JP2002148733A - Radiation image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain bright radiation images which are additionally improved in resolution by using a linear amplifier as an amplification system of a radiation image reader which reads the radiation images obtained by photographing as image signals, amplifies the image signals and outputs the same. SOLUTION: The stimulated light emitted from a stimulable phosphor sheet 50 accumulated with the radiation images by irradiating the stimulable phosphor sheet 50 with the exciting light emitted from a broad area laser 11 is detected by a line sensor 20 to execute photoelectric conversion and the image signals based on the radiation images outputted from the line sensor 20 are read by an image reading means 30. The read image signals are amplified by the linear amplifier 31 disposed in the image reading means 30 in accordance with the gain and offset meeting the photographic menu inputted from a photographic menu input means 60 and is digitized by an analog-to-digital converter 32, by which the allocation of the resolution is optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic image reading apparatus for reading a radiographic image obtained by radiography and amplifying and outputting an image signal based on the radiographic image.

[0002]

2. Description of the Related Art Conventionally, various radiation image reading apparatuses have been proposed which detect radiation and output it as an image signal in radiation imaging for medical diagnosis and the like.

For example, when a stimulable phosphor is irradiated with radiation, a part of the radiation energy is accumulated, and thereafter,
When irradiated with excitation light such as visible light or laser light, stimulated emission light is emitted according to the accumulated radiation energy.
The stimulable phosphor (stimulable phosphor) is used to irradiate a stimulable phosphor sheet having the stimulable phosphor laminated on a support with radiation transmitted through a subject such as a human body. An image is temporarily stored and recorded, and the stimulable phosphor sheet is irradiated with excitation light such as a laser beam to generate stimulated emission light, and a radiation image reading for photoelectrically converting the stimulated emission light to obtain an image signal. The apparatus is widely used as CR (Computed Radiography).

[0004] In the radiation image reading apparatus using the stimulable phosphor sheet, a specific method of reading a radiation image from the stimulable phosphor sheet is as follows. Dimensional scanning,
The stimulated emission light emitted from the sheet at that time is transmitted to a photodetector via a light collector (light guide) having a light incident end surface extending along the main scanning line of the excitation light, and the photodetector emits light. A method has been proposed in which the emitted light is photoelectrically detected to obtain an image signal. As the photodetector, those using an internal photoelectric effect such as a phototransistor or a photodiode, and a photomultiplier tube ( Some photomultipliers have a photocathode and utilize the photoelectron emission effect of the photocathode.

Further, from the viewpoint of shortening the reading time of the stimulated emission light and reducing the size and cost of the apparatus, a line light source that irradiates the sheet with excitation light linearly is used as the excitation light source. A line sensor in which a large number of photoelectric conversion elements are arranged along a length direction (hereinafter, referred to as a main scanning direction) of a linear portion of a sheet irradiated with excitation light by a line light source is used. And scanning means for moving one of the line sensor and the phosphor sheet relative to the other in a direction substantially perpendicular to the length direction of the linear portion (hereinafter referred to as a sub-scanning direction). (Japanese Patent Laid-Open No. 60-111568,
JP-A-60-236354, JP-A-1-101540, etc.).

[0006] A solid-state radiation sensor is also used as a device that accumulates a radiation image and reads it as an image signal. For example, in medical radiation imaging, radiation transmitted through a subject is irradiated to the radiation solid-state sensor and irradiated. The amount of charge corresponding to the dose of the emitted radiation is stored as a latent image charge in a power storage unit in the solid-state radiation sensor, and the radiation image is recorded as a charge latent image, and an image corresponding to the charge latent image is recorded by an image reading unit. A radiation solid-state sensor that reads out a signal from a power storage unit is known. Various types of these solid-state radiation sensors have been proposed. For example, in terms of the charge reading process, there are a TFT reading method and an optical reading method. The TFT readout method scans and drives a TFT to convert a latent image charge stored in a power storage unit into a radiation image signal and outputs the radiation image signal. The optical readout method uses an electromagnetic wave for reading (generally, visible light). Is used to convert latent image charges accumulated in the power storage unit into image signals and output them (Japanese Patent Application Laid-Open No. 7-72256, Japanese Patent Application No. 10-243379, etc.).

