JPS63241374A - Radiation detector - Google Patents

Abstract

PURPOSE:To reduce adverse effect due to radiation with a higher vibration resistance properly preparing detection characteristic, by providing an photoelectric transducer at an end of a bar-like scintillator to scan with radiation as converted into a spot-like radiation. CONSTITUTION:A fan-like X ray beam 6 from an X ray tube 4 is converted with a collimator 7 into a spot-like X ray beam 6' to scan on a line sensor 1 along the length thereof. Radiation incident into a scintillator core 2a of a bar-like scintillator 2 is converted into light, which is introduced to photodiodes 3a and 3b at both ends of the scintillator reflecting on a junction surface between the scintillator core 2a and a glass clad 2b. On the other hand, at a data collecting section 11, output signals of both the photodiodes 3a and 3b from an adder/amplifier 12 are integrated with an integrator 14 based on a pulse signal outputted at a motor control section 21 corresponding to the rotational speed of a rotary collimator 9 and an X ray projection data of an object 5 to be inspected is collected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention 1 (Industrial Application Field) The present invention relates to a radiation detection device suitable as a radiation detector in a CT scanner, an X-ray television, or the like.

(Prior Art) As a conventional radiation detection device of this type, a detector in which a scintillator and a photodiode are combined for each detection channel is widely used. This detector allows radiation, for example, X-rays, to enter a scintillator that is partitioned off by a light-shielding plate for each channel. When X-rays enter the scintillator, light is instantaneously generated, and this light is transmitted to the corresponding scintillator. The X-ray intensity is converted into an electric signal by a photodiode connected to the X-ray beam, and the X-ray intensity is converted into an electric signal and extracted.

However, this type of conventional radiation detector has the following problems. That is, when applied to a CT scanner or the like, hundreds of detection channels are required to obtain sufficient resolution, so the detector is constructed by combining the same number of scintillators and photodiodes. For this reason, it has been difficult to match detection characteristics such as sensitivity, temperature characteristics, and linearity between each detection channel. Furthermore, since there are many adhesive parts, such as the scintillator and the light-shielding plate, or the scintillator and the photodiode, the mechanical strength tends to deteriorate due to changes over time, and the vibration resistance is weak. Furthermore, since the photodiode is located in the direction of irradiation of the X-rays, there is a risk that the photodiode will be destroyed by the influence of the X-rays.

(Problems to be Solved by the Invention) As mentioned above, in conventional radiation detectors of this type, a large number of scintillators and photodiodes are used in order to obtain sufficient resolution. The characteristics tend to vary, making it difficult to detect radiation with high precision, and there are problems with vibration resistance, radiation resistance, etc., and improvements have been desired.

Therefore, the present invention has the same resolution as the conventional one without causing variations in detection characteristics for each detection channel, improves radiation detection accuracy, has excellent mechanical strength and improves vibration resistance, and It is an object of the present invention to provide a radiation detection device that can significantly reduce adverse effects.

[Structure of the Invention] (Means for Solving the Problems) The radiation detection device of the present invention includes a photoelectric conversion element provided at at least one end of a rod-shaped scintillator, and a method for transmitting radiation from a radiation source to the scintillator. radiation scanning means for converting it into a spot-like radiation and scanning it in the longitudinal direction of the scintillator; and collecting radiation data photoelectrically converted by the photoelectric conversion element based on the scanning speed of the spot-like radiation scanned by this means. The radiation data collection means for outputting radiation data is provided.

(Function) With a radiation detection device that employs such means, a spot-shaped radiation beam is scanned in the longitudinal direction on a rod-shaped scintillator, and data collection is performed at a predetermined timing according to the scanning speed. resolution can be obtained. Also,
Since it is formed from one rod-shaped scintillator and a small number of photoelectric conversion elements, detection characteristics can be easily aligned, and
It has strong mechanical strength, and since the photoelectric conversion element is separated from the main cone of radiation, it is hardly affected by radiation.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall configuration diagram of an embodiment in which the present invention is applied to an X1iCT scanner. In the figure, 1 is a line sensor which is the main part of the present invention, and a rod-shaped scintillator 2
It has a structure in which photodiodes 3a and 3b having the same characteristics are bonded to both ends of the .

As shown in FIG. 2, the rod-shaped scintillator 2 has a core portion 2a.
The scintillator fiber is made of a scintillator with an excellent X-ray capture rate, and the cladding part 2b is made of glass with a refractive index that operates as a fiber. Many scintillator fibers are bundled together and finished in a rod shape, and the radiation incident on the scintillator core 2a is is converted into light, and this light is propagated in the longitudinal direction of the rod-shaped scintillator 2 while being reflected at the joint surface between the scintillator core 2a and the glass cladding 2b, and is guided to photodiodes 3a and 3b at both ends. Note that the rod-shaped scintillator 2 and the photodiodes 3a and 3b are in close contact with each other, so that the light that reaches them is not reflected again.

