JPH04142487A - Emission ct device - Google Patents

Abstract

PURPOSE:To improve the picture quality of a tomographic image by providing a collecting memory storing the data of the relative interference component of two nuclear species at the time of measurement. CONSTITUTION:The data of the radioactive ray distribution image of a nuclear species 1 are stored in the region corresponding to the rotation angle of the first collecting memory 2a, the data of the radioactive ray distribution image of a nuclear species are stored in the region corresponding to the second collecting memory 2b, and the data of the relative interference component of the above two nuclear species are stored in the region corresponding to the third collecting memory 2c. The data of radioactive ray distribution images removed with scattered components S1, S2 of the nuclear species 1 and the nuclear species 2 are stored in the first image memory 6a and the second image memory 6b respectively. Image data are read out from these image memories 6a, 6b and fed to an image data procession section 3 for image processing, the noise due to the relative interference of the radioactive ray distribution images of two nuclear species is removed, and the picture quality of a tomographic image can be improved.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention detects radiation emitted from a radioactive isotope (hereinafter abbreviated as rRIJ) administered into a subject from all directions and detects the radiation from the subject. Regarding emission CT equipment that obtains tomographic images of diagnostic parts of specimens, there are two different types of RI (
Emission C that can improve the image quality of tomographic images by removing noise caused by mutual interference of data in systems that simultaneously measure radiation distribution images of two nuclides (hereinafter referred to as "two nuclides")
Regarding the T device.

[Conventional technology]

Conventionally, an emission CT device capable of simultaneously injecting two different types of RI into a subject and measuring radiation distribution images of two nuclides at the same time has been able to simultaneously measure radiation distribution images of two nuclides, as shown in Figure 4. A scintillation camera 1 that detects emitted radiation, measures its incident position, and captures a radiation distribution image in the entire circumferential direction, and a two-system system that stores data on radiation distribution images of two nuclides measured with this scintillation camera 1. Collection memories 2a, 2b and these collection memories 2a
, and an image data processing section 3 that reconstructs an image using data from 2b.

and 1 e.g. thallium (TQ) and pyrophosphate (Tc)
The two nuclides are simultaneously administered into the body of the subject, the radiation emitted from the two nuclides distributed in the body is detected by the scintillation camera 1, and the data of the radiation distribution image from, for example, thallium is stored in the first collection memory 2a. , data of the radiation distribution image from pyrophosphoric acid is stored in the second collection memory 2b in an area corresponding to the rotation angle of the detector of the scintillation camera 1 (for example, 0@, 90', 180', 270'). At the same time, these collection memories 2a, 2
The measurement data is read from the image data processor 3, and the image data processing unit 3 reconstructs a tomographic image of the diagnostic region of the subject.

[Problem to be solved by the invention]

However, in such a conventional emission CT device, the first and second acquisition memories 2a.

Since the data of the radiation distribution image of each nuclide read from 2b was directly input to the image data processing unit 3 for processing, the image was displayed with the data of mutual interference components of the two nuclides remaining as they were. That is, as shown in Fig. 5, the energy histogram of the emitted radiation when only nuclide 1 (e.g., thallium) is administered is shown by a dashed-dotted line Q, and when only nuclide 2 (e.g., pyrophosphate) is administered, If the energy histogram of the emitted radiation becomes as shown by the two-dot chain line Q2, the energy histogram of the emitted radiation measured when the two nuclides mentioned above are administered at the same time becomes as shown by the solid line Q. In the case of simultaneous measurement of these two nuclides, the noise component N due to scattering etc. is on the low level part, and due to mutual interference between the energy peak P1 of nuclide 1 and the energy peak P2 of nuclide 2, the valley between them is originally data Even though this is a place where there is not much of a nuclides, as shown with diagonal lines in Figure 5, the valley is filled in state A, and data of the mutual interference component of the two nuclides mentioned above is generated. There is.

Furthermore, the peak values P□ and P2 of each nuclide are also higher than the actual values.

Therefore, in the processing of the image data processing section 3.

