JP2000037373A - Device for detecting irradiation field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recognize an irradiation field at high speed, which is required for executing a proper image processing. SOLUTION: An electric signal corresponding to an irradiated radiation dose is generated by an imaging panel 11. The area of the image pickup panel 11 is divided into plural blocks and image data is generated from the electric signal by an image data generating part 16 which is arranged in accordance with each block. One or plural contour candidate points considered to be on an irradiation field contour are detected based on image data at every block. A graphic obtained by connecting the contour candidate points is made to be the irradiation field contour and the region enclosed by the irradiation field contour is made to be the irradiation field region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an irradiation field of a radiation image. Specifically, the radiation image is divided into a plurality of blocks, contour candidate points are detected in each block,
A figure formed by connecting the detected contour candidate points is defined as an irradiation field contour, and an area surrounded by the irradiation field contour is defined as an irradiation field.

[0002]

2. Description of the Related Art Conventionally, there has been known a radiation image reading apparatus capable of obtaining a radiation image for diagnosing a disease or the like. In this radiation image reading device, for example, a part of radiation energy is stored, and then a stimulable phosphor that emits stimulable light in accordance with the stored energy when irradiated with excitation light such as visible light is formed into a sheet. A stimulable phosphor sheet is used. In an apparatus using the stimulable phosphor sheet, radiation image information of the subject is recorded by irradiating radiation transmitted through the subject to the stimulable phosphor sheet, and the stimulable phosphor sheet on which this information is recorded. By stimulating stimulated emission obtained by irradiating a laser beam or the like with the laser beam and converting it into an electric signal by a photoelectric element, image data of a radiation image is generated based on the electric signal. In addition, Flat Panel
An apparatus called an Detector (FPD) that generates an electric signal corresponding to the dose of radiation irradiated by a plurality of two-dimensionally arranged detection elements and generates image data based on the electric signal is also used. You.

Here, when obtaining a radiation image, a portion to be irradiated with radiation is made small to prevent radiation from being irradiated to a portion not related to diagnosis or the like, or scattered from a portion not related to diagnosis or the like. In order to prevent the resolution from deteriorating due to the rays being incident on the part required for diagnosis, a lead plate may be placed on a part of the subject, or the radiation generator may have a radiation source such as a lead plate called an irradiation field stop. Install the permeable material,
Imaging is generally performed to limit the irradiation field of the radiation to the subject.

Further, in order to obtain a radiation image suitable for diagnosis or the like, image processing of the radiation image is performed. In this image processing, processing conditions are determined from the statistical properties of the image data (for example, the maximum value, minimum value, average value, histogram, etc. of the image data). Here, as described above, when imaging is performed with the radiation irradiation area limited using the irradiation field aperture, the image data of the irradiation field inside the irradiation field and the irradiation field outside the irradiation field that is not irradiated with the radiation are used. If the processing conditions are determined, the entire radiation image will be deviated in the direction of lower radiation dose by the image data of the irradiation field outside area, and it will be appropriate for the image of the irradiation field inside area required for diagnosis etc. Image processing is not performed. For this reason, the irradiation field recognition is performed to determine the irradiation field inside the irradiation field, the processing conditions are determined based on the image data of the subject image in the irradiation field area, and the image processing is performed.

In this irradiation field recognition, the shape of the irradiation field stop is often a polygon, particularly a rectangle. For this reason, for example, as disclosed in JP-A-63-259538,
Contour candidate points are determined on a scanning line radially drawn from a predetermined point in the irradiation field, and a figure formed by connecting the obtained contour candidate lines is defined as the irradiation field.

[0006]

In recent years, devices capable of obtaining radiation images as moving images have been studied. In such an apparatus, it is required that the degree of diffusion of a contrast agent injected into a blood vessel, a digestive organ, or the like for diagnosis be displayed in real time. In addition, in order to obtain a radiation image as a moving image and to display a moving image suitable for diagnosis or the like, image data of the entire radiation image must be acquired at high speed, and the above-described image processing is executed at high speed. There is a need to.

Here, in the case of using a stimulable phosphor,
Since the radiation image information is recorded on the stimulable phosphor sheet and then image data is obtained by sequential scanning with laser light or the like, image data of the entire radiation image cannot be acquired at high speed.

