JP2000262501A - Radiation solid state detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable immediate re-shooting in case of poor imaging by quickly judging the propriety of the imaging after shooting in a device equipped with a radiation solid state detector. SOLUTION: This radiation solid state detector used for taking radiation images is especially a cassette type radiation solid state detector equipped with a radiation solid state detector 12 which detects radiation carrying image information to output a picture signal carrying the image information. The propriety of imaging is judged based on the picture signal outputted from the radiation solid state detector 12. In case of poor imaging, the condition is reported to a photographer by a reporting means 15 while a picture signal of the poor imaging read out of the radiation solid state detector 12 and stored in an image memory 13 is eliminated by an image elimination means 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state radiation detector for use in radiographic imaging, comprising a radiation solid-state detector for detecting radiation carrying image information and outputting an image signal carrying the image information. Related to the device.

[0002]

2. Description of the Related Art Conventionally, radiation solids mainly composed of semiconductors, which detect radiation carrying image information and output an electric image signal (image signal which is an electric signal) carrying the image information. Various detectors have been proposed (JP-A-59-211263, JP-A-2-164067, JP-A-1-21667)
No. 290).

The solid-state radiation detector is used mainly for radiographic imaging for medical diagnosis and the like. For example, when radiation is transmitted through a subject to the solid-state radiation detector and imaging is performed, the solid-state radiation detector is used. Electric charges corresponding to the dose of the incident radiation are accumulated, and by reading out the electric charges by an appropriate method, an electric image signal of the subject can be output.

[0004] In the case of radiographic imaging using a stimulable phosphor sheet currently used in many hospitals, in order to obtain an image signal, for example, the stimulable phosphor sheet is scanned with excitation light to scan from the sheet. The emitted photostimulated light must be photoelectrically converted by a photomultiplier tube, and it takes a long time to read and obtain an image signal after photographing. An advantage is that an image signal can be output immediately and real-time reading is possible.

[0005] Further, with respect to the radiation solid state detector,
In order to enhance its convenience, a solid-state radiation detection cassette in which a solid-state radiation detector and an image memory for storing an image signal output from the solid-state radiation detector are housed in a flat case has also been proposed. (US Pat. No. 5,661,309)
No. 5773839, JP-A-6-342099, etc.). If the solid-state radiation detector is configured as such a cassette, it is easy to carry and handle the solid-state radiation detector, and the image signal is read out immediately after imaging and stored in the image memory.
By repeating the above, it is possible to enjoy an advantage that a plurality of continuous shootings can be performed.

[0006]

In radiographic imaging, imaging failures may occur due to various causes. For example, due to a trouble on the radiation source side, a subject may be irradiated with radiation of a dose smaller or larger than an appropriate dose at the time of imaging, and in such a case, a high quality image with high diagnostic ability is obtained. Since it is not possible to do so, it is necessary to take another shot with an appropriate dose.

Conventionally, such a photographing defect includes displaying a visible image on a display means such as a CRT based on an image signal read after the photographing, including a case of photographing using a stimulable phosphor sheet, It is common to find out only by observing this visible image.

[0008] However, the quality of the photographing is determined by observing the visible image on the display means such as a CRT based on the image signal read after the photographing. However, there has been a problem in that re-imaging is difficult because a patient who is the subject is not in the imaging room because a considerable time has already passed since the imaging.

[0009] In particular, in the case of imaging using the radiation solid-state detection cassette as described above, it is expected that imaging is often performed without an image display device nearby. In such a case, There is a problem that it is difficult to make the determination itself in the quality determination based on the visible image observation.

In view of the above circumstances, an object of the present invention is to provide a device equipped with a solid-state radiation detector, which determines the quality of radiography immediately after radiographing, and immediately enables re-imaging in the case of radiographing failure. A detection device is provided.

[0011]

In order to achieve the above object, a solid-state radiation detecting apparatus according to the present invention detects a radiation carrying image information and outputs an image signal carrying the image information. A radiation solid-state detection device used for radiographic imaging, comprising: a radiographic quality determination unit that determines radiographic quality based on an image signal output from the radiation solid-state detector. I do.

