JPH0415587A - Scintillation camera - Google Patents

Abstract

PURPOSE:To automatically correct variance against a difference of the amplification degree of a photoelectric multiplier by executing a feedback control in the inside of a device by an A/D converting circuit, a CPU circuit and a D/A converting circuit. CONSTITUTION:A CPU circuit 14 sets a reference value of an energy signal of every photoelectric multiplier 4 to the inside of the CPU 14 from an energy signal of a radioisotope RI used for adjustment. A scintillator 2 is irradiated with gamma rays from the RI, and also, the irradiated position is informed the CPU 14, and an energy signal from an adding circuit 10 in this case is A/D-converted 13 and read in the CPU 14. In the CPU 14, the read-in value and a reference value set previously are compared, and when the read-in value is large (small), a small (large) control signal is outputted so that a correction value of a D/A converting circuit 6 becomes small (large), and a correction value of the converting circuit 6 being the nearest to an incident position of the gamma rays is determined so that the read-in value becomes equal to the reference value. By repeating the operation, the correction values of all the converting circuits 6 are derived automatically.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to radioactive isotopes (hereinafter abbreviated as rRIJ).
A substance labeled with is administered to a subject, and radiation such as gamma rays emitted from the R1 is detected to detect RI in the subject.
The present invention relates to a scintillation camera that determines the distribution of , and particularly to a scintillation camera that automatically corrects variations in the amplification of a plurality of photomultiplier tubes.

[Conventional technology]

As shown in FIG. 5, a conventional scintillation camera includes a collimator 1 that allows only gamma rays incident perpendicularly to the five surfaces of the scintillator 2 to pass among the gamma rays emitted from the RI inside the subject; A scintillator 2 that emits light due to gamma rays incident through it, and a light guide 1 that transmits the optical signal of this scintillator 2;
3rd, this light (see Guide 3) is optically coupled to the above-mentioned lunch 1 hearter 2, and a photomultiplier tube (hereinafter referred to as r P M
It will be abbreviated as TJ. ) 4, 5, 2 I) Briand-f circuit 5 that amplifies the output signal of M T 4, and a plurality of P IνiT4 that receive the output signal of P M T 4 amplified by this preamplifier circuit r') A y-in adjustment circuit 21 that corrects variations in the amplification degree of the gain adjustment circuit 21, an integration circuit 7 that integrates the signal from the gain adjustment circuit 21, and a scintillator 2 according to the signal strength of the output signal from the integration circuit 7.
a position calculation circuit 8 for calculating the position of the gamma ray incident on the
A display device 9 that displays a bright spot and creates a scintigram according to the gamma ray position signal obtained by the position calculation circuit 8, and all PM signals output from the gain adjustment circuit 21 described in -1-
an addition circuit 10 that adds the signals of T4 to determine the incidence of gamma rays and calculates the energy of the incident gamma rays;
A pulse height analysis circuit J2 that determines whether the energy signal from this addition circuit 10 is a gamma ray of the target energy.
and 1, °゛ wave height + 11 circuit 1; 2 or ;) judgment signal ^ the above-mentioned adding circuit 10 or l゛) power ゛/masu ray person shooting confidence +
E+, 1-Record portion circuit 79 position dI calculating circuit and timing control circuit for controlling 3] 1, +r L, .

In contrast to the conventional non-synthetic camera,
t9 and turn] If the t non-ma ray of the channel X- is crossed by the scintillator L7, then any 11゛ position is the same tS ::
J<Kisa's energy (Is it necessary to put it in the IT issue?

, "two τ, the above-mentioned scintillation l) - kt shift sensitivity for evening gamma rays varies depending on the position (for example, about 3%), and the amplification degree of the PMT4 is large (for example, about 100%).
00 times), the amplification degree between the scintillators 21 and 21J differs over time. Energy Shin - Does not become a bow. As a method of solving this problem, the gain adjustment path 21 performs a modulation V and adjusts the energy signals in the adder circuit so that they have the same magnitude.

This gain adjustment circuit 21 is configured as shown in FIG.
A variable resistor 41 that adjusts the output signal of T 4, and this variable resistor 41 and the subsequent integrating circuit 7 and adding circuit 10
Operational amplifiers (hereinafter abbreviated as "operational amplifiers") 33 are used to isolate circuits and prevent circuit matching and electrical interference.
It consists of a buffer made up of . The adjustment is made so that gamma rays of the same energy are sequentially incident on each part of the scintillator 2 shown in Fig. 5, and then the variable resistor 41 in the gain adjustment circuit 21, into which the signal of the PMT 4 near the gamma ray incident position is input, is operated. The energy signal output from the adder circuit]0 was adjusted so that it would be the same regardless of the incident position of the gamma ray.

[Problem to be solved by the invention]

However, in such conventional scintillation cameras, the operator must manually operate the variable resistor 41 in the gain adjustment circuit 21 and make adjustments while observing the output of the adder circuit 0. It took a lot of time and effort to set it up. Further, the adjustment using the variable resistor 41 described above requires a measuring instrument and requires skill, and cannot be easily carried out by the administrator or user of the device on a daily basis. .

