JPS61162037A - Method and apparatus for reading radiation picture information - Google Patents

Abstract

PURPOSE:To obtain a regenerative radiation picture having high diagnosis aptitude by setting up the reading condition/picture processing condition of radiation picture information on the basis of the accumulated recording information of a subject detected by an image intensifier camera. CONSTITUTION:To execute the radiation photographing of a subject 43, fine radiant rays for fluoroscopy is irradiated from a radiant ray source 42 to the subject before the arrangement of the accumulative fluorescent sheet 30 between endless belts 2, 3. The fine radiant rays for fluoroscopy transmitted through the subject 43 are made incident upon an image intensifier 45A and the radiation picture is photographed by a television camera 45B. A CRT63 displays the radiation picture of the subject 43 on the basis of a picture signal S1 outputted from the television camera 45B. In the radiation photographing technique, the photographing conditions such as a radiant ray irradiation field can be properly set up while observing the display picture on the CRT63.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention is directed to irradiating excitation light onto a stimulable phosphor sheet on which radiation image information is accumulated and recorded, thereby excitation light emitted from the stimulable phosphor sheet. It relates to a radiation image information reading method of photoelectrically detecting the stimulated luminescence light and reading the radiation image information, and an apparatus for carrying out the method. The present invention relates to a radiation image information reading method and apparatus that allow an overview of information to be grasped.

(Technical Background and Prior Art of the Invention) When a certain kind of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, T-rays, electron beams, ultraviolet rays, etc.), a part of this radiation energy is emitted into fluorescent light. It is known that when this phosphor is accumulated in the body and is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy; The fluorophore is called a storage fluorophore.

Using this stimulable phosphor, radiation that has passed through an object such as a human body is irradiated onto the stimulable phosphor sheet, and radiation image information of the object is recorded on the sheet. Scanning is performed with excitation light such as a laser beam to generate stimulated luminescence light, and the resulting stimulated luminescence light is read photoelectrically to obtain an image signal. Based on this image signal, recording materials such as photographic light-sensitive materials, CRTs, etc. etc. display! ! The present applicant has already proposed a radiation image information recording and reproducing system that outputs a radiation image of a subject as a visible image at every location. (Unexamined Japanese Patent Publication No. 55-
No. 12429, No. 56-11395, etc. ) This system has the practical advantage of recording images over a much wider range of radiation exposure compared to conventional radiographic systems using silver halide photography. In other words, in stimulable phosphors, it is recognized that the amount of emitted light that is stimulated and emitted by excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range, and therefore, depending on various imaging conditions, radiation exposure Even if the amount fluctuates considerably, the amount of stimulated luminescent light emitted from the stimulable phosphor sheet is read by a photoelectric conversion means by setting the reading gain to an appropriate value and converted into an electrical signal. By outputting a radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT using an electric signal, a radiation image that is not affected by fluctuations in the amount of radiation exposure can be obtained.

Furthermore, according to this system, radiation image information accumulated and recorded on a stimulable phosphor sheet is converted into an electrical signal, then subjected to appropriate signal processing, and this electrical signal is used to produce recording materials such as photographic light-sensitive materials, CRTs, etc. By outputting a radiographic image as a visible image on a display device such as the above, it is possible to obtain a very large effect that a radiographic image with excellent observation and interpretation suitability (diagnosis suitability) can be obtained.

In this way, in a radiation imaging system that uses a stimulable phosphor sheet, the reading gain can be set to an appropriate value to charge and convert the stimulated luminescence light and output it as a visible image, making it possible to No. 1! Fluctuations in radiation exposure due to fluctuations in voltage or MAS value, variations in sensitivity of stimulable phosphor sheets, variations in sensitivity of photodetectors, changes in exposure due to subject conditions, or radiation transmittance depending on the subject. Even if the energy accumulated in the stimulable phosphor differs due to factors such as these, and even if the amount of radiation exposure is reduced, it is possible to obtain radiographic images that are not affected by fluctuations in these factors. Become.

