JP4383610B2 - Nuclear medicine diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a nuclear medicine diagnostic apparatus that detects gamma rays emitted from a radioisotope (Radioisotope, hereinafter referred to as “RI”) administered to a subject and images the distribution of RI in the subject.
[0002]
[Prior art]
A nuclear medicine diagnostic apparatus administers to a subject a radiopharmaceutical labeled with a compound having a property of being easily taken into a normally functioning part of a specific tissue or organ of a living body, and is released from the RI. By detecting the gamma rays and imaging the distribution of RI in the subject, it is possible to diagnose the function and metabolism of the living body.
[0003]
As a technique for imaging the RI distribution, there is a technique for forming a two-dimensional RI distribution on a tomographic plane of a subject.
[0004]
Specifically, for example, a radiopharmaceutical having RI as a single photon emitting nuclide that emits one photon (hereinafter referred to as “photon” as appropriate) upon collapse is administered to the subject, and γ-ray detection is installed outside the subject. The instrument is rotated at predetermined unit angles around the body axis of the subject, and γ rays emitted from the RI for the same collection time at each unit angle are detected by the γ ray detector, and photons are counted. By performing image reconstruction processing such as a corrected backprojection method, a tomographic image is obtained for a two-dimensional distribution of RI on a tomographic plane substantially perpendicular to the body axis of the subject.
[0005]
Note that the γ-ray detector counts photons in each small region obtained by equally dividing the detection surface vertically and horizontally by, for example, 256 × 256, and this small region is referred to as a “pixel” herein. I will do it.
[0006]
[Problems to be solved by the invention]
As described above, when a γ-ray detector rotates around the subject for each predetermined unit angle and collects γ-rays at the same collection time, as described above, Gamma rays are collected.
[0007]
For this reason, in each pixel of the γ-ray detector, the photon count value may vary, and the image quality of the tomographic image may deteriorate. That is, if there are pixels with a photon count value of zero or extremely small, an artifact (virtual image) is generated on the tomographic image.
[0008]
In order to improve the variation in the photon count value, it is conceivable to lengthen the γ-ray collection time, but the subject is forced to remain stationary for a long time. End up.
[0009]
Further, when the γ-ray collection time is shortened, there is a problem that the photon count value is decreased, so-called S / N ratio is lowered, and the image quality of the tomographic image is deteriorated.
[0010]
The present invention has been made in view of the above, and an object of the present invention is to prevent variation in the count value of photons for each pixel of the γ-ray detector and collect γ-rays in an appropriate collection time. It is to provide a nuclear medicine diagnostic apparatus that can be terminated.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the nuclear medicine diagnostic apparatus according to the present invention as set forth in claim 1 is released from a radioisotope administered into the subject while rotating around the subject for each unit angle. Detecting γ-rays on the detection surface of a γ-ray detector in a nuclear medicine diagnostic device with a γ-ray detector that detects γ-rays or γ-rays emitted from a γ-ray source placed outside the subject for each photon Region setting means for setting a region on the detection surface of the γ-ray detector that collects γ-rays from the position, and a count value setting for setting a photon count value for each pixel in the region set by the region setting means Means for collecting gamma rays at the unit angle when the photon count value at all the pixels in the region at the unit angle is equal to or greater than the count value set by the count value setting means; , and it is required to have a.
[0013]
The present invention according to claim 2 is a gamma ray emitted from a radioisotope administered into the subject or rotated outside the subject while rotating around the subject for each unit angle. Γ-ray detector that collects γ-rays from the position where γ-rays are detected on the detection surface of the γ-ray detector in a nuclear medicine diagnostic apparatus having a γ-ray detector that detects γ-rays emitted from each photon An area setting means for setting an area on the detection surface, a total count value setting means for setting a sum of count values of photons in all pixels in the area set by the area setting means, Collecting means for terminating the collection of γ rays at the unit angle when the total count value of photons in all the pixels becomes equal to or greater than the total count value set by the total count value setting means;
It is summarized as having .