Further, as disclosed in Japanese Patent Application Laid-Open No. 7-72562, a radiographic image is divided into a plurality of sections, a specific pixel signal value in each section is read out, and the signal value is used. It has also been proposed to read and process image data for a section in which a pixel having a signal value equal to or greater than a predetermined threshold value exists. However, in such a method, a section including both the image data outside the irradiation field and the image data inside the irradiation field may be read out. In order to perform appropriate image processing, the irradiation field recognition processing is performed to execute the image data outside the irradiation field. It is necessary to obtain the processing conditions except for the above.

Further, in the method disclosed in Japanese Patent Application Laid-Open No. 63-259538, since image data of the entire radiation image is required to obtain a contour candidate point, processing is performed until an image is completely obtained. Since it cannot be performed, it takes time to recognize the irradiation field, and image processing cannot be performed at high speed.

Therefore, the present invention provides an irradiation field recognition apparatus capable of performing irradiation field recognition at high speed.

[0011]

According to the present invention, there is provided an irradiation field recognizing apparatus which detects a radiation dose applied to a subject by using an irradiation field stop by a plurality of two-dimensionally arranged detection elements.
Radiation image detecting means for generating image data of a radiation image, image data acquiring means for dividing the radiation image into a plurality of blocks, and reading out image data of each block from the radiation image detecting means in parallel, and each block Based on the block position storage means for storing the position on the image and the image data of each block read from the radiation image detecting means by the image data obtaining means, it is considered that each block is on the irradiation field contour. Translocation candidate point detecting means for detecting one or a plurality of contour candidate points to be detected, irradiation field contour forming means for forming a figure formed by connecting the contour candidate points detected by the contour candidate point detecting means as an irradiation field contour. And detects an area surrounded by the irradiation field contour formed by the irradiation field contour forming means as the irradiation field area.

[0012]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. Radiation output from the radiation generator to obtain a radiation image of the subject passes through the subject to the Flat Panel De of the image processing apparatus.
irrespective to the TEC (FPD). The area A of the FPD (hereinafter, referred to as “imaging panel”) 11 is divided into a plurality of blocks AR- (0,0) to AR- (m, n) as shown in FIG. In one block, for example, block AR- (0,0), as shown in FIG. 2, detection elements DT (0,0) to DT (j, k) which output electric signals in accordance with the dose of irradiated radiation. ) Are two-dimensionally arranged and scanning lines 114-0 to 114
-k and the signal lines 116-0 to 116-j are arranged to be orthogonal, for example.

The scanning lines 114-0 to 114-k correspond to the scanning drive unit 1.
4, the scanning drive unit 14 generates a readout signal RS based on a control signal CTA supplied from a control unit 40 described later, and outputs one of the scanning lines 114-0 to 114-k.
Is output to one scanning line 114-p (p is any value from 0 to k). In response to the read signal RS, the electric signals SV-0 to SV-j corresponding to the dose of the irradiated radiation are output from the detection elements DT (0, p) to DT (j, p) connected to the scanning line 114-p. Is output and supplied to the image data generator 16- (0,0) via the signal lines 116-0 to 116-j.

The other blocks AR- (0,1) to AR- (0, n), A
R- (1,0) to AR- (1, n),..., AR- (m, n) similarly to the block AR- (0,0) by the read signal RS from the scan driving circuit 14. From (j × k) detection elements in each block, an electric signal SV corresponding to the irradiated radiation dose is output, and the image data generation unit 16 corresponding to each block is output.
-(0,1) to 16- (0, n), 16- (1,0) to 16- (1, n), ...
, 16- (m, n).

The scanning lines 114-0 to 114-k used in the block AR- (0,0) are also used in the other blocks as the block AR- (0,0).
If used in the same way as-(0,0), the electric signal SV can be easily output at the same timing from, for example, the detection elements of the same column number in each block.

