JPH05100032A - Nuclear medicine diagnostic device - Google Patents

Abstract

PURPOSE:To luminescent-spot-display the position of a radioactive source administered in vivo on a display screen in a short time while generating little artifact. CONSTITUTION:Multiple photomultipliers 1 convert the scintillation light detected and converted with radioactive rays by a scintillator 4 into the electric signals and output them. A calculation region selecting circuit 6 selects the calculation region for calculating the center of gravity based on the electric signals from multiple photomultipliers 1. A center of gravity calculating circuit 8 calculates the center of gravity in the selected calculation region. A converting circuit 11 converts the calculation value by the center of gravity calculation into the true value stored in a conversion data memory 9 and outputs it to an image output circuit 12.

Description

Detailed Description of the Invention

 [Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear medicine diagnostic apparatus for determining the position of a radiation source administered in a living body by calculating the center of gravity and displaying it on a display screen.

[0002]

2. Description of the Related Art A nuclear medicine diagnostic apparatus detects radiation emitted by a radiation source administered in a living body, for example, γ-rays by a scintillator and converts it into scintillation light, and the scintillation light has a hexagonal shape as shown in FIG. A large number of photomultiplier tubes arranged in a row (hereinafter simply referred to as "photomal")
By converting to an electric signal proportional to the light quantity of the scintillation light by 1 and outputting it, the position of the radiation source is calculated by the center of gravity calculation based on the output value, and displayed at the corresponding position on the display screen such as a CRT display. Is.

The calculation of the center of gravity is performed as follows, for example. First, as shown in FIG. 9, a search is made for the photomaru 1a that has detected the maximum intensity of radiation, and as shown in FIG.
A calculation area 2 consisting of a predetermined number of, for example, 7 photo-mals 1 centered on a is selected. The calculation area 2 is a hexagonal area circumscribing the seven photomarus 1. This calculation area 2
Using the output value of each Photomaru 1 in the above, for example, weighting or the like is added to each output value and average addition is performed to obtain the center of gravity, that is, the position of the radiation source. The position of the true radiation source is in the true region 3. The calculation of the center of gravity is sequentially performed corresponding to the position of the radiation source that moves or gathers in the living body every moment, a radiation distribution image appears on the display screen, and this image is used for diagnosis.

[0004]

However, since the center of gravity calculation is performed using a limited number of photomarus 1 in a predetermined calculation area 2, the information of the radiation leaked outside the calculation area 2 is used for the center of gravity calculation. I can't. Therefore, as shown in FIG. 10, the calculation result of the position of the center of gravity is pulled toward the area 3a indicated by the diagonal lines with respect to the true area 3 in the center direction and is degenerated and distorted. Therefore, there is a problem that the image degenerates toward the center, discontinuity occurs between the calculation regions 2 (or the regions 3a), and an artifact occurs in the image.

Further, if all of the photomultipliers for detecting the incident radiation are used for the calculation of the position of the center of gravity, the problem of the above-mentioned degeneracy distortion does not occur, but the calculation time is long and the circuit scale is large, so this method is not realistic.

Therefore, the present invention has been made in view of the above circumstances, and the generation of the radiation source injected into the living body is less likely to cause artifacts, the circuit scale is small, and
It is an object of the present invention to provide a nuclear medicine diagnostic device capable of displaying on a display screen in a short time.

[Constitution of Invention]

[0008]

In order to achieve the above object, the present invention provides a large number of detection elements for detecting radiation, a detection element which has detected the maximum intensity of radiation among the plurality of detection elements, and this detection element. Based on the selection means for selecting a predetermined number of detection elements in the periphery and the detection value output by the detection elements selected by this selection means, the center of gravity calculation means for obtaining the position of the radiation source injected into the living body by the center of gravity calculation And a nuclear medicine diagnostic apparatus for displaying the position obtained by the centroid calculating means at a corresponding position on the display screen, having a distortion eliminating means for eliminating the degeneracy distortion of the calculated value by the centroid calculation. Is.

According to a second aspect of the present invention, in the first aspect of the invention, the distortion eliminating means is arranged with the large number of detection elements in association with a calculated value by the centroid calculation and a true value. Storage means for storing in advance over the entire area,
And a conversion unit for converting the calculated value obtained by the gravity center calculation unit into a true value stored in the storage unit.

According to a third aspect of the present invention, in the first aspect of the present invention, the distortion eliminating means removes less than a predetermined intensity of the detection value output by the detection element and inputs the detected value to the center of gravity calculating means. Is.

[0011]

[Operation] Next, the operation of each invention of the above construction will be described.