[0012] The imaging quality determination means may be configured to determine imaging quality based on a histogram of an image signal output from the solid-state radiation detector.

The photographing quality determination means determines a desired image signal portion of the image signal based on the histogram, and determines whether a representative value of the desired image signal portion is within a predetermined appropriate range. It can be configured to determine the quality of photographing.

[0014] The representative value of the desired image signal portion may be a central image signal value of the desired image signal portion and / or a signal range of the desired image signal portion.

An image memory for storing an image signal output from the solid-state radiation detector, wherein when the result of the pass / fail judgment is a photographing failure, the image signal of the photographing failure is read from the image memory. Image erasing means for erasing can be provided.

If the result of the photographing quality judgment is a photographing failure, it is possible to provide a notifying means for reporting that the photographing is defective.

A specific example of the radiation solid state detection device is a radiation solid state detection cassette in which the radiation solid state detector is housed in a case. In this case, the notification means is integrated with the case. Can be provided.

The solid-state radiation detector is a detector that detects radiation carrying image information and outputs an image signal carrying the image information. After converting to
This means that an electric image signal representing the image information can be obtained by temporarily storing the electric charge in the power storage unit and then outputting the electric charge to the outside.

There are various types of solid-state radiation detectors. For example, from the viewpoint of a charge generation process for converting radiation into electric charges, fluorescence emitted from a phosphor by irradiation with radiation is photoelectrically converted. A signal charge detected and detected by the conversion element is temporarily stored in a power storage unit of the photoelectric conversion element, and the stored charge is converted into an electric signal (image signal) and output. No. 59-211263, JP-A-2-64067, PCT International Publication No.WO92 / 06501, SP
IE Vol.1443 Medical Imaging V; Image Physics (1991)
, P.108-119, etc.) Alternatively, the signal charges generated in the radiation conductor by the irradiation of radiation are collected by the charge collection electrode, temporarily stored in the power storage unit, and the stored charges are converted into electric signals and output. MATERIAL PARAMETERS IN THICK HYDROGENATED AMORPH
OUS SILICON RADIATION DETECTORS, Lawrence Berkeley
Laboratory.University of California, Berkeley.CA 94
720 Xerox Parc.Palo Alto.CA 94304, Metal / Amorphous
Silicon Multilayer Radiation Detectors, IEE TRANSA
CTIONS ON NUCLEAR SCIENCE.VOL.36.NO.2.APRIL 1989,
From the viewpoint of the charge readout process of reading out the stored charge to the outside, a TFT readout method of scanning and reading out a TFT (thin film transistor) connected to the power storage unit is used. A reading method (an electromagnetic wave for reading) by irradiating a detector with an optical reading method, and the like. Further, Japanese Patent Application No. 10-232824 by the present applicant combining the direct conversion method and the optical reading method, Id 10-27
There is an improved direct conversion method proposed in No. 1374. The radiation solid state detector according to the present invention may use any type of detector regardless of the type of detector.

[0020]

According to the present invention, the quality of radiography is determined based on the image signal itself output from the solid-state radiation detector, that is, by processing the image signal. The quality of the imaging can be determined, and as a result, for example, re-imaging can be performed while the patient who is the subject is still in the imaging room, and re-imaging can be facilitated.

The solid-state radiation detector can be read out immediately after imaging to obtain an image signal. The present invention has been made by paying particular attention to the characteristic that an image signal of the solid-state radiation detector can be obtained immediately after this imaging. That is,
For example, in the case of photographing using a stimulable phosphor sheet, the image signal is read by scanning the stimulable phosphor sheet with excitation light after photographing. Although a pass / fail judgment based on the image cannot be made immediately after the imaging, in the case of the solid-state radiation detector, the image signal can be read out immediately after the imaging, so that if the pass / fail judgment is made based on the image signal, the imaging can be performed. The determination can be performed immediately afterward, and the advantage unique to the solid-state radiation detector that re-imaging is facilitated is obtained.

The quality judgment based on the image signal is
If you make it based on the histogram of the image signal,
Since the photographing state is faithfully reflected in the histogram, more accurate determination can be made.

