JPS6271882A - Positioning device for junction type scintillator - Google Patents

Abstract

PURPOSE:To remove the influence of the reflection of light on a junction surface by comparing outputs of photoelectric transducers nearby the junction surface of the scintillator, and shifting the scintillator in position and using outputs of photoelectric transducers distant from the junction surface when there is discontinuance between the outputs. CONSTITUTION:Scintillators 11 and 12 are joined on the junction surface 13 and numbers of photomultipliers (PMT) 1, 2... are provided on the reverse across a light guide 15. Output signals S3-S6 of the PMTs 3-6 closest to the junction surface 13 are compared by a comparing circuit 22 to decide discontinuance when S3<S4>S5 or when S4<S5>S6, so that the scintillators are moved in a direction determined by a value (S6-S3)/(S6+S3). Consequently, outputs of PMTs nearby the junction surface are excluded and an output signal of scintillation which is not affected by the reflection of light on the junction surface is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a light emitting positioning device for a scintillator such as a gamma camera, which is a radionuclear medicine diagnostic device, and particularly in the vicinity of a joint of a joint type scintillator in which a plurality of scintillators are joined. The present invention relates to a positioning device.

Conventionally, as a light emitting positioning device for a conventional scintillator (for example, NaI), a position calculation device known as the Anger method has been mainly used (for example, Japanese Patent Application Laid-Open No. 70680/1983). .

That is, when a large number of PMTs (photo multipliers) 1, 2, . , S2, . . . according to the position X, position information in the X direction can be obtained.

However, as shown in the 31st Δ, the problem that the invention attempts to solve is that the scintillary lake 1
, 12 are not integral but of a joined type, it is difficult to accurately position them near the joint surface 13.

This is because total reflection occurs at the bonding surface 13.

Nal's 1/nitillator 1,! When joining 2, a silicone plate 14 is actually used as shown in FIG.

The L thickness is approximately $0, 1mm. The refractive index of these is 733 for Nal and 15 for silicone grease.
In addition, total reflection of light occurs at the interface with the non-contact crystal 14, causing a problem.

Experimentally, a radiation source was placed near this joint surface I3, and
When the output 54 of the PMT 4 closest to the junction 513 was observed by moving it in the direction shown in FIG. 5, data as shown in FIG. 5 was obtained. Here, W is PMT, 2. In this χ experiment, a PMT with a diameter of 53111 mm is used. The photoelectric peak is at its highest at the center of f'MT4, and gradually decreases as it deviates from that position, which is the same as usual; however, in the vicinity of the bonding surface 13, it is affected by reflection at the bonding surface 13. Joint surface ■3 position (O position 'f!
1) When moving from the negative side (left side) to the positive direction (right side), reflected light also enters, so the amount of light j-2 that enters the PMT 4 increases, and when it is around 10 mm from the 0 position to the negative side, You can see the excitement. And joint surface 13 (0th place,
T! i) On the right side, PMT due to reflection at the joint surface 13
Since the light incident on 4 becomes extremely small, it becomes low. In the vicinity of the bonding surface 13, two peaks are observed.

In this way, if there is a ridge at any position 10 mm from the joint surface 13, it is impossible to determine one position from the output s4 of the PMT 4. Therefore, in this experimental example, positioning cannot be performed within ±10 mm of the joint surface 13 (20 mm in total).

In the case of a normal scintillation camera, the scintillator can be formed into a flat plate shape, so there is not much need to join multiple scintillators in this way, but in a ring type ECT device for single photons or positrons, , since the scintillator must be formed into a ring shape,
Since it is difficult to manufacture an integrated type, a joint type is inevitable, and defects at such joint surfaces are a serious problem.

Therefore, in this invention, the PMT output near the bonded surface (which is affected by C reflection) is not used for positioning, and the It is an object of the present invention to provide a positioning device & that can eliminate this problem at the joint surface and perform accurate positioning in the vicinity of the joint surface by using the FMT output.

Means to Solve the Problem In the positioning device according to the present invention, the outputs of the photoelectric conversion means near the joint surface of the scintillator are compared (by comparison, it is determined that light emission has occurred near the joint surface). means for selecting the output of the photoelectric conversion means located away from the bonding surface based on the output of the comparison means; , a positioning calculation means for performing a positioning calculation on the selected light "i:" using the relationship read from the storage means when the output of the conversion means is sent.

