JP2997340B2 - Detector for positron measurement equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positron CT (pos.
itron computed tomograph
y) or PET (positron emission)
The present invention relates to a detector for a positron measurement device called "on tomography" or the like.

[0002]

2. Description of the Related Art PET is a technique in which a drug labeled with a nuclide that emits a positron (positron) is administered to a patient, and the in vivo distribution of the radionuclide is extracted as a transverse tomographic image by in vitro measurement. That is, the nuclide taken into the living body emits a positron, which loses kinetic energy in the vicinity thereof, emits a pair of gamma rays, and disappears. At this time, since the gamma rays of the pair are emitted simultaneously and in the opposite directions, the position of the nuclide can be specified by simultaneously counting the radiation of the pair with a pair of detectors.

FIG. 8 shows the concept. Cylindrical P
It is assumed that a patient exists inside the ET detector 3 and that a nuclide is administered to the patient. It is assumed that gamma rays are emitted in the opposite direction from the position P by the positron from this nuclide, and the emission direction is an azimuth angle φ from the x axis to the y axis direction and a horizontal angle θ in the z axis direction. The coordinates of this position P are (x, y, φ, θ),
This position P corresponds to the detection cell C ₁ where gamma rays are simultaneously detected,
On the line connecting the C _2. Therefore, the distribution of nuclides can be known by repeatedly detecting such gamma rays at the same time and obtaining the solution of the simultaneous equations obtained therefrom.

[0004] As a detector used in such PET technology, the following reference 1 "HIGH RESOLUTION BLOCK DE
TECHTORS FORPET ”(IEEE TRAN
SACTIONS ON NUCLEAR SCIEN
CE, Vol. 37-2 (1990)) or the following reference 2 “DEVELOPMENT OF A HIGH RE
SOLUTION PET ”(IEEE TRANSA
CTIONS ON NUCLEAR SCIENC
E, Vol. 37-2 (1990)). That is, Literature 1 shows a PET detector in which a detector combining a scintillator and a two-dimensional photomultiplier tube (2D-PMT) is arranged in a cylindrical shape, and Literature 2 shows an axial direction of the cylinder (z axis). 2) shows a PET detector capable of moving the detector in the direction (1).

[0005]

The above prior arts are all techniques for improving the detection density of gamma ray pairs by a detector, that is, for improving the sampling density of simultaneously detected data. That is, to increase the sampling density, it is possible to cope with the problem by reducing the size of the PMT and arranging it at a high density. However, this has a structural limit of the PMT. Reference 1 is 2D-P as PMT.
Although the number of detection cells is equivalently increased by using MT, this leads to an increase in cost and is not a desirable method. Further, if an attempt is made to expand the detectable range of the gamma ray pair, the PMT is increased and the detector is lengthened in the axial direction of the cylinder, but this inevitably leads to an increase in cost.

On the other hand, in Document 2, the sampling density is increased by moving the detector in the axial direction of the cylinder. However, this does not change the axial length of the detector.
The detection range of the gamma ray pair does not expand.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a detector for a positron measurement device which can increase the sampling density of a gamma ray pair, can widen the detection range of a gamma ray pair, and can reduce the cost.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a positron measurement apparatus for simultaneously counting a pair of radiations from a subject to which a positron-emitting nuclide is administered in opposite directions to each other. In a detector for a positron measurement device configured by arranging a plurality of detectors in a cylindrical shape about a predetermined axis, a plurality of detectors are arranged in a predetermined number in a predetermined axis direction to form a plurality of detector arrays. And a part of the plurality of detector arrays is moved relative to another detector array in an opposite direction along a predetermined axial direction.

[0009]

The detector according to the present invention is constituted by arranging an array of a plurality of detectors in a cylindrical shape, and since these detector arrays are separately moved in the axial direction, the number of detectors can be increased. Instead, the sampling density of the gamma ray pair can be increased, and the detection range can be widened.