In the above-described radiation image reading apparatus, the magnitude of an image signal output from an image reading unit of a photodetector (phototransistor, photodiode, line sensor, photomultiplier, etc.) or a solid-state radiation sensor. Is relatively small, and is usually amplified by an amplifier or the like and then output to an image processing device or the like.

As an amplifier for amplifying this image signal, since the size of the input image signal is in the range of several digits, this image signal is logarithmically amplified and digitally converted by an A / D converter. Although a log amplifier that facilitates the use of a solid-state sensor was used, a phototransistor, a photodiode, a line sensor, and a solid-state sensor such as a solid-state radiation sensor were used in the photodetector and the solid-state radiation sensor. Compared to a system that has both a detection system and an amplification system, such as a multiplier, the output current range is even lower, so it is necessary to amplify more efficiently.Use a linear amplifier rather than a log amplifier Is preferred. Further, when a semiconductor sensor is used, it can be said that a linear amplifier is more appropriate than a log amplifier even when considering that an appropriate response speed is required.

[0009]

However, when the linear amplifier is used as described above, since the input image signal has a range of several digits, if this image signal is linearly amplified by the linear amplifier, When digitizing with an A / D converter, it is difficult to uniformly assign the resolution to image signals in a range of several digits. When this image signal is displayed on a film or the like for observation, the region of interest may be a part of the image. In such a case, if the resolution is evenly allocated to the image signal in the range of several digits, It is inefficient, and it is preferable to assign the resolution so that the resolution is increased only in the image portion of the region of interest.

In view of the above problems, a radiation image reading apparatus according to the present invention reads a radiation image as an image signal and amplifies and outputs the image signal. An object of the present invention is to provide a radiation image reading apparatus which can use an amplifier and can obtain a clear image with improved resolution by optimizing the resolution assignment in the A / D converter. It is.

[0011]

According to the present invention, there is provided a radiation image reading apparatus comprising a radiation image detecting means for detecting a radiation image obtained by imaging and outputting an image signal based on the radiation image. A linear amplifier that linearly amplifies and outputs an image signal output from the radiation image detecting means, and adjusts at least one of a gain and an offset of the linear amplifier in accordance with an imaging menu; .

Here, the "photographing menu" includes an imaging part (head, neck, chest, abdomen, etc.), a photographing method (simple, contrast, tomography, etc.), a region of interest (lung of the chest, lumbar vertebrae of the abdomen). ), Imaging conditions (such as the type of subject, radiation dose, tube voltage, tube current, irradiation time, etc.), setting of a photo timer that measures the dose of radiation and controls the dose, ID information ( Object information).

[0013] "Adjusting at least one of the gain and offset of the linear amplifier in accordance with the menu of radiography" means, for example, pelvic measurement, scoliosis, pediatrics, etc. for which the exposure dose should be kept low in the radiography menu. For example, when the imaging of the chest is selected, when the imaging of the lumbar vertebra is selected in the imaging of the abdomen, or when the imaging that can determine that there is no high dose is selected from the setting conditions of the photo timer, so-called so-called. When high sensitivity shooting is required, 0mR ~ 1m
The gain is adjusted so that the radiation dose of R is reduced to an electric signal of 0 V to 2 V, and the case where imaging is selected from the bones such as the lumbar spine to the periphery of the skin in the imaging menu of the abdominal side in the imaging menu. When imaging with a wide dynamic range is required, the gain is adjusted so that the radiation dose in a wide range from 0 mR to 20 mR becomes an electric signal of 0 V to 2 V,
Furthermore, when so-called narrow dynamic range imaging is required, such as when chest tomography or abdominal tomography is selected in the imaging menu, a gain is set so that the radiation dose in a narrow range of 0.5 mR to 2 mR is 0 V to 2 V. And adjusting the offset.

Further, the radiation image detecting means can be a radiation solid state sensor.

