JPH10160849A - Nuclear medicine diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute an image pick-up in various modes and the collection and correction of absorption correction data in real time in parallel by combining the position relationship between two main detectors and a semiconductor detector that can be rotated around a subject. SOLUTION: Main detectors 3 and 9 and reference line ray sources 4 and 10 that rotate while they are shifted by approximately 90 deg. and 270 deg. in rotary direction for them are provided at stands 2 and 11 and the surrounding of a specimen on a bed 1 is rotated, thus detecting gamma rays from dosed isotope. Also, a line semiconductor detector 5 that can be rotated is provided opposite to a line ray source 4 at the stand 2. By combining the position relationship of the main detectors 3 and 9 properly, the image of the subject can be picked up in a mode such as a 2-detector opposition SPECT mode, a 90 deg. SPECT mode, and an individual mode. In parallel with the above, a series of operations from the collection of the detection data by a line semiconductor detector 5 and absorption correction data in each mode to the execution of absorption correction can be performed in real time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nuclear medicine diagnostic apparatus for detecting gamma rays emitted from a radioisotope administered to a subject and imaging the distribution of the radioisotope in the body.

[0002]

2. Description of the Related Art A nuclear medicine diagnostic apparatus detects a single gamma ray when a radioisotope decays using a single photon nuclide, and obtains a two-dimensional gamma ray accumulated image based on the detected data. Using a single photon camera and emitting a pair of gamma rays in the opposite direction when the positron is annihilated using a positron nuclide,
It is classified into a positron camera characterized in that a two-dimensional gamma ray accumulated image is obtained by specifying an emission place.

In recent years, gamma rays have been repeatedly detected at a plurality of angles while rotating the detector around the subject, and a tomographic imaging technique (ECT (emission) for reconstructing a tomographic image based on the obtained data. compu
ted trophy)) has been commercialized.
This ETC is a single photon ECT (SPECT)
And positron ECT (PET).

In the conventional scintillation, a photomultiplier tube is two-dimensionally and densely arranged via a light guide on a scintillator (single crystal of NaI) which gives gamma rays to light, as typified by an Anger type camera. The location of the gamma ray is calculated from each output signal by weight addition calculation. Since the photomultiplier tube is used as the photoelectric conversion element, the detector has an extremely thick structure, and a dead space in which the position cannot be calculated is located at the outermost periphery of the photomultiplier tube. Is generated, and the detector becomes an extremely large area for the effective visual field. When the lead shield and collimator on the periphery and back are inserted, it becomes a very large detector, and even if this detector is set according to the purpose of collection, control is added to the degree of freedom and the means for realizing the operation is Since it is extremely mechanically difficult and the detector is as heavy as several hundred kg, there is a case where the image is saved due to the mechanical distortion from the ideal operation. In addition, since the distance from the effective visual field end to the physical end face of the detector is large, and the detector is thick, the cardiac SPEC is increased.
At the time of T, it is necessary to raise the arm greatly to the head side, and there is a problem that the subject is distressed and the cerebellum does not enter in the head SPECT.

Conventionally, when performing SPECT of the heart, the subject holds his or her arms for at least 10 minutes during data acquisition (imaging), for example, in order to avoid interference with a very large Anger-type detector. It was necessary to keep raising it greatly toward the head, which was very painful for the subject.

Further, even when the absorption correction is performed in the two-detector system, the inherent absorption correction in each of the two-detector facing photographing mode, the 90 ° SPECT photographing mode, and the one-detector photographing mode due to the limitation of the gantry mechanism. The method had to be applied, and it was impossible to achieve absorption correction in all shooting modes. In addition, specific methods of absorption correction include the line source scanning method and the plane source method. With the current Anger-type scintillation camera, the absorption correction must be performed simultaneously without reducing the sensitivity of normal SPECT acquisition. Was not possible due to detector performance limitations.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to image a subject in various modes by freely combining the positional relationship of two detectors, and to perform absorption correction from collection of absorption correction data in each mode. It is an object of the present invention to provide a nuclear medicine diagnostic apparatus capable of performing the above operations in real time in parallel with imaging.

[0008]

According to the present invention, there is provided a nuclear medicine diagnostic apparatus comprising: a first stand rotatably provided; and a first stand rotatably provided around the subject by the first stand. A main detector and the first stand substantially 90 ° in the rotational direction with respect to the first main detector.
A first reference source provided in a displaced state, a semiconductor detector provided in a state facing the first reference source by the first stand, and a second detector provided in a freely movable manner. A stand, a second main detector rotatably provided around the subject by the second stand, and approximately 270 in the rotational direction with respect to the second main detector by the second stand. And a second reference source provided in a shifted state.

