JPS60144682A - Collimator for ring type ect device - Google Patents

Abstract

PURPOSE:To obtain high resolution and high sensitivity by forming the whole in a ring shape, arraying numbers of holes which extend from the inside to the outside circumferentially in specific directions, and scanning all holes stepwise within a specific angle area. CONSTITUTION:The ring type ECT device is constituted by arraying number of radiation detectors 1 at the circumference of an object in the ring shape, and arranging a ring type collimators 2 inside of them rotatably. The collimator 2 is formed in the ring shape on the whole and has numbers of radiation through holes which pierce the collimator from the inside to outside circumferentially. Each radiation through hole faces substantially in the same direction within a specific circumferential angle range, and differ in direction from a hole in another angle range. The holes are scanned stepwise over the entire angle range of at most 360 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a collimator used when a single photon is used as a radionuclide in a ring-type ECT device.

(b) Conventional ring-type ECT devices arrange a large number of radiation detectors in a ring shape around a subject, and obtain an image of the distribution of radioactive substances in the subject in a tomographic plane traversed by this ring-shaped detector ring array. However, when using a single photon as a radionuclide, it is necessary to know the direction of the radiation incident on each detector. Therefore, a collimator is required that scans so that the radiation incident angle changes little by little so that the incident angle covers the imaging area. As such a collimator, the one shown in FIG. 1 has been proposed (see Japanese Patent Application No. 163317/1982). That is, in FIG. 1, reference numeral 1 denotes each radiation detector arranged in a ring shape, and a ring-shaped collimator 2 is rotatably placed inside this ring-shaped arrangement as shown by an arrow 3. The ring-shaped collimator 2 is made up of a large number of partition plates made of radiation shielding material, and radiation enters through slits between each partition plate, thereby determining the direction of radiation incidence, and the direction in which the partition plates are arranged. In the case of Fig. 1, when the collimator 2 rotates 180 degrees, the direction of incidence on the detector l at position A changes little by little from the direction of the solid line to the direction of the dotted line, and the image is taken. The area is now scanned.

By the way, conventionally, the direction of this slit changes continuously, so when the collimator 2 continuously rotates, the direction of incidence changes continuously. Therefore, conventionally, this collimator 2 is intermittently rotated, for example, in 10° steps, and data is collected from the radiation incident on each detector 1 while the collimator 2 is stopped. Therefore, the time during which data is actually collected is only about half of the time for one scanning operation in which the collimator 2 rotates by 180 degrees, and the time during which the collimator 2 is rotating is wasted. Also,
Since the operation of rotating the collimator 2 by lθ° and stopping is repeated, the entire l scanning takes a relatively long time of 5 to 6 seconds.

These problems can be solved by continuously rotating the collimator 2 and collecting data during the entire rotation, but in this case, the incident direction changes continuously during data collection, so
Blurring occurs with respect to the direction of incidence, resulting in degraded resolution.

(C) Objective The object of the present invention is to provide a ring-type collimator for an ECT device that can perform high-resolution and highly sensitive data acquisition without causing blurring in the direction of radiation incidence even when continuously rotated.

(D) Structure The ring-type collimator for an ECT device according to the present invention is formed into a ring shape as a whole, and a large number of radiation-transmitting holes penetrating from the inside to the outside are arranged in the circumferential direction. A predetermined angular range of direction (e.g. lO
o) are formed to face substantially the same direction, and to face different directions for each angular range (that is, from other lOo), and have a range of at most 360° (such as 180° or 90°). (may be within the range of
It is designed to scan everything step by step.

(E) Embodiment The collimator 2 shown in FIG. 2 is formed so that the direction of the slit changes every 20 degrees.

In other words, within a range of 20 degrees, the slits are made to face the same direction, and when they exceed 20', they enter the adjacent 20' range and face in a different direction from the previous direction within the 200 range. It is like that.

Consider a case where this collimator 2 is continuously rotated in the direction of arrow 3 from the illustrated position. Focusing on the detector l at position A, the direction of the incident radiation is the direction a during the first 20° rotation, and does not change during this rotation. During the next 20° rotation, the direction is always b.

If the collimator 2 is continuously rotated in the range of 180' in this way, the radiation incident direction will take nine different directions from a to i every 20 degrees, and in nine steps from a to i. By using different directions, l scanning is performed within an angular range sufficient to cover the imaging area. Since the direction of radiation incidence does not change within the range of rotation by 20 degrees and remains the same, blurring in the direction of radiation incidence does not occur and resolution does not deteriorate. In this way, data can be collected while continuously rotating the collimator 2, so there is no wasted time, the sensitivity is high, and the time for l scanning due to 180' rotation is shortened.

In the above, for convenience of explanation, the angle is changed every 20 degrees, but in reality, it is changed every smaller angle (for example, 10' or less).

Also, we assumed that 180° rotation would result in 1 scanning, but 3
It is also possible to perform scanning at rotations of 60 degrees, 90 degrees, or other angle ranges.

(F) Effects With the collimator of the present invention, even if data is collected while the collimator is continuously rotated, no blurring occurs and the resolution does not deteriorate. Additionally, since data is collected during continuous rotation, there is no wasted time and the sensitivity is high. Furthermore, since it is a continuous rotation, the rotation speed can be increased and the rotation speed can be increased to 180° or 360°.
It is also possible to shorten the time required for one scanning operation by rotating the image by an angle of 90° (or an angle such as 90°).

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional example, and FIG. 2 is a schematic diagram of an embodiment of the present invention. 1...Radiation detector 2...Ring type collimator Applicant: Shimadzu Corporation

Claims (1)

[Claims] (1) It is formed into a ring shape as a whole, and a large number of radiation-transmitting holes penetrating from the inside to the outside are arranged in the circumferential direction, and each radiation-transmitting hole is substantially the same within a predetermined angular range in the circumferential direction. For ring-type ECT devices, which are formed to face different directions depending on their angular ranges, and scan everything within a predetermined angular region in a stepwise manner over a range of at most 360°. Collimator.