JPH0543426Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention is used in the field of measuring distribution images of radioisotopes (RI).

This invention relates to a γ camera correction circuit, and for details
When RI is administered to a subject, the γ released from the subject
This invention relates to a position calculation correction circuit for a scintillation camera or a γ camera, which can obtain an RI distribution image by making a beam incident on a detector consisting of a scintillator, a photomultiplier tube, etc.

[Prior Art] Unger type scintillation cameras are currently commonly used as RI image measuring devices.

As shown in FIG. 3, when gamma (γ) ray photons emitted from a target organ cause a scintillator 12 to emit light through a collimator 10, some photomultiplier tubes (PMTs) 14 in the vicinity of the scintillator 12 emit light. , a pulse signal with a wave height corresponding to each mutual position is obtained.

This signal is passed through a position calculation circuit 16 using a resistance matrix, etc., to obtain X and Y signals that have voltages corresponding to the position of the light emitting point, and guide them to the CRT 22.
On the other hand, energy is created by adding the outputs of all the photomultiplier tubes 14, and the energy is selected by the pulse height analyzer 18. This is outputted from the brightness modulation circuit 20 as a CRT brightness signal, which corresponds to the γ-ray incident position on the CRT 22. A spot appears.

By accumulating a large number of spots over a certain period of time, a distribution image of RI drugs in the body can be obtained.

[Problems to be Solved by the Invention] In this manner, the conventional Anger type camera calculates a position signal by arranging a plurality of photomultipliers (photomultiplier tubes) and adding their outputs.

Scintillation occurs in response to input of one gamma ray, and the nearest photomultiplier tube and the surrounding photomultiplier tubes receive light emission input, and these output signals are combined to calculate one position signal.

By the way, for γ-rays input to the peripheral part of the photomultiplier tube within the field of view, the photomultiplier tube that should be involved in position calculation is missing because it is outside the field of view, causing distortion in the calculation result.

An object of the present invention is to provide a gamma camera correction circuit that can correct distortion of peripheral images within the field of view.

[Means for Solving the Problems] The above object is to provide a scintillator, a plurality of photomultiplier tubes arranged on the back surface of the scintillator to input scintillation light from the scintillator, and a plurality of photomultiplier tubes that input scintillation light from the scintillator using the outputs of these photomultiplier tubes. In a scintillation camera or gamma camera that has a position calculation circuit that calculates the position of the light emitting point, a virtual photomultiplier tube is set outside the field of view and the virtual setting is performed according to the output of the photomultiplier tube around the field of view. This is achieved by interposing a calculation correction circuit that calculates the output value of the photomultiplier tube and correcting the position calculation.

[Operation] Scintillation is performed using out-of-field photomultiplier tubes that line up with photomultiplier tubes in the periphery of the field of view as being in the same field of view, and the output of these in-field photomultiplier tubes is A ROM in which the output of the multiplier is actually measured, an arithmetic formula is established between them, an arithmetic circuit is inserted, and the input/output relationship is written.
The position calculator is configured by:

[Embodiment] A preferred embodiment of the present invention will be described based on the drawings.

As mentioned above, the position calculation of the Unger type camera usually uses the output signals of the photomultiplier tube closest to the location where γ-ray scintillation occurs and the photomultiplier tubes in the vicinity.

As shown in FIG. 2, when focusing on the X direction, the output of each column changes as a, b, c, etc. depending on the position where scintillation occurs.

Therefore, if we assume that the energy of the gamma rays that cause scintillation is constant, in other words, only a constant energy is always used for position calculation due to energy discrimination, so in the range A and B in the range shown in Figure 2,
Considering the inputs of columns B and C, the output of column A can be roughly estimated from the outputs of columns B and C.

In other words, when the signal outputs are VA, VB, and VC, and the energy signal is Q, the following arithmetic expression holds true.

Va=Q−K(Vb+Vc) However, K is a coefficient.

FIG. 1 shows an embodiment in which an example of an arithmetic circuit based on this formula is inserted.

The rows of photomultiplier tubes 14 are B, C... (within the field of view)
exists, and only the position calculation in the X direction will be explained.

If scintillation occurs near column B,
The outputs of columns B and C are passed through the arithmetic circuit 15 using the above formula to obtain the converted output of column A, and the position is calculated based on the total signal.

Set coefficients Kb and Kc in place of coefficient K, and Va=Q
-KbVb+KcVc may also be used.

Note that when the signal sum of column C becomes larger than the signal sum of column B, the output of column A is set to 0 to prevent miscalculation.

Although the above embodiment uses a simple arithmetic circuit,
A ROM with input/output related data written through simulation is used, and a high-speed A/D converter is used before and after the ROM.
A circuit to which a converter and a D/A converter are connected may be used as the arithmetic circuit 15b.

Although the embodiment has been described for the X direction, a similar arithmetic circuit is inserted for the Y direction as well.

[Effect] Corrects distortion in the peripheral field of view of the γ camera, allowing accurate linearity correction to be performed over the entire field of view.

[Brief explanation of drawings]

Fig. 1 is an exemplary diagram of an arithmetic correction circuit showing one embodiment of the present invention, Fig. 2 is a diagram of the principle of the present invention, and Fig. 3 is a γ
FIG. 3 is a block diagram of a camera. 12 is a scintillator, 14 is a photomultiplier tube, 1
5 is an arithmetic correction circuit.

Claims (1)

[Scope of utility model registration request] A scintillator having a scintillator, a plurality of photomultiplier tubes arranged on the back surface of the scintillator to input scintillation light from the scintillator, and a position calculation circuit that calculates the position of a light emitting point in the scintillator based on the output of these photomultiplier tubes. In a camera or a γ camera, an arithmetic correction circuit is provided that sets a virtual photomultiplier tube outside the field of view and calculates the output value of the virtually set photomultiplier tube according to the output of the photomultiplier tube in the periphery within the field of view. γ, characterized in that the position calculation is corrected by interposition.
Camera correction circuit.