Here, the detecting element DT may be any element that outputs an electric signal corresponding to the dose of the irradiated radiation. For example, when a detection element is formed using a photoconductive layer in which an electron-hole pair is generated when radiation is irradiated and the resistance value changes, the amount of radiation generated in the photoconductive layer depends on the amount of radiation generated in the photoconductive layer. An amount of charge is stored in the charge storage capacitor, and the charge stored in the charge storage capacitor is supplied to the image data generator 16 as an electric signal. It is preferable that the photoconductive layer has a high dark resistance value, such as amorphous selenium, lead oxide, cadmium sulfide, mercuric iodide, or a photoconductive organic material (a photoconductive layer to which an X-ray absorbing compound is added). And the like, and amorphous selenium is particularly desirable.

When the detecting element DT is formed using, for example, a scintillator or the like that generates fluorescence when irradiated with radiation, a photodiode generates an electric signal based on the intensity of the fluorescent light generated by the scintillator. The information may be supplied to the image data generator 16. An imaging panel 11 using such a configuration is disclosed in
As disclosed in JP-90048, X-rays are absorbed by a phosphor layer such as an intensifying screen to generate fluorescence, and the intensity of the fluorescence is detected by a photodetector such as a photodiode provided for each pixel. There is something. As other means for detecting fluorescence, CC
There is also a method using a D or C-MOS sensor. In particular, an imaging panel (FP) of the type disclosed in JP-A-6-342098
In D), since the X-ray dose is directly converted into the electric charge amount for each pixel, the sharpness in the FPD is hardly deteriorated and an image with excellent sharpness can be obtained. The effect of the image recording method is great and suitable.

The image data generator 16- (0,0) converts the supplied electric signals SV-0 to SV-j into digital pixel data based on the control signal CTB supplied from the controller 40. Are stored as image data SD- (0,0) in a memory (not shown) of the image data generation unit 16- (0,0). Also, the image data generation units 16- (0,1) to 16- (0, n), 16- (1,
0) to 16- (1, n),..., 16- (m, n)
The image data SD- (0,
1) to SD- (0, n), SD- (1,0) to SD- (1, n), ..., S
D- (m, n) is held. Further, the image data generation unit 16
Is read out based on the control signal CTB and supplied to the irradiation field output unit 25 and the image output unit 35 shown in FIG.

FIG. 3 shows the configuration of the irradiation field output unit 25. The image data SD- (0,0) supplied from the image data generator 16- (0,0) is supplied to the contour candidate point detection circuit 251- (0,0). Similarly, image data SD- (0,1),.
D- (m, n) is a contour candidate point detection circuit 251- (0,1),.
, 251- (m, n).

The contour candidate point detecting circuit 251- (0,0) detects a contour candidate point using the image data SD- (0,0). For example, a difference value between neighboring pixels is calculated, and a position where the absolute value of the difference value is larger than a predetermined threshold value is set as a contour candidate point. Further, the detection of the contour candidate points is not limited to the case where the difference value is used. For example, each block is further divided into several small areas, and the variance value in each divided basin is calculated, and the variance value is calculated. May be used as a contour candidate point.

Here, the contour candidate point detecting circuit 251- (0,0)
When the contour candidate point is detected in step (1), position information indicating the position of the contour candidate point is supplied to the irradiation field contour candidate forming circuit 253. Further, block information indicating in which block the contour candidate point is detected is also supplied to the irradiation field contour forming circuit 253. Similarly, another contour candidate point detection circuit 251 detects a contour candidate point, and
When a contour candidate point is detected, position information and block information of the contour candidate point are supplied to the irradiation field contour forming circuit 253.

In the irradiation field contour forming circuit 253, the position information and the block information from the contour candidate point detecting circuit 251 at which the contour candidate points are detected are temporarily stored in the memory of the irradiation field contour forming circuit 253. The position information and the block information are held at predetermined positions in the memory based on the positions of the blocks.

Next, it is determined which block the contour candidate point is detected by using the block information, and the contour candidate points of two adjacent blocks for which the contour candidate point is determined to be detected are represented by a straight line. Are tied together. When two contour candidate points are connected by a straight line, a block of one contour candidate point connected by a straight line and a contour candidate point of a new block in which a contour candidate point close to this block is detected are connected by a straight line. It is. Similarly, contour candidate points of adjacent blocks are sequentially connected by a straight line.

In this way, the contour candidate points are sequentially connected by a straight line, and the area surrounded by this straight line is recognized as an irradiation field. The irradiation field information indicating the area of the irradiation field is supplied to the condition setting unit 30 shown in FIG. The operation of the irradiation field output unit 25 is controlled based on a control signal CTC from the control unit 40.

