JP2013033009A - Gamma camera system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gamma camera system capable of providing a highly accurate image in which changes in detection sensitivity and spatial resolution (partial volume effect) of a view field of the gamma camera are corrected.SOLUTION: The gamma camera system includes: a gamma camera 2; a distance measuring device 6 capable of scanning and measuring a distance to an imaging object 10; a position computing device 81 for calculating a positional relationship between the gamma camera 2 and the imaging object 10; a sensitivity correction information estimating device 82 for estimating measurement sensitivity; a resolution correction information estimating device 83 for estimating the resolution; and an image generation computing device 84 for generating a gamma-ray distribution image on the basis of the measurement sensitivity, the resolution, and gamma-ray count data.

Description

  The present invention relates to a gamma camera system that generates image information measured by a gamma camera.

A gamma camera system is known in which gamma rays emitted from an imaging target are measured by a gamma camera to generate a gamma ray image of the imaging target. Here, detection sensitivity and spatial resolution of data measured by a gamma camera using a general collimator are degraded depending on the distance between the gamma camera and the imaging target. However, it is rare that the object to be imaged is a plane with a constant distance from the gamma camera. For example, structures that are installed outdoors, in public facilities, in indoor radiation control areas, etc. should be used as the object to be imaged. In a gamma camera system with a large field of view capable of capturing a wide area at once, it is assumed that an imaging target region having a different distance from the gamma camera is included in the imaging field of view of the gamma camera.
This means that even if there is a region with the same dose and the same area, the measured gamma ray count number and the size on the detected image change depending on the positional relationship with the gamma camera. This is a factor that impairs the reliability of the detected image.

As shown in FIG. 10, the width of the gamma ray detection elements 104a, 104b... Of the gamma ray detector 103 and the aperture diameter of the collimator 105 are not infinitely small but have a finite width. For this reason, the measurement range 115a of the gamma ray detection element 104a on the imaging plane 111 has a range 116 that overlaps with the measurement range of other gamma ray detection elements (in FIG. 10, the gamma ray detection element 104b).
As shown in FIG. 11, when the range 117a for the gamma ray detection element 104a is set so as to pass through the center 105c of the collimator 105, the range 117a for the detection element 104a is set as shown in FIG. The actual measurement range 115a of the gamma ray detection element 104a is not the same.

  As described above, the detection sensitivity and the spatial resolution decrease as the distance between the gamma camera and the imaging target increases.

On the other hand, a general medical gamma camera system as described in Patent Document 1, Non-Patent Document 1, and Patent Document 2 has a system configuration on the premise of proximity imaging by manual or automatic control. Yes. For this reason, the distance between the gamma camera and the object to be imaged is close, and changes in detection sensitivity and spatial resolution in the field of view are not a major problem.
In addition, as described in Non-Patent Document 2, the Blind Deconvolution method for the purpose of sharpening an image is known, but this is also premised on that changes in detection sensitivity and spatial resolution in the field of view are not large.

  Non-Patent Document 3 and Non-Patent Document 4 describe a combination of a gamma camera and a laser scanner. However, the gamma camera itself needs to be capable of three-dimensional measurement, and is inexpensive. It is different from large-field imaging with a two-dimensional measurement type gamma camera that can be used simply, and there is no description about correction of detection sensitivity and spatial resolution change due to a change in the distance between the gamma camera and the imaging target.

Also, Patent Document 3 describes a combination of a gamma camera (radiation detector) and a laser scanner. This is because environmental radiation (background) other than the imaging target whose radiation dose is to be measured is apparent. It is an invention to correct the phenomenon that is mistakenly measured as radiation from the upper imaging target, and the measurement result of the laser scanner is used to estimate the influence of environmental radiation scattered and attenuated in the imaging target by numerical calculation It has been.
For this reason, detection sensitivity and spatial resolution are not corrected based on the distance between the gamma camera (radiation detector) and the imaging target.