Reference numeral 4 denotes an X-ray tube, from which a fan-shaped X-ray beam 6 having a predetermined angle sufficient to encompass the object 5 to be inspected is continuously emitted. A collimator 7 is interposed between the X-ray tube 4 and the object to be inspected 5, and includes a linear collimator 8 having an opening that matches the longitudinal direction of the line sensor 1, and a collimator 7 provided above the linear collimator 8. and a rotary collimator 9 having a cross-shaped opening,
The rotary collimator 9 is configured to rotate in a fixed direction by a collimator drive section 10. That is, as shown in FIG. 3, a hole 7a is formed by the opening of the linear collimator 8 and the opening of any one of the rotary collimators 9, and the hole 7a is opened in the longitudinal direction of the line sensor 1 by the rotation of the rotary collimator 9. Move to. Therefore, the fan-shaped X-ray beam 6 projected from above the collimator 7 is converted into a spot-shaped X-ray beam 6' by passing through the hole 7a of the collimator 7, and as the rotary collimator 9 rotates, the fan-shaped X-ray beam 6 is projected onto the line sensor 1. is scanned in a certain longitudinal direction, and a specific cross section of the object to be inspected 5 is transmitted.

11 is a data collection unit that collects the X-ray projection data detected by the linear sensor 1, and includes an adder/amplifier 12 that adds and amplifies the output signals of both photodiodes 3a and 3b, and a motor control unit that will be described later. a timing controller 13 that generates a timing pulse in response to a pulse signal from the timing controller 21; an integrator 14 that integrates the output signal of the adder/amplifier 12 based on the timing pulse sent from the timing controller 13; and an amplifier 15 that amplifies the output of. 16 is a central processing unit (CPtJ) connected to the correction calculator 17 and the console section 18, and has a preprocessing function for converting the X-ray projection data sent from the data acquisition section 11 into input data for the reconstruction algorithm; A correction function that performs a correction calculation for the scanning speed of the spot X-ray beam 6' on preprocessed data, and a specific cross section of the object 5 to be inspected according to the reconstruction algorithm on the corrected data. It has a reconstruction function for reconstructing a tomographic image based on the X-ray transmittance distribution, and the reconstructed tomographic image is displayed on the CRT display 19 by the action of the console section 18. The console section 18 also includes an X-ray control section 2
0, connects the motor control section 21 and the scan mechanism section 22, and outputs operation commands to them. Then, in accordance with this operation command, the X-ray control section 20 controls the X-ray radiation from the X-ray tube 4, and the collimator control section 21 controls the collimator drive section 1.
0 and outputs a pulse signal according to the rotational speed to the timing controller 13, and the scanning mechanism section 22 rotates or horizontally moves the inspected object 5 at a predetermined pitch.

In the CT scanner of this embodiment configured as described above, a fan-shaped X-ray beam 6 is continuously emitted from the X-ray tube 4,
While rotating the rotary collimator 9, the line sensor 1 detects X-ray projection data of the object to be inspected 5, and the data collection unit 11 collects the X-ray projection data at a predetermined timing.

Here, the scanning speed V of the spot-shaped X-ray beam 6' scanning the line sensor 1 by the rotation of the rotary collimator 9 is expressed by the following equation (1) at the middle point in FIG.

v-dx/dt -℃・(1/cosθ)・dθ/dt...
(1) However, dθ/dt-ω (ω (angular velocity) - constant)
Therefore, the scanning speed ■ is v-(λ/0052θ)ω...■
and is expressed as a function of the angle θ.

Since the sampling pitch of the X-ray projection data in the data acquisition section 11 matches the number of detection channels, it is necessary to set the sampling pitch at a constant interval in the longitudinal direction of the line sensor 1. Therefore, in the data collection section 11, based on the pulse signal (A in FIG. 5) outputted from the motor control section 21 corresponding to the rotational speed of the rotary collimator 9, the timing controller 13 generates a signal as shown by B in FIG. A timing pulse is created, and each time the timing pulse falls, an integrator 14 integrates the output signals of both photodiodes 3a and 3b, which are summed and amplified by an amplifier 12, thereby collecting X-ray projection data. That is, X-ray projection data is collected at a sampling pitch having the functional relationship expressed by equation (2) above. Then, CPL is applied to this collected data.
At step 116, speed correction is performed using the correction calculator 17 so that the sampling pitch becomes a constant interval. The X-ray projection data collected and corrected in this way is
6, the tomographic image of a specific cross section of the subject 5 is reconstructed according to the reconstruction algorithm, and is displayed on the CRT display 19.

As described above, in this embodiment, the fan-shaped X-ray beam 6 from the X-ray tube 4 is converted into a spot-shaped X-ray beam 6 by the collimator 7, and is scanned over the line sensor 1 in the longitudinal direction. A large number of X-ray projection data are collected at timings related to the scanning speed as if they were detected by multiple stacking elements, and X-ray projection data at regular intervals is obtained by correcting for changes in the scanning speed. I did it like this,
X-ray projection data is obtained with a resolution similar to that obtained with conventional multi-channel X-ray detectors.

