JPH0419638A - Method for recording positioning marker image, radiation image recording device and cassette - Google Patents

Abstract

PURPOSE:To make it possible to imprint reference points or a reference line independently of the width of a radiant ray irradiating field by recording marker images on an accumulative phosphor sheet by using marker recording radiant rays radiated from a radiation source in the case of recording the radiation image of a subject on the sheet. CONSTITUTION:This radiation image recording device is provided with an X-ray source 3 arranged on the upper part of a photographing board 2 to irradiate the surface of a subject 1 with X-ray and an accumulative phosphor sheet storing cassette 5 arranged on a position on which the X-ray image of the subject 1 can be recorded and provided with marker image forming radiant ray radiation parts 4A, 4B on its upper face. Respective radiating parts 4A, 4B are arranged on two corner parts to be the diagonal positions of the upper face of the cassette 5 to form maker images on the corner parts of each accumulative phosphor sheet stored in the cassette 5 at the time of photographing the subject 1. Thus, the marker images constituting reference points or a reference line can surely be formed on the corner parts of the sheet independently of the width of the irradiating field.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a recording method, a radiation image recording device, and a cassette for recording a marker image for alignment on a stimulable phosphor sheet. In order to obtain an image signal with a good /N or an image signal that extracts and represents only a part of the structure in the image, it is necessary to align the plurality of sheets when photographing the above-mentioned sheets in an overlapping manner or in succession. The present invention relates to a method for recording a marker image for alignment, and a radiation image recording apparatus and a cassette that utilize the method for recording marker images for alignment.

(Prior art) When a certain type of phosphor is irradiated with radiation (X-rays, α-rays, β-rays, γ-rays, ultraviolet rays, electron beams, etc.), part of the energy of this radiation is accumulated in the phosphor. Then, when the phosphor is irradiated with excitation light such as visible light, the phosphor exhibits stimulated luminescence depending on the accumulated energy. A phosphor exhibiting such properties is called a stimulable phosphor (stimulable phosphor).

Using this stimulable phosphor, radiation image information of a subject such as a human body is recorded on a stimulable phosphor sheet (hereinafter referred to as a stimulable phosphor sheet), which is then scanned with excitation light and illuminated. A method has been proposed in which the stimulated emitted light is photoelectrically read to obtain an image signal, and the image signal is processed to obtain a radiographic image of a subject that is suitable for diagnosis (for example, Japanese Patent Application Laid-Open No. 1983-1981). No. 12429, No. 55-116340, No. 55-IEi3472, No. 5B-11395,
5B-104645, etc.). This final image can be reproduced as a hard copy or on a CRT.

On the other hand, a radiation image superimposition process has been known for some time (for example, see Japanese Patent Laid-Open No. 5FT-11399). Generally, radiological images are used for diagnostic and other purposes, but
In its use, it is required to detect minute differences in radiation absorption of the subject. The degree of detection in a radiographic image is called contrast detectability or simply detectability, and it can be said that the higher the detectability, the higher the diagnostic performance, and the radiological image has higher practical value. Therefore, in order to improve diagnostic performance, it is desirable to increase this detection ability, but the most important factor that hinders this is various noises.

In a radiation image recording system using a stimulable phosphor sheet, the presence of various noises is recognized in the step of accumulating and recording a radiation image on the stimulable phosphor sheet and reading it out. Superposition processing is a method that greatly reduces these various noises and makes it possible to clearly observe even the slightest radiation absorption difference in the subject in the final image, in other words, it greatly improves detection ability. The method and action are to photograph (accumulate and record) radiation images on each of multiple stimulable phosphor sheets that are stacked or consecutively stacked, and to superimpose multiple image signals obtained by reading the multiple sheets. It was designed to match. In other words, the various types of noise mentioned above often exhibit different distributions for each image on each sheet, so by overlapping the images of these sheets, each noise is averaged, and the noise is not noticeable in the overlapping image. It disappears. In other words, an image signal with a good S/N ratio can be obtained. In the superimposition process described in 2, for example, two stimulable phosphor sheets are placed in a cassette or one after the other and the subject is photographed.
The method used is to sequentially perform reading processing similar to normal reading processing on two stimulable phosphor sheets to obtain two sets of image signals, and then superimpose these image signals. It is being

On the other hand, subtraction processing of radiographic images has been conventionally known. This radiographic image subtraction is a process in which two radiographic images taken under different conditions are photoelectrically read out to obtain digital image signals, and then these digital image signals are subtracted by matching each pixel of both images. , is a method of obtaining a difference signal that extracts a specific structure in a radiation image, and by using the difference signal obtained in this way, it is possible to reproduce a radiation image in which only the specific structure has been extracted.