  In Patent Document 4, an optical camera or shape data acquired in advance is used in place of the laser scanner, but it is intended to improve the measurement accuracy of the radiation dose of the imaging target, and the distance between the imaging target and the gamma camera is set. Although the corresponding detection sensitivity correction is performed, changes in spatial resolution are not taken into consideration, and the technique is not a technique for accurately imaging the radiation dose distribution in the imaging target.

  In the field of SPECT (Single photon emission computed tomography) equipment that obtains tomographic images by rotating a gamma camera around the subject and acquiring projection images from multiple directions, depending on the distance between the gamma camera and each pixel in the field of view. For example, Patent Literature 5 discloses a method for correcting the changing sensitivity and resolution. However, the correction in the SPECT field is performed when reconstructing a tomographic image based on a plurality of acquired projection images.

JP 2007-107932 A JP 2010-164485 A JP 2003-57349 A JP 2009-145112 A Special table 2010-523965 gazette

IEEE Transactions on Nuclear Science, Vol.57, No.3, pp.1132-1138,2010 Journal of Optical Society of America, Vol.9, No.7, pp.1052-1061, 1992 IEEE Transactions on Nuclear Science, Vol.56, No.2, pp.479-486,2009 ESRADA BULLETIN, No38, pp.17-24,2008

  In this way, with a gamma camera that performs single imaging from a single projection direction using a general collimator, detection sensitivity and spatial resolution are taken into account for the change in distance between the imaging target and the gamma camera within a single projection. There is no known technique for correcting these simultaneously.

  Accordingly, an object of the present invention is to provide a gamma camera system capable of obtaining a highly accurate image in which changes in detection sensitivity and spatial resolution (partial volume effect) in the field of view of the gamma camera are corrected.

  In order to solve such a problem, the present invention provides a gamma camera having a gamma ray detector and a collimator, a distance measuring unit capable of scanning and measuring the distance between the imaging target of the gamma camera, and the distance measuring unit. Position calculation means for calculating the positional relationship between the gamma camera obtained by scanning measurement and the imaging target of the gamma camera, and based on the positional relationship obtained from the position calculation means, the imaging target is determined by the gamma camera. Sensitivity correction information estimation means for estimating measurement sensitivity at the time of measurement, and resolution correction information estimation for estimating resolution when measuring the imaging object with the gamma camera based on the positional relationship obtained from the position calculation means And the measurement sensitivity estimated by the sensitivity correction information estimation means, the resolution estimated by the resolution correction information estimation means, and the gamma camera In on the basis of the detected gamma ray count data, a gamma camera system comprising: the image generation operation means for generating a gamma ray distribution image.

  According to the present invention, it is possible to provide a gamma camera system capable of obtaining a highly accurate image in which changes in detection sensitivity and spatial resolution (partial volume effect) in the field of view of the gamma camera are corrected.

1 is an overview diagram of a gamma camera system according to a first embodiment. 1 is a configuration diagram of a gamma camera system according to a first embodiment. It is a figure which shows the relationship between the distance from a gamma camera to an imaging plane, and the imaging range of a gamma ray detection element at the time of using a pinhole collimator. It is a figure explaining the production | generation of the gamma ray distribution image which an image generation calculating apparatus performs. It is a figure explaining the imaging target used for simulation. It is a figure which shows a simulation result. It is a general-view figure of the gamma camera system which concerns on 2nd Embodiment. It is a block diagram of the gamma camera system which concerns on 2nd Embodiment. It is a figure explaining the display range which each pixel of an output image takes charge of. It is a figure explaining the actual measurement range of a gamma ray detection element. It is a figure explaining the measurement range which a gamma ray detection element takes charge of. It is a figure explaining the shift | offset | difference of the measurement range which a gamma ray detection element takes charge, and an actual measurement range.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate. In each figure, common portions are denoted by the same reference numerals, and redundant description is omitted.