According to the first aspect of the present invention, when the detecting means detects the radiation, the selecting means selects the detecting element detecting the maximum intensity of the radiation and a predetermined number of detecting elements around the detecting element. The center of gravity calculation means obtains the position of the radiation source injected into the living body by the center of gravity calculation based on the detection value output by the detection element selected by the selection means. The calculated value by the calculation of the center of gravity causes a distortion that degenerates toward the center of the region in which the detection element selected by the selection unit is arranged, except that the radiation is incident near the center of the detection element that has detected the maximum intensity of radiation. Since the distortion eliminating means eliminates this degenerate distortion, the true value of the position of the radiation source can be obtained.

According to the second aspect of the present invention, even if the calculation value obtained by the center-of-gravity calculation means causes degeneracy distortion, the conversion means converts the calculated value into a true value stored in the storage means. , Degenerate distortion can be eliminated.

According to the third aspect of the present invention, when the removing means removes a predetermined intensity or less of the detection value output by the detecting element, the center-of-gravity calculating means outputs the detecting elements that are substantially equidistant from the radiation incident position. The calculation of the center of gravity is performed based on the detected value, and the same effect as that when the radiation is incident on the center of the detection element that has detected the maximum intensity of the radiation is produced, thereby preventing the occurrence of degeneracy distortion.

[0015]

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

FIG. 1 is a schematic block diagram of a nuclear medicine diagnostic apparatus 10 according to the first embodiment of the present invention.

This device 10 is arranged in a hexagonal shape as shown in FIG. 9 and scintillator 4 for detecting the radiation emitted from the radiation source administered in the living body and converting it into scintillation light, which scintillator 4 outputs. A large number (for example, 61) of Photomars 1 as detection elements for converting scintillation light into an electric signal proportional to the light quantity and outputting the electric signal.
And, corresponding to these Hotaru 1
Of a plurality of amplifiers 5 for integrating the output signals of, the calculation area selection circuit 6 for selecting the calculation area 2 for the calculation of the center of gravity from the output value of each amplifier 5, and the analog output signal of the selection circuit 6 is converted into a digital signal. A / D converter 7 and A / D
The center of gravity calculation circuit 8 for calculating the center of gravity based on the digital signal from the converter 7, the converted data memory 9 for storing the converted data as a true value, and the calculated value by the calculation of the center of gravity are stored in the converted data memory 9. The schematic configuration includes a conversion circuit 11 for converting into conversion data, and an image output circuit 12 for displaying at a position corresponding to a value after conversion by the conversion circuit 11 on a display screen such as a CRT display (not shown).

FIG. 2 shows the calculation area 2 when the calculation area selection circuit 6 selects seven photo-mals 1 as one block. The center-of-gravity calculation circuit 8 uses the calculation area 2
The center of gravity is calculated in the same manner as in the conventional case, and the calculation result remains degenerated toward the center as shown in the area 3a in FIG. The center of gravity calculating circuit 5 is shown in FIG.
As shown in, the X-axis and the Y-axis corresponding to the calculation area 2 have 10-bit addresses respectively, and the result of the center of gravity calculation is output with high accuracy by the resolution of 1024 × 1024 matrix.

In the conversion data memory 9, the calculated value by the calculation of the center of gravity and the true value (conversion data) are associated with each other and stored in advance over the entire area in which the large number of detection elements 1 are arranged. There is. The conversion data memory 9 is shown in FIG.
As shown in, the X'axis and the Y'axis each have an 8-bit address and correspond to the matrix size of the display screen.
The conversion data is stored in the mapping area 13 shown in FIG. The conversion data to be stored in the conversion data memory 9 is obtained by, for example, injecting radiation from the radiation source at a position known in advance by computer simulation or the like into the photomultiplier 1 and determining the correspondence between the position and the output position of the center of gravity calculation circuit 8. The correct incident position with respect to the output position which is the calculation result may be created as the conversion data, or may be obtained by calculation.

Next, the operation and effect of the device 10 of the first embodiment thus constructed will be described.

As an example, a case where seven photo-mals 1 are used as the calculation area 2 as shown in FIG. 2 will be described.

As shown in FIG. 2, if radiation is incident on the point A 0 (x 0, y 0) on the end side of the central photomultiplier 1 a, the calculation area selection circuit 6 outputs the photomultiplier 1 input via the amplifier 5. Based on the output value, the Photomaru 1a that has detected the maximum intensity of radiation is searched for. Next, the calculation area selection circuit 6
As shown in the same figure, the calculation area 2 for calculating the center of gravity is selected with seven photomarus 1 as one block. Further, the calculation area selection circuit 6 outputs the output values of the seven photomultipliers 1 in the calculation area 2 to the center of gravity calculation circuit 8 via the A / D converter 7.