[0015]
According to the third aspect of the present invention, a gamma ray emitted from a radioisotope administered into the subject or a gamma ray source installed outside the subject while rotating around the subject for each unit angle. In a nuclear medicine diagnostic apparatus having a γ-ray detector for detecting γ-rays emitted from each photon, an overall count value setting means for setting the sum of the count values of photons in all pixels of the γ-ray detector, and a unit And a collection unit that terminates the collection of γ rays at the unit angle when the total count value of photons of all pixels at the angle becomes equal to or greater than the total count value set by the total count value setting unit. And
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
[First Embodiment]
FIG. 1 is a cross-sectional view showing a schematic configuration of the nuclear medicine diagnosis apparatus according to the first embodiment. The nuclear medicine diagnosis apparatus of FIG. 1 includes a γ-ray detector 1 that two-dimensionally detects γ-rays emitted from an RI administered to a subject 3 on a detection surface, and the subject 3 is disposed on the upper surface. The figure which performs data processing etc. based on the detection result of a gamma ray besides control of the bed 2 and the mechanism part which is not illustrated for rotating the gamma ray detector 1, and the gamma ray detector 1, the mechanism part, etc. This is a configuration having a console not shown.
[0023]
Inside the γ-ray detector 1, a collimator in which a large number of minute cylindrical holes are arranged on a lead plate or a tungsten plate having excellent γ-ray absorption characteristics is installed and administered to the subject 3. In addition, the incident direction of γ rays is regulated so that γ rays emitted radially from the RI do not enter from a direction other than perpendicular to the detection surface.
[0024]
In addition, γ-ray energy is converted to light by a scintillator (not shown) installed behind the collimator, and photons are counted by converting light to an electrical signal by a photomultiplier tube (not shown). . At this time, photons are counted for each pixel obtained by equally dividing the vertical and horizontal directions of the detection surface into, for example, 256 × 256. Such a γ-ray detector 1 is a so-called anger type, but a semiconductor array type γ-ray detector may be used. The semiconductor array type is generally configured to have a semiconductor element that converts γ rays into an electrical signal having an amplitude corresponding to energy behind the collimator.
[0025]
FIG. 2 is a block diagram showing the configuration of the control system of the nuclear medicine diagnostic apparatus. In the same figure, the control part 21, the data processing part 24, the operation part 25, and the display part 26 comprise the console mentioned above.
[0026]
The mechanism unit 23 rotates the γ-ray detector 1 in the clockwise direction shown in FIG. 1 for each predetermined unit angle about the designed rotation axis C.
[0027]
Next, processing for capturing a tomographic image of the subject 3 will be described.
[0028]
First, a radiopharmaceutical having the property of being easily taken into the organ 4 is administered to the subject 3, and the subject 3 is placed on the bed 2 so that the body axis thereof is substantially perpendicular to the rotation axis C. When the operator instructs to take a tomographic image using the operation unit 25, the control unit 21 follows the collection process of γ rays at a unit angle described later in a state where the rotation angle of the γ-ray detector 1 is 0 °. The gamma ray detector 1 collects gamma rays. When the collection of γ-rays is completed, the control unit 21 transmits the data obtained by the γ-ray detector 1 detecting the γ-rays and counting the photons to the data processing unit 24 and also to the mechanism unit 23. Command to rotate the γ-ray detector 1 by a unit angle. Here, it is considered that the unit angle is preferably about 4 to 6 °, but it may be a coarser angle or a narrower angle.
[0029]
After the mechanism unit 23 rotates the γ-ray detector 1 by a unit angle, the control unit 21 causes the γ-ray detector 1 to collect γ-rays at that angle in the same manner as described above, and the obtained data is used as data. The data is transmitted to the processing unit 24. This process is repeated until the γ-ray detector 1 makes a round around the subject 3.
[0030]
Subsequently, the data processing unit 24 performs image reconstruction processing such as a filtered back projection method using the data for one round around the subject 3 transmitted from the control unit 21, thereby tomulating the subject 3. Get an image. This tomographic image is an image of the organ 4 that has taken in the radiopharmaceutical. The control unit 21 transmits this tomographic image to the display unit 26 and displays it so that the operator can visually recognize it.
[0031]
Next, the γ-ray collection process at the unit angle described above will be described with reference to the flowchart shown in FIG.
[0032]
First, in step 1, when the control unit 21 instructs to start collecting γ rays at a unit angle, the γ ray detector 1 starts collecting γ rays according to this command.