<< First Embodiment >>
FIG. 1 is an overview of the gamma camera system according to the first embodiment.
The gamma camera system 1 is a large-field gamma camera system capable of imaging a wide area at once using a pinhole collimator 5, and scans the distance between the gamma camera 2 and the imaging target 10 (see FIG. 2) of the gamma camera 2. A laser distance meter (distance measuring device) 6 capable of measurement and a computer 8 are provided, gamma rays flying from the imaging object 10 (see FIG. 2) are measured, a gamma ray distribution image is generated, and the image display device 9 is provided. It can be displayed.

The gamma camera 2 includes a gamma ray detector 3 (see FIG. 3), a pinhole collimator 5, and various electronic components (not shown).
The gamma ray detector 3 is a semiconductor detector such as cadmium telluride (CdTe) or thallium bromide (TlBr), and is composed of n × n gamma ray detection elements 4 (see FIG. 3). It is a pixel type semiconductor detector which handles the signal output from each corresponding channel. The detection signal of the gamma ray detection element 4 is input to a radiation measurement circuit (not shown). A radiation measurement circuit (not shown) can transmit a gamma ray count at each gamma ray detection element 4 to a computer 8 (an image generation arithmetic device 84 (see FIG. 2) described later).

The pinhole collimator 5 selects gamma rays emitted from the imaging target 10 (see FIG. 2) and allows only gamma rays in a predetermined direction to pass through the gamma ray detection element 4.
Although the collimator used in the gamma camera 2 according to the first embodiment is described as being the pinhole collimator 5, the collimator is not limited to this, and may be a parallel hole collimator or a fan beam collimator. There may be.

The laser rangefinder 6 can be scanned and can measure the distance between the gamma camera 2 and each area of the imaging target 10. The laser distance meter 6 can transmit the measured distance information to a computer 8 (a position calculation device 81 (see FIG. 2) described later).
Although the gamma camera system 1 according to the first embodiment is described as using the laser distance meter 6, the gamma camera system 1 is not limited to this and measures the distance between the gamma camera 2 and each area of the imaging target 10. A distance measuring device, for example, a distance measuring device using a stereo camera or a millimeter wave radar may be used.

FIG. 2 is a configuration diagram of the gamma camera system according to the first embodiment.
The computer 8 (see FIG. 1) includes a calculation device, a storage device, and the like (not shown), and functions as a position calculation device 81, a sensitivity correction information estimation device 82, a resolution correction information estimation device 83, and an image generation calculation device 84. It can be done.

The position calculation device 81 receives the distance information measured by the laser distance meter 6, converts it into distance information between the gamma camera 2 and a structure (imaging target 10) existing in all regions in the field of view, and outputs it. Be able to.
The sensitivity correction information estimation device 82 is inputted with the distance information converted by the position calculation device 81 and can output detection sensitivity as sensitivity correction information.
The resolution correction information estimation device 83 receives the distance information converted by the position calculation device 81 and can output a point spread function as resolution correction information.
The image generation calculation device 84 includes gamma ray counts (detection data) at each gamma ray detection element 4 of the gamma camera 2, detection sensitivity (sensitivity correction information) of the sensitivity correction information estimation device 82, and points of the resolution correction information estimation device 83. A spread function (resolution correction information) is input, and a gamma ray distribution image can be generated and output.

  The image display device 9 can display the gamma ray distribution image generated by the image generation calculation device 84 (computer 8). In FIG. 1, the computer 8 and the image display device 9 are illustrated as a laptop computer in which these are integrated, but the present invention is not limited to this, and the computer 8 and the image display device 9 are separated. It may be a body.

<Effect of distance between gamma camera and imaging target>
Here, the influence of the distance between the gamma camera 2 and the imaging target 10 will be described.

  The geometric detection sensitivity S of the gamma rays flying from the gamma ray source (radiation source) is inversely proportional to the square of the distance r between the gamma ray source and the gamma ray detector 3 (gamma camera 2), as shown in equation (1). To do.