Further, the radiation image detecting means may be a line sensor in which a large number of photoelectric conversion elements are linearly arranged.

Further, a CCD can be used as the photoelectric conversion element.

[0017]

According to the radiation image reading apparatus of the present invention, there is provided a linear amplifier for linearly amplifying and outputting the image signal output from the radiation image detecting means, and the gain of the linear amplifier is adjusted in accordance with a menu of photographing. And at least one of the offsets is adjusted, so that the image signal output from the radiation image detecting means can be efficiently amplified, and the resolution can be efficiently increased in accordance with the photographing menu at the time of A / D conversion. Can be assigned,
A clear image with higher resolution can be obtained.

Further, when a radiation solid-state sensor is used as the radiation image detecting means, the radiation image can be detected more efficiently.

When a line sensor having a large number of photoelectric conversion elements arranged in a straight line is used as the radiation image detecting means, the reading time can be reduced, and the size and cost of the apparatus can be reduced. Can be.

Further, when a CCD is used as the photoelectric conversion element, stimulated emission light based on a radiation image can be detected with higher sensitivity.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the basic concept of the radiation image reading apparatus according to the present invention.

As shown in FIG. 1, a radiation image reading apparatus according to the present invention includes a linear amplifier (described later) corresponding to an imaging menu having information such as an imaging part, a region of interest, imaging conditions, a photo timer setting condition, and ID information. Radiographing menu input means 6 for adjusting the gain and offset of the radiograph, radiographic image detecting means 1 for detecting a radiographic image obtained by radiography and outputting an image signal based on the radiographic image, and analog output from the radiographic image output means 1 It comprises a linear amplifier 3 that linearly amplifies the image signal 2 and outputs it as an analog electric signal 4, and an A / D converter 5 that digitizes the analog electric signal 4 output from the linear amplifier 3 and outputs it to an image processing device or the like. Have been.

The radiation image detecting means 1 reads a radiation image obtained by radiography, and outputs the read analog image signal 2 to the linear amplifier 3.

The linear amplifier 3 is adjusted to a gain and an offset according to the photographing menu. The linear amplifier 3 linearly amplifies and adds the offset to the analog image signal 2 based on the gain and the offset, and outputs an analog electric signal 4. The gain and offset according to the radiographing menu are, for example, when pelvic measurement, scoliosis, child chest radiography that is desired to be suppressed in the radiographing menu are selected, or when you want to see only the lumbar spine in radiographing the abdomen When radiography is selected, and when so-called high-sensitivity radiography is required, such as when radiography that can determine that there is no high dose is selected from the setting conditions of the photo timer, a low radiation dose of 0 mR to 1 mR is 0 V to 2 V. 0 mR when a wide range of dynamic range is required, such as when the gain is set to be an analog electric signal, or when imaging from the bones such as the lumbar vertebrae to the skin margin is selected in the imaging menu on the abdominal side. Radiation dose in a wide range of ~ 20mR is 0V ~ 2
When a so-called dynamic range is required when a so-called dynamic range is required, for example, when a chest tomography or abdominal tomography is selected in a photographing menu, the gain is set so as to be an analog electric signal of V. The gain and offset mean that the radiation dose becomes an analog electric signal of 0V to 2V.

The amplified analog electric signal 4 is digitized by an A / D converter 5 and then output to an image processing device or the like.

Next, a schematic configuration diagram of an embodiment of the radiation image reading apparatus according to the present invention is shown in FIGS. FIG.
3 is a perspective view of the radiation image reading apparatus of the present embodiment, FIG. 3 is a cross-sectional view showing a cross section taken along line II of the radiation image reading apparatus shown in FIG. 2, and FIG. 4 is a radiation view shown in FIGS. FIG. 2 is a diagram showing a detailed configuration of a line sensor 20 of the image reading device.