The center-of-gravity calculation circuit 8 adds a weight or the like to each output value to perform the center-of-gravity calculation by average addition, and converts the signal at the calculated position A1 (x1, y1) (see FIG. 3) into the conversion circuit 11. Output to. The conversion circuit 11 converts the converted value A0 '(x0', x0 ', corresponding to the input position A1 (x1, y1).
y0 ') (see FIG. 4) is searched in the converted data memory 9 and the data of the converted value A0' is output to the image output circuit 12. The image output circuit 12 displays at a corresponding position on the display screen of the CRT display. As the radioactive source administered in the living body moves or collects, each part acts as described above, and the radiation distribution image appears on the display screen of the CRT display as the trajectory or set of the radioactive source, which is caused by the degenerate distortion of the calculation area 2. A good image with few artifacts can be obtained. Moreover, since the calculation area 2 is limited to a narrow range, an image can be obtained in a single time.

FIG. 5 is a schematic block diagram of a nuclear medicine diagnostic apparatus 20 according to the second embodiment of the present invention.

This apparatus 20 has a scintillator 4, a large number of photomultipliers 1, a large number of amplifiers 5, a calculation area selection circuit 6, and an A / D which are constructed in the same manner as the apparatus 10 of the first embodiment shown in FIG.
A converter 7, a center of gravity calculation circuit 8, and an image output circuit 12 are provided,
The response correction circuit 21 is provided in the preceding stage of the center-of-gravity calculation circuit 8 and is generally configured.

FIG. 6 shows the calculation area 22 when the calculation area selection circuit 6 selects 19 photomultipliers 1 as one block.
FIG. 7 is a diagram showing an input value (signal) to the response correction circuit 21, and FIG. 8 is a diagram showing an output value (signal) from the response correction circuit 21. As shown in FIG. 7, the response correction circuit 21 cuts a signal equal to or lower than a threshold value Lc set in a range that does not affect the calculation of the inner center of gravity of the transmitted signal, that is, in a range in which the contribution rate to the center of gravity calculation is low, and is a photomultiplier. The response of No. 1 is corrected and a signal as shown in FIG. 8 is output. That is, when signals below this threshold value Lc are cut, in principle, the output signal from within the radius r1 from the point where the radiation is incident is used for the center of gravity calculation, and the output signal from the position away from the radius r1 or more is set to zero, and the center of gravity calculation is performed. Will not be used for. Specifically, as shown in FIG. 6, when the radiation is incident on the center point B of the photomultiplier 1a at the center of the calculation area 22, the response correction circuit 21 outputs the output value of the photomultiplier 1 in the calculation area 22. Of which the center of Photomar 1 does not include the radius r1 from point B
The output values of 1 to 1t are set to zero, and only the signals detected by the central photomaru 1a and the peripheral photomarus 1b to 1g are used for the center of gravity calculation. Further, the true region 23 where the radiation source of Photomaru 1a in the center of the calculation region 22 is located
Even when the radiation is incident on the point C at the end of, the output values of the photomarus 1i to 1o in which the center of the photomaru 1 is not included in the radius r1 from the point C among the output values of the photomaru 1 in the calculation area 22 are zero. Then, only the central photomaru 1a and the peripheral photomarus 1b to 1g and 1p to 1t are used for the center of gravity calculation. In this way, the output value from the photomultiplier 1 at the symmetrical position about the points B and C on which the radiation is incident is used for the calculation of the center of gravity to prevent the generation of degeneracy distortion. Although the threshold value Lc varies depending on the shape of the calculation area 22, the diameter of the photomultiplier 1, and the like, the optimum value can be obtained using the continuity between the calculation areas 22 on the display screen as an index. Note that the low-intensity portion of the output value of the photomultiplier 1 is usually accompanied by a noise component (noise level Ln) as shown in FIG. 7, and this noise component is also cut, so that calculation accuracy can be improved. Therefore, when the threshold value Lc is smaller than the noise level Ln, the threshold value Lc is determined as the noise level Ln.

Next, the operation and effect of the second embodiment device 20 thus constructed will be described.

An example will be described in which 19 photomultipliers 1 are used as the calculation area 22 as shown in FIG.

It is assumed that radiation enters the end C of the true area 23 of the photomultiplier 1a at the center of the calculation area 22. Similar to the apparatus 10 of the first embodiment, the calculation area selection circuit 6 finds the photomaru 1a that has detected the maximum intensity of radiation based on the output value of each photomaru 1, and as shown in FIG. The calculation area 22 is selected with 1 as a block. Further, the calculation area selection circuit 6 outputs the output value of the photomultiplier 1 in the calculation area 22 via the A / D converter 7 to the response correction circuit 21.
Output to.