FIG. 3 is a diagram showing the relationship between the distance from the gamma camera to the imaging plane and the imaging range of the gamma ray detection element when the pinhole collimator is used.
As shown in FIG. 3, the width of one gamma ray detection element 4 of the gamma ray detector 3 is d, the opening diameter of the pinhole collimator 5 is b, and the distance between the detection surface of the gamma ray detector 3 and the pinhole collimator 5 is a. In the gamma camera 2, the imaging range when imaging a gamma ray source on the imaging plane 11 that is a distance R away from the pinhole collimator 5 (gamma camera 2), that is, the spatial resolution L is expressed by the following equation (2). become.

As shown in Expression (2), the deterioration of the spatial resolution L as the distance R increases leads to the underestimation of the measured dose due to the partial volume effect in addition to affecting the resolution of the captured image. Further, as shown in Expression (1), when the distance r between the gamma ray source and the gamma ray detector 3 (gamma camera 2) is increased, the detection sensitivity S is lowered, and the gamma ray count detected by the gamma ray detecting element is also lowered.
For this reason, when there are a plurality of gamma ray sources having the same magnitude as the dose intensity in the field of view of the gamma camera 2, the farther the distance from the gamma camera 2, the smaller the dose, the lower the resolution, and the greater the statistical noise. It will be.

  As described above, from the viewpoint of detection accuracy, it is not preferable to capture images at a distance (r, R) between the gamma camera 2 and the imaging target 10. The gamma camera system is configured on the premise of proximity imaging, including the case where the type of collimator is different from that of the embodiment (see, for example, Patent Document 1, Non-Patent Document 1, and Patent Document 2).

  However, the gamma camera system according to the first embodiment assumes that a structure installed in, for example, an outdoor, public facility, indoor radiation management area, or the like is used as the imaging target 10 and covers a wide area at once. In order to realize a gamma camera system 1 with a large field of view that can be imaged, it is assumed that images are taken at a distance from the imaging object 10 using the pinhole collimator 5. Assuming that such a wide imaging object 10 is imaged at a time with a large field of view, the imaging object 10 is not only at a long distance from the gamma camera 2 but also the imaging object 10 and the gamma camera existing in the field of view of the gamma camera 2. It is rare that the distance to 2 is constant.

<Generation of gamma ray distribution image of gamma camera system>
In order to appropriately correct the detection sensitivity S and the spatial resolution L under the above imaging conditions, it is necessary to measure the distance between the structure (imaging target 10) in the field of view of the gamma camera 2 and the gamma camera 2. is there.
Therefore, in the gamma camera system 1 according to the first embodiment, as shown in FIG. 1, a scanning laser distance meter 6 is installed near the gamma camera 2, and the gamma camera 2 removes the structure (imaging target 10). The flying gamma rays are measured, and the distance to the structure (imaging target 10) in the field of view of the gamma camera 2 is measured by the laser distance meter 6.

  The distance information measured by the laser distance meter 6 is input to the position calculation device 81 and converted into distance information between the gamma camera 2 and a structure (imaging target 10) existing in all regions in the field of view. At this time, for example, it is possible to set a region of interest within the field of view of the gamma camera 2 and calculate only distance information between the structure (imaging object 10) in the region of interest and the gamma camera 2.

Next, the sensitivity correction information estimation device 82 performs analytical or ray tracing simulation or Monte Carlo simulation based on the equation (1) based on the distance information obtained by the position calculation device 81, and captures the image of the gamma camera 2. The detection sensitivity is obtained for each region of the range. At this time, the sensitivity information of each gamma ray detection element 4 obtained in advance by actual measurement is reflected in the detection sensitivity.
Also, the resolution correction information estimation device 83 performs analytical or ray tracing simulation or Monte Carlo simulation based on the formula (2) based on the distance information obtained by the position calculation device 81, and the imaging range of the gamma camera 2. A point spread function is obtained for each region.