However, in order to eliminate the influence of fluctuations in imaging conditions or obtain radiographic images that are not suitable for observation and interpretation, it is necessary to , recording patterns (hereinafter collectively referred to as "accumulated recorded information") determined by the subject's region such as the abdomen, imaging methods such as plain imaging and contrast imaging, etc., are used for observation and interpretation. The system determines the visual image before outputting it, adjusts the reading gain to an appropriate value based on the acquired recorded information, and adjusts the recording scale factor so that the resolution is optimized according to the contrast of the recorded pattern. Then, perform gradation processing on the read image signal]! When performing image processing such as, it is necessary to optimally set image processing conditions.

As a method of grasping the accumulated record information of radiation images before outputting visible images, Japanese Patent Application Laid-Open No. 58-47240
The method disclosed in No. This method uses excitation light of a lower level than the excitation light that should be irradiated during the reading operation (hereinafter referred to as "single reading") to obtain a visible image for observation and interpretation. A reading operation (hereinafter referred to as "pre-reading") is performed to grasp the accumulated record information of the radiographic image stored and recorded on the stimulable phosphor sheet, and an overview of the accumulated record of the radiographic image is grasped. , When performing the main reading, set the reading gain appropriately based on this pre-read information: itwt, , the recording scale.
This is used to determine the shift factor or image processing conditions. This method is used, for example, in Japanese Patent Application Laid-Open No. 58-672
No. 42, No. 58-67243, excitation light irradiation means for irradiating excitation light onto a stimulable phosphor sheet on which radiation image information is accumulated and recorded, and means for transporting the stimulable phosphor sheet. , and a main reading reading system comprising a photodetecting means for photoelectrically reading stimulated luminescence light carrying radiation image information emitted from the stimulable phosphor sheet by excitation light irradiation;
A pre-reading reading system is provided that performs pre-reading using excitation light having an energy lower than that of the excitation light used in the main reading, prior to main reading to obtain a visible image of radiographic image information, and a pre-reading system that performs pre-reading using excitation light having an energy lower than that of the excitation light used in the main reading. This is carried out by a radiation image information reading apparatus including a control means for setting the reading conditions and/or image processing conditions for the main reading based on the accumulated record information of the sheet.

Note that the excitation light used for pre-reading is at a lower level than the excitation light used for main reading because the effective energy of the excitation light that the stimulable phosphor sheet receives per unit area during pre-reading is lower than the excitation light used for main reading. This means that it is smaller than the actual value. As a method of making the excitation light of the pre-reading lower than the excitation light of the main reading, there is a method of reducing the output of the excitation light source such as a laser light source, a method of reducing the output of the excitation light source such as a laser light source, and a method of using an NO filter, AOM, etc. in the optical path of the excitation light emitted from the light source. A method of attenuation, a method of providing a light source for pre-reading and a light source for main reading separately and making the output of the former smaller than the output of the latter, and a method of increasing the beam diameter of the excitation light,
Examples include a method of increasing the scanning speed of excitation light and a method of increasing the transport speed of the stimulable phosphor sheet.

According to the above method, the recording state and recording pattern of the radiographic image information accumulated and recorded on the stimulable phosphor sheet can be known in advance before the actual reading, so the reading system has an exceptionally wide dynamic range. Even if you do not use the recording pattern, you can adjust the reading gain appropriately based on this recorded information, determine the recording scale factor, and apply signal processing to the electrical signal after reading according to this recording pattern. It becomes possible to obtain radiographic images with excellent interpretation suitability.

However, when we perform the above-mentioned read-ahead, of course,
The time required for the radiation image information reading process is longer than when only the actual reading is performed.

(Purpose of the Invention) The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to grasp the accumulated record information of a stimulable phosphor sheet without reducing the speed of the radiation image information reading process, and to It is an object of the present invention to provide a method for reading radiation image information that can optimally set reading conditions for stimulated luminescence light or image processing conditions based on recorded information, and a ll1H that implements the method.