The response correction circuit 21 has a calculation area 22.
The threshold value Lc or less of the output value of Photomaru 1 is cut out and output to the center of gravity calculation circuit 8. When a signal in which the response of Photomaru 1 is corrected is input to the center-of-gravity calculation circuit 8, the center-of-gravity calculation circuit 8 calculates the center-of-gravity similarly to the apparatus 10 of the first embodiment, and outputs the calculation result to the image output circuit 12. To do.
The image output circuit 12 displays at a corresponding position on the display screen of the CRT display. Therefore, as described above, the radius r1
If is selected, since the Photomaru 1 used for the center of gravity distribution is symmetrically distributed around the respective points B and C, the center of gravity calculation is also performed symmetrically with respect to the radiation incident position. .. Therefore, similar to the apparatus 10 of the first embodiment, a good image with less generation of artifacts due to the degeneracy distortion of the calculation area 22 can be obtained on the display screen of the CRT display in a single time.

The present invention is not limited to the above embodiment,
Various modifications can be made without departing from the spirit of the invention.
For example, in the device 10 of the first embodiment shown in FIG.
The D converter 7 may be connected to the subsequent stage of the center-of-gravity calculation circuit 8, and the center-of-gravity calculation circuit 8 may be configured by an analog circuit.

[0032]

According to the invention described in claim 1 described above in detail, since the degenerate distortion of the calculated value by the calculation of the center of gravity is eliminated, the position of the radiation source administered in the living body causes the occurrence of the artifact. It is possible to provide a nuclear medicine diagnostic device that has a small number of cells, a small circuit scale, and can be displayed on a display screen in a single time.

According to the second aspect of the present invention, since the calculated value having the degenerate distortion due to the calculation of the center of gravity is converted into a true value, the occurrence of the degenerate distortion of the calculated value is eliminated. Has the same effect.

Further, according to the third aspect of the present invention, a low-intensity signal having a low contribution to the calculation of the center of gravity is removed, and based on the output value from the detection element located symmetrically with respect to the true position. Since the center of gravity is calculated to prevent the generation of the degenerate distortion, the same effect as that of the first aspect can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a nuclear medicine diagnostic apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the operation of the conversion circuit of the nuclear medicine diagnostic apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing an operation of a conversion circuit of the nuclear medicine diagnostic apparatus according to the first embodiment of the present invention.

FIG. 4 is a diagram showing an operation of a conversion circuit of the nuclear medicine diagnostic device according to the first embodiment of the present invention.

FIG. 5 is a schematic block diagram of a nuclear medicine diagnosis apparatus according to a second embodiment of the present invention.

FIG. 6 is a diagram showing an operation of a response correction circuit of the nuclear medicine diagnostic apparatus according to the second embodiment of the present invention.

FIG. 7 is a diagram showing an input signal to a response correction circuit of the nuclear medicine diagnostic apparatus according to the second embodiment of the present invention.

FIG. 8 is a diagram showing an output signal of a response correction circuit of the nuclear medicine diagnostic device according to the second embodiment of the present invention.

FIG. 9 is a plan view showing an array state of Photomal.

FIG. 10 is an explanatory diagram showing the calculation of the center of gravity by the conventional nuclear medicine diagnostic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 photomaru (detection element) 8 centroid calculation circuit 9 conversion data memory (distortion elimination means) 11 conversion circuit (distortion elimination means) 10, 20 nuclear medicine diagnostic apparatus 21 response correction circuit (distortion elimination means)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuhiro Tsuda 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock company Toshiba Nasu factory

Claims (3)

[Claims] 1. A large number of detecting elements for detecting radiation, a detecting element which detects the maximum intensity of radiation among the large number of detecting elements, and a selecting means for selecting a predetermined number of detecting elements around the detecting elements, Based on the detection value output by the detection element selected by the selection means, the center of gravity calculation means for obtaining the position of the radiation source injected into the living body by the center of gravity calculation, and the position obtained by this center of gravity calculation means on the display screen. A nuclear medicine diagnostic apparatus for displaying at a corresponding position, comprising a distortion eliminating means for eliminating the degenerate distortion of the calculated value by the calculation of the center of gravity. 2. The distortion canceling means stores, in advance, a storage means for associating a calculated value by the gravity center calculation with a true value over the entire area in which the plurality of detection elements are arranged, and the gravity center calculation. The nuclear medicine diagnostic apparatus according to claim 1, further comprising: a conversion unit that converts the calculated value obtained by the unit into a true value stored in the storage unit. 3. The nuclear medicine diagnostic apparatus according to claim 1, wherein the distortion elimination means removes a predetermined value or less of the detection value output by the detection element and inputs the strength to the centroid calculation means.