In the condition setting section 30, based on the control signal CTD from the control section 40, the irradiation field contour candidate forming circuit 253
Using image data in the irradiation field area indicated based on the irradiation field information from the user, image processing conditions for a radiation image for obtaining a radiation image suitable for diagnosis or the like are set, and conditions indicating the image processing conditions are set. The setting signal JC is supplied to the image output unit 35.

In the image output unit 35, image processing of a radiation image based on the image data supplied from the image data generation unit 16, for example, radiation of a density and contrast suitable for diagnosis or the like, under image processing conditions based on the condition setting signal JC. Gradation processing to obtain an image, frequency emphasis processing to control sharpness, and radiographic image with a wide dynamic range to keep the whole of the radiographic image within the easy-to-view density range without reducing the contrast of the fine structure of the subject A dynamic range compression process or the like is performed.

The operations of the condition setting unit 30 and the image output unit 35 are controlled based on control signals CTD and CTE from the control unit 40.

The control unit 40 controls the control signals CTA to CTA so that a good radiation image suitable for diagnosis or the like can be obtained.
A CTE is generated and supplied to each unit as described above.

Next, the operation will be described. Imaging panel 1
4A, for example, as shown in FIG. 4A.
It is divided into 25 regions from (0,0) to AR- (5,5). Here, when the irradiation of the radiation ends, the readout control signal RC from the control unit 40 outputs an electric signal from the detection element of each block, and the image data generation unit 1
The memory 6 stores the image data of each block. For example, the image data of the area AR- (0,0) is held in the memory of the image data generation unit 16- (0,0),
The image data of-(0,1) is held in the memory of the image data generation unit 16- (0,1).

Next, the image data held in each image data generating section 16 is read out based on a control signal CTB from the control section 40, and the contour candidate point detecting circuit 251 of the irradiation field output section 25 and the image output section 35.

As shown in FIG. 4B, the contour candidate point detection circuit 251 scans one block in the horizontal direction at, for example, an intermediate point of the vertical width, and outputs image data between pixels adjacent to each other on a scanning line. A difference value is calculated. Here, the absolute value of the difference value is calculated, and when a point where the maximum of the obtained absolute value is larger than the threshold value Thd is detected,
This point is set as a contour candidate point. It should be noted that the number of scanning lines is not limited to one in one block as shown in FIG. 4B, and a plurality of scanning can be performed to obtain a plurality of contour candidate points in one block.

Here, the upper left position in each block is defined as a pixel position (QH, QV), and the number of pixels in one block is represented by "Q
When “BH” × “QBV”, the pixel positions (PH, PV) of the detected contour candidate points P1 to P8 are in the area AR- (0,0).
If the upper left position of is used as a reference for the pixel position, it can be obtained by Expression (1). In equation (1), “BH” and “BV” are block positions based on the block AR- (0,0). (PH, PV) = (QH + QBH × BH, QV + QBV × BV) (1) Therefore, for example, when the pixel position in the block is (QH1, QV1), BH = BV = 0, PH = QH1 and PV = QV1. In addition, the contour candidate point P5 sets the pixel position in the block to (Q
H5, QV5), BH = 3, BV = 4, so PH = QH5 + 3 × QBH, PV = QV5 + 4 × QB
V. When a contour candidate point is detected, block information is supplied to an irradiation field contour candidate line forming circuit.

The method of indicating the position of a block is not limited to the method of using the upper left position as described above, but may be, for example, using the center of the image as a reference. Further, not only rectangular coordinates but also polar coordinates may be displayed. In this case, by deforming Expression (1) according to the polar coordinate display, the relative positional relationship between the contour candidate points can be correctly represented.

When the position of the contour candidate point is obtained in this manner, this position information is stored together with the block information at a predetermined position in the memory of the irradiation field contour forming circuit 252.
Here, using the block information held in the memory,
For example, a block in which a contour candidate point closest to the upper left end is detected is determined. With the determined block as a start block, the contour candidate points of this block are shown in FIG.
As shown in FIG. Next, the contour candidate point of the block closest to the block of the contour candidate point P1 is set as P2, and the straight line connecting the contour candidate point P1 and the contour candidate point P2 is stored as a contour candidate line in the memory. In addition, by holding the slope and intercept of the straight line in the memory, the straight line can be held in the memory with a small capacity.

