JPH0369086B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention involves irradiating excitation light onto a photostimulable phosphor that has absorbed radiation that has passed through the human body, and measuring the intensity of the stimulated light generated at that time. The present invention relates to a radiation image information reading device that reads radiation image information recorded on a photostimulable phosphor.

[Technical background of the invention and its problems]

Stimulation is a phenomenon in which incident radiation energy is stored in lattice gaps in a phosphor, and after the radiation has stopped, the material emits light when excitation light is irradiated, and is a type of recording development.

This stimulable phosphor is formed into a sheet shape, which absorbs the radiation that has passed through a subject such as a human body to accumulate and record a radiation image of the subject, which is later scanned with excitation light such as a laser beam. There is a device that detects the stimulated light generated at that time with a photodetector, converts it into an electrical signal, and then records and reproduces it again as a radiation image on a photographic film or CRT display (for example, US Pat. No. 3,859,527).

However, such a device scans a phosphor sheet with spot-shaped excitation light, and collects radiation image information stored and recorded in advance on the phosphor sheet into a spot of a size corresponding to the diameter of the excitation light spot. By breaking it down into pixels, it can be read out as photostimulated light in chronological order.
For example, this is a photomultiplier tube (hereinafter simply referred to as "PM").
It is common that the signal is converted into an electrical signal using a photodetector such as a photodetector.

However, the photostimulance generated by excitation light irradiation is very small compared to the excitation light (for example,
55-15025, the ratio of excitation energy to emission energy is usually 10 ⁴ :1 to 10 ⁶ :1), and for this reason, the reproduced radiation image is susceptible to adverse effects from the excitation light. S/N ratio decreases,
A problem occurred in that the resolution decreased. As a countermeasure to this problem, conventional devices have a transmittance of 0.01% for excitation light and photostimulation light, respectively, as disclosed in Japanese Patent Laid-Open No. 11397/1983.
An 80% strong filter was placed in front of the PM to reduce the negative effects of excitation light.

However, such a powerful filter cannot be used with P.
Even though it was placed in front of M, it was not possible to sufficiently improve the adverse effects caused by the excitation light.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a radiation image information reading device that can improve the adverse effects of excitation light and obtain radiation images with excellent resolution. .

[Summary of the invention]

The outline of the present invention for achieving the above object is to detect photostimulated light obtained by irradiating excitation light onto a phosphor sheet on which radiographic image information is stored, and to convert it into an electrical signal and output it. The radiation image information reading device includes: a pulsed excitation light generating means for generating pulsed excitation light that is intermittently irradiated onto the phosphor sheet; and a timing detection means for detecting the generation timing of the pulsed excitation light. The apparatus is characterized by comprising a data importing means for importing image data due to photostimulated light generated when the pulsed excitation light is not irradiated, based on the detection result of the timing detection means.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the configuration of a radiation image information reading device according to the present invention. First, the configuration of a pulsed excitation light generating means 2a that generates pulsed excitation light (hereinafter also referred to as "pulsed light") is shown. I will explain about it. This pulsed excitation light generating means 2a is, for example,
The light source 1 includes a He--Ne laser tube having a wavelength of 633 mm, and a shutter that modulates the beam-shaped laser light generated from the light source 1 into pulsed light. This shutter includes, for example, a disc 4 in which a plurality of light passage holes 3 are formed, and
and a motor 5 that rotates the motor at a predetermined speed. That is, the laser beam passes only when the light passing hole 3 of the disk 4, which is rotationally driven by the motor 5, is located in the optical path of the laser beam generated from the light source 1, and in other cases, the laser beam is mechanically The structure is such that light is blocked.

Next, the configuration of the timing detection means 2b for detecting the generation timing of pulsed light will be explained.
This timing detecting means 2b is, for example, a part other than the optical path of the laser beam, and is arranged so that the light passes through any one of the plurality of light passing holes 3 of the disk 4. The first light detection means 7 is arranged to face the lamp 6 with the disk 4 in between and detects the light from the lamp 6 that has passed through the light passage hole. .
Thus, the detection signal (pulse signal) of the first light detection means 7 is output in synchronization with the generation timing of the pulsed light.

