JPH03277989A - Apparatus for measuring concentration ri in blood - Google Patents

Abstract

PURPOSE:To enhance sensitivity and to reduce background counting by coincidence counting beta-rays and annihilation gamma-rays by two or more detectors using scintillators easily permitting beta-rays to transmit and having high density. CONSTITUTION:The beta-rays from a tube 10 through which blood passes are absorbed by a plastic scintillator 12a to be converted to light which is, in turn, measured by the PMT (photosensor) 12b of a side surface. Annihilation gamma-rays emit fluorescence by the opposed scintillator 14b provided on the outside to be measured. The signals of the scintillator 12a and the opposed scintillator 14a are coincidence counted by a coincidence counting circuit 22 through respective PMTs 12b, 14b. By this method, even when the threshold of beta-rays is set low, the coinicidence counting with gamma-rays is performed to make the effect of a background hard to receive and, in the same way, the background counting due to the coincidence counting of scattering gamma-rays can be also removed. By this method, the measuring sensitivity of radioactivity is enhanced and background counting is reduced and the shielding of lead can be reduced and miniaturization and wt. reduction can be achieved.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention is utilized in the field of radiation detection.

The present invention relates to a blood R1 concentration measuring device that measures isotope (R1) concentration in blood and is used as an accessory for a positron CT device.

(b) Prior art Conventionally, beta (β) rays in the blood are measured by a plastic scintillation detector surrounding a tube that passes through the blood, or by simultaneously attaching a similar tube to two scintillation detectors such as BGO facing each other. A counting circuit is connected and measurements are taken while fishing on a boat.

(c) Problems to be solved by the invention In the plastic scintillation detector described above,
There are problems in that T-rays are measured in addition to beta-rays, and only high-energy nuclides of beta-rays can be measured.

In the conventional opposing scintillation detector, bank ground counting due to puncture ground T-rays was a problem at a low counting rate.

Both of these conventional methods require a large shielding material such as lead in order to reduce the background, which is a problem.

The purpose of the present invention is to reduce background counting, increase sensitivity, and at the same time reduce shielding such as lead.
An object of the present invention is to provide a blood R1 concentration measuring device.

(d) Means for Solving the Problem The above object is to provide at least two scintillation detectors including a scintillation detector surrounding a tube through which blood passes, a scintillation detector surrounding the scintillator with a high density of scintillators, and a scintillation detector that uses scintillation detectors that surround the tube through which blood flows, This is accomplished by providing a coincidence counting circuit connected to the device.

(e) Function The scintillation detector that surrounds the tube through which the blood passes - Low-density plastic scintillators are used for boat fishing, which allow beta rays to easily pass through, and high-density scintillators such as BGO are used. With at least two scintillation detectors, annihilation gamma rays are easily transmitted, and by counting these beta rays and annihilation T rays simultaneously, sensitivity is increased and bank ground counting is reduced.

(f) Example A preferred embodiment of the invention will be explained based on the drawings.

Before explaining the embodiment, the conventional example described above is shown in FIGS. 3 to 6.
The diagram will be explained.

In the first conventional example, positrons coming out of the tube 10 are measured by a plastic scintillator detector 12. The detector 12 consists of a plastic scintillator 12a and a PMT (photomultiplier tube or photomultiplier) 12b.

In this case, annihilation gamma rays (511 keV) are also
Since it is measured by the scintillator detector 12, the energy spectrum will be as shown in FIG.

As shown in the example, the 51 l keV T-line becomes the background, so the energy threshold is usually set to 51 l keV.
Set the value to exceed 11 keV. At this temperature, the sensitivity is low, and the low-energy β-ray emitting nucleus! (18F etc.) cannot be measured.

FIGS. 5 and 6 illustrate other conventional examples.

FIG. 5 shows an example of measurement using two opposing scintillation detectors 14 sandwiching a tube 10 through which blood passes.

14a is a scintillator BG0. 20 is a coincidence counting circuit, whereby the annihilation T-rays are counted in coincidence. Although simultaneous counting is less susceptible to the influence of background, bank ground counting occurs at a low counting rate because the counts between scattered T-rays outside the tube 10 are measured as shown in FIG.

Therefore, in both conventional methods, it is necessary to increase the lead shield size in order to reduce the background count.
It becomes difficult to use.

Therefore, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

The configuration is such that opposing scintillation detectors 14 are arranged so as to surround a plastic scintillator 12a with a hole into which the tube IO is inserted.

Each scintillator 12a, 14a is a photo sensor (PMT) 1
In order to eliminate optical crosstalk, it is preferable to coat surfaces other than the connecting surfaces with 2b and 14b with a reflective material.

The principle of operation is shown in FIG.

Beta radiation from tube 10 is absorbed by plastic scintillator 12a and converted into light.

This light is measured by the PMT 12b on the side.

The annihilation gamma rays fluoresce at the opposing scintillator 14b on the outside and are subjected to tfS. The signals of the plastic scintillator 12a and the opposing scintillator 14a are transmitted through the respective PMTs 12b.
, 14b, the coincidence counting circuit 22 performs coincidence counting.

According to the present invention, even if the beta ray threshold is set low, coincidence counting with the T ray is performed, so that it is less susceptible to bank ground counting. Furthermore, for the same reason, bank ground counting based on scattering coincidence shown in FIG. 6 can also be eliminated.

Note that the shape of the plastic scintillation detector and the opposed scintillation detector may be other than the shape of the embodiment, for example, a plate shape.

In addition, the scintillator is also a plastic scintillator, B
It can be replaced with various things other than GO12J.

(g) Effects According to the present invention, the sensitivity of radioactivity measurement can be increased, and in this case, the bank ground count can be lowered and lead shielding can be reduced, so that the apparatus can be made smaller and lighter.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a diagram explaining the principle of the present invention, FIG. 3 is a configuration diagram of a conventional example, FIG. 4 is an energy spectrum diagram of the conventional example, FIG. 5 is a diagram of another conventional example, and FIG. is a diagram illustrating coincidence of scattered T-rays according to the conventional example. 1O is a tube, 12a is a plastic scintillator, 12b is a PMT, 14 is a BGO scintillator, 14b
is a PMT, and 20 and 22 are coincidence circuits.

Claims (1)

[Claims] 1. A scintillation detector surrounding a tube through which blood passes, and at least two scintillation detectors using a scintillator with high density surrounding the scintillator;
A blood RI concentration measuring device characterized by comprising a coincidence counting circuit connected to all of these detectors.