Further, when two-detector opposed SPECT imaging is performed in a state where the first main detector and the second main detector face each other across the subject, the first reference source Is emitted from the radioisotope administered to the subject and detected by the first main detector based on the first information on gamma rays emitted from the subject and detected by the semiconductor detector through the subject. The second information about the gamma ray and the third information about the gamma ray emitted from the radioisotope and detected by the second main detector are absorption-corrected, and the absorption-corrected second information and the third information are corrected. Generating an in-vivo distribution image of the radioisotope based on the information of the first main detector and the second
90 ° SPE when the main detector is shifted by approximately 90 °
When CT imaging is performed, the second reference source based on fourth information about gamma rays emitted from the second reference source, passed through the subject, and detected by the first main detector.
And the third information is absorbed based on fifth information on gamma rays emitted from the first reference source, passed through the subject, and detected by the second main detector. The radiometric isotope distribution image is generated based on the corrected second information and the third information, and the first main detector and the second main detector perform the correction. When taking images of individually separate parts, the second information is absorption-corrected based on the first information, and the radioisotope relating to the first part is corrected based on the absorption-corrected second information. And a means for generating a biodistribution image of the radioisotope for the second site based on the third information.

According to the present invention, the subject can be imaged in various modes by freely combining the positional relationships of the two detectors, and the operation from the collection of the absorption correction data to the execution of the absorption correction in each mode is performed. And can be done in real time.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the nuclear medicine diagnostic apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of the nuclear medicine diagnostic apparatus according to the present embodiment, and FIG.
3 shows the appearance of the first and second main detectors in FIG. 1, and FIG.
FIG. 1 is a diagram showing the first and second photographing systems of FIG.
FIG. 4A shows the structure of the first imaging system of FIG. 1 viewed from the subject head side, and FIG. 4B shows the structure of the second imaging system of FIG. 1 viewed from the subject head side. Shows the structure. In FIG. 1, the structural connection is shown by a dotted line, and the electrical connection is shown by a solid line. In the present embodiment, two photographing systems are provided.

The first imaging system has a first main detector 3. The first main detector 3 may be an Anger-type detector similar to the conventional one, but is preferably a semiconductor detector as shown in FIG. The semiconductor detector includes a semiconductor element array 101 in which a plurality of semiconductor elements, such as CdZnTe, for directly converting a gamma ray into an electric signal, are arranged two-dimensionally. It comprises a collimator 102 for restricting the direction, a circuit board 103 on which a preamplifier, a lead-out circuit and the like are mounted, and a lead shield 104 for shielding unnecessary gamma rays from the back or the like.

The first main detector 3 is provided by the first stand 2 so as to be rotatable around the subject P placed on the bed 1. The first stand 2 is a bed 1
Are arranged on the floor so as to be able to travel in parallel with the long axis of the vehicle, and this travel is realized by the stand traveling mechanism 8. The stand traveling mechanism 8 is, for example, a rail 3 provided on a floor surface.
7, the bottom groove 38 of the stand frame 36 is fitted,
The stand frame 36 is configured to be electrically driven via a rack and pinion mechanism.

The first stand 2 is provided with a first reference source serving as a rod-shaped reference source in which the radiation density of gamma rays is substantially uniform in space.
While maintaining a state in which the line source 4 is shifted by approximately 90 ° with respect to the rotation direction of the first main detector 3,
Around the subject together with the first main detector 3 is provided rotatably. In the first stand 2, a line semiconductor detector 5, which is basically in the same structure as that shown in FIG. 2 and is formed in a rod shape, is maintained in a state facing the first line source 4. It is provided rotatable around the subject. In addition,
The first line source 4 and the line semiconductor detector 5 need not have a one-dimensional structure, but may have a structure having a width of, for example, 1 cm to 3 cm.

Rotation (total rotation) of the first main detector 3, the first line source 4, and the line semiconductor detector 5
Is realized by the entire rotation mechanism 6. The whole rotation mechanism 6 is configured such that, for example, a rotation ring 32 rotatably provided on a fixed ring 31 is
And a driving belt 33 for rotational driving. In addition, the first line source 4 and the line semiconductor detector 5 can slide along the body axis of the subject P while facing each other, and this is realized by the slide mechanism 7. ing.

