JPS6044633B2 - scintillation camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a scintillation camera used in nuclear medicine diagnosis, and particularly to an improvement in its position calculation circuit.

A so-called anchor-type scintillation camera is constructed as shown in FIG. 1, and includes a plurality of photomultiplier tubes (hereinafter referred to as "photomultipliers") 2-1, 2-2 optically coupled to a scintillator 1. The output signals of , . . . pass through preamplifiers 3-1, 3-, .
The weights are weighted in correspondence to the geometrical position coordinates of each photomul 2-1, 2-2, . . . .

This weighted signal is, for example, in Cartesian coordinates,
They are added by adding circuits 5-X and 5-Y in each of the X and Y directions,
The outputs of these adder circuits 5-X and 5-Y are equally weighted for each potomaru and summed by the adder circuit 5-Z.
The signal is divided by the dividers 6)-X and 6-Y as a divisor, respectively, and the result is 1 corresponding to the incident position of the incident gamma ray.
These position signals serve as position signals for displaying points on the display screen, and these position signals, together with an unblank signal generated by the brightness signal circuit 7 based on the Z signal, are transmitted to a CRT (cathode ray tube).
For example, a bright spot is displayed corresponding to the incident position of the gamma ray. The portion of the resistance matrix 4 mentioned above will be described in more detail.
As shown in FIG. 2, the output signal of the preamplifier 3-1 corresponding to a certain photomultiplier 2-1 is passed through resistors corresponding to + and 1 in the X and Y directions, that is, X (
+), X(-), Y(+), and Y(-), respectively, with four types of resistances R(X+)I, R(X-)I, R
(Y+)I, R(Y-)i to the addition (amplification) circuit 5-X(+) etc. for each direction as position information, and at the same time the Z signal is transmitted through predetermined resistors R and Z for the Z signal. The energy information is transmitted to the adder (amplification) circuit 5-Z as energy information. Here, if we extract only the X (+) and
The signals are amplified by a preamplifier 3-1 and added in the X(+) direction by an adder circuit 5-X(+) in the (+) direction via a resistor R(X+)1. The X(-) direction is added by the X(-) direction adding circuit 5-X(-) via the resistor R(X-)1. Similarly, Photomaru 2-
2. The signal passing through the preamplifier 3-2 is also connected to the resistor R(X+)2.
, R(X-)2. At this time, the resistances R(X+)1, (X-)1, R(X+)2, R(
The value of X-)2,... is photomar2-1,2-2,...
The resistance value is determined in accordance with the geometrical coordinate position of the scintillator 1 of A high degree of stability is also required. In such a conventional device, the resistance values of the elements forming the resistance matrix 4 are determined by the corresponding photomultiplies 2-1 and 2-2.
,..., extremely high precision was required in order to directly correspond to the geometric position coordinates.

The present invention was made based on these circumstances, and
To provide a scintillation camera that improves the resistance matrix and makes it possible to increase the overall accuracy compared to the resistance value accuracy of each individual resistor using a simple configuration, and facilitates high accuracy. This is what I am most concerned about.

In other words, the feature of the present invention is that the resistor matrix is configured such that the resistors are arranged in series between the input points of the input signal in the direction of the coordinate axis, and the input signal is connected to the series resistor. The purpose is to inject it into an intermediate position corresponding to the coordinate position and extract a signal in the coordinate direction from the end of the series resistor.

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

FIG. 4 is a one-dimensional illustration of one embodiment of the basic structure of the resistance matrix of the present invention, in which the same parts as in FIG. 3 are denoted by the same reference numerals.

In FIG. 4, the resistor groups connected between the adder circuits 5-X(+) and 5X(-) were in parallel rows in the conventional device, but in the present invention, each resistor R, XlR of the illustrated resistance matrix 9 ，
They are configured in series as X2, .

According to this configuration, the signals from each photomultiplier 2-1, 2-2, . . .
, . . . to adder circuit 5. -X(+), 5
Enter -X(-). The accuracy required for each resistance value in this case varies depending on the number of photomultiples (1), but it is possible to obtain a result (that is, accuracy) approximately 1/i times as high as that of the conventional device. In other words, in the subsequent stage of the resistance matrix, the position signal is obtained by calculating the difference between the outputs of the adder circuits in each direction in the same direction (for example, X(+) and X(1)), so In a conventional device that distributes weight according to position, the accuracy of weighting according to position is at the same level as the accuracy of each resistor, and if a resistor with an error of 1% is used, the weighting accuracy is also at the level of an error of 1%.

Therefore, the difference in weighting between adjacent photomars is the difference in resistance value, but the accuracy of the difference is at a level where the absolute value of the error is 1%, so the smaller the difference compared to the total resistance, the greater the relative error. increases. For this reason, as mentioned above, extremely high-precision resistors are required. However, in the present invention, the difference in weighting between adjacent photomultiplier signals is the resistance value itself, so the relative error is the resistance value itself. This will result in an error.