(Structure of the Invention) The radiation image information reading method of the present invention irradiates excitation light onto a sheet on which radiation image information of the object is stored and recorded by irradiating the radiation that has passed through the object, as described above. In the radiation image information reading method for obtaining an image signal carrying the radiation image information by reading the stimulated luminescence light emitted from the sheet by light irradiation using a photoelectric reading means, the radiation image is irradiated to the object and transmitted through the object. the radiation is incident on an image intensifier camera, and based on subject information detected by the image intensifier camera, reading conditions for the stimulated luminescence light and/or image processing conditions for the read image signal are set. It is characterized by the fact that

The radiation image information reading device of the present invention that implements the above method includes excitation light irradiation means for irradiating excitation light onto the stimulable phosphor sheet on which radiation image information has been accumulated and recorded as described above;
a means for transporting the stimulable phosphor sheet; a photoelectric reading means for obtaining an image signal by chargeably detecting stimulated luminescent light, which carries ms image information, emitted from the stimulable phosphor sheet by irradiation with the excitation light; Based on the image intensifier camera that detects the radiation transmitted through the object and the object information detected by this image intensifier camera,
It is composed of a control circuit that sets reading conditions for the stimulated luminescence light and/or image processing conditions for the image signal.

When recording radiation image information of a subject (radiography), in general, in order to determine the radiation field, etc., the subject is irradiated with weak radiation prior to radiography, and the transmitted radiation image of the subject is recorded using an image intensifier camera. In many cases, the image is photographed and displayed on a CRT, etc. for observation.In such cases, this image intensifier camera can be used to grasp the above-mentioned subject information, and it is also possible to do so. is preferred.

(Embodiments) Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows a radiation image information reading device according to one embodiment of the present invention. As an example, the device of this embodiment has the following features:
This device is incorporated into a radiation image information recording/reading device that records and reads radiation image information while circulating a stimulable phosphor sheet. As shown in the figure, the radiographic image information recording/reading apparatus includes endless belts 1.2.
3.4.5.6.7.8.9.10, guide rollers 11.12.13.14 and guide plates 15.16.17, which rotate following the endless belt 1.6.7.10, respectively.
．． 18.19.20.21 and nip roller 22.23
．． A circulation path 26 for sheet conveyance is constructed of sheets 24 and 25, and within this circulation path 26, a plurality (in this example, five sheets) of stimulable phosphor sheets 30 are placed at appropriate intervals. These stimulable phosphor sheets 3
0 is circularly conveyed in the six directions of arrows in the figure by the endless belts 1 to 10 as sheet circulation conveyance means and nip rollers 22, 23, 24, and 25.

The endless belts 2.3 are configured to hold a stimulable phosphor sheet 30 vertically between each other, and a photographing stand is placed on the side of these endless belts 2.3 (left side in the figure). 41 is provided, and a radiation source 42 such as an X-ray source is provided at a position facing the endless belt 2.3 with the imaging table 41 in between. A recording section 40 is configured. During radiographic imaging of a patient (subject) 43, the sheet 30 used for imaging is held between the endless belts 2.3 as shown in the figure, and the patient 43 is positioned in front of the imaging table 41. Radiation source 42 is activated. As a result, the transmitted radiation image of the subject 43 is projected onto the sheet 30, and the radiation image information of the subject 43 is stored and recorded on the sheet 30.

An image intensifier camera 45, which constitutes a part of the radiation image information reading device of this embodiment, is provided on the opposite side of the imaging table 41 across the endless belt 2.3. This image intensifier camera 45 consists of an image intensifier 45A and a television camera 45B, and the image signal S1 outputted from the television camera 453 is passed through an amplifier 60 including a logarithmic conversion circuit.
and a control circuit 6, which will be described later, via an A/D converter 61.
2 and CRT63. Endless belt 2. To radiograph the subject 43.
Before the stimulable phosphor sheet 30 is placed between the 3 and 3, the subject 43 is irradiated with weak fluoroscopic radiation from a radiation source 42. The weak radiation for fluoroscopy that has passed through the subject 43 enters the image intensifier 45A, and the image intensifier 45A intensifies the radiation of the subject 4.
No. 3 radiation image is taken by the television camera 45B. The CRT 63 displays a radiation image of the subject 43 based on the image signal S1 output from the television camera 45B. Therefore, the radiographer can set preferable imaging conditions such as the radiation irradiation field while observing the displayed image on the CRT 63.