On the other hand, the second imaging system has a second main detector 9. The structure of the second main detector 9 is the same as that of the second main detector 3 as shown in FIG. The second main detector 9 detects the object P
Is provided by the second stand 11 so as to be rotatable around. Like the first stand 2, the second stand 11 is arranged on the floor so as to be able to travel in parallel with the long axis of the bed 1, and this traveling is realized by the stand traveling mechanism 12. The stand traveling mechanism 12 includes, for example, a bottom groove 48 of a stand frame 46 on a rail 47 provided on the floor surface.
The stand frame 46 is configured to be electrically driven via a rack and pinion mechanism.

The second stand 11 is provided with a second line source 10 as a rod-shaped reference source having a radiation density of gamma rays substantially spatially uniform, similar to the first line source 4. 2 with respect to the rotation direction of the main detector 9
It is provided rotatable around the subject together with the second main detector 9 while maintaining the state shifted by 0 °. Note that, unlike the second imaging system, a line semiconductor detector is not intentionally provided in the second imaging system. Accordingly, it is possible to cope with the absorption correction without interfering with the main detectors 3 and 9 in various photographing modes as described later.
Further, the second line source 10 need not have a one-dimensional structure but may have a structure having a width of, for example, 1 cm to 3 cm.

The rotation (total rotation) of the second main detector 9 and the second line source 10 is controlled by a total rotation mechanism 13.
Has been realized. The overall rotation mechanism 6 includes, for example, a driving ring 45 and a driving belt 43 that are rotatably provided on a fixed ring 41 by an electric motor 44.
It is configured to be driven to rotate via the. In addition, the second line source 10 can slide along the body axis of the subject P.
Has been realized.

The length of each of the line semiconductor detector 5, the first line source 4, and the second line source 10 is set to 40 cm or more in consideration of the thickness of the subject P. The movable section controller 15 controls the movements of the above-described overall rotation mechanisms 6 and 13, slide mechanisms 7 and 14, and stand traveling mechanisms 8 and 12 as instructed by the operator via the console 16.

The absorption correction data calculation circuit 17 calculates absorption correction data by appropriately combining the detection data of the first main detector 3, the second main detector 9, and the line semiconductor detector 4 in accordance with the imaging mode. Absorption correction circuit 18
Calculates the number of gamma rays incident from the outputs of the first main detector 3 and the second main detector 9 for each incident position, and converts the counted data into the absorption correction data calculated by the absorption correction data calculation circuit 17. The absorption is corrected based on. The image generation processor 19 generates an in-vivo distribution image of the radioisotope administered to the subject based on the count data corrected for absorption by the absorption correction circuit 18. Display 20
Displays the body distribution image generated by the image generation processor 19. (Operation) In the shooting mode, the first mode as shown in FIGS.
The main detector 3 and the second main detector 9 of the subject P
A so-called two-detector facing SPECT mode in which gamma rays from the same site are detected while facing each other across the, and a SPECT image (cross-sectional distribution) is generated from both data, and a first mode as shown in FIGS. When the main detector 3 and the second main detector 9 are shifted from each other by approximately 90 °, gamma rays from the same part of the subject P are detected, and the SPE is detected from both data.
The so-called 90 ° SPECT mode for generating a CT image, and the first main detector 3 and the second main detector 9 individually detect gamma rays from different parts and individually respectively obtain a static image or a SPECT image (cross section). Distribution) is generated. These shooting modes will be described in order. (2 detector facing SPECT mode) 2 detector facing SPE
In the CT mode, as described above, the first main detector 3
And the second main detector 9 are set to face each other. In this mode, the second line source 10 is not used,
It is retracted to a position where it does not interfere with the first main detector 3.
In the retracted position, a storage box 2 for storing the second line source 10 so that gamma rays do not leak outside.
2 (see FIG. 9B). In some modes, the first line source 3 may not be used. At this time, the storage box 2 provided at the retreat position is not used.
1 (see FIG. 9A).

As described above, when the first main detector 3 and the second main detector 9 face each other, the first main detector 3 and the second main detector 9 are disposed between the first main detector 3 and the second main detector 9. The line source 4 and the line semiconductor detector 5 are set to face each other.

At the time of photographing, the first main detector 3 and the second main detector 3
The main detector 9 rotates intermittently while maintaining the facing state. In each period during which the entire rotation is stopped, gamma rays emitted from the radioisotope administered to the subject P are detected by the first main detector 3 and the second main detector 9, respectively. Is counted by the absorption correction circuit 18 for each incident position.