The pulsed light generated by the pulsed excitation light generating means 2a is focused into a beam by a condenser lens 8, and then enters a vibrating mirror 9. This vibrating mirror 9 can vibrate in the direction shown by arrow A, and irradiates the phosphor sheet 10 with pulsed light incident through the condensing lens 8 within an angle B. , scanning is performed using pulsed light. still,
The precision feed table 11 is used to place the phosphor sheet 10 and convey it in the direction of arrow C by the rotation of rollers 12, 12.

Stimulated light obtained by irradiating the phosphor sheet 10 with pulsed light is focused by a focusing means 13. Here, the light condensing means 13 is, for example,
56-11396, a transparent acrylic plate processed or a plurality of optical fibers bundled together may be used. This light collecting means 1
The stimulated light focused by 3 is incident on the second photodetecting means 14 (for example, a photomultiplier tube, etc.) and converted into an electric signal, after which it is converted into an electrical signal, and then an amplifying means (AMP) disposed at a subsequent stage. 15 is input. This amplification means 1
The electrical signal amplified by 5 is input to data acquisition means 19 arranged at a subsequent stage. below,
The configuration of this data importing means 19 will be explained.

The data acquisition means 19 includes, for example, a control means 18 capable of outputting a control signal based on a detection signal of the photodetection means 7, and a holding means 18 for holding an electrical signal output from the amplification means 15 in accordance with this control signal. It is configured to include a means (for example, a hold circuit) 16 and an A/D (analog-digital) conversion means 17 for converting the contents held in the holding means 16 into a digital signal in accordance with a control signal from the control means 18. .

Next, the operation of the apparatus constructed as above will be explained with reference to FIGS. 2 and 3. When the disc 4 is rotated by the motor 5, the beam-shaped laser light generated from the light source 1 is modulated into pulsed light. After this pulsed light is focused into a beam by a condenser lens 8, it is irradiated onto a phosphor sheet 10 by a vibrating mirror 9 and subjected to scanning.

Here, when a specific portion of the phosphor sheet 10 is irradiated with pulsed light as shown in FIG. 2a, for example, the stimulated light becomes as shown in FIG. 2b. In other words, immediately after one pulse of excitation light is irradiated, a specific time (t1) is required for the intensity of stimulated light to decay to a predetermined intensity (this specific time is called the "luminescence lifetime"). ). For example, when the material of the phosphor sheet 10 is BaFBr:Eu ²⁺ , the luminescence lifetime is 0.8 μs. Furthermore, this luminescence lifetime is independent of the pulse width of the excitation light. Furthermore, the amount of radiation stored in the phosphor sheet 10 in advance is
For example, when a part changing as shown in Figure 3a is excited with the pulsed light shown in Figure 3b, the stimulated light is a pulse whose light intensity changes according to the radiation dose as shown in Figure 3c. It becomes a waveform.

In this way, the stimulated light obtained by the excitation of the pulsed light is collected by the light collecting means 13 and the second
After being converted into an electrical signal by the photodetecting means 14, it is amplified by the amplifying means 15. Electrical signal (image information) amplified by the amplifying means 15
In the data capturing means 19, only desired electrical signals are captured, and the captured electrical signals are converted into digital signals and then sent to a data processing device (not shown). The details of the operation of this data importing means 19 will be explained below.

The control means 18 inputs the detection signal of the first light detection means 7 which is outputted in synchronization with the generation timing of the pulsed light, and outputs an operation command signal according to this detection signal. In response to this operation command signal, the holding means 16 holds the electrical signal output from the amplifying means 15 for a predetermined period of time. That is, the holding means 16
inputs the electrical signal caused by the photostimulated light that occurs after a specific time (t2) has elapsed from immediately after the irradiation of one pulse of the excitation light pulsed light, and uses this electrical signal as the pulsed light that is irradiated next. It is held for a period of time from immediately after the completion of one pulse of irradiation until a specific time (t2) has elapsed. The output waveform of the holding means 16 operating in this manner is shown in FIG. 3d. The contents held in the holding means 16 are converted into digital signals by the A/D converting means 17 operated by the operation command signal outputted from the control means 18, and then converted into digital signals by the data processing means (not shown). It will be used for data processing.