The radiation image reading apparatus according to the present invention includes a scanning belt 40 on which a stimulable phosphor sheet (hereinafter, referred to as a phosphor sheet) 50 on which a radiation image is accumulated and recorded is conveyed in a direction indicated by an arrow Y. An excitation light source 11 for emitting the secondary excitation light (hereinafter simply referred to as excitation light) L substantially parallel to the surface of the phosphor sheet 50, a collimator lens for condensing the linear excitation light L emitted from the excitation light source 11, and An optical system 12 composed of a combination of toric lenses that expands a beam only in one direction is disposed at an angle of 45 degrees with respect to the surface of the phosphor sheet 50, and the excitation light L is directed substantially perpendicularly toward the phosphor sheet 50. A dichroic mirror 14 that is set to reflect and transmit a stimulating light M to be described later, a linear excitation light L reflected by the dichroic mirror 14,
The light is condensed in a linear shape extending along the X direction on the phosphor sheet 50, and the stimulated emission light M according to the stored and recorded radiation image emitted from the phosphor sheet 50 by irradiation of the excitation light is converted into a parallel light flux. Refractive index distributed lens array 15
(This is a lens in which a large number of gradient index lenses are arranged, and is hereinafter referred to as a first selfoc lens array.) The first selfoc lens array 15 converts the light into a parallel light beam and transmits the dichroic mirror 14. The second selfoc lens array 16 for condensing the photostimulated light M on the line sensor 20, which will be described later, and the phosphor sheet slightly mixed with the photostimulated light M transmitted through the second selfoc lens array 16. Excitation light L reflected by 50 surfaces
, And stimulated emission light M is transmitted through the excitation light cut filter 17, the line sensor 20 that receives the photostimulated emission light M transmitted through the excitation light cut filter 17 and performs photoelectric conversion, and a signal output from the line sensor 20. Image reading means 30 for reading the image.

As the excitation light source, the light source itself may emit linear excitation light, or may be made linear by an optical system.

The selfoc lens array 16 has a function of forming an image of the photostimulated light M on the phosphor sheet 50 on the light receiving surface of the line sensor in a one-to-one size.

An optical system 12 composed of a collimator lens and a toric lens is provided with an excitation light L
On the phosphor sheet 50 to a desired irradiation area.

More specifically, as shown in FIG. 4, the line sensor 20 has a configuration in which a large number (for example, 1000 or more) of photoelectric conversion elements 21 are arranged along the X direction.

The image reading means 30 reads an analog image signal output from the line sensor 20 in accordance with the speed of the belt 40. The image reading means 30 converts the analog image signal output from the line sensor 20 into a photographing menu input means. 60
Linear amplifier 31 that linearly amplifies based on the gain and offset according to the shooting menu input from
And an A / D converter 32 for digitizing an analog electric signal output from the linear amplifier 31.

Next, the operation of the radiation image reading apparatus according to this embodiment will be described. First, when the scanning belt 40 moves in the direction of arrow Y,
The phosphor sheet 50 on which the radiation image is stored and recorded is transported in the direction of the arrow Y. At this time, the conveying speed of the phosphor sheet is equal to the moving speed of the belt 40, and the moving speed of the belt 40 is input to the image reading means 30.

On the other hand, the excitation light source 11 generates linear excitation light L
Is emitted substantially parallel to the surface of the phosphor sheet 50, the excitation light L is converted into a parallel beam by an optical system 12 including a collimator lens and a toric lens provided on the optical path, and the fluorescent light is emitted by a dichroic mirror 14. The light is reflected in the orthogonal direction perpendicular to the body sheet 50, and the reflected light is linearly extended along the X direction on the phosphor sheet 50 disposed on the phosphor sheet 50 by the first Selfoc lens 15. Is incident substantially perpendicularly.