There are basically two methods for this subtraction process: That is, (1) A specific structure is extracted by subtracting the image signal of a radiographic image in which no contrast agent has been injected from the image signal of a radiographic image in which a specific structure has been emphasized by contrast agent injection. (2) irradiating the same subject with radiation having different energy distributions, or irradiating the radiation after passing through the subject to two radiation detection means with different energy distribution states; , thereby creating an image in which a specific structure differs between two radiographic images, and then subtracting (subtracting) the image signals of these two radiographic images with appropriate weighting to identify the specific structure. This is a so-called energy subtraction process that extracts images of objects.

Since this subtraction processing is an extremely effective method, especially in medical diagnosis, it has attracted much attention in recent years, and its research and development are actively progressing by making full use of electronic engineering technology.

In order to perform energy subtraction processing using this stimulable phosphor sheet, it is necessary to record (photograph) images on two stimulable phosphor sheets so that the image information of the part corresponding to a specific structure is different. Often, specifically, two types of radiation with different energy distributions are used to perform two types of imaging.
By using the 2-shot method, which is performed twice in succession, and by simultaneously exposing two stacked stimulable phosphor sheets with the radiation that has passed through the subject, both sheets are irradiated with radiation that has different energy distributions. l5hot
Law or known.

In this method of recording and reproducing radiation image information using a stimulable phosphor sheet, the radiation image information recorded on the sheet is directly read in the form of an electrical image signal. For example, it becomes possible to easily perform the superposition processing and subtraction processing as described above.

However, when attempting to obtain a desired image by superposition processing or subtraction processing using the above-mentioned stimulable phosphor sheets, it was found that the following problems occurred.

That is, two (sometimes three or more) different stimulable phosphor sheets are sequentially or simultaneously inserted into an imaging platform to capture radiation images to be superimposed or subtracted, and then the stimulable phosphor sheets are In the process of individually inserting phosphor sheets into a reading device and reading out the radiation image to be processed, even if the mechanical precision of all devices involved in imaging and reading is improved, the image to be processed Positional and rotational deviations occur between the images, and as a result, images that should be erased are not erased in the above processing, or images that should be extracted are erased, resulting in false images, resulting in accurate superimposition and subtraction images. It was found that this poses a serious problem in diagnosis.

If such a discrepancy occurs between the radiation image information stored and recorded on the stimulable phosphor sheet, the radiation image is stored and recorded in the stimulable phosphor as a latent image, so the X-ray image cannot be taken as a visible image. Unlike the case of X-ray photographic film, which can be photographed, it is not possible to align two X-ray photographs by visual inspection, making misalignment correction extremely difficult.

Furthermore, even if positional and rotational deviations that occur between two radiological images can be detected by some means, the data of the read radiographic images must be corrected. A large amount of time is spent on this process, which poses a very serious problem in practice.

In order to solve this problem, the present applicant has filed a patent application filed in
45473 (Japanese Unexamined Patent Publication No. 58-163338), a metal ring-shaped marker that provides a reference line or point when recording a radiation image on a stimulable phosphor sheet is imprinted at the same time. , detect the positional coordinates of the reference point or reference line from the digital image data of the radiation image read out from the stimulable phosphor sheet, and determine the position between the two radiation images to be subjected to subtraction processing from the detected positional coordinates. The displacement and rotational displacement are calculated, one of the radiation images to be processed is rotated and moved on the digital image data based on the positional displacement and rotational displacement, and then each corresponding pixel of the two radiation images is We proposed a subtraction processing method for radiographic images that performs subtraction of image data between the stimulable phosphor sheets.

According to this method, it is possible to automatically correct positional and rotational deviations that occur between radiation images stored and recorded on a stimulable phosphor sheet, resulting in high contrast resolution, high spatial resolution, and no false images. It is possible to obtain subtraction images with excellent suitability for observation and interpretation.

(Problem to be Solved by the Invention) By the way, when it is sufficient to obtain the above-mentioned superimposed image or subtraction image of only a part of the patient, for example, it is necessary to avoid irradiating the patient with more radiation than necessary. Therefore, it is desirable to narrow down the irradiation field to only a part of the area.

However, the above-mentioned markers are usually placed at the corners of the stimulable phosphor sheet so that the reference points and lines do not overlap with the desired subject image as much as possible. Therefore, when the irradiation field is narrowed down, there is a problem in that the reference points and reference lines cannot be imprinted on the stimulable phosphor sheet if the markers are fixed at normal positions.