The action comparison means determines that one light emitting position is near the bonding surface. When it is determined in this way, the output of the photoelectric conversion means close to the bonding surface is excluded, and only the output of the photoelectric conversion means distant from the bonding surface is selected.

First, the storage means stores in advance the relationship between the light emitting position and the output of the converting means for the light leaving the joint surface.

Therefore, when it is determined that the light emitting position is near the bonding surface as shown in -1L, the relationship stored in the storage means is read out, and the light emitting position is calculated from the output of the photoelectric conversion means located away from the bonding surface. can do.

Here, since the position calculation is performed using the position of the photoelectric conversion means which is away from the bonding surface and is not affected by reflection on the bonding surface, accurate positioning calculations in the vicinity of the bonding surface are possible.

In Example 2F, Figure 1, the scintillators 1 and 12 are joined at the joint surface i3, and a large number of PFs, ITl, 2,... are arranged on the back surface of the scintillators through the IDO 5. There is. Each output SL, S2,... of PMTl, 2,...
are outputted through A/D conversion n21, respectively. This P
The arrangement direction of MTl, 2, . . . is X, the PMT closest to the joint 13 is PMT 4.5, and the diameter of each PMT is W. This closest PMT4゜5 and the PMT next to I~ra
Output S3゜S4, S5, S6 of MT3.6 is comparator circuit 2
Sent to 2.

The comparison circuit 22 compares these outputs and determines that light emission has occurred in the range of ±W from the bonding surface 13 when S3<54>55 or S4<S5>S6, producing its output and opening gate 23.24, P
MT3.6 output S3. Pass S6. This output S
3. S6 is sent to the arithmetic circuit 25, where the calculation (S6-53)/(S6+33) is performed. This calculation result is calculated by the position calculation circuit 26.
The position information is sent to , the position is calculated, and position information X is obtained.

Here, if it is determined that the range is within ±W from the junction 13, the output S4 of the PMT4.5 closest to the junction 13
, S5 is excluded and the output S3 of the adjacent PMT3.6 is
Output S4 of C PMT4.5 using S6
, S5 are affected by the total reflection of light at the bonding surface 13, but the adjacent PMT3.6 is far from the bonding portion 13 and is therefore hardly affected by this. (36
-53)/(S6+33), a graph like the one shown in FIG. 2 is obtained. In this way, the joint surface is discontinuous at [S6-S3], but the position in the X direction and (S6-S3
)/(S6+S3) corresponds to l:1.

Therefore, if the relationship in FIG. 2 is investigated in advance and stored in the ROM 27, and the stored contents are read out and the position calculation circuit 2G performs the position calculation, (S6-
The position in the X direction is uniquely determined from the value of S3)/(S6+S3).

In addition, when it is out of the range of the soil W from the joint surface 13, the position is determined by weighting calculation using the normal Anger method without excluding a specific PMT output as in the above.

Effects of the Invention According to the positioning device for a bonded scintillator of the present invention, accurate positioning in the vicinity of the bonded surface of the scintillator is possible without being affected by light reflection on the bonded surface of the scintillator.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between the position and the value of (S6-S3)/(S6+S3), and Fig. 3 shows the problems of the conventional example. Explain 7;
FIG. 4 is an enlarged cross-sectional view of the vicinity of the junction of the scintillator, and FIG. 5 is a graph showing the characteristics of the output of the PMT near the junction surface. 1 to 8...PMT 1, +2...Scintillator 13...Joint surface 14...Silicon grease 15...Light kite 21...A/D converter 22...Comparison circuit 23.24 ...Gate 25...Arithmetic circuit 26...Position 21 Calculation circuit 27...ROM

Claims (1)

[Claims] (1) Comparison means for determining that light emission has occurred near the junction surface by comparing the output of the photoelectric conversion means near the junction surface of the scintillator, and a comparison means for determining that light emission has occurred near the junction surface by comparing the output of the photoelectric conversion means near the junction surface of the scintillator, and a comparison means for determining that light emission has occurred near the junction surface, and a a means for selecting an output; a storage means in which a relationship of a light emitting position with respect to the selected output of the photoelectric conversion means is stored in advance; and a relationship read from the storage means from the output of the selected photoelectric conversion means. 1. A positioning device for a bonded scintillator, comprising: a positioning calculation means for performing positioning calculations using a positioning calculation means.