[0033]
In step 2, when the γ-ray detector 1 is collecting γ rays, the control unit 21 sets a collection region for collecting γ rays from the position on the detection surface where the γ rays are detected. In addition, when collecting γ-rays, if γ-rays are detected outside the set area, the collection area is set again. This collection region is a region in which γ rays emitted from the organ 4 are incident on the γ ray detector 1 perpendicularly by the restriction of the incident direction by the collimator, and corresponds to the range indicated by A in FIG. . Since almost no γ rays are detected in the region other than this collection region, this collection region can be set by determining the position where the γ rays are detected.
[0034]
In step 3, a photon count value is set for each pixel in the collection region. In order to prevent the count value from becoming zero, the count value is set to an appropriate numerical value of 1 count or more for all the pixels in the collection region.
[0035]
In step 4, it is determined whether or not the count value of the photons actually counted for all the pixels in the collection area is equal to or greater than the set count value. If this condition is not satisfied, the process returns to the same step and continues collecting γ rays. On the other hand, if this condition is satisfied, the process proceeds to step 5 to end the collection of γ rays at the unit angle.
[0036]
Thereafter, the control unit 21 instructs the mechanism unit 23 to rotate the γ-ray detector 1 by a unit angle, and shifts to collecting γ-rays at the next angle.
[0037]
Therefore, according to the present embodiment, since γ rays can be collected at different times for each unit angle, the γ ray detector 1 by collecting γ rays at the same collection time at each unit angle. It is possible to prevent variation in the count value of photons for each pixel.
[0038]
Specifically, a collection region for collecting γ rays from the position on the detection surface where the γ rays are detected is set, and a count value of photons is set for each pixel in the collection region to When the actual count value of the pixel becomes equal to or greater than the set value, the collection of γ rays at the unit angle is terminated, so that the variation of the photon count value for each pixel can be prevented.
[0039]
[Second Embodiment]
The basic configuration of the nuclear medicine diagnostic apparatus according to the second embodiment is the same as that of FIG. 1, and the basic configuration of the control system is the same as that of FIG. As a feature of the present embodiment, in the collection process of γ rays at a unit angle, a collection region for collecting γ rays is set from the position on the detection surface where the γ rays are detected, and the entire pixels in the collection region are set. Set the total photon count value at, and when the actual photon total count value for all the pixels in the collection area exceeds the set value, the collection of γ rays at that unit angle is terminated. There is. Hereinafter, a description will be given with reference to the flowchart shown in FIG.
[0040]
Since the processing in step 11 and step 12 is the same as the processing in step 1 and step 2 described with reference to FIG. 3, the description thereof is omitted here.
[0041]
In step 13, the control unit 21 sets the total count value of photons in all the pixels in the collection region. For example, when the organ 4 is a myocardium, the count is about 4000 counts.
[0042]
In step 14, it is determined whether or not the actual total photon count value for all the pixels in the collection region is equal to or greater than the set total count value. If this condition is not satisfied, the process returns to the same step to continue collecting γ rays. On the other hand, when this condition is satisfied, the process proceeds to step 15 to end the collection of γ rays at the unit angle.
[0043]
Therefore, according to the present embodiment, a collection area for collecting γ-rays is set, and the total count value of photons in the entire pixels in the collection area is set, so that When the total count value of actual photons exceeds the set value, the collection of γ rays at that unit angle is terminated, so that sufficient photons can be counted and the S / N ratio is improved. can do.
[0044]
In this embodiment, the total count value of photons is set for all the pixels in the collection region. However, the processing for setting the count value for each pixel as described in the first embodiment You may combine. For example, when both the condition of step 4 shown in FIG. 3 and the condition of step 14 shown in FIG. 4 are satisfied, or when any of the conditions is satisfied, Let the collection end. In such a case, the S / N ratio can be improved and variations in the photon count value for each pixel can be prevented.
[0045]
[Third Embodiment]
The basic configuration of the nuclear medicine diagnostic apparatus according to the third embodiment is the same as that of FIG. 1, and the basic configuration of the control system is the same as that of FIG. As a feature of the present embodiment, in the process of collecting γ rays at a unit angle, an upper limit time for collecting γ rays is set, and when the upper limit time has elapsed, collection of γ rays at that unit angle is terminated. It is in doing so. Hereinafter, a description will be given with reference to the flowchart shown in FIG.
[0046]
First, before starting the processing shown in this flowchart, the control unit 21 sets in advance an upper limit time for collecting γ rays at a unit angle. The upper limit time is, for example, about 20 seconds to 30 seconds.