An image reading unit 50 is provided at the lower right end position of the circulation passage 26 in the figure. In this image reading section 50,
A laser light source 51 is installed above the endless belt 8 that constitutes a part of the reading section 50, and a mirror 53 is used to scan the output laser light 52 onto the sheet 30 on the endless belt 8 in the width direction thereof. and a galvanometer mirror 54.

By this reciprocating movement of the galvanometer mirror 54, the laser beam 52 is main-scanned over the sheet 30 on which the radiation image has been accumulated and recorded. Note that after a radiation image is recorded on the sheet 30 in the image recording section 40, the sheet circulation conveyance means is driven to convey it to the image reading section 50. At the scanning position of the laser beam 52 on the sheet 30, there is a condensing reflective mirror 55 and a condensing optical element 5 along the main scanning line.
6 is placed. Sheet 3 irradiated with laser light 52
The stimulated luminescence light emitted from the sheet 30 and directly proceeding to the condensing optical element 56 and the stimulated luminescence light emitted from the sheet 30 and reflected by the condensing reflecting mirror 55 are transmitted to the incident end surface 56A of the condensing optical element 5G. The light enters the condensing optical element 5G, is guided therein by total reflection, and reaches the exit end face 5 of the element 56.
The stimulated luminescent light is received by a photomultiplier 57 connected to the photomultiplier 6B, and the stimulated luminescence light is read out photoelectrically. As mentioned above, the laser beam 52
At the same time as the main scanning is performed, the sheet 30 is conveyed by the endless belt 8 in the six directions indicated by the arrows in the figure (that is, directions substantially perpendicular to the main scanning direction) to perform the sub-scanning, so that the entire surface of the sheet 30 is scanned. The stored radiation image information is read. The image signal S2 read by the photomultiplier 57 is input to an amplifier 64 including a logarithmic conversion circuit, and is inputted based on the read gain setting value a set by the control circuit 62! This main reading amplifier 19, whose ti is set to 11 degrees, amplifies the electric signal to an appropriate level. The amplified electrical signal is input to the A/D converter Mk 65, and the control circuit 62
Based on the recording scale factor setting kIib set by
It is input to G. This signal processing circuit 66 is a control circuit 62
The playback image processing condition setting value C (parameter is 1) set by
The above digital signal is subjected to signal processing (IN image processing) to obtain an excellent radiation image suitable for observation and reading, and this signal-processed digital signal is The image is transmitted to an image reproduction device G7 that outputs the image as a visible image. The signal processing performed in the signal processing circuit 66 is described in Japanese Patent Application Laid-open No. 55
-87970, 5G-11038, 56-75
No. 137, No. 5G-75139, No. 56-75141
Frequency processing disclosed in Japanese Patent Application Laid-open Nos. 55-116339 and 55-1163, etc.
Examples include gradation processing disclosed in No. 40, No. 55-88740, and the like.

The image reproducing device G7 reproduces the radiation image based on the image signal sent from the signal processing circuit 66.

Reproduction methods include recording by scanning a photosensitive material with a laser beam, electronic display on a CRT, etc., and CR.
Video printer for radiation images displayed on T etc.! Various methods can be used, such as a method of recording on a heat-sensitive recording material using a heat ray.

Next, the settings of the reading gain, recording scale factor, and image processing conditions in the I control circuit 62 will be explained. Figure 2 shows the image intensifier camera 45.
It shows the relationship between the image signal output by the stimulable luminescent light, the image density of the subject (thickness of the subject), and the amount of stimulated luminescence light emitted from the stimulable phosphor sheet 30. As shown in the figure, if the intensity of the weak radiation for fluoroscopy, the sensitivity of the image intensifier camera 45, the intensity of the imaging radiation and the intensity of the laser beam 52 (excitation light) are given, then the stimulable phosphor sheet The stimulated luminescent light layer from 30 can be ascertained from the output signal S1 of the image intensifier camera 45. To explain in more detail, in general, the amount of stimulated luminescence is ε, and the image intensifier camera 45
When the output signal of is S, the following relationship holds approximately: log E=mlog S+n (m is approximately a constant, n is a constant determined by the intensity ratio of the weak radiation for fluoroscopy and the radiation for imaging). Therefore, the condition determining section 62G of the control circuit 62 includes the radiation control section 46.
A signal S3 indicating the intensity of the weak radiation for fluoroscopy and a signal S4 indicating the intensity of the radiographic radiation are input from. Further, information regarding the sensitivity of the image intensifier camera 45 and information regarding the intensity of the laser beam 52 are given to the condition determining section 62G as fixed conditions.

