JPS6058836B2 - Radiation measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in radiation measuring devices used in radioimmunoassays, etc., which quantitatively measure biochemical substances such as hormones contained in blood etc. using radioactive substances. be.

In general, radioimmunoassay is one of the representative microanalytical methods that combines an isotope labeling method and an immunoassay method.

The radiation measurement equipment used for such microanalyses is
As shown in Figure 1, the distribution of the number and energy of radiation, that is, the number and energy of the particles of radiation that fly into the detector, is the result of taking statistics (
Radiation is measured by determining this result, which is called the radiation energy spectrum. Generally, as shown in FIG. 2, the radiation measurement circuit for creating the energy spectrum of the radiation converts gamma rays emitted from a radioactive substance 1 into light using a scintillator 2, and photomultiplies the light. The tube 3 converts it into an electrical signal.

The electric signal is waveform-shaped by a DC amplifier circuit 4 having functions such as differentiation and integration. As shown in FIG. 3, this waveform-shaped electrical signal has a voltage proportional to the energy of the gamma rays, so the energy distribution is determined by determining the energy value from this voltage peak value. Then, the energy spectrum is created by counting how many radiations correspond to the energy determined by the voltage of the electric signal.

In the conventional radiation counting device for radioimmunoassay that is actually used, the nuclide of the radiation source is known, so it is possible to know which range of energy in the energy distribution should be counted for electrical signals. As shown in Figure 2, the discriminator 5 has an upper limit reference voltage set.
U and the discriminator 5D to which the lower limit reference voltage is set, the detector AND detects a significant pulse corresponding to the energy within the set range, and the
The pulses are cumulatively counted by a counter CNT. However, such conventional radiation counting devices suffer from (1) fluctuations in the high voltage power supply supplied to the photomultiplier tube 3, (2) fluctuations in electric circuit elements due to temperature, etc., and (3) special shapes such as side holes. When using a scintillator with As shown in the energy Spectrum), the pulse height value and upper and lower limit reference voltage values fluctuate, and the same amount of radiation source 1
Even if the radiation emitted from the radiation source is counted, the cumulative count value is not necessarily constant, and this poses a problem in that a warming-up of several tens of minutes or more and high precision in the position of the radiation source are required.

Furthermore, when the AD conversion method is adopted, the circuit is expensive because it uses a high-quality Wilkinson type circuit. The present invention was made to solve the above problem, and its features include a peak hold circuit that holds the peak value of an input pulse, an AD conversion circuit that converts the output of this peak hold circuit into a digital signal, a memory circuit that inputs the output of this AD conversion circuit as its address data; an adder that adds 1++ to the address data of this memory circuit and returns it to the memory circuit; It is equipped with a means to detect the peak value from the histogram corresponding to the spectrum, captures all input pulses, creates an energy spectrum, and calculates the set energy by performing mathematical processing on the obtained energy spectrum. An inexpensive model that matches the spectrum.゜Some provide radiation measurement equipment.

The present invention will be explained in detail below with reference to Examples.

In addition, in all the figures, parts having equivalent functions are given the same symbols. FIG. 5 is a block diagram of an embodiment of the present invention.

In the figure, 5E is a discriminator for detecting pulses with a predetermined energy value or more, 6 is a peak hold circuit for holding the peak value of the input pulse, and 7 is a converter for converting the output of the peak hold circuit 6 into 4 digital signals. 8 is a memory circuit, 9 is an addition circuit,
10 is a control circuit of the circuit, 11 is a central processing unit such as a microcomputer, and E is a set reference voltage.
Next, the operation of this embodiment will be explained. When starting measurement, all contents of the memory circuit 8 are set to zero.

Among these input pulses, pulses having a predetermined energy value or more are detected by the discriminator 5E, and the peak value thereof is held by the peak hold circuit according to a command from the control circuit 10.

Next, when the input pulse becomes lower than the reference voltage E of the discriminator 5E, or after a certain period of time after the pulse is detected, the control circuit 10 instructs the AD conversion circuit 7 to AD convert the peak value. issue. A digital signal corresponding to the converted peak value is input as address information to the memory circuit 8. The data at the address input from the memory circuit 8, that is, the address corresponding to the peak value, is transferred to the adder 9, where it is added by 1+L, and then the data is sent to the memory circuit 1 again.
Returned to 0. As a result, the memory circuit 8 adds 1+1 to the count value before the address corresponding to the peak value of the input pulse.
is accumulated. In this way, pulses are sequentially input and the count values are accumulated one after another at the addresses corresponding to the respective peak values.

FIG. 6 shows the results, with the data of the memory circuit 8 on the vertical axis.
This is a histogram in which the address of the memory circuit 8 is plotted on the horizontal axis. This histogram corresponds to the energy spectrum of B in FIG. 7 (A is the set energy spectrum, B is the measured energy spectrum), and is transferred to the central processing unit 11 in this memory 8. and find the peak point M″.The obtained peak point M″
and the peak value M of the set energy spectrum shown in FIG. Find the cumulative count value. As explained above, according to the present invention, when calculating the cumulative count value, the peak value is calculated from the energy spectrum, and the comparison and correction are performed with the set value. Radiation measurement can be easily carried out without the need for setting the position of the radiation source with high accuracy.

Further, even if the oil conversion circuit does not have to be of the high-grade Wilkinson type as in the past, a sequential comparison type or the like can be sufficiently put to practical use, and the cost thereof can be reduced.

[Brief explanation of the drawing]

Figure 1 is a radiation energy spectrum diagram, Figure 2 is a block diagram of a conventional radiation measurement circuit, Figures 3 and 4 are diagrams for explaining the operation of the conventional example in Figure 2, and Figure 5. 6 is a block diagram of an embodiment of the present invention, FIG. 6 is a diagram showing the contents stored in the memory, and FIG. 7 is a diagram showing the case where the peak point deviates from the set value. 1...Radiation source, 2...Scintillator,
3...Photomultiplier tube, 4...DC amplifier, 5
U, 5D, 5E... Discriminator, 6.
... Peak hold circuit, 7 ... AD conversion circuit, 8 ... Memory circuit, 9 ... Adder, 10 ... Control circuit, 11 ...Central processing unit.

Claims (1)

[Claims] 1. In a radiation measuring device that counts radiation emitted from radioactive substances and quantitatively determines the chemical substance contained in the subject from the counted value, there is a peak hold circuit that holds the peak value of the input pulse, and a peak hold circuit that holds the peak value of the input pulse. An AD conversion circuit that converts the output of the hold circuit into a digital signal, a memory circuit that inputs the output of this AD conversion circuit as its address data, and a memory circuit that adds "+1" to the address data of this memory circuit. What is claimed is: 1. A radiation measuring device comprising: an adder that feeds back a radiation energy spectrum; and means for detecting a peak value from a histogram corresponding to a radiation energy spectrum stored in the memory.