[0047]
In the flowchart shown in the figure, the processing from step 21 to step 26 except for step 25 is the same as the processing from step 1 to step 5 described with reference to FIG. 3 in the first embodiment. Omitted.
[0048]
If the control unit 21 determines in step 24 that the actual photon count value is not equal to or greater than the set count value for all the pixels in the collection region, the same is true in the first embodiment. Returning to the step, the collection of γ rays is continued, but in the present embodiment, the process proceeds to step 25.
[0049]
In step 25, the control unit 21 determines whether or not the upper limit time for collection has elapsed. If the upper limit time has not elapsed, the process returns to step 24 to continue collecting γ rays. On the other hand, if the upper limit time has elapsed, the process proceeds to step 26 and the collection of γ rays at the unit angle is terminated.
[0050]
Therefore, according to the present embodiment, the upper limit time for collecting γ rays is set, and when the upper limit time has elapsed, the collection of γ rays at the unit angle is terminated. Even when the photon count value is not equal to or higher than the set value for all of the pixels, the collection of γ rays can be completed in an appropriate time.
[0051]
In the present embodiment, the upper limit time is set for the γ-ray collection processing in the first embodiment, but the upper limit time is similarly applied to the γ-ray collection processing in the second embodiment. In such a case, the same effects as described above can be obtained.
[0052]
[Fourth Embodiment]
In the fourth embodiment, a case will be described in which the present invention is applied to a transmission CT apparatus in which a γ-ray source is installed facing a γ-ray detector.
[0053]
A transmission-type CT apparatus having a γ-ray source is arranged so that a set of a γ-ray source and a γ-ray detector rotates around the subject at a predetermined unit angle so that the γ-ray source A tomographic image of a subject is obtained by detecting a γ-ray that has been emitted and partially absorbed in the subject while passing through the subject with a γ-ray detector and performs a predetermined image reconstruction process. .
[0054]
The tomographic image obtained in this way is a so-called absorption coefficient map of γ rays in the subject. This γ-ray absorption coefficient map relates to tomographic images obtained by the nuclear medicine diagnosis apparatus (hereinafter referred to as “emission type CT apparatus” as appropriate) described in each of the above embodiments, and is based on the absorption of γ-rays in the subject. It is used to correct image quality degradation.
[0055]
However, in the collection of γ rays by such a transmission type CT apparatus, since the path through which the γ rays pass through the inside of the subject is long, the γ rays are completely absorbed in the subject, and the photon count value is increased. There is a tendency to become zero. In such a case, this is equivalent to the presence of an infinite γ-ray absorption coefficient within the subject, which causes a strong artifact in the absorption coefficient map. It was.
[0056]
In general, an emission type CT apparatus and a transmission type CT apparatus provided with a γ-ray source are integrated as a nuclear medicine diagnostic apparatus for convenience of use.
[0057]
FIG. 6 is a cross-sectional view showing a schematic configuration of the nuclear medicine diagnostic apparatus according to the present embodiment. The nuclear medicine diagnostic apparatus of FIG. 1 includes a γ-ray source 64 that emits γ-rays, a γ-ray detector 61 that is disposed opposite to the γ-ray source 64 and detects γ-rays emitted from the γ-ray source 64, The bed 62, which is disposed between the γ-ray source 64 and the γ-ray detector 61 and on which the subject 63 is disposed on the upper surface, and the set of the γ-ray source 64 and the γ-ray detector 61 are maintained in the positional relationship. In this state, there is a mechanism unit (not shown) that rotates around the rotation axis C, and a console (not shown) that controls the γ-ray detector 61 and the mechanism unit, performs data processing, and the like.
[0058]
The γ-ray detector 61 detects the γ-rays emitted from the γ-ray source 64 and transmitted through the subject 63 disposed on the bed 62 for each photon, and counts photons. Note that the γ-ray detector 61 has the same configuration and function as the γ-ray detector 1 described in FIG.
[0059]
The basic configuration of the control system of the nuclear medicine diagnostic apparatus is the same as that shown in FIG. 2 except that the γ-ray detector 61 detects γ-rays emitted from the γ-ray source 64. Therefore, the description is omitted here.
[0060]
Next, the collection process of the gamma ray in a unit angle is demonstrated using the flowchart of FIG.