The above-mentioned scattering component (N) and mutual interference component (A) will be mixed in as noise, and the image quality will deteriorate when observing a tomographic image of an organ, and the original organ information will be obscured, making it difficult to see the image of the organ. It was something. In addition, since the data count is increased by the above-mentioned scattering component (N) and mutual interference component (A), when quantifying in the image data processing unit 3, there is a risk of misjudgment of the event due to quantification. . For these reasons, the diagnostic performance of the device may be reduced.

Therefore, an object of the present invention is to provide an emission CT apparatus that can solve such problems and improve the image quality of tomographic images by removing noise caused by mutual interference between radiation distribution images of two nuclides. do.

[Means to solve the problem]

In order to achieve the above object, an emission CT apparatus according to the present invention detects radiation emitted from a radioisotope administered into a subject and determines its incident position I! A scintillation camera that measures radiation distribution images in all circumferential directions, two collection memories that store data on the radiation distribution images of two nuclides measured with this scintillation camera, and data from these collection memories. In an emission CT apparatus having an image data processing unit that reconstructs an image using the image data, another acquisition memory is provided in parallel with the two systems of acquisition memory to store data of mutual interference components of two nuclides during measurement, Means for subtracting mutual interference component data from the data of the radiation distribution images of the two nuclides from the two systems of collection memories is provided, and storage means are provided for storing the data of the subtraction results.

[For production] The emission CT device configured in this way.

Data of mutual interference components of radiation distribution images of two nuclides measured with a scintillation camera are stored using another collection memory installed in parallel with the two collection memories, and the data of the two nuclides from the two collection memories are stored using data subtraction means. Subtract the mutual interference component data from the radiation distribution image data,
The storage means operates to store the data of the subtraction results from the data subtraction means. By processing the data read from the storage means in the image data processing section, it is possible to remove noise caused by mutual interference between the radiation distribution images of the two nuclides and improve the image quality of the tomographic image.

〔Example〕

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

FIG. 1 is a block diagram showing an embodiment of an emission CT apparatus according to the present invention. This emission CT device is
The radiation emitted from the RI of two nuclides administered into the subject is simultaneously detected from all directions to obtain a tomographic image of the diagnostic site of the subject. As shown in the figure, a scintillation camera 1, It has first and second acquisition memories 2a, 2b, and an image data processing section 3, and further includes a third acquisition memory 2c, subtracters 4a to 4d and 5a to 5d,
and a second image memory 6a, 6b.

The scintillation camera 1 detects radiation emitted from R1 administered into a subject (not shown), for example, γ rays, measures the incident position, and captures a radiation distribution image in the entire circumferential direction of the subject. Something.

Although not shown, a plurality of detectors are arranged around the opening into which the subject is inserted, facing each other and surrounding the subject.

The first and second collection memories 2a and 2b respectively store data of radiation distribution images of two nuclides, for example, thallium and pyrophosphate, measured by the scintillation camera 1. The second collection memory 2b stores data on the radiation distribution image from nuclide 1 (thallium), and the second collection memory 2b stores data on the radiation distribution image from nuclide 2 (pyrophosphoric acid). The first and second acquisition memories 2a and 2b are configured to capture data at angles 1, for example, O@, 90'', 180°, 270° while rotating the detector of the scintillation camera 1.
It is divided into four storage areas corresponding to rotation angles of .degree., and radiation distribution image data collected at each rotation angle is stored in the corresponding areas.

The image data processing section 3 reconstructs an image and obtains a tomographic image using the data read out from the first and second acquisition memories 2a and 2b. It has a central processing unit (CPU) 7.

Here, in one aspect of the present invention, a third collection memory 2c is provided in parallel with the first and second collection memories 2a and 2b, and subtractors 4a to 4d and 5a to 5a are provided on the output side thereof.
5d, and second and second image memories 6a and 6b are provided at the subsequent stage.