Here, the specific time (t2) is a time determined by taking into account the delay in response time in the second photodetector 14, the amplifier 15, etc. ) is incident on the second photodetecting means 14 via the condensing means 13 and is generated, which is a delay time for preventing the holding means 16 from holding the component.

In this way, by using pulsed light as the excitation light irradiated to the phosphor sheet 10 and controlling the operation of the holding means 16 in synchronization with the generation timing of this pulsed light, only image information by photostimulated light can be obtained. It becomes possible to import. Therefore, the excitation light component can be eliminated without using a filter or the like as in conventional devices, and the adverse effects of the excitation light can be prevented.

Further, the amplification means 15 does not need to be a DC amplifier that can also amplify DC components. The reasons for this will be explained below.

In the conventional device, the waveform of stimulated light from the phosphor sheet 10 is equal to the amount of radiation accumulated in the phosphor sheet 10 (Fig. 3a), and this waveform must be faithfully amplified. Therefore, a DC amplifier was used. On the other hand, the waveform of stimulated light in this device is pulsed (Fig. 3c) due to excitation by pulsed light, and what is required is mainly the attenuation part (the amount of light during the luminescence life t mentioned above), and the DC Contains almost no ingredients.
Therefore, the amplifying means 15 does not need to be a DC amplifier. This is because the second light detection means 1
This means that the DC component can be blocked in the signal transmission path from 4 to the output of the amplification means 15, and an AC amplifier is applied to the amplification means 15, or even if a DC amplifier is applied, the DC component is blocked with a capacitor. By this, the second photodetection means 14 (e.g. photomultiplier tube) and the amplification means 15
drift can be ignored. Therefore, the data acquisition means 15 is not adversely affected by the drift of the previous stage.

It goes without saying that the present invention is not limited to the embodiments described above, and that modifications can be made as appropriate within the scope of the gist of the present invention.

For example, in the embodiment described above, the laser beam is mechanically blocked by the shutter to generate pulsed light, but the present invention is not limited to this, and for example, an AO optical modulator or the like may be used. In short, any means can be used as long as it can modulate laser light into pulsed light.

Similarly, the timing detection means 2b for detecting the generation timing of the pulsed light is not limited to the above embodiment, and may be configured to directly detect a portion of the pulsed light, for example.

〔Effect of the invention〕

As explained above, according to the present invention, the phosphor sheet is excited by pulsed light, and the photostimulated light generated when the pulsed light is not irradiated is captured as image data. The S/N ratio can be improved because it is possible to prevent the adverse effects of the excitation light without using the excitation light, and also to prevent the adverse effects of the drift of the second photodetection means and the amplification means. Therefore, it is possible to provide a radiation image information reading device that can improve the resolution of radiation images and obtain radiation images that are suitable for observation and interpretation.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of a radiation image information reading device according to the present invention, and FIGS. 2 and 3 a to 3 d are waveform diagrams for explaining the operation of the device shown in FIG. 1. 2a... Pulse excitation light generating means, 2b... Timing detection means, 10... Fluorescent sheet, 19...
...Data acquisition means.

Claims (1)

[Claims] 1. In a radiation image information reading device capable of detecting photostimulated light obtained by irradiating excitation light onto a phosphor sheet on which radiation image information is stored, and converting it into an electrical signal and outputting it, the phosphor sheet A pulsed excitation light generation means that generates pulsed excitation light that is intermittently irradiated to the pulsed excitation light, a timing detection means that detects the generation timing of this pulsed excitation light, and based on the detection result of this timing detection means,
A radiation image information reading device characterized by comprising: data acquisition means for acquiring image data due to photostimulated light generated when the pulsed excitation light is not irradiated.