[0010]

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

FIGS. 1A and 1B are perspective views showing the basic structure of a conventional PET detector and the PET detector of the present invention in comparison with each other. FIG. 1A is a conventional one, FIG. FIG. 2C shows the array of the present invention slid in the opposite direction. In FIG. 1, although not shown, each detector 1 is configured to include a scintillator and a PMT. In a conventional device, a detector ring 2 is configured by a large number of detectors 1. Then, a plurality of detector rings 2 are multi-layered in the Z-axis direction to form one PET detector 3 (shown in FIG. 1A). On the other hand, in the case of the present invention, the detector array 4 is constituted by a large number of detectors 1. Then, a plurality of detector arrays 4 in the Z-axis direction are arranged in a ring shape, and one P
An ET detector 3 is formed (shown in FIG. 3B). Here, the individual detector arrays 4 are separately movable in the Z-axis direction. Therefore, when they are moved in the opposite direction by one pitch, the state shown in FIG.

Therefore, when it is assumed that the number of the detectors 1 is not increased, according to the present invention, it is possible to simultaneously improve the sampling density and expand the detection range.
That is, in the conventional configuration shown in FIG. 1A, even if the detector ring 2 forming the PET detector 3 is moved in the Z-axis direction, the emission direction (direction of the angle θ) of the gamma ray pairs that can be simultaneously detected does not increase. This is shown in the sectional view in the Z-axis direction of the PET detector 3 shown in FIG. As shown, given the pair of detectors 1 _{11-1 13} facing the detector 1 _{21-1 23,} for example, for detection 1 _11, subject to gamma-emitting line of simultaneous detection of gamma ray pairs, in the drawing A,
In the conventional configuration shown in FIG. 1A, since the plurality of detector rings 2 similarly move in the Z-axis, the angles θ _a , θ _b , and θ _{c in} the detection direction do not always change.

On the other hand, in the present invention, as shown in FIG. 1 (c), the detectors 1 separately move in the Z-axis for each array, so that the detection directions obtained by a corresponding set of detectors are different. The angle θ varies. That is, before the Z-axis movement, the angles are θ _a , θ _b , and θ _c as shown in FIG. 2 (a).
As shown in (b), the detection directions are the angles θ _a1 , θ _b1 , θ _c1 , and the angles θ _a2 , θ _b2 , θ _c2 by the movement in the other direction.
Becomes Thus, the sampling density will obviously increase.

The above increase in sampling density is shown in detail in FIG. When the angle θ is set as shown in FIG. 7A and the coordinate position in the Z-axis direction is t, the sampling point when the detector 1 is fixed becomes like a black dot in FIG. . On the other hand, when the detector array 4 is individually moved in the Z-axis direction, the cross mark in FIG. When the rotation is further performed about the Z axis, a triangle mark and a square mark are newly added to the sampling points. On the other hand, if the whole is moved in the Z-axis only, only the triangular marks are added to the sampling points, so that it is clear that the present invention can greatly improve the sampling density.

According to the present invention, in addition to the above-described effects (the effect of improving the sampling density), the effect of expanding the detection range also occurs. That is, in the conventional configuration, since the detectors 1 move only integrally (Z-axis movement), the maximum value of the horizontal angle θ in the detection direction does not basically change. However, in the configuration of the present invention,
Since the detector 1 moves in the reverse direction for each detector array 4,
When the moving range is increased, the PET detector 3 becomes relatively long in the Z-axis direction, and the maximum value of the angle θ also increases.
That is, as shown in FIG. 4, the detection range can be expanded in both directions of θ.

Next, a PET apparatus according to an embodiment of the present invention will be described more specifically.

FIGS. 5A and 5B show the main configuration of the PET detector 3, wherein FIG. 5A is a plan view and FIG. 5B is a perspective view showing the relationship between one detector array 4 and a guide rail 13. .
As shown, each detector 1 has a scintillator 11 and a PM.
The detector array 4 configured by T12 and having the detectors 1 arranged in the Z-axis direction is provided in a ring shape to configure the PET detector 3. And each detector array 4
Are guide rails 13 provided between the detector arrays 4
, And can be individually moved in the Z-axis direction.