The stimulable phosphor in the light condensing area is excited by the linear excitation light L incident on the phosphor sheet 50, and is incident from the light condensing area into the inside of the phosphor sheet 50 to be in the vicinity of the light condensing area. It diffuses and excites the stimulable phosphor in the vicinity of the light collection area. As a result, stimulated emission light M having an intensity corresponding to the stored and recorded radiation image is emitted from the light-collecting region of the phosphor sheet 50 and its vicinity. This stimulated emission light M is
It is made into a parallel light beam by the first Selfoc lens 15,
The light passes through the dichroic mirror 14 and is condensed on the photoelectric conversion element 21 of the line sensor 20 by the second selfoc lens array 16. At this time, even if there is a slight amount of the excitation light L reflected on the surface of the phosphor sheet 50 in the stimulated emission light M transmitted through the second Selfoc lens array 16, the excitation light L is cut by the excitation light cut filter 17. Therefore, it does not enter the line sensor surface. The stimulated emission light is detected by the line sensor 20 and photoelectrically converted. The analog image signal is read by the image reading means 30. The analog image signal read by the image reading means 30 is input to the shooting menu input means 6 by the linear amplifier 31.
It is amplified based on the gain and offset according to the shooting menu output from 0 and output to the A / D converter 32. The A / D converter 32 digitizes the input analog electric signal and outputs it to an image processing device or the like.

It should be noted that the radiation image reading apparatus of the present invention is not limited to the above-described embodiment, but includes a light source, a condensing optical system between the light source and the sheet, an optical system between the sheet and the line sensor, and a line. Sensors and various known configurations can be employed. The image processing apparatus further includes an image processing device that performs various kinds of signal processing on the signal output from the image reading unit, and further includes an erasing unit that appropriately emits radiation energy still remaining on the sheet whose excitation has been completed. It is also possible to adopt a configuration that is different.

In the above embodiment, the radiation image detecting means uses a stimulable phosphor sheet and a line sensor. However, the radiation image detecting means may use a solid radiation sensor. In this case, the analog image signal output from the solid-state radiation sensor is input to the linear amplifier as in the above-described embodiment,
The linear amplifier amplifies an analog image signal by a gain and an offset based on the photographing menu input from the photographing menu input means, and converts the analog image signal into an analog electric signal.
Output to D converter.

According to the radiation image reading apparatus of the present invention, there is provided the linear amplifier 31 for linearly amplifying and outputting the image signal output from the line sensor 20, and the gain and offset of the linear amplifier 31 according to the photographing menu. Is adjusted, it is possible to more efficiently amplify the image signal output from the line sensor 20, and to efficiently assign resolution according to the shooting menu when performing A / D conversion. Therefore, a clear image with higher resolution can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a basic concept of a radiation image reading apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram of an embodiment of a radiation image reading apparatus according to the present invention.

FIG. 3 is a cross-sectional view showing a cross section taken along line II of the radiation image reading apparatus shown in FIG. 1;

FIG. 4 is a diagram showing details of a line sensor of the radiation image reading apparatus shown in FIGS. 2 and 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radiation image detection means 2 Analog image signal 3, 31 Linear amplifier 4 Analog electric signal 5, 32 A / D converter 6 Imaging menu input means 11 Broad area laser 12 Optical system 16 Selfoc lens 17 Excitation light cut filter 20 Line sensor 21 Photoelectric conversion element 30 image reading means 40 transport belt 50 stimulable phosphor sheet 60 photographing menu input means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G083 AA03 AA04 BB04 CC10 DD11 DD18 EE02 2H013 AC05 5B047 AA17 BA01 BB02 BC05 CA07 DA01 5C072 AA01 DA02 EA02 EA05 RA06 UA05 VA01

Claims (4)

[Claims] 1. A radiographic image reading apparatus comprising a radiographic image detecting means for detecting a radiographic image obtained by imaging and outputting an image signal based on the radiographic image, wherein the image signal output from the radiological image detecting means is provided. A linear amplifier that linearly amplifies and outputs the linear image, and adjusts at least one of a gain and an offset of the linear amplifier in accordance with the imaging menu. 2. The radiation image reading apparatus according to claim 1, wherein said radiation image detecting means is a radiation solid state sensor. 3. The radiation image reading apparatus according to claim 1, wherein said radiation image detecting means is a line sensor in which a large number of photoelectric conversion elements are linearly arranged. 4. The radiation image reading apparatus according to claim 3, wherein said photoelectric conversion element is a CCD.