An object of the present invention is to provide a scintillation camera that can solve these problems.

[Means to solve the problem]

To achieve the above object, the present invention includes a scintillator that emits light due to incident radiation, a PMT that is optically coupled to the scintillator and converts the light into an electrical signal, and an integrating circuit that integrates the signal from the PMT. , a position calculation circuit that calculates the position of the radiation incident on the scintillator based on the signal from the integrating circuit, a display device that displays the incident position of the radiation determined by the position calculation circuit, and a signal from the preamplifier circuit described in -. In a scintillation camera that has an addition circuit that adds up all the energy signals to obtain an energy signal, - A comparison is made between the energy signal from the addition circuit and a preset reference value of the energy signal [P IVi 'T' Correction of the difference in amplification (controls ll''I (C do tJ circuit that outputs the 1+ signal, and Ci P
Control from the 0 circuit, No. 1i, 4-man power, and the above P M
A correction value for the difference in the amplification degree of T is formed 41, and the compensation I [is performed on the signal from the preamplifier circuit described in -D/'
It is equipped with an A conversion circuit.

[Action 1] The scintillator camera configured in this way has the following features:
/D conversion circuit CPU circuit and I) /A conversion circuit performs F-F back control inside the device, and the difference in amplification degree of I3MT is 1. −λ, 1 t, −r
Part 8) Automatically compensate for shine.

〔Example〕

Embodiments of the present invention will now be described with reference to the accompanying drawings.

Figure 1 (Scintillation camera according to the present invention)
A block diagram showing an embodiment includes a collimator, scintillator 2, light 1-guide 3, plvi T4 and 5 preamplifier circuit 5, l)/A conversion circuit (3 and
Integrating circuit 7, position, (1 arithmetic circuit 8 and display device 9.1
, the auxiliary circuit] 0, the timing control circuit 11, the wave height tri" circuit 2, the CP tJ circuit 14, and the A/[
]Conversion circuit t3 and 1-. τ naro 4. 1-Remeter [If i < 1 in the subject, the radiation μ
Behind the gamma rays ++'I on the car surface of Shincho 1 Nota 2
Only gamma rays incident in the direction of angle lj are allowed to pass through)
So, Ororu. 1. On the first side of the meter 1, there are provided scintillators 1, . . . It shields light from L' and is formed into a circular or rectangular flat plate.
Tokaj 1-3 are sunk. This Rai I Guide 3 receives the optical signal emitted by the Shinsen 1 Nork 2.
The first one is shaped like a circular or rectangular plate like the scintillator 2.

A plurality of P M T 4 are arranged in the light guide. This PMT4 is optically coupled to the light signal 2 through the light guide 34, detects the light emitted from light 92, and determines the magnitude of the optical signal 1, 5-Convert into a proportional 7 electrical signal, amplify and output.

The output signal from the PMT 4 is sent to the preamplifier circuit 5. This preamplifier circuit 5 has an upper KW P
Amplify the output signal from MT4.

The output signal from the preamplifier circuit 5 is input to the D/A conversion circuit 6. This D/A conversion circuit 6 converts the output signal of the PUT4 amplified by the preamplifier circuit 5 into T
) Corrected and output according to the difference in the amplification degree of M T4. - The output signal of the D/A conversion circuit 6 is integrated to reduce statistical noise when the scintillator 2 receives gamma rays and emits light. The energy of the gamma rays is input to an adder circuit 10 that calculates the energy of the gamma rays. The output signal from the integration circuit 7 is input to the position calculation circuit 8. This position calculation circuit 8 determines the light emitting point on the scintillator 2 based on the signal intensity from the integration circuit 7, and determines the position of the gamma ray incident on the scintillator 2. The output signal from the position calculation circuit 8 is input to the display device 9. This display device 9 displays the incident position of the gamma rays determined by the position calculation circuit 8, and creates a scintigram.

Addition circuit that determines that gamma rays are incident on the scintillator 2 and calculates the energy of the incident gamma rays]
The gamma ray incident signal from O is manually input to the timing control circuit 11. This timing control circuit 11 outputs signals to the integration circuit 7 and the position H1 calculation circuit 8, and controls the timing of signal integration and position calculation. The Zl signal from the adder circuit 10 is sent to a pulse height analysis circuit 1 that determines whether the energy of the incident gamma ray is within the desired range.
! and convert the energy signal into a digital signal Δ/[
) Manually input to the conversion circuit 13. The output signal of the pulse height analysis circuit 12 is inputted to the timing control circuit 11 described above, and is restricted so that position al calculation or display is not performed for incident gamma rays of energy other than the target. Above A/D
Digital signal H in the conversion circuit 13.

The energy signal of gamma rays changed to C T) U
input to circuit 14; This CPU circuit 14 corrects the difference in the amplification degree of P M T 4 from the digital signal 1.
Creates a digital control signal and outputs it to the D/C conversion circuit (3).

