SU685005A1 - Preliminary amplifying device for scintillation gamma-chamber - Google Patents

Description

(54) PRE-AMPLIFIED BLOCK FOR SCINTILLATION GAMMA-CAMERA

one

This invention relates to a medical diagnostic technique, and is intended to pre-process signals from scintillating gamma cameras.

A scintillation gamma camera is a sophisticated radioisotope diagnostic device and serves to visualize the distribution in the object of a radioactive indicator introduced for diagnostic purposes.

Lime gamma camera, which contains a detecting unit that includes a disc-shaped scintillation crystal and a fiber located on it. A multitude of photomultipliers (PMTs) with preamplifiers, each of which is mounted on a photomultiplier tube, are installed on the light guide. In addition, the detecting unit contains a coordinate matrix and summing amplifiers C.

Closest to the proposed pre-amplification block for a scintilla gamma camera, which contains a photomultiplier, a lamp panel mounted on it with a signal output and a preamplifier,

located in the vicinity of the lamp panel 2).

Gamma quanta emitted by the object under study are transformed by a scintillation crystal into a light flash, the photomultiplier tubes located in the immediate vicinity of the flash point produce electrical pulses whose amplitude is proportional to the gamma photon energy and the solid angle at which the photomultiplier sees the light

flash The pulse from the signal output of the PMT is fed through the signal contact of the lamp panel to the preamplifier input. The contacts of the lamp panel, in addition to the signal, are supplied with the voltage of the power of the photomultiplier, which serves to set the operating mode for direct current to all the dynodes of the photomultiplier; From the outputs of all preamplifiers, signals are fed to the inputs of the coordinate matrix. In the coordinate matrix of the signal

Each PMT is assigned a weighting factor according to the location of that PMT. From the output of the coordinate matrix to the inputs of summing amplifiers are fed

X-X + Y-Y signals, corresponding to the coordination and energy of the registered gammaquant, and a signal equal to the sum of the signals from all the preamplifiers, characterizing the gamma-quantum energy.

The disadvantage of this gamma camera is the noise immunity of the preamplifier input circuits. The contacts of the lamp panel (as already mentioned) are supplied with a high supply voltage. The random and volumetric leakage currents across the lamp panel, which are random in nature, create electrical interference that is amplified by the preamplifier and coded along with the useful signal in the coordinate matrix. Thus, false information arises related to the specificity of processing input signals in scintillation gamma cameras , reducing the reliability of diagnosis.

The purpose of the invention is to increase the reliability of diagnostic information by eliminating the influence of electrical noise and leakage currents on the lamp panel on the input signal.

This goal is achieved by the fact that in the pre-amplification unit for a scam gamma camera containing a photoelectric multiplier (PMT), a lamp panel mounted on it with a signal output and a preamplifier located in the immediate vicinity of the lamp panel, the signal output of the lamp panel is in the form of two coxially arranged tubes separated by a dielectric bushing, and the signal input of the amplifier is a coaxially arranged central pin and tube joining A circuit with a signal output from the lamp panel, with the outer tubes of both contacts grounded. All conductive parts of the contacts are made of metal with low electrical resistivity.

The drawing shows a pre-amplification unit consisting of a photomultiplier and a preamplifier.

The pre-amplification unit contains a photomultiplier 1, a lamp panel 2 mounted on it, an amplifier 3 located in the immediate vicinity of the lamp panel on the columns 4. A resistor divider 5 is located on the contact lugs of the panel (indicated conventionally in the drawing). The signal output of the lamp panel is two coaxial tr} bki 6 and 7, separated by a dielectric sleeve 8. Reliable electric 850054

 A coherent contact is achieved due to the dimensions of pin 9 and the elasticity of the central tube 6. The signal input of the amplifier is a centrally located pin 10 and the tube 11 connected to the signal output of the lamp panel. The outer tubes of both contacts are grounded. All conductive parts are made of low resistivity metal.

In the process of operation, the signal from output 9 of the PMT 2 is fed to the signal input 10 of amplifier 3 via tube 6. The outer tubes 7, 11 and dielectric sleeve 8 reliably isolate the output of the PMT or high-voltage voltage

j power present on other panels.

The proposed design of the pre-amplification unit allows to reliably shield the signal input of the amplifier from external interference, as well as to eliminate the influence over the bone and volume leakage currents from adjacent contacts of the lamp panel. This increases the accuracy of the diagnostic information formula of the invention.

1. A preamplifier unit for scintillation gamma cameras containing a photoelectric multiplier (PMT), a lamp panel mounted on it with a signal output and a preamplifier located in close proximity to the lamp panel, in order to increase the reliability of the diagnostic information By eliminating the influence of ha, the input signal of electrical noise and leakage currents on the lamp panel, the signal output of the lamp panel is made in the form of two coaxially arranged tubes, times divided by a dielectric bushing, and the signal input of the amplifier is

A coaxially located 1 stub and tube connected to the signal output of the lamp panel, with the outer tubes of both contacts eazem.

2. The pre-amplification unit of claim 1, which is distinguished by the fact that all conductive parts are made of material

with low electrical resistivity.

Sources of information taken into account in the examination

1. US Patent (f 3983394, CL 250-369, published 1972.

2. US patent number 3683180, cl. 950-71.5, publ. 1976.

Claims (2)

SUMMARY OF THE INVENTION ²⁵ 1. Preamplifier unit for a gamma-ray scintillation camera, comprising a photomultiplier (PMT), a lamp panel with a signal output mounted on it, and a preamplifier ³⁰ located in the immediate vicinity of the lamp panel, characterized in that, for the purpose of increasing the reliability of diagnostic information by eliminating the influence of the input signal of electrical noise and leakage currents through the lamp panel, the signal output of the lamp panel is made in the form of two coaxially memory location tubes separated by a dielectric sleeve, and the signal input of the amplifier is 40 coaxially located central pin and tube, interfaced with the signal output of the lamp panel, and the outer tubes of both contacts are grounded. 2. Block pre-amplification lo π. 1, 45 characterized in that all the conductive parts are made of a material with low electrical resistivity.