Therefore, according to this embodiment, since the line sensor 1 only needs to be constructed from one rod-shaped scintillator 2 and two photodiodes 3a and 3b, detection of sensitivity 9m degree characteristics, linearity, etc. for all X-ray projection data is possible. Variations in characteristics can be suppressed as much as possible. Further, since there are only two bonding parts between the scintillator 2 and the photodiodes 3a and 3b, mechanical strength such as vibration resistance is excellent. Furthermore, the photodiodes 3a and 3b are connected to the X-ray beam 6.
Since the X-ray beam 6 is away from the main beam cone and there is no fear that the X-ray beam 6 will be directly projected onto the photodiodes 3a and 3b, the influence of X-rays can be suppressed. Furthermore, since the configuration is simple, it can be assembled at low cost and maintainability is also excellent.

Furthermore, in the embodiment described above, among the scattered rays of the spot-shaped X-ray beam 6' incident on the rod-shaped scintillator 2, the scattered ray component in the longitudinal direction is transmitted to the photodiode 3a.

3b, it is possible to improve the X-ray capture rate. Furthermore, since the number of detection channels depends on the data collection timing, it is possible to obtain the same resolution as in the conventional method and to increase the number without limit.

Note that the present invention is not limited to the above embodiments.

For example, although the above embodiment shows a case in which it is applied to an X-ray CT scanner, it goes without saying that it can be applied to radiation detection devices other than X-rays, and it can also be applied to radiation detection devices other than CT scanners, such as X-ray televisions. Applicable to inspection systems.

Further, although the above embodiment shows the case where the photodiodes 3a and 3b are provided at both ends of the rod-shaped scintillator 2, they may be provided only at one end. In addition, as shown in FIG. 6, the line sensor 1 has a multi-stage configuration, and each data collection unit 11 collects X-ray projection data for each wavelength of the spot radiation 6' that passes through the rod-shaped scintillator 2. Radiographic projection data may also be obtained. By doing so, radiation having a specific wavelength can be extracted. In this case, it goes without saying that the line sensor 1 may be one in which photodiodes 3a and 3b are provided at both ends.

Further, in the embodiment described above, the data collection timing is created based on the rotational speed of the rotary collimator 9, but the present invention is not limited to this. FIG. 7 shows a modification thereof, in which the outputs of photodiodes 3a and 3b provided at both ends of the rod-shaped scintillator 2 are connected to amplifiers 31a and 31, respectively.
After amplification in b, adder 32 and phase difference detection circuit 33
Send to. The adder 32 adds both detection signals and outputs the result to the integrator 14. The phase difference detection circuit 33 discriminates both detection signals to determine the phase difference, and the timing controller 34
Based on the phase difference, it is determined to which position on the rod-shaped scintillator 2 the spot-shaped X-ray beam 6' is projected, and a data acquisition timing pulse is output to the integrator 14. By doing so, X-ray projection data can be collected at any position on the scintillator 2. In this case, a photodiode for outputting a detection signal and a photodiode for phase detection may be provided separately. It goes without saying that various other modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to improve the radiation detection accuracy without causing variations in the detection characteristics of each detection channel with the same resolution as conventional ones, and to improve the mechanical It is possible to provide a radiation detection device that has excellent strength and can improve vibration resistance, and can also significantly reduce the adverse effects of radiation.

[Brief explanation of the drawing]

1 to 5 are diagrams showing an embodiment in which the present invention is applied to a CT scanner, in which FIG. 1 is a block diagram showing the overall configuration, FIG. 2 is a diagram for explaining a rod-shaped scintillator, Figure 3 is an enlarged view of the collimator, Figure 4 is a diagram for explaining the scanning speed of the spot X-ray beam, Figure 5 is a diagram for explaining the data collection timing, and Figures 6 and 7 are for explaining the scanning speed of the spot X-ray beam. It is a figure which shows the modification of this invention. 1... Line sensor, 2... Rod-shaped scintillator, 3
a, 3b... photodiode, 4... X-ray tube, 8...
...Linear collimator, 9...Rotary collimator,
11... Data collection unit, 12... Adder/amplifier, 1
3... Timing controller, 14... Integrator,
16...CPU, 17...Correction calculator, 19...
CRT display, 33...phase difference detection circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] a rod-shaped scintillator, a photoelectric conversion element provided at at least one end of the scintillator, and a radiation scanning device that converts radiation from a radiation source into a spot shape on the scintillator and scans the scintillator in the longitudinal direction of the scintillator; Radiation detection characterized by comprising radiation data collection means for collecting and outputting radiation data photoelectrically converted by the photoelectric conversion element based on the scanning speed of the spot-like radiation scanned by the radiation scanning means. Device.