In other words, the difference in weighting between adjacent photomultiplier signals is the error in the resistance values between them, and the difference in weighting levels is one order of magnitude more accurate (in first approximation) than the conventional device. It will improve. In addition, each preamplifier 3-1,
The outputs of the preamplifiers 3-2, . . . are connected, but empirically it is desirable to insert resistors Rl, R2, . This embodiment is actually expanded to two dimensions in the X direction and the Y direction as shown in FIG. 5 for practical use.

In other words, in the same figure, 2-, 1, 1, 2-1, 2,...
・ is a photomultiplier, 3-, 1, 1, 3-, 1, 2, ... is a preamplifier, 5-X (+), 5-Y (+) is an adder circuit, and resistance matrix 9 is a resistor. R,l,lRl,2,・
・,R,X,ll,R,X,l2,...,R,Y,ll
, R, Y, l2, . However, in the figure, there is a thick line where the end of the matrix in each direction is input to the adder circuit, but this conceptually means that there is an input to be added, so this thick line does not necessarily indicate the electrical This does not mean a short circuit. As detailed above, according to the present invention, the resistance matrix is improved and the overall accuracy can be made higher than the resistance value accuracy of each individual resistor using a simple configuration. It is possible to provide a scintillation camera that can easily achieve high precision.

Note that the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications without changing the gist thereof. For example, instead of configuring the resistance matrix 9 in the X and Y directions as individual resistors, it can also be configured as continuous resistors such as planar or cotton-like resistors. For example, the 6th
As shown in the figure, a sheet resistor RS is used, and this sheet resistor R
Output signal electrodes for the adder circuit in the X and Y directions are attached around S. Each photomal 2-, 1, 1, 2-, 1, 2,...
The signals of are sent to the preamplifiers 3-, 1, 1, 3-, 1,
2, . . . and then injected into each electrode P of the sheet resistor RS. The process in which the injected signals enter the adder circuits 5-X(+), etc. in each direction and calculate the differences to create a position signal is the same as described above. Furthermore, when using the above-mentioned sheet resistor RS, if the signal injection point to the sheet resistor RS is not a fixed electrode but a contact whose contact position is variable and the resistance value can be adjusted, higher accuracy can be obtained. can do.

Furthermore, in the example using the above-mentioned sheet resistor RS, in order to correct the signal injection amount in each direction to the sheet resistor RS as shown in FIGS. An island (land) L, a ring, a line segment, etc. may be formed using an insulator, or the shape and dimensions of the electrode P itself may be adjusted as appropriate, such as by forming the electrode P into a circular electrode D.

In this case, a nonconductor portion or the like may be formed as appropriate by etching or the like.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an example of a scintillation camera, and FIGS. 2 and 3 are circuit configuration diagrams illustrating the configuration of a resistance matrix in a conventional device.
FIG. 4 is a circuit configuration diagram for explaining the configuration of one embodiment of the present invention, FIG. 5 is a circuit configuration diagram showing the configuration of the same embodiment in actual use, and FIG. 6 is another embodiment of the present invention. FIGS. 7a and 7b, which are block diagrams showing the configuration of an example, are diagrams for explaining the configurations of other different embodiments of the present invention. 2-1 to 2-12-, 1, 1, 2-, 1, 2,... photomultiplier tube (photomultiplier), 3-1 to 3-i; 3-, 1, 1
, 3-, 1, 2,... preamplifier, 9... resistance matrix, R1 to Ri; R, l, l, R, l, 2...
...;R,X,l〜R,X,noi;R,X,ll,R,
X, l2... ・;R, Y, ll, R, Y, l2, ・
・Resistance, RS... Planar resistor, 5-X(+), 5-
X(-), 5-Y(+)...addition circuit.

Claims (1)

[Scope of Claims] 1. A scintillator that emits light due to incident radiation, a plurality of photoelectric conversion elements that are provided corresponding to the scintillator and that detect the light emission and convert it into an electrical signal, and a signal that is obtained by the photoelectric conversion element. On the other hand, there is a resistance matrix that performs weighting corresponding to the coordinate position, an adder that adds the signals output from this resistance matrix for each coordinate axis, and the output of this adder corresponds to the sum of the signals obtained from the photoelectric conversion element. In a scintillation camera equipped with a divider that obtains a coordinate position signal by dividing by a value, and a display device that displays a bright spot at a coordinate position according to the coordinate position signal obtained by the divider, the resistance matrix is The configuration is such that resistors are arranged in series connection in the coordinate axis direction between the input points of the input signal, and the input signal is injected into the middle position of the series resistor corresponding to the coordinate position, and the input signal is injected from the end of the series resistor. A scintillation camera that extracts signals in the coordinate direction. 2. The scintillation camera according to claim 1, wherein the resistance matrix is constructed by connecting individual resistance elements in a mesh pattern. 3. The scintillation camera according to claim 1, wherein the resistance matrix is constituted by a continuous resistor into which signals are injected at locations corresponding to coordinate positions. 4. Claim 3 constituted by a movable contact whose position of a signal injection electrode is variable with respect to a continuous resistor of a resistance matrix.
The scintillation camera described in Section 1.