JPS6135515B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scanning device for a positron emission CT apparatus.

Various scanning methods and detector arrangement methods have been proposed for positron emission CT devices to improve sampling density. Among these, the one in which the detector ring is wobbled is advantageous because the sampling density can be increased even with a small number of detectors. In addition,
The wobbling refers to an operation in which each center point of a large number of detectors arranged in a ring revolves on an arc of a predetermined radius (usually smaller than the detector spacing).

An object of the present invention is to obtain a scanning device for a positron emission CT device having a novel mechanism for wobbling of a radiation detector.

In the scanning device of the present invention, two supporting members having tracks of different diameters are arranged at positions that are not concentric with each other, and a plurality of rolling elements are arranged between the supporting members so as to maintain the displacement and contact both tracks. Disposed and fixed in relative position, a detector ring is mounted on one of the support members with the center of the array coincident with the center of the track.
Furthermore, if the rolling elements are rotated between the inner and outer tracks without changing their mutual positions, the radius of the detector ring attached to the support member is the distance between the centers of the tracks of both support members. It can be made to revolve on the circumference, that is, it can be made to wobble. In this way, the wobbling of the detector ring can be made with an extremely simple structure, and since the constituent elements are cylindrical, processing and assembly accuracy can be easily maintained.

Each rolling element may be a single roller, two coaxial rollers each contacting a track of the support member, or three rollers arranged in a triangle, one roller It is also possible to have two rollers in contact with the track of the support member supporting the detector ring and the remaining roller in contact with the other support member, or conversely, with two rollers in contact with the track of the support member supporting the detector ring and one roller in contact with the other support member. They may be disposed between the support members so as to contact respective tracks of the support members. The relative positioning of the rolling elements can be achieved by attaching the rolling elements to a third unitary member independent of the support member.

In the present invention, the roller shafts constituting each rolling element
Detector ring when the rolling elements are rotated by changing the distance between them, or by changing the mounting position of the rolling elements of the above member that connects the rolling elements to keep the mutual distance constant. The diameter of the center locus (diameter of wobbling motion) can be set arbitrarily.

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

In FIG. 1, 11 is a detector ring, 12, 13
denotes a support member, and 14, 15, and 16 denote rolling elements, respectively. The detector ring 11 supports a plurality of radiation detectors by supporting members 12 at regular intervals along one circumference.
and is fixed to the support member. The support member 112 is itself ring-shaped and has a circular track 17 formed on its outer circumferential surface concentrically with the center of the detector arrangement circle. On the other hand, the support member 13 is also ring-shaped, and a circular track 18 is provided on its inner peripheral surface. Track 18 is track 17
has a larger diameter. The support member 12 is arranged inside the support member 13 together with the detector ring. However, the centers 0 and 0' of the tracks of these support members are displaced from each other. The rolling elements are, for example, a pair of coaxially arranged rollers 21,
It consists of 22. Each set of rollers is arranged between eccentrically arranged tracks of the support member, with rollers 21 located on the outer surface track 1 of support member 12.
7 and the roller 22 is brought into contact with the inner track 18 of the support member 13. Each set of rollers is rotatably attached to an arm 23 fixed to a ring 24 having a gear cut on its outer periphery, and the relative positional relationship is fixed.

The support member 13 is held on a base (not shown) or the like so that its center is a fixed point 0'.

An electric motor 25 is installed on this base, and a gear 26 is fixed to its rotating shaft. This gear is meshed with the gear of the ring 24 and allows the support member 13 to be rotated about its center 0' by the electric motor. As the support member 13 rotates, the rolling element rotates around its axis and moves together with the support member 13 around the center 0'. Therefore, the support member 12 that supports the detection ring rotates around the center 0 on the rolling element, and at the same time revolves around a circle C whose radius is the distance between the centers 0 and 0' of the track of the support member. become. In other words, the detector ring is caused to wobble.

The subject is placed inside the support member 12 so that its cross section to be measured coincides with the plane on which the radiation detectors are arranged. As the detector ring wobbles, a pair of opposing radiation detectors detects gamma rays generated by the annihilation of positrons from radioisotopes distributed in the cross section of the object. Each detector is connected to several opposing radiation detectors by a coincidence circuit, and when a pair of opposing detectors detects gamma rays, a signal is output from the coincidence circuit. This signal is input to an image reconstruction device that constitutes a positron emission CT device together with this scanning device, and a cross-sectional image of the subject as a radioisotope distribution image is reconstructed.

Each rolling element may be composed of three rollers 31, 32, and 33, as shown in FIG. The three rollers are rotatably attached to a support plate 34, and the support plate has a pin 3 at the tip of an arm 35.
It is supported so that it can rotate around 6. Three sets of such rolling elements are arranged between the track 18 of the support member 12 and the track 19 of the support member 13, with the roller 31 of each set of support rollers being on the track 18 and the rollers 32 and 33 being on the track 19. The center of rotation 0 of the support member 12 and the center of rotation 0' of the support member 13 are shifted from each other. FIG. 3 shows still another configuration of the rolling element. This rolling element consists of three rollers.
The two rollers 42 and 43 are attached to a support plate 44, and an arm 45 fixed to the ring 24
It is attached by pin 46 to. Another roller 41 has its axis connected to two arms 47, 4.
7'. On the other hand, rollers 42,4
Arms 48 and 48' are rotatably attached to the shafts 3 and 3, respectively. The ends of the arms 48, 48' are threaded shafts, and the arms 47, 4
At the end of 7', there is a threaded shaft having a thread opposite to that of the arms 47, 47'. Nut members 49, 49'
It has a screw hole that corresponds to each screw,
Arms 47 and 49 and arms 47' and 49' are connected, respectively. Three sets of such support rollers, rollers 42 and 43 facing the track 19?
rollers 41 are arranged facing the track 18;
Rotation of the nut members 49, 49' brings them into contact with the respective tracks. Such a support roller allows the detector ring to change the size of the circle C shown in FIG. 1 by turning the nut members 49, 49'. Note that the size of the circle C can be changed by changing the length of the arm supporting each rolling element, or by changing the length of the arm supporting each rolling element and the support member 1.
This can also be done by changing the attachment point for 3.

As described above, the scanning device of the present invention not only allows the detector ring to wobble, but also has an extremely simple structure and can easily maintain the precision of the components.

[Brief explanation of the drawing]

The drawings show one embodiment of the scanning device of the present invention, and FIG. 1 is an explanatory diagram showing its configuration, and FIGS. 2 and 3 are explanatory diagrams showing other configurations of the rolling elements. 11...Detector ring, 12, 13...Support member, 1
4, 15, 16... Support roller, 18, 19... Track, 0, 0'... Center. 〓〓〓〓〓

Claims (1)

[Claims] 1. Two support members having tracks with different diameters and disposed with the centers of the tracks displaced;
a plurality of rolling elements arranged between the support members so as to maintain the displacement and come into contact with both tracks, and supported by the outer support member while maintaining a mutual relative positional relationship; and the inner support member. A detector ring is attached so that the center of the detector array coincides with the center of the track of the member, and by rotating the outer support member, the detector ring is moved between the centers of both tracks via the rolling element. 1. A scanning device for a positron emission CT device, comprising: a drive means for revolving on a circumference having a distance as a radius.