  The image generation calculation device 84 is a detection sensitivity (sensitivity correction information) output from the sensitivity correction information estimation device 82, a point spread function (resolution correction information) output from the resolution correction information estimation device 83, and the gamma camera 2. The measured gamma ray count (detection data) at each gamma ray detection element 4 is input to generate a gamma ray distribution image.

In the first embodiment, as shown in FIG. 4, each of the imaging ranges 12 (corresponding to the pixels of the output image) divided in m to represent the imaging target 10 from the detection sensitivity and the point spread function, respectively, The detection probability detected by the n gamma ray detection elements 4 is obtained. FIG. 4 shows a case where the number of gamma ray detection elements 4 is 4 and the number of imaging ranges 12 is 6 (n = 4, m = 6).
Here, in FIG. 4 and formulas (3) to (8) described later, y _j is a gamma ray count measured by the gamma ray detection element j. λ _i is a pixel value of the pixel i, that is, a dose existing in the region i when the imaging target 10 is divided into m. C _ij is a detection probability that a gamma ray flying from the pixel i is detected by the gamma ray detection element j.
In this way, by using the detection sensitivity that is the output of the sensitivity correction information estimation device 82 and the point spread function that is the output of the resolution correction information estimation device 83, the detection probability C in which sensitivity and resolution are considered in the distance information. _ij can be obtained.

Next, the expected value of the gamma ray count y _j of the gamma ray detection element j is as shown in Expression (3).

  Further, an event in which gamma rays are emitted from the gamma ray source and detected by the gamma ray detection element j follows a Poisson distribution shown in Equation (4).

From the equations (3) and (4), when the gamma ray source is distributed with the source distribution λ (λ ₁ , λ ₂ ,..., Λ _m ), the probability that the gamma ray detection element j detects the gamma ray count y _j is It becomes like (5).

Equation (5) the total gamma ray detecting elements j (j = 1,2, ... n ) extended to, gamma ray sources radiation source distribution _{λ (λ 1, λ 2,} ..., λ m) when distributed in a gamma ray detection The probability that the detector 3 detects the detection data y (y ₁ , y ₂ ,..., Y _n ) is as shown in Equation (6).

Since the purpose is to estimate the dose distribution λ (λ ₁ , λ ₂ ,..., Λ _m ) from the detection data y (y ₁ , y ₂ ,..., Y _n ) detected by the gamma ray detector 3, Equation (7) As shown, λ that maximizes the log likelihood of the dose distribution λ in the field of view of the gamma camera 2 is obtained from the detected detection data y (maximum likelihood estimation calculation).

This is sequentially approximated, and in particular, Equation (8) is used. In the image generation arithmetic device 84 according to the first embodiment, the dose distribution λ (λ ₁ , λ ₂ ,..., Λ _m ) is estimated using the equation (8), and a gamma ray distribution image is generated.

In this way, the image generation calculation device 84 obtains the detection probability C _ij using the detection sensitivity that is the output of the sensitivity correction information estimation device 82 and the point spread function that is the output of the resolution correction information estimation device 83, and Using (8), the dose distribution λ (λ ₁ , λ ₂ ,... Of the imaging target 10 from the detection data y (y ₁ , y ₂ ,..., Y _n ) detected by the gamma ray detector 3 (gamma camera 2). , Λ _m ).
Then, the image generation calculation device 84 transmits the generated dose distribution λ of the gamma ray source to the image display device 9 (see FIG. 1) as a gamma ray distribution image.