Next, the contour candidate point of the block closest to the block of the contour candidate point P2 is set to P3, and the straight line connecting the contour candidate point P2 and the contour candidate point P3 is set to the contour candidate line and stored in the memory. Is done. Similarly, the last contour candidate point P8 is connected to the contour candidate point P1 of the start block.

When two contour candidate points are connected by a straight line, the present invention is not limited to the case where the nearest block is detected and the contour candidate points of the detected block are connected by a straight line. For example, since the irradiation field stop is often rectangular, as shown in FIG.
The contour candidate point Q is set in the direction of the straight line L1 connecting
It is assumed that the closest contour candidate point which is within the predetermined range W from 2 is detected, and the detected contour candidate point Q3 is connected by a straight line. Next, the contour candidate points may be detected in the same manner from the contour candidate point Q3 and connected by a straight line, and the contour candidate points may be sequentially connected by a straight line in the same manner. Alternatively, the contour candidate points may be selected based on the change amount of the coordinates of the contour candidate points and connected in order by a straight line.

The straight line connecting the contour candidate points, that is, the area surrounded by the contour candidate line is set as the irradiation field, and irradiation field information indicating the area of the irradiation field is supplied to the condition setting unit 30.

As described above, since the image data is generated in parallel from each block and the contour candidate points are detected, the irradiation field can be recognized at high speed by connecting the contour candidate points with a straight line. Since the irradiation field can be recognized at high speed, the condition setting unit 30 sets image processing conditions using image data in the irradiation field, and the image output unit 35 sets the radiation image based on the set image processing conditions. By performing image processing on, a radiation image suitable for diagnosis or the like can be obtained at high speed.

In the above-described embodiment, the irradiation field information is supplied to the condition setting section 30 to set the image processing conditions. However, a correct / incorrect judgment section is provided to determine whether the irradiation field information is correct. It is also possible to set image processing conditions based on irradiation field information determined to be correct. Here, the correct / incorrect judgment unit obtains a representative value of the obtained irradiation field, for example, an average value or a median value of image data included in the irradiation field or a signal of a predetermined ratio of an accumulated histogram, an area, and the like. Is determined based on whether or not satisfies a predetermined condition.

The blocks AR- (0,0), AR- (0,1)-
If the readout signal RS is sequentially output to any one of the scanning lines connected to AR- (0, n), the blocks AR- (0,0), AR- (0,1) One image data generation unit may be provided for ~ AR- (0, n). For this reason, if the other blocks have the same configuration, the image data for one screen can be generated by the m image data generation units, and the configuration can be simplified.

[0041]

According to the present invention, the irradiation field recognition required for performing appropriate image processing can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an irradiation field recognition device.

FIG. 2 is a diagram showing a block AR- (0,0).

FIG. 3 is a diagram showing a configuration of an irradiation field output unit.

FIG. 4 is a diagram for explaining the operation of the irradiation field recognition device.

FIG. 5 is a diagram for explaining another method of connecting contour candidate points.

[Description of Signs] 11 Imaging panel 14 Scan driver 16 Image data generator 25 Irradiation field output unit 30 Condition setting unit 35 Image output unit 40 Control unit

Claims (1)

[Claims] 1. A radiation image detecting means for detecting radiation dose applied to a subject using a field stop by a plurality of two-dimensionally arranged detection elements and generating radiation image data, Image data obtaining means for dividing the image data of each block into a plurality of blocks and reading out the image data of each block in parallel from the radiation image detecting means; block position storing means for storing the position of each block on the image; A translocation for detecting one or more contour candidate points considered to be on the irradiation field contour for each block based on the image data of each block read from the radiation image detecting means by the data acquiring means. Candidate point detecting means, and irradiation field contour forming means for forming a figure formed by connecting the contour candidate points detected by the contour candidate point detecting means as an irradiation field contour. And, irradiation field detection device and detects the region surrounded by the irradiation field contour formed by the irradiation field profiling means as a radiation area.