JPH0684988B2 - Bed absorption correction device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention belongs to the field of nuclear medicine, and more particularly to a device for correcting radiation absorption in a bed.

[Prior art]

Radiation absorption by the bed can be a problem in nuclear medicine measurements. Especially, SPECT (Single Photon Emiss
Ion Computed Tomography) detects γ-rays from RI (radioisotope) inside the human body outside the human body, collects projection data in each direction, and backprojects this projection data to detect RI within the human body. Although it is to reconstruct the concentration distribution image, in order to collect projection data in each direction, it is necessary to collect data from the lower part of the patient lying on the bed, so the γ-rays emitted from the patient's body Is greatly absorbed in this bed. When the measurement is performed from the bottom of the bed in this way, several tens of percent may be absorbed, resulting in a large loss of count, which adversely affects the image. Therefore, conventionally, measures have been taken such as forming the bed from a material that absorbs less, and making the cross-sectional shape into an arc shape so as to reduce the absorption width.

[Problems to be Solved by the Invention] However, since the bed has to perform the original function of mounting a patient, it is necessary to have a strength sufficient to support an appropriate weight. Even if the material, shape, etc. are devised, the problem of absorption cannot be fundamentally solved. SUMMARY OF THE INVENTION It is an object of the present invention to provide a bed absorption correction device that adds an operation of correcting the absorption of a bed to collected data.

[Means for solving problems]

A bed absorption correction device according to the present invention includes a storage unit that stores a cross-sectional shape of a bed, a unit that detects the position of the bed, and a cross-sectional shape at a slice position read from the storage unit by this position detection signal. And a correction means for correcting the projection data in the projection direction based on the absorption body distribution in the projection direction.

[Action]

Since the shape of the bed does not change, the cross-sectional shape at each position of the bed to be used is obtained in advance and stored. If the position of the bed is known, the position to be sliced by a detector such as a gamma camera can be known, and the sectional shape at that position can be read from this memory. Further, the material of the bed is known in advance, that is, the absorptivity is known, and is generally formed of a uniform material. Therefore, if the projection direction is determined, the distribution of the absorber in that direction can be obtained. Therefore, absorption of the projection data in that direction by the bed can be corrected by the absorber distribution in this direction.

【Example】

In FIG. 1, the bed position detector 11 detects the relative position of the bed 2 with respect to the gamma camera 3 (see second). The subject (patient) 1 is laid on the bed 2 and SP
The bed 2 is moved back and forth, left and right, and up and down according to the part to be ECT-photographed. Gamma camera 3 is arm 4
And is rotated by a rotation drive mechanism housed in the gantry 5. When the bed 2 is moved, its relative position with respect to the gantry 5 makes it possible to know the slice plane on which the gamma camera 3 collects data and a tomographic image is taken. In the memory 12, the cross-sectional shape of the bed 2 is stored in advance for each position. For this, a design drawing at the time of manufacturing the bed 2 is used, or a cross-sectional shape is measured by an X-ray CT apparatus. Once stored, the shape of the bed 2 does not change unless the bed 2 is replaced, so there is no need to input the shape again. Since the position of the bed 2 can be changed depending on the part to be imaged, the position of the bed 2 is detected each time an image is taken, the position signal is sent to the memory 12, and the signal is stored in the memory 12.
The cross-sectional shape data at the position of the slice plane for the current imaging is read out. That is, the cross-sectional shape of the bed 2 as shown by the diagonal lines in FIG. 3 is read out and sent to the arithmetic circuit 13. On the other hand, the camera angle detector 14 detects the angle of the gamma camera 14 from the drive mechanism in the gantry 5 and sends the angle signal to the arithmetic circuit 13. Since the cross-sectional shape of the bed 2 and the projection direction are input as shown in FIG. 3, the arithmetic circuit 13 can calculate the absorber distribution of the bed 2 projected in that direction. That is, since the material of the bed 2 is known, the nuclide used is also known, and the energy of the γ-ray is known, the absorption coefficient can be obtained. When the gamma camera 3 is at an angle as shown in FIG. 3, if the projection data of the γ-ray emitted from the subject 1 is collected, the γ-ray is absorbed by the bed 2 before reaching the gamma camera 3. Therefore, the collected data will include the effect of the absorption. Therefore, the correction device 15 corrects the projection data in the direction in which the gamma camera 3 is facing, based on the absorber distribution data obtained as described above, and the influence of bed absorption can be removed. Therefore, when the gamma camera 3 rotates around the subject 1 and collects projection data in various projection directions,
Each time the projection data in each direction is collected, the correction device 15
Since the bed absorption correction is performed by the method to remove the influence of the bed absorption, this data can be sent to the image reconstructing device 16, so that an image of excellent image quality without the influence of the bed absorption can be reconstructed. In addition, not only the SPECT data as described above, but also bed absorption correction can be performed on data in general nuclear medicine imaging using a scintillation camera.

【The invention's effect】

According to the bed absorption correction device of the present invention, the collected data can be corrected so as to remove the influence of absorption by the bed, and the image such as SPECT can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a perspective view, and FIG. 3 is a schematic diagram for explaining projection in a certain angle direction. 1 ... Subject, 2 ... Bed, 3 ... Gamma camera, 4
…… Arm, 5 …… Gantry, 11 …… Bed position detector, 12 …… Memory, 13 …… Computation circuit, 14 …… Camera angle detector, 15 …… Correction device, 16 …… Image reconstruction device.

Claims (1)

[Claims] 1. A storage unit for storing the cross-sectional shape of a bed, a unit for detecting the position of the bed, and a projection focusing on the cross-sectional shape at the slice position read from the storage unit by the position detection signal. A bed absorption correction device having a calculation means for obtaining an absorber distribution in the projection direction according to the direction and a correction means for correcting projection data in the projection direction based on the absorber distribution in the projection direction.