<Effect>
Here, in order to show the effect of the present invention (this embodiment), a numerical simulation was performed by simulating the imaging target 10 as shown in FIGS. 5 (a) and 5 (b).
As shown in FIG. 5A, the imaging target 10 is composed of two different surfaces, a surface 10a whose distance from the pinhole collimator 5 is 200r and a surface 10b whose distance from the pinhole collimator 5 is 300r. Suppose that an image is taken from a position in which the stepped portion of the two surfaces is the center of the field of view of the gamma camera 2 in a direction parallel to the perpendicular of the surfaces 10a and 10b. Note that r is a unit of distance used in the simulation.
Further, as shown in FIG. 5B, it is assumed that the surface 10a has a circular Hot region 10c having a radius 5r and a circular Hot region 10d having a radius 3r, and the surface 10b has a circular Hot region having a radius 5r. It is assumed that there is a region 10e and a circular hot region 10f having a radius 3r, and the dose of the hot region (10c, 10d, 10e, 10f) is five times that of the background surface.

  For such an imaging target 10, detection data y was created by ray tracing simulation. As evaluation conditions, detection data y itself (measurement image (without correction)), detection data y subjected to sensitivity correction according to the distance to each imaging range (pixel) (with sensitivity correction), detection data y The ratio of the pixel values of two types of Hot regions between the surfaces with different distances from the pinhole collimator 5 for those with sensitivity and resolution correction (with sensitivity and resolution correction) according to the distance to the imaging range (pixel) (10e pixel value / 10c pixel value, 10f pixel value / 10d pixel value), and a ratio of pixel values of two Hot regions having different radii in each plane (10d pixel value / 10c pixel value, 10f pixel value / 10e pixel value).

The simulation results are shown in FIG. As a result, the pixel ratio between the two surfaces where the distance from the pinhole collimator 5 is different and the sensitivity is changed is improved by 39% from 0.50 to 0.70 on average, and the pixel ratio between the Hot regions having different radii is increased. Improved by 15% from 0.56 to 0.65 on average.
Further, although not shown in FIG. 6, the background ratio between the surfaces was improved from 0.46 to 0.99.

  Although these values are 1 when the detection sensitivity is uniform and there is no partial volume effect, it has been confirmed that the values that actually fall below 1 as described above can be improved by the correction method of the present invention. Note that this improvement rate depends on the imaging conditions and the calculation accuracy at the time of creating correction information. Therefore, the improvement rate is not always such a value, and it is possible to improve the improvement rate by devising the mounting method. . The above simulation results are only an example of the effect of the present invention.

  Thus, according to the gamma camera system 1 according to the first embodiment, a highly accurate gamma ray distribution image in which changes in detection sensitivity and spatial resolution (partial volume effect) in the field of view of the gamma camera 2 are corrected can be obtained. . In particular, when a wide area is imaged at once, that is, when the pinhole collimator 5 is used as a collimator, the distance from the gamma camera 2 is assumed to be different for each region of the imaging target 10, which is useful.

<< Second Embodiment >>
Next, a gamma camera system 1A according to the second embodiment will be described with reference to FIGS.
FIG. 7 is an overview of a gamma camera system according to the second embodiment. FIG. 8 is a configuration diagram of a gamma camera system according to the second embodiment.
In addition to the gamma camera system 1 (see FIGS. 1 and 2) according to the first embodiment, the gamma camera system 1A according to the second embodiment includes an optical camera 7 near the gamma camera 2 as shown in FIG. The gamma rays which are arranged and fly from the structure (imaging object 10) are measured by the gamma camera 2, and the distance to the structure (imaging object 10) in the field of view of the gamma camera 2 is measured by the laser distance meter 6 and optical. A visible light image of a structure (imaging target 10) within the field of view of the gamma camera 2 is acquired by the camera 7.
In addition to the computer 8 (see FIG. 1) according to the first embodiment, the computer 8A according to the second embodiment can function as an image integration device 85 as shown in FIG. Yes.

  The image integration device 85 generates an image obtained by superimposing (overlaying) the gamma ray distribution image generated by the image generation arithmetic device 84 and the visible light image acquired by the optical camera 7 and outputs the generated image to the image display device 9. It has become. For this reason, the gamma camera system 1A according to the second embodiment superimposes the gamma ray distribution image and the visible light image, so that the pixel 13 of the output image and the display range 14 of one pixel on the imaging plane 11 are shown in FIG. It is prescribed as follows.