Further, in the apparatus provided with an image memory for storing the image signal output from the solid-state radiation detector, if the result of the pass / fail determination is a photographing failure, the image signal of the photographing failure is erased from the image memory. By doing so, it is possible to avoid wasting the memory and also avoid various troubles caused by the remaining image signals of poor photographing.

If it is determined that photographing is defective, means for notifying the photographer or the like, for example, a means for issuing an alarm by light or voice, can be easily and overlooked. The user can be notified without fail, and the convenience of re-imaging can be improved.

When the solid-state radiation detecting device is a solid-state radiation detecting cassette, as described above, photographing is performed without an image display device nearby, and it is possible to determine the quality of photographing by observing a visible image. Although it may be difficult, it is very convenient to determine based on the image signal even if there is no nearby image display device.

[0026]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a front view of a solid-state radiation detecting cassette according to an embodiment of the present invention, as viewed from its detection surface side.

The illustrated solid-state radiation detecting cassette 10 includes a flat case 11 formed in a substantially rectangular parallelepiped shape as a whole,
Radiation solid state detector 12 housed inside the case 11
Is read (output) from the detector 12 for each photographing.
An image memory 13 having a storage capacity for a plurality of images for storing an electric image signal D1 digitized by an A / D converter (not shown), and an image signal D1 read from the image memory 13 or an image from the detector 12. A photographing quality judgment means 14 for judging the quality of photographing based on the image signal D1 inputted without passing through the memory 13; , An image erasing means 16 for erasing the image signal D1 of the photographing failure from the image memory 13 when the result of the quality determination is a photographing failure, and an image signal D1 read from the image memory 13. An image processing means 17 for performing predetermined image processing and an image signal D1 before image processing or an image signal D2 after image processing stored in the image memory 13 are used. Output component of the display device or the like, or via a network or the like formed by a transfer means 18 for transferring to the outside of the clinical room or the like. Although not shown, a power supply such as a battery for driving the detector 12 and the like is provided in the case 1.
1.

The case 11 includes a box-shaped housing portion 11a having an open top surface and an openable / closable lid portion 1 for covering the upper surface of the housing portion 11a.
1b. As shown in FIG. 2, a radiation absorbing member 19 made of lead or the like that absorbs radiation transmitted through the detector 12 is provided on the bottom surface of the housing 11a.

The image processing means 17 reads out the image signal D1 from the image memory 13 and performs a predetermined image processing on the image signal D1. As specific examples of the image processing, for example, a pixel density conversion processing, a predetermined normalization processing (E
DR processing), enlargement / reduction processing, dynamic range compression processing, data compression processing, gradation processing, frequency conversion processing, image feed processing for image confirmation, and the like.

The transfer means 18 adopts a wireless system, and includes a transmission processing circuit 18a for converting various data into wireless data and an antenna 18b. Wired transfer means other than the wireless transfer method may be employed. The transfer means 18 outputs the image signal D1 before image processing or the image signal D2 after image processing recorded in the image memory 13.
Is transferred to a predetermined transfer destination set in advance.

With respect to the radiographic image capturing using the cassette 10, the basic flow excluding the parts relating to the pass / fail determination means 14, the notifying means 15 and the image erasing means 16 will be described by taking chest radiography as an example. FIG. 2 shows the cassette 1
FIG. 1 is a schematic diagram showing an entire configuration of a radiation image recording apparatus using a subject 0 together with a subject.

The radiation image recording apparatus 50 includes a cassette 1
0, a radiation source 51, and a display device 52 for controlling imaging (all of them are installed in an imaging room). The display device 52 is connected to a clinical room (not shown) via a network. The cassette 10 is arranged such that, with respect to the radiation source 51, the radiation R emitted from the radiation source 51 and transmitted through the subject 53 is detected by the detection surface 12a of the detector 12.
It is arranged so that it may be incident. The cassette 10 is wirelessly connected to the display device 52, and various control signals are transmitted from the display device 52 to the cassette 10 at the time of photographing. For example, a signal indicating an image processing method for specifying image processing to be performed on the post-imaging image signal D1, a signal indicating a processing parameter, and a signal indicating a transfer destination of the image signals D1 and D2 are transmitted. On the cassette 10 side, the image processing method and the processing parameters are set, and the transfer destination is set based on the information.