FIG. 6 schematically shows the individual movement in the Z-axis direction in this embodiment. Multiple guide rails 13
Are provided in parallel with the Z-axis, and a detector array 4 (not shown) is attached thereto (illustration in FIG. 3A). Since half of the detector arrays 4 are alternately moved in the opposite direction in the Z-axis direction, the gamma ray incident surfaces 14 of the scintillators 11 included in the detector arrays 4 are alternately moved in the opposite directions. FIG.

FIG. 7 shows the overall configuration of a PET apparatus using the PET detector of the present invention. A gantry 5 is constituted by a PET detector, a Z-axis drive mechanism, a Z-axis position sensor, etc., and its detection output is processed by a tomographic data processing unit 6 to indicate at which position the gamma ray was detected by the detector 1 at which position. The data is sent to the coincidence unit 7. In the coincidence counting unit 7, coincidence of so-called detection output is obtained in response to the simultaneous occurrence of the gamma ray pair, and data satisfying the coincidence is sent to the image reconstruction unit 8. Then, the reconstructed image is displayed on the display unit 9 such as a display. Here, the detailed configurations of the tomographic data processing unit 6, the coincidence counting unit 7, and the image reconstructing unit 8 are the same as those of the conventional apparatus, and thus the description is omitted.

[0020]

As described above in detail, the detector of the present invention is configured by arranging an array of a plurality of detectors in a cylindrical shape, and these detector arrays are separately moved in the axial direction. Therefore, it is possible to increase the sampling density of the gamma ray pair and increase the detection range without increasing the number of detectors. The detector of the present invention is extremely low-cost because there is no need to particularly increase expensive detectors.

[Brief description of the drawings]

FIG. 1 is a perspective view comparing a basic configuration of a detector of the present invention with a conventional detector.

FIG. 2 is a cross-sectional view in the Z-axis direction of a detector for describing improvement in sampling density according to the present invention.

3A and 3B are a sectional view in the Z-axis direction of a detector and an explanatory diagram of sampling points for explaining an improvement in sampling density according to the present invention.

FIG. 4 is a diagram showing expansion of a detection range according to the present invention.

FIG. 5 is a top view of the PET detector 3 according to the embodiment,
FIG. 3 is a perspective view of a detector array 4.

FIG. 6 is a perspective view showing the arrangement of the guide rails 13 according to the embodiment and the movement of the gamma ray incident surface of the detector array 4.

FIG. 7 shows a PET to which the PET detector of the present invention is applied.
It is a block diagram of an apparatus.

FIG. 8 is a diagram illustrating a principle of detecting a gamma ray pair by a positron.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Detector 2 ... Detector ring 3 ... PET detector 4 ... Detector array 5 ... Gantry 6 ... Tomographic data processing part 7 ... Simultaneous counting part 8 ... Image reconstruction part 11 ... Scintillator 12 ... PMT (photomultiplier tube)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-79880 (JP, A) JP-A-2-167488 (JP, A) JP-A-63-238487 (JP, A) 181385 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/161 G01T 1/20

Claims (2)

(57) [Claims] 1. A positron measurement apparatus for simultaneously counting a pair of radiations from a subject to which a positron-emitting nuclide has been administered in opposite directions to each other. In a detector for a positron measurement device configured to be arranged in a cylindrical shape with a center at a center, the plurality of detectors are arranged in a predetermined number in the predetermined axial direction to form a plurality of detector arrays, A detector for a positron measurement apparatus, wherein a part of a plurality of detector arrays is moved relative to another detector array in an opposite direction along the predetermined axial direction. 2. The detector according to claim 1, wherein half of the plurality of detector arrays are alternately moved in opposite directions.