42, in the present invention, the above D/A conversion circuit 6
As shown in FIG. 2, it is composed of a D/A converter 31, an operational amplifier 33, and a latch 32. Latch: PMT4 from 32-digit CP tJ circuit 14
Compensate for the difference in the degree of amplification of the control signal'i! hold f l,
1-)/A converter: 31 and operational amplifier 33
2 to correct the difference in amplification degree of PMT4. Details of the D/A converter 31 are shown in FIG. 3. In the D/A converter 31, V is the input terminal, Il, , T2 is the output terminal, 1,) n
, , Do is a control terminal, which is composed of a resistor and a switch. The resistor has a resistance ratio R:2R of 1:2, and is configured so that the current flowing into the branch points of the resistor from the left in Figure 3 is sequentially divided by half at the branch points. There is. A switch for distributing the current from the resistor to the output terminals T+ and T2 is switched by control terminals D, , . . . , Do that receive a digital control signal from the latch 32. Output type iXt (II, I2)
changes depending on the switching of each switch, so r'l /
'The magnitude of the output signal of the A converter 31 is latched; 32
2 and 7' are controlled by the digital control of 1 and 3, and the control number 13 from the CPU circuit 14 is held by the digital controller 32. Out!
J signal is controlled by 1, operational amplifier 33 is controlled by 1, ) / A
By amplifying the output signal of converter 7-3F, the signal of PMT4, which is generated by the preamplifier circuit 3 and 11, is
C, PU times'+I! t, 1.4 or IE, can be varied by the ω control signal layer.

Next, Ii)/A conversion circuit 6 configured in this way
゜Addition circuit 10. A/[1] The operations of the conversion circuit 13 and the CPU circuit 14 will be explained. First, C shown in Figure 1
P U circuit - 1 is the reference value of the energy signal for each PMT from the R I energy signal used for adjustment.
It is set inside the PU circuit 14. Gamma rays from 11<I are irradiated onto the scintillator 2 shown in FIG. After converting, (L l' Read into the L1 circuit 14. C'', PU circuit) 4 compares the previously set reference value with the value read from the A/D conversion circuit 13, and determines that the read value is If the read value is small, output a small control signal to make the correction value of the D/A conversion circuit 6 small, and if the read value is small, output a large control signal to make the correction value of the D/A conversion circuit 6 large. Then, the correction value of the D/A conversion circuit 6 closest to the gamma ray incident position is determined so that the read value is equal to the reference value.By repeating this operation, the correction value of the D/A conversion circuit 6 is determined so that the read value is equal to the reference value. Correction values are automatically determined.

Instead of notifying the CPU circuit 14 of the gamma ray irradiation position, as shown in FIG. The correction value of the D/A conversion circuit 6 is further automatically determined by controlling the D/A conversion circuit 6.

〔Effect of the invention〕

The present invention is configured as follows, and the CPU circuit 14 and L
)/ Feedback control with the A conversion circuit 6 is performed,
A correction value for correcting the difference in the amplification degree of PMT4 is automatically determined by the D/A conversion circuit 6, and the operator manually operates the knob of the variable resistor 41 to adjust the PMT4 as in the past. This process can be omitted, and variations in the amplification degree of each PMT 4 can be adjusted easily and in a short time.

Further, the adjustment described in item 1-1 does not require any skill at all, and can be carried out by the administrator or user of the apparatus on a daily basis, thereby improving the operability of the scintillation camera as a whole.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing details of a D/Δ conversion circuit, FIG. 3 is a diagram showing details of a D/A converter, and FIG. 4 is a diagram showing details of a D/A converter. FIG. 5 is a block diagram showing the second embodiment, FIG. 5 is a block diagram of the conventional device, and FIG. 6 is a diagram showing details of the gain adjustment circuit of the conventional device R. 1. Collimator, 2.Scintillator, 3.Light guy 1-14.Photomultiplier tube, 5. Preamplifier circuit. 6.D/A conversion circuit, 7-.integration circuit, 8. position calculation circuit, 9-.display device, 10. addition circuit,] 1. timing control circuit, j2.. pulse height analysis circuit, 3A, /
I) Conversion circuit,] 4-cP 0 circuit, J5... Source cylinder drive device, 16 - Source cylinder, 21 - Gain adjustment circuit,
3]...D/A converter, 32...Latch, 33...Operation amplifier, 41-...Variable resistor.

Claims (1)

[Claims] 1. A scintillator that emits light due to incident radiation, a photomultiplier tube that is optically coupled to this scintillator and converts the light into an electrical signal, a preamplifier circuit that amplifies the signal from this photomultiplier tube, and this preamplifier. an integrating circuit that integrates a signal from the circuit; a position calculation circuit that determines the position of the radiation incident on the scintillator based on the signal from the integration circuit; and a display device that displays the incident position of the radiation determined by the position calculation circuit. In a scintillation camera comprising an adder circuit that adds all the signals from the preamplifier circuit to obtain an energy signal, the energy signal from the adder circuit is compared with a preset energy signal reference value. A CPU circuit outputs a signal to control a correction value for the difference in amplification of the photomultiplier tubes, and a control signal from the CPU circuit is inputted to create a correction value for the difference in amplification of the photomultiplier tubes. A scintillation camera comprising: a D/A conversion circuit that corrects a signal from the preamplifier circuit.