After setting the image processing method and the like, the radiation source 51
The image signal D1 obtained by this imaging is stored in the image memory 13, and the image signal D1 is read out from the memory 13 to obtain the image processing means 17.
Then, image processing is performed based on the image processing method and processing parameters set in advance as described above.

The image signal D2 after the image processing is once stored in the image memory 13 and then read out from the image memory 13 and transmitted by the transfer means 18 to the transfer destination set in advance as described above. Is done. The image signal D1 before the image processing stored in the image memory 13 can also be transmitted by the transfer means 18.

In the above embodiment, the image processing is performed on the image signal D1 read from the image memory 13, but the image signal D1 output from the detector 12 is directly input to the image processing means 17. Alternatively, the image signal D2 after the image processing may be directly output to and transferred to the transfer unit 18 without passing through the image memory 13.

Next, a description will be given of the above-described photographing quality judgment means 14, notifying means 15, and image erasing means 16. The pass / fail determination unit 14 and the notification unit 15 determine whether or not the imaging has been performed properly, that is, whether or not the captured image is appropriate (in the case of a medical diagnostic image, an image having information necessary for diagnosis). If it is determined that the photographing is defective, the notifying means notifies the photographer that the photographing can be performed immediately so that re-photographing can be performed immediately. Is performed before doing

In this embodiment, when the photographing is completed, the image signal D1 output from the detector 12 is read out after being stored in the image memory 13 or is judged as pass / fail without passing through the image memory 13. The quality is input to the means 14, and the pass / fail determination means 14 creates a histogram of the input image signal D1, and makes a determination based on the histogram.

An example of a specific determination method will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of the created histogram. As shown in the figure, the histogram of the image signal obtained by the radiography has a subject transmission portion that is an image signal portion that has transmitted a normal subject, and a plain portion that is an image signal portion that has not transmitted a subject. The transparent portion is located away from the transmitting portion of the subject and forms an independent mountain on the side where the image signal level is higher than that of the transmitting portion.

The transparent portion is due to the radiation that has not passed through the subject, and since the image information of the subject exists only in the subject transmitting portion, it is determined whether or not shooting is appropriate if the subject transmitting portion is appropriate. Whether or not there is, that is, a desired image signal portion of the image signal output from the detector 12 (an image signal portion necessary for imaging purposes, for example, an image signal portion necessary for diagnosis in the case of imaging for diagnostic purposes) Therefore, it is preferable to make a determination based on whether or not the subject transmitting portion other than the plain portion as in the present example) is appropriate.

Therefore, first, a blank portion and a subject transmitting portion are distinguished based on the shape of the histogram, and the signal range A of the subject transmitting portion, that is, the minimum signal value Smin of the subject transmitting portion is determined.
A to the maximum signal value Smax and the signal range A
Of the central image signal Sc (Sc-Smin
= Smax-Sc). For example, the histogram is scanned from the high image signal level side. The signal range A can be determined by setting the boundary where the frequency first exceeds a predetermined threshold value by scanning the histogram from the low image signal level side, as Smin, The boundary value obtained as described above is Smax
It can be calculated by:

The extent to which the above A and Sc when properly photographed are within a certain range is determined in accordance with the photographing conditions such as the photographing site and the photographing method, and this is known in advance by experimental experience. be able to. Therefore, the appropriate ranges of A and Sc are determined in advance in correspondence with the imaging region and / or the imaging method, and the appropriate ranges are compared with the A and Sc actually obtained from the histogram, and both are determined as appropriate. If it is within the range, appropriate photographing is performed, and if at least one of them is not within the appropriate range, photographing failure is determined.

When the quality of the photographing is determined as described above, the quality determining unit 14 outputs a photographing failure signal to the notifying unit 15 when the photographing is determined to be defective.
Notifies the photographer or the like of a photographing failure based on the photographing failure signal. This notification may be any notification as long as it can notify the photographer or the like of some kind of notification and recognize that the photographing is defective, and typically means for emitting sound or emitting light or Means for blinking light or the like can be used.

