JPS62133442A - Reader for radiographic image information - Google Patents

Abstract

PURPOSE:To obtain radiographic image information with fine picture quality by providing the titled reader with an adjusting means for adjusting the reading condition of stimulated luminescence in accordance with the driving condition information of a radiant ray generating source. CONSTITUTION:An X-ray generating source 1 is controlled by a control device 2 and control information at the radiation of X rays is inputted to a reader 3 through interfaces 18, 19. The control information is applied to a reading gain adjusting circuit 20 and the circuit 20 adjusts the optical beam intensity of an optical beam generating part 5, the power supply voltage of a high voltage power supply 21 for a photomultiplexer (gain adjustment of the photomultiplexer), the gain of a current/voltage converter 11 and an amplifier 12, and the input dynamic range of an A/D converter 13 in accordance with the control information to adjust the reading gain of the radiographic image information. Consequently, the radiographic image information with high picture quality can be read out in spite of the variation of dosage of radiant rays.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a reading device for radiation image information stored and recorded on a stimulable phosphor plate.

-Background of the Invention- When a stimulable phosphor is irradiated with radiation such as X-rays or ultraviolet rays, it can accumulate part of the energy of this radiation, and when it is irradiated with excitation light, it can accumulate some of the energy of this radiation. It emits stimulated light with an intensity that corresponds to the energy. Utilizing this property, radiation image information of the subject is recorded and accumulated as a latent image by irradiating the stimulable phosphor plate with radiation that has passed through the subject, and this stimulable phosphor plate is then exposed to a laser beam. A radiation image is created by irradiating excitation light such as light, detecting the amount of stimulated luminescence corresponding to the density of the latent image (energy storage field in each part of the phosphor) with a photodetector, and further processing the detection signal. Devices that read the image information and record the read image information on photographic film or display it on a display device have been developed.

In such a device, variations in the radiation emission 14 result in variations in the amount of radiation received by the stimulable phosphor plate.

That is, there is a problem in that fluctuations in recording energy lead to inappropriate reading processing signal levels, resulting in deterioration of image quality, such as overexposure or underexposure, when recording on photographic film, for example.

-Object of the Invention 1 An object of the present invention is to provide a reading device that can read radiographic image information with excellent image quality even when the amount of radiation emitted varies.

- Structure of the Invention 1 The present invention provides a method for scanning a stimulable phosphor plate, on which a radiation image of the subject is recorded as a latent image by receiving radiation from a radiation source through the subject, with an excitation light beam. In a reading device that reads the stimulated luminescence of a stimulable phosphor plate as an electrical signal to obtain radiation image information of the subject, adjustment is made to adjust reading conditions of the stimulated luminescence according to drive condition information of the radiation generation source. It is equipped with means.

One Embodiment - FIG. 1 is a configuration diagram of an apparatus showing one embodiment of the present invention, which is applied to chest X-ray photography. An X-ray generation source 1 emits X-rays whose radiation amount is controlled by a control device 2 toward a subject (human chest) M. The radiation image information reading device 3 is equipped with a stimulable phosphor plate 4 on a surface facing the X-ray source 1 with the subject M in between, and the X-ray transmittance of the subject with respect to the amount of X-ray radiation from the X-ray source 1 is adjusted. By accumulating energy according to the distribution on the stimulable phosphor plate 4, a latent image of the subject is obtained on the stimulable phosphor plate 4.

A light beam generator ff1I (gas laser, solid-state laser, semiconductor laser, etc.) 5 generates a light beam whose emission intensity is controlled, and a scanner 6 receives light provided from the light beam generator 5 through various optical systems (not shown). The beam is deflected, and the reflecting mirror 7 reflects the deflected light beam from the scanner 6 to guide the optical scanning beam to the stimulable phosphor plate 4 as excitation light.

The condenser 8 has an optical fiber condensing end positioned at a portion of the stimulable phosphor plate 4 scanned by the excitation light, and collects a latent image from the stimulable phosphor plate 4 scanned by the excitation light beam. Receives stimulated luminescence that is approximately proportional to energy. The filter 9 is the condenser 8
Only light in the stimulated emission wavelength region is transmitted from the light introduced from the source. Photomaru (Photo.

M u l L i p l t e r Tu b
e) 10 receives the light that has passed through the filter 9 on the photocathode, and is proportional to the amount of incident light? It is converted into an It flow signal.

The current-voltage converter 11 converts the current signal from the photomulti IO into a voltage signal, the amplifier 12 appropriately amplifies the voltage signal, and the A/D converter 13 converts the voltage signal amplified by the amplifier 12 into a voltage signal. The image information memory 14 sequentially stores the digital signals from the A/D converter 13, and the memory control unit 15 performs various image processing (levels) on the image information stored in the memory 14. The image display device IB receives the processed image information from the memory 14 and displays the chest X-ray image of the subject. Performs transmission control for transmitting image information to the outside.