In parallel with such a shooting operation, FIG.
As shown in (a), during each of the periods in which the entire rotation is stopped, the first line source 4 and the line semiconductor detector 5 slide while being opposed to each other.
The gamma ray emitted from the device and passed through the subject P is detected by the line semiconductor detector 5, and the absorption correction data is calculated by the absorption correction data calculation circuit 17 based on the detected data.
Further, based on the absorption correction data, the absorption correction circuit 18 corrects the absorption of the count data. Based on the absorption-corrected count data, the image generation processor 19 generates a spatial distribution of radioisotopes with respect to the cross section of the subject P.

As described above, in the two-detector opposed SPECT mode, collection of absorption correction data and absorption correction are performed using the first line source 4 and the line semiconductor detector 5 in parallel with the two-detector opposed SPECT imaging. And can be performed in real time. (90 ° SPECT mode) Next, in the 90 ° SPECT mode, the first main detector 3 and the second
Of the main detector 9 are set to be shifted from each other by approximately 90 °. In this mode, since the line semiconductor detector 5 is not used, it is removed or retracted to a position where it does not interfere with the main detectors 3 and 9.

In a state where the first main detector 3 and the second main detector 9 are shifted by 90 °, the first line source 4 faces the second main detector 9 and Is set in a state facing the first main detector 3.

At the time of photographing, as in the above-described mode, the first
Of the main detector 3 and the second main detector 9 rotate intermittently while maintaining the state of being shifted by 90 °, and the radioactivity administered to the subject P during each period during which the entire rotation is stopped. Gamma rays emitted from the isotope are detected by the first main detector 3 and the second main detector 9, respectively, and the gamma rays are counted for each incident position by the absorption correction circuit 18 based on the detected data.

Further, the first line source 4 is slid during each period during which the entire rotation is stopped, as shown in FIG.
Gamma rays emitted from the first line source 4 and passing through the subject P are detected by the second main detector 9. In addition, in each period when the entire rotation is stopped, FIG.
As shown in (b), the second line source 10 is slid, and the object P emitted from the second line source 10 is
Is detected by the first main detector 3. The absorption correction data is calculated by the absorption correction data calculation circuit 17 based on the detection data detected by the main detectors 3 and 9, and the count data is corrected by the absorption correction circuit 18 based on the absorption correction data.

In this mode, the line sources 4,
Since the gamma rays from 10 and the gamma rays from the radioactive isotope administered to the subject P are detected by the same main detectors 3 and 9, there is a concern that the respective detection data may be mixed. Compared with the detector, the energy resolution is 器 or less, and the count rate characteristic is over 500 Kcps.
It is easy to select each component from the detection data by making the energy of the emitted gamma ray of the radioisotope to be administered to the subject P for T imaging different.

As described above, even in the 90 ° SPECT mode, the collection of the absorption correction data and the absorption correction can be performed in real time in parallel with the photographing. (Individual mode) In this individual mode, the first main detector 3 and the second main detector 9 individually detect gamma rays from the first part and the second part, respectively, and individually respectively form static images. Or SPECT image (cross-sectional distribution)
Generate At the time of imaging, gamma rays emitted from the radioisotope administered to the subject P are detected by the first main detector 3 and the second main detector 9, respectively, and the number of incident gamma rays is determined by the absorption correction circuit 18. Counting is performed for each incident position.

In parallel with such a shooting operation, FIG.
As shown in (a), while the first line source 4 and the line semiconductor detector 5 are slid while facing each other, gamma rays emitted from the first line source 4 and passed through the subject P are detected as line semiconductors. The absorption correction data is calculated by an absorption correction data calculation circuit 17 based on the detected data, and the first correction data is further calculated based on the absorption correction data.
The absorption correction circuit 18 corrects the absorption of the count data on the first portion detected by the main detector 3. The spatial distribution of the radioisotope for the first portion of the subject P is generated by the image generation processor 19 based on the absorption-corrected count data.

On the other hand, since the absorption correction data cannot be obtained for the second part, the count data for the second part detected by the second main detector 9 is used as it is without performing the absorption correction. And the second of the subject P
For the generation of the spatial distribution of radioisotopes at the site.

As described above, in the individual mode, collection of absorption correction data and absorption correction can be performed in real time for the first imaging system in parallel with imaging. For the second imaging system, the absorption correction cannot be performed. However, for example, since the absorption rate of the head is relatively uniform, the second imaging system is assigned to the head imaging and accurate absorption correction is performed. For example, it is possible to use the first imaging system for necessary heart imaging.