Further, the pass / fail judgment means 14 outputs a photographing failure signal to the notifying means 15 and also to the image erasing means 16, and the image erasing means 16 is stored in the image memory 13 based on the photographing failure signal. That is, the image signal D1 of the photographing failure is erased. Note that the image processing and the signal transfer are performed only on the image signal determined to be good in the good or bad shooting.

Although the preferred embodiment of the radiation solid-state detection device according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and various changes can be made without changing the gist of the invention. It is possible.

For example, in the above-described embodiment, the radiation solid-state detection cassette has been described as an example. However, the radiation solid-state detection device does not necessarily need to be of the cassette type. The solid-state detector may be incorporated in the imaging device together with any of the image memory, the image processing means, the display means, and the like. Also, even in the case of cassette type,
The above-mentioned cassette is one example, and the present invention is not limited thereto.

The determination of good or bad of photographing may be made based on any image signal, and the determination based on the histogram is not limited to the above method. Also, the representative value of the histogram is not limited to the central image signal value Sc and the signal range A of the desired image signal portion, and only one of the central image signal value Sc and the signal range A is used as the representative value. It can also be used to judge whether or not it is within an appropriate range.

Further, the desired image signal portion is not limited to the one described in the above embodiment. In short, any signal portion may be used as long as the image signal portion carries the desired image portion. The signal part may be a part of the transmission part, or may be the whole read image signal.

[Brief description of the drawings]

FIG. 1 is a front view of a solid-state radiation detecting cassette according to an embodiment of the present invention as viewed from a detection surface side.

FIG. 2 is a schematic diagram showing an overall configuration of a radiation image recording apparatus using the cassette shown in FIG.

FIG. 3 is a diagram for explaining a method of determining whether or not a photograph is good;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Radiation solid-state detection apparatus 11 Case 12 Radiation solid-state detector 13 Image memory 14 Imaging quality judgment means 15 Notification means 16 Image erasure means 17 Image processing means 18 Transfer means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G21K 4/00 G06F 15/62 390A F-term (Reference) 2G083 AA04 BB05 CC09 CC10 DD11 DD12 DD16 EE10 2H013 AC01 AC06 4C093 AA01 CA15 CA29 CA39 EB05 EB13 EB17 FB12 FD03 FF21 FH02 5B057 BA12 CH11 DA03 DA15 DC23 DC36

Claims (8)

[Claims] 1. A radiation solid state detection device used for radiographic imaging, comprising: a radiation solid state detector for detecting radiation carrying image information and outputting an image signal carrying the image information. A solid-state radiation detecting apparatus, comprising: an imaging quality determination unit configured to determine imaging quality based on an image signal output from a detector. 2. The solid-state radiation detecting apparatus according to claim 1, wherein the imaging quality determining unit determines the quality of the imaging based on a histogram of an image signal output from the solid-state radiation detector. apparatus. 3. The photographing quality determination unit determines a desired image signal portion of the image signal based on the histogram, and determines whether a representative value of the desired image signal portion is within a predetermined appropriate range. 3. The solid-state radiation detecting apparatus according to claim 2, wherein the quality of the radiography is determined according to the condition. 4. The radiation solid according to claim 3, wherein the representative value of the desired image signal portion is a central image signal value of the desired image signal portion and / or a signal range of the desired image signal portion. Detection device. 5. An image memory for storing an image signal output from the solid-state radiation detector, wherein when the result of the pass / fail judgment is a photographing failure, the image of the photographing failure is read from the image memory. An image erasing means for erasing a signal is provided.
Item 3. The solid-state radiation detecting device according to Item 1. 6. The radiation solid according to claim 1, further comprising a notifying unit for notifying that the imaging is defective when the result of the imaging quality determination is an imaging defect. Detection device. 7. The radiation solid according to claim 1, wherein the radiation solid detection device is a radiation solid detection cassette in which the radiation solid detector is housed in a case. Detection device. 8. The radiation solid state detection device according to claim 7, wherein the notification means is provided integrally with the case.