  As described above, according to the gamma camera system 1A according to the second embodiment, in addition to the effects of the gamma camera system 1 according to the first embodiment, an image in which the gamma ray distribution image and the visible light image are overlaid. However, since it is displayed on the image display device 9, the gamma ray distribution of the imaging target 10 can be easily determined.

«Third embodiment»
In the gamma camera system 1 according to the first embodiment and the gamma camera system 1A according to the second embodiment described above, sensitivity correction information estimation processing by the sensitivity correction information estimation device 82 and resolution correction information estimation processing by the resolution correction information estimation device 83. However, the image obtained by the image generation arithmetic device 84 without performing these processes and the image obtained by the image generation arithmetic device 84 after performing these processes are recorded in a database. Data may be projected by a projector (not shown).
Note that the database in which the image data is recorded may be an external database by communication in addition to the gamma camera system.

  That is, the gamma camera 2 having the gamma ray detector 3 and the collimator 5, the image generation arithmetic device 84 that performs image generation based on the gamma ray count data detected by the gamma camera 2, and the image generation arithmetic device 84 The gamma ray distribution state measured in the field by the gamma camera system having a projector (not shown) for projecting and displaying the gamma ray distribution image is not the screen of the image display device 9 of the computer 8 but the field position of the field worker. Can be easily confirmed.

  Then, the distribution state of gamma rays measured in the field may be displayed superimposed on the measurement object (imaging object 10) with a projector (not shown), and the field worker can display the measurement object (imaging object 10). The gamma ray distribution can be easily recognized just by looking.

  As described above, by allowing the field worker to grasp the gamma ray distribution state directly in real time, it is possible to save labor and personnel for monitoring the screen of the image display device 9 of the computer 8, and to reduce the exposure dose. In addition to being able to plan, it is possible for the worker himself / herself to check in real time for changes in dose such as leakage during work, elimination of shields, and decontamination effects.

Further, the projection display in which the image from the projector is superimposed on the measurement target (imaging target 10) may be adjusted by a person, or may be adjusted by a control device (not shown) of the gamma camera system.
When adjustment is performed by the control device to obtain overlay accuracy, a projection range of the projector corresponding to the distance of the measurement object (imaging object 10) is set in advance, and the distance measurement device (laser distance meter 6). The projection range of the projector may be adjusted to be enlarged or reduced according to the distance measured using. Thereby, the adjustment work of the projection display in the field can be reduced.

Further, when the projection display of the projector according to the distance, the image to be projected and displayed according to the distance to the measurement target (imaging target 10) may be corrected.
The correction here refers to the sensitivity correction described above, the resolution correction described above, the image distortion correction due to the difference between the position of the gamma camera 2 and the projector, and the projection target as the distance between the projector and the projection target (imaging target 10) increases. Projection image correction in which the amount of light reaching the (imaging target 10) decreases and the amount of light and brightness are adjusted more strongly as the distance increases. The projected image of the projector is normally projected onto a plane such as a screen. It means any one or a combination of image distortion corrections due to deviation of the projection position due to the unevenness of the object 10).

  The image distortion correction due to the difference between the positions of the gamma camera 2 and the projector may be performed by correcting the image distortion amount according to the distance. For example, the image distortion is measured according to the distance in advance, and the distance and The distortion correspondence is recorded, the image distortion is calculated from the recorded correspondence based on the measured distance of the projection target (imaging target 10), the image is corrected, and the projection display on the projector is controlled. To do.

  In the projection image correction of the light quantity and the brightness, the light quantity and the brightness are adjusted in consideration of the fact that the light quantity per unit area reaching the projection target (imaging target 10) decreases as the distance between the projector and the projection target (imaging target 10) increases. The distance may be adjusted more strongly as the distance increases. For example, the correspondence relationship between the distance and the light amount is recorded so as to compensate for the decrease in light amount according to the distance in advance, and the projection target (imaging target 10) The amount of light of the output image is controlled by obtaining the amount of light from the recorded correspondence based on the result of measuring the distance.