As described above, according to the present embodiment, the subject can be imaged in various modes by freely combining the positional relationships of the two detectors, and in each mode, from the collection of the absorption correction data to the execution of the absorption correction. Work can be performed in real time in parallel with shooting. The present invention is not limited to the embodiments described above, and can be implemented with various modifications.

[0034]

According to the present invention, the subject can be imaged in various modes by freely combining the positional relationship between the two detectors.
In addition, in each mode, work from collection of absorption correction data to execution of absorption correction can be performed in real time in parallel with imaging.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a nuclear medicine diagnostic apparatus according to one embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic structure of a main detector of FIG. 1;

FIG. 3 is a diagram showing a structure of first and second imaging systems in FIG. 1 as viewed from a side of a subject.

FIG. 4 is a diagram showing a structure of first and second imaging systems in FIG. 1 as viewed from a subject head side.

FIG. 5 shows first and second detectors in a two-detector facing SPECT mode.
FIG. 2 is a diagram showing the positional relationship of the imaging systems viewed from the side of the subject.

FIG. 6 shows the first and second detectors in the two-detector facing SPECT mode.
FIG. 2 is a diagram showing the positional relationship of the imaging systems viewed from the subject head side.

FIG. 7 is a diagram showing a positional relationship between first and second imaging systems in a 90 ° SPECT mode as viewed from a side of a subject;

FIG. 8 is a diagram showing a positional relationship between first and second imaging systems in a 90 ° SPECT mode as viewed from a subject head side.

FIG. 9 is a view showing slides of first and second line sources.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... bed, 2 ... 1st stand, 3 ... 1st main detector, 4 ... 1st line source, 5 ... line semiconductor detector, 6 ... whole rotation mechanism, 7 ... slide mechanism, 8 ... stand Traveling mechanism, 9: second main detector, 10: second line source, 11: second stand, 12: stand traveling mechanism, 13: overall rotation mechanism, 14: slide mechanism, 15: movable section controller Reference numeral 16: console, 17: absorption correction data calculation circuit, 18: absorption correction circuit, 19: image generation processor, 20: display.

Claims (4)

[Claims] A first stand rotatably provided; a first main detector rotatably provided around the subject by the first stand; and a first main detector provided by the first stand. A first reference source provided at a position shifted from the main detector by about 90 ° in the rotation direction, and a first reference source provided by the first stand so as to face the first reference source. A semiconductor detector, a second stand rotatably provided, a second main detector rotatably provided around the subject by the second stand, and a second main detector provided by the second stand. A second reference line source provided at a position shifted by about 270 ° in the rotation direction with respect to the second main detector. 2. When two-detector opposed SPECT imaging is performed in a state where the first main detector and the second main detector face each other across the subject, the first reference ray source is used. Is emitted from the radioisotope administered to the subject and detected by the first main detector based on the first information on gamma rays emitted from the subject and detected by the semiconductor detector through the subject. The second information about the gamma ray and the third information about the gamma ray emitted from the radioisotope and detected by the second main detector are absorption-corrected, and the absorption-corrected second information and the third information are corrected. And generating a body distribution image of the radioisotope based on the information of the first main detector and the second main detector in a state where the first main detector and the second main detector are shifted from each other by approximately 90 °.
When imaging is performed, the second information is absorbed and corrected based on fourth information on gamma rays emitted from the second reference source, passed through the subject, and detected by the first main detector. The third information is absorbed and corrected based on fifth information relating to gamma rays emitted from the first reference source, passed through the subject, and detected by the second main detector. A body distribution image of the radioisotope is generated based on the corrected second information and the third information, and the first main detector and the second main detector are individually separated. When performing shooting, the first
Absorption correction of the second information is performed based on the information of the above, a radioisotope distribution image of the radioactive isotope relating to the first site is generated based on the absorption-corrected second information, and the third information is generated. The nuclear medicine diagnostic apparatus according to claim 1, further comprising: a unit that generates an image of the radioisotope distribution in the body based on the second site. 3. The apparatus according to claim 1, further comprising: means for sliding the semiconductor detector and the first reference source along the body axis direction of the subject while maintaining the facing state. A nuclear medicine diagnostic apparatus according to claim 1. 4. The nuclear medicine diagnostic apparatus according to claim 1, wherein each of the semiconductor detector, the first reference source, and the second reference source has a length of 40 cm or more.