The histogram creation section 62A of the control circuit 62
A histogram of the output signal of the D converter 61 is created, and the histogram is analyzed in the histogram analysis section 62B. Analysis information regarding this histogram is input to the condition determining unit 62G, which determines the signals S3 and S4, fixed conditions, and the imaging site and/or imaging method input by the human resources department. Based on this information and this analysis information, the above-mentioned reading gain setting value a1 recording scale factor setting 61b and image processing condition setting value C are determined as follows.

First, based on the relationship shown in FIG.
and fixed conditions and image intensifier camera 4
The histogram of the amount of stimulated luminescence during photographing is estimated from the histogram of the output image signal in step 5. Next, the reading gain and recording scale factor are determined from the estimated histogram information described above so that electrical image signals having approximately the same level range can be input to the image processing stage even if the imaging site or imaging method is different. Specifically, as shown in FIG. 3, if the width of the histogram is too narrow, the recording scale factor is increased, and if it is too wide, the recording scale factor is adjusted to be low. Further, if the signal level of the entire histogram is small, the reading gain is increased, and if the signal level is large, the reading gain is set low. Image processing conditions are mainly determined by the area to be imaged and/or the imaging method; for example, in the case of low-dose imaging, frequency processing
Lower it by 1 degree.

If the accumulated record information of the subject 43 recorded on the sheet 30 is known in advance as described above, and the reading conditions (reading gain and recording scale factor) and image processing conditions are determined based on the results, the density , appropriate contrast and effective use of the dynamic range of the image reproduction medium in the image reproduction device 61, suitability for observation and interpretation (diagnosis performance)
An image with an excellent reproduction number fI4m can be obtained.

The sheet 30 whose image has been read is conveyed along the guide plate 18 by the endless belt 9.10, and sent to the erasing section 70 through the nip roller 22, the guide plate 19, and the nip roller 23. The erasing section 70 includes a box 71 and a large number of fluorescent lamps, tungsten lamps, and sodium lamps arranged inside the box 71.

The sheet 30 is composed of an erasing light source 72 such as a xenon lamp or an iodine lamp, and after the shutter 13 is opened, the sheet 30 is conveyed into the box 11 by the nip rollers 23. When the sheet 30 is sent into the box 71, the shutter 13 is closed. The erasing light source 72 inside the box 11 mainly emits light in the excitation wavelength range of the stimulable phosphor of the sheet 30, and the radiation energy remaining in the sheet 30 after reading the image is transferred to the sheet 30. When such light is irradiated, it is emitted from the sheet 30. Note that since the shutter 13 is closed at this time, the erasing light does not leak and enter the image reading section 50 and generate noise in the read signal.

The sheet 30 in which the image (afterimage) has been erased to such an extent that radiation image information can be recorded again is transferred to the nip roller 2.
4 is rotated and discharged to the outside of the erasing section 70. The discharged sheet 30 is sent to the nip roller 25 through the guide plate 20, and then the nip roller 25 transfers the sheet 30 to the guide plate 2.
1 to the endless belt 1, and thereafter sent to the image recording section 40 in the same manner as described above and used for radiography.

The above is an example of the present invention applied to a device that records and reads radiation image information in one device/7I! Although the embodiment has been described, the present invention can of course be applied to a device exclusively for reading radial JJ-ray image information. In such a case, when the radiographic image information recording (radiographing) device and the radiographic image information reading device are connected online, the intensity signal of the weak radiation for fluoroscopy and the intensity signal of the radiographic radiation described above are different from each other. It can be transmitted online to the radiation image information reading device. In addition, if the radiation image information recording device and the radiation image information reading device are not connected online as described above, information regarding the intensity of weak radiation for fluoroscopy and radiation for imaging may be stored on a magnetic card, floppy disk, etc. Record it on the medium or the stimulable phosphor sheet 1-30 itself,
The above information may be read when reading radiation image information and used to determine reading conditions and image processing conditions.

