JPS6239943B2 - - Google Patents

Description

[Detailed description of the invention] By detecting the radiation (in most cases gamma rays) emitted from a radioisotope (RI) injected into the body of a subject (for example, a patient) outside the body of the subject, the radiation isotope is determined. A scintillation camera (also called a gamma camera, etc.) is a device that images the distribution of elements as a two-dimensional image and provides it for diagnosis.
The image does not have information about the depth direction, but
In recent years, similar to X-ray CT (computer tomography) equipment, detectors have been
RI-CT devices are beginning to become popular, in which a computer or the like performs image reconstruction using a computer or the like based on a large number of image information for each angle by rotating the object, thereby obtaining, for example, a tomographic image perpendicular to the body axis. RI-CT can be divided into RI-CT-specific devices that have a dedicated detector, and general-purpose devices that use a conventional scintillation camera detector and add a rotation mechanism to it.
The latter is characterized in that it can also be used as a conventional scintillation camera, and the present invention relates to this type of general-purpose RI-CT device.

Figure 1 shows an overview of a general-purpose RI-CT system that uses a scintillation camera detector. This first
The one shown in the figure is a one-detector type, which requires the detector to be rotated 360 degrees around the subject in order to obtain an RI-CT image. There is a detector type, and RI-
CT images can be obtained.

In FIG. 1, a gantry 2 supported by a pedestal 1 can rotate 360 degrees in the direction of arrow A in the figure with respect to the pedestal 1. The lifter 3 is supported by the gantry 2 so that it can slide toward or away from the center of rotation of the gantry 2, which is indicated by arrow B in the figure, and this movement causes rotation of the surface of the detector 4. Determine the radius. The radius of rotation of the surface of the detector 4 must be such that the detector 4 does not hit the subject, but
From the viewpoint of resolution etc., it is desirable to place the detector 4 as close as possible to the subject. It is sufficient for the detector 4 to be capable of these two movements as an RI-CT device, but in order to use it as a conventional scintillation camera, in addition to the above, an arm 5 supporting the detector 4 is required. The lifter 3 supporting the arm 5 can be rotated ±90 degrees in the direction of arrow C in the figure, and the detector 4 can be rotated 180 degrees in the direction of arrow D with respect to the arm 5. . Furthermore, the top plate 7 of the bed 6 on which the subject is placed can be moved in the longitudinal direction indicated by arrow E in the figure while the subject is placed thereon, thereby obtaining an RI-CT image. It can be used to image any tomographic plane in any case. When capturing RI-CT images, the subject must be reliably located within the imaging area (if there is a part that protrudes outside the imaging area, image reconstruction becomes difficult, and the quality of the reconstructed image may be affected by the (It is desirable to position the specimen as centrally as possible in the imaging field of view.) Therefore, at least in the width direction of the top plate 7, which corresponds to the body width (generally larger than the body thickness) of the specimen in normal cases, It is necessary to align the central axis (axis along the longitudinal direction) of the top plate 7 with the rotational center position of the gantry 2. (There is some margin in the vertical direction, that is, in the body thickness direction, and the center position in the body thickness direction is not determined by the top plate position due to individual differences among subjects, so the vertical direction does not necessarily have to match.) Normally, when used as a scintillation camera, the top plate can be moved in the width direction to expand the field of view.

Figure 2 shows subject 8 when taking an RI-CT image.
and the positional relationship of the detector 4 (FIG. 1 is a view of the gantry 2 rotated 90 degrees counterclockwise and viewed from above). Generally, in this RI-CT imaging, a parallel porous collimator 9 whose hole axis direction is perpendicular to the detector 4 surface is used, so as shown in the figure, the rotation angle of the detector 4 with respect to the arm 5 is 0°, The rotation angle of should also be 0°.

As shown in Fig. 3, the effective field of view E1 of a conventional scintillation camera detector is generally circular, but when trying to obtain an RI-CT image, a square or rectangular area E2 is formed in the center as shown in the figure. is set electrically, and a reconstructed RI-CT image is obtained using only the radiation detection data in that area.

By the way, in contrast to the circular field of view of a scintillation camera, the outer diameter of the outer circumferential surface OS of the detector 4 is quite large due to the lead shield and the like. When used as a normal scintillation camera, by effectively utilizing the rotation of the detector 4 and the rotation of the arm 5, images of the head can be taken with the detector 4 in close contact with the subject. However, when obtaining an RI-CT image, the rotation angle of the detector 4 and arm 5 is limited to 0° as shown in Fig. 2.
In particular, it is difficult to make it fit closely against the head. That is, when photographing the head, if the detector 4 is brought too close, the subject's shoulders will hit, and the detection surface of the detector 4 cannot be brought closer to the rotation center axis of the gantry 2 than the shoulder width of the subject. The biggest drawback of the conventional RI-CT apparatus using a scintillation camera is that the detector 4 cannot be brought into close contact with the subject's head in such head photography. As already mentioned, the shorter the distance between the detector 4 and the subject 8, the better the resolution of the obtained tomographic image, and if the distance is long, only a low-resolution tomographic image will be obtained.

