed tomography apparatus for observing organ movement due to respiration, contrast agent flow, etc. in the body axis direction during continuous scan imaging. .

  DESCRIPTION OF SYMBOLS 100 ... Gantry, 101 ... X-ray tube, 102 ... Rotation support mechanism, 103 ... Aria detector (two-dimensional array type X-ray detector), 104 ... Data acquisition circuit, 105 ... Non-contact data transmission device, 106 ... Pre-processing device , 107: gantry drive unit, 108 ... slip ring, 109 ... high voltage generator, 110 ... host controller, 111 ... collimator unit, 112 ... projection data storage unit, 114 ... reconstruction processing unit, 115 ... operation unit, 116 ... Display device 121, perspective image creation unit 122, perspective image correction unit 123, difference processing unit 124, comparison unit 125, message generation unit

Claims (7)

An X-ray tube that generates X-rays;
A multi-row X-ray detector for detecting X-rays transmitted through the subject;
A support mechanism for rotatably supporting the X-ray tube and the multi-row X-ray detector;
A storage unit for storing a plurality of projection data sets detected by the multi-row X-ray detector;
In parallel with continuous rotation of the X-ray tube and the multi-row X-ray detector, a projection data set collected when the X-ray tube is positioned at a specific angle is selectively read from the storage unit. A fluoroscopic image creation unit that instantly creates fluoroscopic image data;
In parallel with continuous rotation of the X-ray tube and the multi-row X-ray detector, a display unit that immediately displays the created fluoroscopic image data;
An X-ray computed tomography apparatus comprising: a reconstruction unit configured to reconstruct three-dimensional image data based on the plurality of projection data sets. The X-ray computed tomography apparatus according to claim 1, wherein X-rays are continuously generated from the X-ray tube. 2. The X-ray computed tomography apparatus according to claim 1, wherein X-rays are intermittently generated from the X-ray tube in synchronization with a timing at which the X-ray tube passes through the specific angle. A comparison unit that compares a pixel value of a specific position or a specific region of the created fluoroscopic image data with a predetermined threshold;
And a message generating unit that generates message data for causing the display unit to display a message indicating that the pixel value exceeds the predetermined threshold when the pixel value exceeds the predetermined threshold. The X-ray computed tomography apparatus according to claim 1. A comparison unit that compares a pixel value of a specific position or a specific region of the created fluoroscopic image data with a predetermined threshold;
4. The apparatus according to claim 3, further comprising: a control unit that shifts the X-ray intermittent generation operation to the X-ray continuous generation operation when the pixel value exceeds the predetermined threshold. The X-ray computed tomography apparatus described. The X-ray computer according to claim 3, further comprising an operation unit for an operator to input an instruction for shifting from the intermittent X-ray generation operation to the continuous X-ray generation operation. Tomography equipment. A difference processing unit that instantly creates difference image data by subtracting the created perspective image data from specific perspective image data;
2. The X-ray computed tomography apparatus according to claim 1, wherein the display unit immediately displays difference image data together with the generated fluoroscopic image data or instead of the generated fluoroscopic image data. .

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