In addition, the entire output signal S1 of the image intensifier camera 45 is not used to determine the reading conditions and image processing conditions, but is based on the output signal S1 for only a part of the region of interest within the stimulable phosphor sheet 30. The reading conditions and image processing conditions may be determined based on the image processing conditions. In this way, it is possible to obtain 1q reproduced radiographic images that are not affected by accumulated recorded information other than the region of interest and have particularly excellent suitability for observation and interpretation of the region of interest. This region of interest can be arbitrarily set, for example, by specifying 11 regions in the perspective image displayed on the CRT 63 using a light pen. In order to determine the reading conditions from the histogram for this region of interest or the entire sheet 30, the highest density signal 3 within the region of interest or the entire sheet 30 must be
max1 A method of setting the reading conditions so that the minimum density signal 5IIlin carries the desired maximum image density and minimum image density, respectively, and furthermore, the region of interest or the sheet 30.
It is possible to adopt a method of setting reading conditions so that the average level of the image signal within the entire area has a desired average image density.

In the embodiment described above, both the reading conditions (reading gain and recording scale factor) and image processing conditions are set based on the subject information detected by the image intensifier camera 45.
The present invention is of course applicable to a radiation image information reading device that sets only reading conditions based on subject information detected by an image intensifier camera, or a radiation image information reading device that sets only image processing conditions based on the above subject information. The same applies to

(Effects of the Invention) As described in detail above, according to the present invention, the reading conditions and/or image processing conditions for radiation image information are optimally set based on the accumulated record information of the subject detected by the image intensifier camera. Therefore, reconstructed radiographic images with excellent diagnostic suitability can be obtained. Further, according to the present invention, there is no need to reduce the processing speed of reading radiation image information in order to grasp the accumulated record information of the subject in advance.
The radiation image information reading processing capacity can be improved compared to the case where the above-mentioned pre-reading is performed.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a radiation image information recording/reading device equipped with a radiation image information reading device according to an embodiment of the present invention, and FIG. 2 shows an output image signal of an image intensifier camera according to the present invention and a subject 81 It is an explanatory view showing the relationship between degree and -ta. 1-10...Endless belt 11-14...Guide roller 15-21...Guide plate 22-25...Nip roller 26...Circulation passage 30...Storage phosphor sheet 50...・Image*M taking part 45...Image intensifier camera 46...
・Radiation control unit 60.64...Amplifier 61.65...A/
D converter 62...control circuit 66...signal processing circuit 68...imaging site/imaging method manual section a...reading gain setting value

Claims (2)

[Claims] (1) Excitation light is irradiated onto a stimulable phosphor sheet that has been irradiated with radiation that has passed through the subject and recorded radiation image information of the subject, and stimulated luminescence is emitted from the sheet due to the irradiation with the excitation light. A radiation image information reading method for reading light with a photoelectric reading means to obtain an image signal carrying the radiation image information, comprising: irradiating the subject with radiation; and causing the radiation that has passed through the subject to enter an image intensifier camera; A radiation image information reading method, comprising setting reading conditions for the stimulated luminescence light and/or image processing conditions for the image signal based on subject information detected by the image intensifier camera. (2) excitation light irradiation means for irradiating excitation light onto a stimulable phosphor sheet on which radiation image information of the subject has been irradiated with radiation that has passed through the subject; and means for transporting the stimulable phosphor sheet. , photoelectric reading means for photoelectrically detecting stimulated luminescent light carrying radiation image information, which is emitted from the stimulable phosphor sheet by irradiation with the excitation light, and obtains an image signal;
An image intensifier camera that detects radiation transmitted through the object, and based on object information detected by the image intensifier camera, read conditions for the stimulated luminescence light and/or image processing conditions for the image signal. A radiation image information reading device consisting of a control circuit to be set.