JPS5948669A - Apparatus for adjusting sensitivity of detector of ect apparatus - Google Patents

Abstract

PURPOSE:To enable automatic sensitivity adjustment so as to accommodate the sensitivity irregularity of a detector within a certain range, by respectively setting the windows of a plurality of single channel analysers. CONSTITUTION:Uniform radiation sources are placed to the central parts of detectors 1 and radiation with a same energy spectrum is uniformly incident to each detector 1 while signal change-over is performed by multiplexers 3, 4. The sensitivity shift between the detectors 1 is discriminated from the mutual relation of the output pulse calculation values of single channel analysers 2 connected to the detectors 1. CPU8 calculates the shift amount of the window of each analyser 2 compensated in the sensitivity irregularity of each detector 1 and the window width compensated in the irregularity of energy decomposing capacity while each energy window setting device 11 is controlled on the basis of the calculated values through an interface 10 and, as the result, each window of the analyser is automatically set. Sensitivity irregularities and irregularities of energy decomposing capacities of a plurality of the detectors 1 can be automatically compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detector sensitivity adjustment device for an ECT apparatus (emission tomography apparatus).

As is well known, an ECT device includes a large number of radiation detectors arranged in a ring shape, and a large number of single channels that detect that the wave height of each detector output is within a predetermined window and generate an output, e. an analyzer, a subject is placed in the center of the ring-shaped detector array, and radiation emitted from radioactive isotopes (hereinafter abbreviated as RI) distributed within the subject is incident on each detector. By counting the output pulses for each detector to obtain data, and calculating the data, a nine-element RI distribution image is reconstructed. A very large number of detectors, for example 64, are required per ring, and the same number of single channel analyzers are also required.

By the way, in conventional ECT apparatuses, the windows of a large number of single channel analyzers are set in a fixed manner by one common window setting device. Therefore, adjusting the sensitivity of multiple detectors to suppress variations has been done by manually changing the dynes of the first-stage amplifiers in single-channel analyzers. Therefore, this adjustment required a great deal of labor and time.

In view of the above, an object of the present invention is to provide a detector sensitivity adjustment device for an ECT apparatus that can automatically adjust the sensitivity so that all sensitivity variations of a large number of detectors fall within a certain range.

An embodiment of the present invention will be described below with reference to the drawings. In the figure, a number of detectors 1 are arranged in a ring shape, and the outputs of each (3) are sent to each single channel analyzer 2.
An output pulse is generated from each analyzer 2 when each output peak value is within a predetermined window. This window is determined for each analyzer 2 by an energy window setter 11, which will be described later. This output pulse is sequentially switched for each combination of detector 1 and analyzer 2 by a digital multiplexer 3, and sent to a CPU (central processing unit) 8 via an interface 5, where the output pulse is detected. The counting is performed for each detector 1, and the counted value for each of the large number of detectors 1 is stored in a storage device such as a magnetic disk device 9.

On the other hand, each output of the detector 1 is taken out as an analog signal from the first stage amplifier of the single channel analyzer 2 and sent to an analog multiplexer 4. This multiplexer 4 sequentially switches each of the sent outputs and sends them to the multichannel analyzer 7. The multi-channel analyzer 7 has a window for each finely divided input signal size (4), and outputs a signal indicating which window the output peak value of the detector 1 falls within. do. This signal is sent to the CPU 8 via the interface 6 and counted, thereby generating a distribution of peak values of a number of output signals due to a number of radiations incident on one detector 1 within a certain period of time, that is, an energy spectrum of the incident radiation. is obtained. This energy spectrum is obtained for each detector 1 and stored in the magnetic disk device 9.

When adjusting the sensitivity, first place a uniform radiation source in the center of the ring-shaped array of detectors 1 so that radiation with the same energy spectrum enters each detector 1 uniformly. In this state, the multiplexers 3 and 4 sequentially switch signals at regular intervals.

In this way, the measured count value and energy spectrum for each detector 1 are stored in the magnetic disk device 9. In this way, the relationship between the output pulse count value of the single channel analyzer 2 connected to the detector 1 with respect to each energy spectrum of the detector 1 is known, so how much the window of the analyzer 2 is from the peak value of the energy spectrum. In other words, is the detector 1
You can see how much the sensitivity is off. Furthermore, if the energy resolution of the detector l is poor, the energy spectrum becomes gentle, so the count value becomes low even if the window is not shifted. In such a case, it is necessary to set a window width that allows a count value that matches the average value of the count values for all detectors 1 to be obtained. CPU
8 is the amount of shift of the window of the single channel analyzer 2 such that variations in sensitivity of each of the detectors 1 are corrected according to the energy spectrum and count value for each of the detectors 1, and the shift amount of the window of the single channel analyzer 2 and The window width is determined such that variations in energy resolution are corrected, and each of the energy window setters 11 is controlled via the interface 10 based on this, and as a result, the individual energy windows of the single channel analyzer 2 are automatically adjusted. is set.

In this way, variations in sensitivity and variations in energy resolution of each of the multiple detectors 1 can be automatically corrected.

Note that determining the window shift amount and window width described above can be realized by either a hardware configuration or a software configuration.

[Brief explanation of drawings]

The figure is a block diagram of an embodiment of the present invention. 1...Detector 2...Single channel analyzer 3...Digital multiplexer 4...Analog multi-channel analyzer 5.6.10...Interface 7...Multi-channel analyzer 8...CPU 9. ...Magnetic disk device 1
1...Energy window setting device applicant Shimadzu Corporation

Claims (1)

[Claims] (1) It has a large number of radiation detectors arranged in a ring shape, and a large number of single channel analyzers that generate output pulses by detecting that the wave height of each detector output is within a predetermined window, and the ring The output pulse obtained when the radiation emitted from the radioactive isotope distributed in the subject placed in the center of the type detector array is incident on each of the detectors is calculated for each of the single channel analyzers. An ECT device that reconstructs the original radioisotope distribution image by calculating data and processing this data uses one multichannel analyzer and sequentially switching the outputs of each detector to calculate the multichannel A switching circuit leads to an analyzer, and the output pulses obtained when a uniform radiation source is placed in the center of the ring-shaped detector array are counted for each detector, and each detection is performed using the output of the multi-channel analyzer. Detector sensitivity of an ECT device, characterized in that it has a control circuit that determines an energy spectrum for each output of the analyzer and sets each window of the plurality of single channel analyzers based on the count value of the output pulse and the energy spectrum. Adjustment device.