Here, the X-ray generation source l is controlled by its control device g12, and the control information at the time of X-ray emission is taken into the reading device 3 through the interface 18.19. This control information is sent to the reading gain adjustment circuit 20, which adjusts the light beam intensity of the light beam generator 5, adjusts the power supply voltage of the photomultiply high voltage power supply 21, etc. according to the control information. (
The reading gain of the radiographic image information is adjusted by adjusting the gain of the photomultiplier), adjusting the gain of the current-voltage converter 11 and the amplifier 12, and adjusting the input dynamic range of the A/D converter 13. This will be explained in detail below.

The X-ray generation source 1 has an X11a tube and a high-pressure generator for generating X-rays in the X-ray tube, and the control device 212 controls the amount of X-ray radiation by controlling the output of the high-pressure generator. For example, this radiation amount varies depending on xkQ tube voltage, current, imaging time (operating time), etc.

Figure 2 shows the X-ray spectral intensity distribution of an X-ray tube targeting tungsten.As the tube voltage increases, the short wavelength component increases, which means that the transmittance distribution of the object (subject contrast) changes. . In addition, Figure 3 shows the X-ray energy distribution due to differences in X-ray tube voltage.
This means that the amount of radiation varies depending on the tube voltage.

The relationship between xk and radiation amount under these control conditions is as shown in the following equation.

However, K is a constant, VX is the tube voltage, n is a constant of 1 or more, and I
X is the tube current, t is the imaging time, and L is the distance between the X-ray source and the stimulable phosphor plate 4.

The amount of stimulated luminescence of the stimulable phosphor plate 4 is approximately proportional to the amount of X-ray radiation.

Therefore, the amount of X-ray radiation from the X-ray generator [1] is determined from its control information (tube voltage, etc.), and the reading gain is adjusted according to this amount of X-ray radiation.

The stimulable phosphor plate 4 changes due to changes in recording conditions due to the X-ray source 1.
Photomul 10. Calculates the X-ray received amount fluctuations and detects the unsuitability of stimulated luminescence during reading, including adjusting the intensity of the excitation light beam.
By adjusting the reading gain of the A/D converter 13, etc., a reading human power signal of a preferable level is obtained for each part, and a reading operation in which the signal is processed and converted with high accuracy is obtained.

For example, as shown in FIG. 4 showing the human output characteristics of each part of the reading system, the output current characteristics (FIG. 2a) with respect to the high voltage power supply voltage to the photomultiplier 10, and the constant S of the stimulable phosphor plate 4 *
Characteristics of stimulated luminescence amount with respect to excitation light intensity in terms of energy (Fig. 2b) and A/D with respect to the reference signal of the A/D converter 13
From the dynamic range characteristic of D conversion Cm2 (C),
1.Each input level or reference signal level according to radiation amount control information! [By doing so, it is possible to obtain the optimal operation for each part.

In addition, although the example shows the case where the reading gain is adjusted only from the X-ray radiation amount of the X-ray source 1, the transmittance distribution of the object can also be taken into consideration from the given control information and the X-ray spectrum distribution shown in Figure 2. By adjusting the reading gain, more suitable image information can be read.

In addition, although the example shows the case of X-ray photography, this also applies to other radiations (α-rays, β-rays, γ-rays).

It can be changed as appropriate depending on the source (ultraviolet rays, etc.), and can also be applied to electrostatic latent image reading devices.

Effects of the Invention As described above, according to the present invention, since the read signal gain is adjusted according to the drive condition information when the radiation generation source generates radiation, the gain is adjusted appropriately even when the radiation dose of the radiation generation source changes. By reading signals at a high level, it is possible to read image information with good quality and obtain radiographic image information with good image quality.

[Brief explanation of drawings]

Fig. 1 is an apparatus configuration diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the X-ray spectrum intensity distribution of an X-ray tube, and Fig. 3 is a diagram showing the X-ray spectrum intensity distribution of an
FIG. 4 is a diagram showing the X-ray energy distribution of the ray tube, and is a characteristic diagram of each part of the reading system in FIG. 1... X-ray generation source, 2... X-ray generation source control device,
3... Radiation image information reading device, 4... Stimulable phosphor plate, 5... Light beam generating section, 8... Light condenser, 1
0...Photomaru, 11...Current-voltage converter,
12...Amplifier, 13...A/D converter. ! 4... Image information memory, 15... Memory control unit. 18.19...Interface, 20...Reading gain adjustment circuit. Patent applicant: Konishiroku Photo Industry Co., Ltd. Figure 2

Claims (1)

[Claims] 1) When the stimulable phosphor plate receives radiation from a radiation source through the subject and the radiation image of the subject is recorded as a latent image, the stimulable phosphor plate is scanned with an excitation light beam. A reading device for obtaining radiation image information of the subject by reading stimulated luminescence as an electrical signal, characterized by comprising an adjusting means for adjusting reading conditions for the stimulated luminescence according to drive condition information of the radiation generation source. Radiation information reading device.