[0061]
First, before starting the processing shown in this flowchart, the control unit 21 sets in advance a total count value of photons in all pixels of the γ-ray detector 61 when collecting γ-rays at unit angles. Assume that an upper limit time for collecting γ rays is set.
[0062]
In step 31, when the control unit 21 instructs to start collecting γ rays at a unit angle, the γ ray detector 61 starts collecting γ rays according to the command.
[0063]
In step 32, when the γ-ray detector 61 is collecting γ-rays, the control unit 21 transmits γ-rays transmitted through the subject from a position on the detection surface where the γ-rays transmitted through the subject 63 are detected. Set the collection area to collect. In addition, when collecting γ-rays, if γ-rays transmitted through the subject other than the set region are detected, the collection region is set again. This collection area corresponds to the range indicated by B in FIG. Since the γ-rays emitted from the γ-ray source 64 are detected as they are in the region on the detection surface other than the collection region, the photon count value differs greatly between the collection region and the region other than the collection region. . This collection area can be set by using this to determine the photon count value.
[0064]
In step 33, a count value of photons to be counted is set for each pixel in the collection area. In order to prevent the count value from becoming zero, a minimum necessary 1 count is set for all the pixels in the collection region.
[0065]
In step 34, it is determined whether or not the actual photon count value has become equal to or greater than the set count value for all the pixels in the collection region. If this condition is not satisfied, the process returns to the same step and continues collecting γ rays. On the other hand, if this condition is satisfied, the process proceeds to step 35. Since the condition in step 34 is to guarantee the collection of the minimum necessary 1 count, it is expected that the S / N ratio will be low even if this condition is satisfied. Image quality is not always obtained.
[0066]
Therefore, in step 35, it is determined whether or not the total count value of the entire pixel is equal to or greater than the preset total count value. If this condition is satisfied, the process proceeds to step 37 to proceed to the unit angle. The collection of γ rays at is terminated.
[0067]
On the other hand, if the condition of step 35 is not satisfied, the routine proceeds to step 36 where it is determined whether the upper limit time has elapsed. If the upper limit time has not elapsed, the process returns to step 34 to continue the collection of γ rays, and if the upper limit time has elapsed, the process proceeds to step 37 to end the collection of γ rays at the unit angle.
[0068]
Therefore, according to the present embodiment, a photon count value is set for each pixel in the collection region of γ-rays transmitted through the subject 63, and a total photon count value is also set for all the pixels in the collection region. By setting the upper limit time for collecting γ rays, and when each condition is satisfied, the collection of γ rays at the unit angle is terminated. Variations in the photon count value can be prevented, the S / N ratio can be improved, and γ rays can be collected in an appropriate collection time.
[0069]
In this embodiment, the setting of the photon count value of each pixel in the γ-ray collection area, the setting of the total photon count value for all the pixels in the γ-ray collection area, and the collection of γ-rays are performed. Although the case where the combination of the three settings of the upper limit time is applied to the transmission type CT apparatus in which the γ-ray source is installed has been described, these three combinations can also be applied to the emission type CT apparatus. Even in this case, the same effects as described above can be obtained.
[0070]
[Application to other embodiments]
The present invention can be applied to SPECT (Single Photon Emission Computed Tomography) in which a single photon emission nuclide that emits one photon at the time of decay is used as RI. The present invention can also be applied to PET (Positron Emission Computed Tomography), which uses a positron emitting nuclide that emits two photons in a direction opposite to the angle of 180 ° as RI.
[0071]
【The invention's effect】
As described above, according to the nuclear medicine diagnostic apparatus according to the first aspect of the present invention, γ-rays can be collected at different times for each unit angle, so that the same collection is performed at each unit angle. It is possible to prevent variation in the photon count value for each pixel of the γ-ray detector by collecting γ-rays with time.
[0072]
According to the nuclear medicine diagnosis apparatus of the present invention as set forth in claim 2, when collecting γ-rays, a region for detecting γ-rays on the detection surface of the γ-ray detector is set, and each pixel in this region is set. The photon count value is set to, and the collection of γ rays at the unit angle ends when the photon count value exceeds the set count value for all pixels in the region at the unit angle. As a result, the collection time of γ rays at each unit angle can be set to an appropriate time, and variation in the photon count value for each pixel of the γ ray detector can be prevented.