  The image distortion correction due to the unevenness of the projection target (imaging target 10) may be performed by correcting the amount of distortion of the image according to the distance. For example, the distortion of the image is measured in advance according to the distance, and the distance and the distortion are corrected. Correspondence is recorded, image distortion is obtained from the recorded correspondence based on the result of measuring the distance of the projection target (imaging target 10), the image is corrected, and the projection display on the projector is controlled. Radiation measured by correcting the image as described above according to the distance measured using the distance measuring device (laser distance meter 6), particularly when the projection target (imaging target 10) is a solid rather than a plane. The amount can be accurately projected from the projector onto the projection target (imaging target 10).

1,1A Gamma camera system 2 Gamma camera 3 Gamma ray detector 4 Gamma ray detector 5 Pinhole collimator (collimator)
6 Laser distance meter (distance measuring device, distance measuring means)
7 optical camera 8 computer 81 position calculation device (position calculation means)
82 Sensitivity correction information estimation device (sensitivity correction information estimation means)
83 Resolution correction information estimation device (resolution correction information estimation means)
84 Image generation calculation device (image generation calculation means)
85 Image integration device (image integration means)
9 Image display device 10 Imaging target y Detection data (gamma ray count data)
λ dose distribution

Claims (9)

A gamma camera having a gamma ray detector and a collimator;
Distance measuring means capable of scanning and measuring the distance from the imaging target of the gamma camera;
Position calculating means for calculating the positional relationship between the gamma camera obtained by scanning measurement of the distance measuring means and the imaging target of the gamma camera;
Sensitivity correction information estimation means for estimating measurement sensitivity when the imaging target is measured by the gamma camera based on the positional relationship obtained from the position calculation means;
Based on the positional relationship obtained from the position calculating means, resolution correction information estimating means for estimating the resolution when the imaging target is measured by the gamma camera;
Image generation calculation means for generating a gamma ray distribution image based on the measurement sensitivity estimated by the sensitivity correction information estimation means, the resolution estimated by the resolution correction information estimation means, and the gamma ray count data detected by the gamma camera; A gamma camera system comprising: 2. The gamma camera system according to claim 1, wherein the gamma ray detector is a pixel type gamma ray detector that handles a signal output from a single element or a plurality of elements for each corresponding channel. The gamma camera system according to claim 2, wherein the gamma ray detector is a semiconductor detector. The gamma camera system according to claim 1, wherein the image generation calculation unit generates a gamma ray distribution image by maximum likelihood estimation calculation. An optical camera that captures an imaging target of the gamma camera;
5. The image integration unit according to claim 1, further comprising: an image integration unit that superimposes an optical image captured by the optical camera and a gamma ray distribution image generated by the image generation calculation unit. The gamma camera system according to item 1. The gamma camera system according to claim 1, further comprising: a projector that projects and displays the gamma ray distribution image generated by the image generation calculation unit. A gamma camera having a gamma ray detector and a collimator;
Distance measuring means capable of scanning and measuring the distance from the imaging target of the gamma camera;
Based on gamma ray count data detected by the gamma camera, taking into account the distance between the gamma camera obtained by scanning measurement of the distance measuring means and the imaging target of the gamma camera and the distance from the radiation source. And a gamma-ray distribution image. A gamma camera having a gamma ray detector and a collimator;
Based on gamma ray count data detected by the gamma camera, image generation calculation means for generating a gamma ray distribution image;
A gamma camera system comprising: a projector that projects and displays a gamma ray distribution image generated by the image generation calculation means. The gamma camera system according to claim 8, wherein the projector projects and displays a gamma ray distribution image on an imaging target of the gamma camera.

Images