The third collection memory 2c stores 2
It stores data on mutual interference components for RI of nuclides, and similarly to the first and second collection memories 2a and 2b, the rotation angle of the detector of the scintillation camera 1 (for example, 0°, 90°, 180°, 270°), and the data of the mutual interference component during measurement at each rotation angle is stored in the corresponding area. And this third collection memory 2C
A multiplier 8 is provided at the subsequent stage. This multiplier 8
is to multiply the mutual interference component data of two nuclides for each rotation angle output from the third collection memory 2C by a preset coefficient according to the ratio of nuclide 1 and nuclide 2. The multiplication results are distributed and sent to subtracters 4a to 4d on the first collection memory 2a side and subtractors 5a to 5d on the second collection memory 2b side, which will be described later. That is, the mutual interference component (A) shown in FIG. 5 includes a scattered component S1 of nuclide 1 and a scattered component S2 of nuclide 2, as shown in FIG. Therefore, using a phantom as a subject, we measure in advance the ratio at which each of the scattered components S1 and S2 appear, and from this we determine the distribution coefficient to be multiplied by the multiplier 8. The distribution coefficient may be set in advance, and the operation of setting the distribution coefficient is controlled by the CPU 7 in the image data processing section 3.

Further, the subtracters 4a to 4d and 5a to 5d extract the mutual interference components output from the multiplier 8 from the data of the radiation distribution image of the two nuclides output from the first collection memory 2a or the second collection memory 2b. For example, four areas corresponding to the rotation angles of the first and second collection memories 2a and 2b are subtracted, and four areas (4a) are subtracted on the first collection memory 2a side. ~4d), four (5a~5d) are provided on the second collection memory 2b side.

Furthermore, a first and second image memory 6a.

Reference numeral 6b serves as a storage means for inputting and storing the data of the subtraction results output from the subtracters 4a to 4d and 5a to 5d, respectively.
Similar to a and 2b, it is divided into, for example, four storage areas corresponding to the rotation angle of the detector of the scintillation camera 1, and data collected and calculated at each rotation angle is stored in the corresponding area. It looks like this. The image data read from these image memories 6a and 6b is sent to the image data processing section 3.

Next, the operation of the emission CT apparatus configured as described above will be explained. First, in FIG. 1, a subject is set at a predetermined position with respect to the scintillation camera 1. Then, the test is started by administering two nuclides, R1, for example, thallium and pyrophosphate, into the body. Then, the gamma rays emitted from the RI dispersed within the subject are detected by the inspection device of the scintillation camera 1, and the
.

Position signals in two directions are collected by the first to third collection memories 2a.

2b and 2c. At this time, the data of the radiation distribution image from nuclide 1 is stored in the first collection memory 2a, and the data of the radiation distribution image from nuclide 2 is stored in the second collection memory 2b.
Then, the data of mutual interference components of nuclide 1 and nuclide 2 are respectively stored in the third collection memory 2c. In this state, the detector of the scintillation camera 1 is
Rotate by 0 degrees, 0°, 90°, 180', 27
Radiation distribution images of two nuclides are measured at each of four rotation angle positions of 0°.

As a result, the data of the radiation distribution image of nuclide 1 is stored in the area corresponding to each rotation angle of the first acquisition memory 2a, and the data of the radiation distribution image of nuclide 2 is stored in the area corresponding to each rotation angle of the first acquisition memory 2a. Furthermore, the data of the mutual interference component of the two nuclides is stored in the corresponding area of the third collection memory 2c.

At this time, in the energy histogram shown by the solid line Ω in FIG. 2, the first collection memory 2a stores data in the range of energy window W of nuclide 1, and the second collection memory 2b stores data in the range of energy window W2 of nuclide 2. The third collection memory 2c collects the data of the energy window W of the mutual interference component.
The data in the range of j is stored respectively.

Next, the data of the radiation distribution images of the two nuclides read out from the first and second collection memories 2a and 2b are processed by the first set of subtractors 4a to 4d or the second set of subtractors 5a to 5a, respectively.
5d. At the same time, the third collection memory 2
The mutual interference component data for the RI of the two nuclides read from c is input to the multiplier 8 and multiplied by a preset partition coefficient, resulting in the scattered component $1 of the nuclide 1 shown in FIG.
and the scattered component S of nuclide 2. Then, the scattered component S of the nuclide 1 is sent to the second set of subtractors 58 to 5d, and the scattered component S2 of the nuclide 2 is sent to the first set of subtractors 4a to 4d.
sent to.