[0073]
According to the nuclear medicine diagnostic apparatus of the present invention as set forth in claim 3, the total count value of photons in the entire pixels in the region for detecting γ rays on the detection surface is set, and the entire pixels in the region at a unit angle Since the collection of γ rays at the unit angle is terminated when the total photon count value at the time becomes equal to or greater than the set total count value, sufficient photons are counted within the region and S / The N ratio can be improved.
[0074]
According to the nuclear medicine diagnostic apparatus of the present invention as set forth in claim 4, the upper limit time for collecting γ-rays is set, and when the upper limit time has elapsed at the unit angle, the collection of γ-rays at the unit angle is terminated. By doing so, the collection of γ-rays can be completed in an appropriate time even when photons exceeding the set value are not counted.
[0075]
According to the nuclear medicine diagnosis apparatus of the present invention as set forth in claim 5, the total count value of photons in the entire pixel of the γ-ray detector is set, and the total count value of photons in the entire pixel is set at a unit angle. Since the collection of γ rays at the unit angle is terminated when the total count value exceeds the predetermined count value, sufficient photons are counted for the entire pixel of the γ ray detector, and the S / N ratio. Can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a nuclear medicine diagnostic apparatus according to a first embodiment.
FIG. 2 is a block diagram showing a configuration of a control system of the nuclear medicine diagnostic apparatus.
FIG. 3 is a flowchart showing a process of collecting γ rays at a unit angle in the first embodiment.
FIG. 4 is a flowchart showing a process of collecting γ rays at a unit angle in the second embodiment.
FIG. 5 is a flowchart showing a process of collecting γ rays at a unit angle in the third embodiment.
FIG. 6 is a cross-sectional view showing a schematic configuration of a nuclear medicine diagnostic apparatus according to a fourth embodiment.
FIG. 7 is a flowchart showing a process of collecting γ rays at a unit angle in the fourth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,61 ... Gamma ray detector 2,62 ... Bed, 3,63 ... Subject, 4 ... Organ, 21 ... Control part, 23 ... Mechanism part, 24 ... Data processing part, 25 ... Operation part, 26 ... Display 64, gamma ray source

Claims (4)

While rotating around the subject for each unit angle, γ rays emitted from the radioisotope administered into the subject or γ rays emitted from a γ-ray source installed outside the subject for each photon In a nuclear medicine diagnostic apparatus having a γ-ray detector to detect
An area setting means for setting an area on the detection surface of the γ-ray detector that collects γ-rays from a position where the γ-ray is detected on the detection surface of the γ-ray detector;
Count value setting means for setting a photon count value for each pixel in the area set by the area setting means;
A collecting means for ending the collection of γ rays at the unit angle when the photon count value is equal to or greater than the count value set by the count value setting means at all the pixels in the region at the unit angle;
Nuclear medicine diagnosis apparatus characterized by having a. While rotating around the subject for each unit angle, γ rays emitted from the radioisotope administered into the subject or γ rays emitted from a γ-ray source installed outside the subject for each photon In a nuclear medicine diagnostic apparatus having a γ-ray detector to detect
  An area setting means for setting an area on the detection surface of the γ-ray detector that collects γ-rays from a position where the γ-ray is detected on the detection surface of the γ-ray detector;
  A total count value setting means for setting the sum of the photon count values for all the pixels in the area set by the area setting means;
  Collection means for terminating collection of γ rays at the unit angle when the total count value of photons in all the pixels in the region at the unit angle becomes equal to or greater than the total count value set by the total count value setting means; ,
A nuclear medicine diagnostic apparatus comprising: While rotating around the subject for each unit angle, γ rays emitted from the radioisotope administered into the subject or γ rays emitted from a γ-ray source installed outside the subject for each photon In a nuclear medicine diagnostic apparatus having a γ-ray detector to detect
  an overall count value setting means for setting the sum of the count values of photons in the entire pixels of the γ-ray detector;
  A collecting means for terminating the collection of γ rays at the unit angle when the total count value of the photons of the entire pixel at the unit angle becomes equal to or greater than the total count value set by the overall count value setting means;
A nuclear medicine diagnostic apparatus comprising: an upper limit time setting means for setting an upper limit time for collecting γ-rays;
The nuclear medicine diagnosis apparatus according to any one of claims 1 to 3, wherein the collecting means ends collection of γ rays at the unit angle when an upper limit time has elapsed at the unit angle.

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