For this reason, conventionally, as shown in FIG. 4, in head photography, the detection area for RI-CT is shifted and the position of the subject 8 in the body axis direction (the above-mentioned E direction) with respect to the detector 4 is determined as shown in E3. An attempt is made to move the detector 4 as close as possible to the head of the subject 8 by moving it as far away as possible, but this is hardly effective in photographing the base of the brain, etc., apart from the top of the head.

The present invention has been made against the background of the above circumstances. For example, in head tomography, it is possible to place a detector sufficiently close to the head of a subject to take an image, and the detector is attached to the subject's head such as the head. RI makes it possible to efficiently detect radiation even in areas that are difficult to approach, and to obtain high-resolution, high-precision reconstructed tomographic images.
- The purpose is to provide CT equipment.

A feature of the present invention for achieving this purpose is that imaging is performed using an inclined parallel multi-hole collimator, in which the hole axis direction is inclined with respect to an axis perpendicular to the detector surface, that is, a so-called slant-hole collimator. The slant hole collimator is used to tilt the detector surface with respect to the axis of rotation so that the detector surface can be brought sufficiently close to the object without coming into contact with the object. It consists in making it possible to do.

An embodiment of the present invention will be described below with reference to the drawings.

The collimator used here is a parallel multi-hole collimator, but it is not the non-tilted type that has the hole axis perpendicular to the detector plane, which is commonly used in the past. It is a so-called slant hole collimator 10 which is inclined by an angle. In this case, it is desirable to prepare a plurality of types of slant hole collimators having different inclination angles as the slant hole collimator 10. Conventionally, when photographing the heart with a scintillation camera, a dedicated slant hole collimator has been used to photograph the heart from the left oblique position, but this may also be used as the slant hole collimator 10. This slant hole collimator 10,
The detector 4 is tilted at an angle θ° with respect to the arm 5 so that the axial direction of the collimator hole is perpendicular to the rotation center axis of the gantry 2. Lifter 3 of arm 5
The angle is 0° as in FIGS. 1 and 2. The gantry 2 that supports the detector 4 arranged in this manner is rotated, and as in FIG. A tomographic image perpendicular to the body axis of the patient is captured. In this case, in order to obtain a tomographic image, the detected data cannot be processed as is using a reconstruction algorithm when using a conventional non-tilted parallel hole collimator. Therefore, the detected data in this case is converted by software processing into data equivalent to the corresponding data in the case of a conventional non-tilted parallel porous collimator. This conversion processing software can be configured by modifying general coordinate axis conversion processing. of course,
When using the plurality of types of slant hole collimators 10 described above, it is necessary to prepare conversion software so that conversion processing can be performed according to each inclination angle.

In this way, as is clear from FIG. 5, by tilting the detector 4 at an angle of θ°, the detector 4 can be brought close enough to the subject's head to almost come into close contact with the subject's head without hitting the subject's shoulders. Gantry 2 can be rotated. Therefore, high-quality RI is possible even in areas where it is difficult to approach the detector 4, such as the head.
CT images can be obtained.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with moderate modifications within the scope without changing the gist thereof.

For example, if a rotary encoder is installed on the rotating support part of the detector 4 to enable angle detection, the inclination angle of the slant hole can be automatically detected under the control of the central processing unit (CPU). It becomes possible to control the inclination angle of the vessel 4. Of course, means for converting data obtained when using a slant hole collimator into data equivalent to data obtained using a non-inclined parallel multi-hole collimator may be configured by hardware instead of software.
Alternatively, an image reconstruction algorithm exclusively for the slant hole collimator may be separately created and equipped.

As detailed above, according to the present invention, it is possible to efficiently detect radiation even in areas where it is difficult to bring a detector close to the subject, such as the head, and to obtain highly accurate reconstructed tomographic images with good resolution. RI-CT equipment can be provided.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the general configuration of a general-purpose RI-CT device using a scintillation camera detector, Figures 2 to 4 are diagrams for explaining problems with conventional equipment, and Figure 5 is FIG. 1 is a diagram for explaining one embodiment of the present invention. 1... Frame, 2... Gantry, 3... Lifter, 4... Detector, 5... Arm, 6... Bed, 7... Top plate, 10...
Inclined parallel porous collimator.

Claims (1)

[Claims] 1. Detecting radiation emitted from a radioactive isotope administered to a subject from multiple directions around the subject using a scintillation camera detector for each directional component,
In an RI-CT device that obtains radiation isotope distribution information on a virtual tomographic plane of a subject through image reconstruction processing based on these detection information, it is attached to the entrance surface of the scintillation camera detector and detects radiation other than incident radiation from a specific direction. As a collimator for removing the radiation of Image reconstruction processing when radiation detection information from multiple directions of a subject is obtained by rotating the scintillation camera detector while tilting the collimator so that the hole axis direction is perpendicular to the rotation axis As a reconstruction means for the tilted type, when using a normal non-tilted parallel hole collimator, the detection data when using the tilted parallel hole collimator is used as a processing means using the reconstruction algorithm when using the corresponding non-tilted parallel hole collimator. An RI-CT device characterized by having a configuration equipped with a data conversion function that converts and provides time data. 2. The tilted type reconstruction means according to claim 1, wherein the configuration corresponds to multiple types of tilted parallel porous collimators having different tilt angles.
RI-CT device.