Then, the first set of subtractors 4a to 4d respectively calculate (W knee S,) for each rotation angle data, and the second set of subtractors 5a to 5d similarly calculate (W, -3 engineering). ) calculations are performed respectively. As a result, as shown in Fig. 3, in the energy window W process for nuclide 1, the scattered component S2 of nuclide 2 is removed from the energy histogram before the calculation in (a), and the energy window after the calculation in (b) is It becomes a histogram.

Similarly, although not shown, in the energy window W2 of nuclide 2, the scattered component S□ of nuclide 1 is removed.

Next, in this way, the scattered components S, S of nuclide 1 and nuclide 2 are
The data of the radiation distribution image from which 2 has been removed are stored in the first image memory 6a and the second image memory 6b, respectively. After that, these image memories 6a, 6
Image data is read out from b and sent to the one-image data processing section 3 where the image is reconstructed, and the tomographic image is displayed on a display section not shown.

Although FIG. 1 shows a case in which the detector of the scintillation camera 1 is rotated, for example, by 90 degrees and radiation distribution images are measured at four rotational angle positions, the present invention is not limited to this. Measurements may be made at the following or five or more rotation angle positions. In this case, the areas or numbers of the first to third collection memories 28 to 2c, subtracters, and first and second image memories 6a and 6b will be increased or decreased as appropriate. Furthermore, measurement of radiation distribution images can be similarly applied to normal static acquisition or dynamic acquisition.

〔Effect of the invention〕

Since the present invention is configured as described above, data of mutual interference components of radiation distribution images of two nuclides measured by the scintillation camera 1 can be collected using the other collection memory 2c provided in parallel with the two collection memories 2a and 2b. The mutual interference component data can be subtracted from the radiation distribution image data of the two nuclides from the two collection memories 2a and 2b using the data subtraction means (4a to 4d, 5a to 5d).

The storage means (6a, 6b) respectively store the data of the subtraction results from the data subtraction means (4a to 4d, 5a to 5d), and the storage means (6a, 6b
) is processed by the image data processing unit 3, noise caused by mutual interference between the radiation distribution images of the two nuclides can be removed, and the image quality of the tomographic image can be improved. Therefore, it is possible to prevent the original organ information from being obscured and to clearly display the image of the organ. Further, since unnecessary data counts such as noise components are reduced, it is possible to prevent erroneous event judgments during quantification in the image data processing section 3. For these reasons, the diagnostic performance of the emission CT apparatus can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the emission CT apparatus according to the present invention, FIG. 2 is an energy histogram for explaining the operating principle of the present invention, and FIG. 3 is for explaining the state in which mutual interference component data is subtracted. FIG. 4 is a block diagram showing a conventional emission CT apparatus, and FIG. 5 is an energy histogram for explaining the influence of data on mutual interference components of two nuclides in a conventional example. 1... Scintillation camera, 2a-2C...
Collection memory, 3... Image data processing section, 4a~
4d, 5a to 5d - subtractor, 6a, 6b - image memory, 7... CPU, 8... multiplier.

Claims (1)

[Claims] A scintillation camera that detects radiation emitted from a radioactive isotope administered into a subject, measures its incident position, and captures a radiation distribution image in all circumferential directions, and the radiation distribution of two nuclides measured with this scintillation camera. In an emission CT device that has two systems of acquisition memories that store image data and an image data processing unit that reconstructs images using data from these acquisition memories, measurement is performed in parallel with the two systems of acquisition memories. In addition to providing another collection memory for storing data on the mutual interference components of the two nuclides at the time, means are provided for subtracting the data on the mutual interference components from the data of the radiation distribution images of the two nuclides from the two systems of collection memories. , and storage means for respectively storing data of the subtraction results.