Furthermore, by moving the marker according to the width of the irradiation field, the reference point or reference line can be imprinted.
It is not preferable to move this marker every time a photograph is taken because the photographer's photographing operation becomes complicated.

The present invention has been developed in view of the above circumstances, and it provides a reference point when performing overlay processing or subtraction processing on a stimulable phosphor sheet, regardless of the width or narrowness of the radiation irradiation field, without moving the marker. It is an object of the present invention to provide a method for recording an alignment marker image that can imprint a reference line and a radiation image recording apparatus and a cassette that utilize the alignment marker image recording method.

(Means for Solving the Problems) The method for recording a marker image for positioning of the present invention is a method for recording a subject image on a stimulable phosphor sheet using radiation from a radiation source. A marker image is recorded on the sheet using radiation from the sheet. That is, the method for recording marker images for alignment of the present invention is such that when recording a radiation image of a subject on a stimulable phosphor sheet using radiation from a main radiation source, the radiation from the radiation source for recording the marker image is A marker image constituting a reference point or a reference line is recorded on the sheet using the method.

Furthermore, the radiation image recording apparatus of the present invention is characterized in that a marker image recording radiation source for recording marker images on the stimulable phosphor sheet is disposed at a position facing the stimulable phosphor sheet. That is, the radiation image recording apparatus of the present invention includes a main radiation source that generates radiation, a subject placement section where a subject is placed, and a position facing the main radiation source with the subject placement section in between. Further, a stimulable phosphor sheet on which a radiation image of the subject is recorded, and a stimulable phosphor sheet disposed at a position facing the stimulable phosphor sheet,
The present invention is characterized by comprising a marker image recording radiation source that records marker images constituting a reference point or a reference line.

Furthermore, the cassette of the present invention includes a marker image recording radiation source for recording a marker image on the sheet at a position facing the sheet when the sheet is stored in the cassette body for storing the stimulable phosphor sheet. It is characterized by the fact that That is, the cassette of the present invention includes a cassette main body capable of storing a stimulable phosphor sheet on which a radiation image is recorded, and a reference point arranged on the cassette main body at a position facing the sheet stored in the cassette main body. Alternatively, the present invention is characterized by comprising a marker image recording radiation source that records marker images constituting the reference line.

Here, the marker image formed on the stimulable phosphor sheet is formed by varying the amount of radiation irradiated from the surrounding area so that the marker image can be clearly identified on the radiation reproduced image. There is a need.

(Function) According to the above-described configuration, the marker image constituting the reference point or reference line is formed on the stimulable phosphor sheet using a radiation source different from the radiation source for photographing the subject. This marker image can be reliably formed at the corner of the stimulable phosphor sheet regardless of the width of the irradiation field. Therefore, even if the subject is imaged by narrowing the irradiation field to only the required area without considering the relationship between the position where the marker image is to be formed and the irradiation field, multiple radiation Image alignment can be performed reliably.

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

FIG. 1 is a schematic perspective view showing an embodiment of the method for recording an alignment marker image according to the present invention.

In this embodiment, there is a photographing table 2 on which the subject 1 is placed and the subject 1 placed at a predetermined X-ray imaging position, and a photographing table 2 placed above the photographing table 2 that irradiates the subject 1 with X-rays. do X
A radiation source 3 and a radiographing table 2 are placed in a position facing the X-ray source 3 and capable of recording an X-ray image of the subject 1.
It is provided with a cassette 5 for storing a stimulable phosphor sheet, on the top of which radiation generating sections 4A and 4B for forming marker images are attached. The radiation generating parts 4A and 4B are respectively arranged at two diagonal corners of the upper surface of the cassette 5,
The stimulable phosphor sheet is arranged so that a marker image can be formed at the corner of the stimulable phosphor sheet housed in the cassette 5 when photographing the subject 1.

FIG. 2 shows a cross section taken along the line X--X in FIG. 1, and shows a cross-sectional view of the cassette 5. As shown in FIG.

Inside this cassette 5 are two stimulable phosphor sheets 6A,
B is housed so as to sandwich the energy separation filter 7. X emitted from the X-ray source 3 and transmitted through the subject 1
The rays pass through the imaging table 2 and the upper wall of the cassette 5 and are irradiated onto the stimulable phosphor sheets 6A, B, whereby the X-ray images of the subject are stored and recorded on the sheets 6A, B. The energy separation filter 7 is a shielding plate made of, for example, a copper plate for shielding X-rays in a low energy region, and among the X-rays transmitted through the sheet 6A and irradiated to this energy separation filter, high energy regions Only the X-rays are transmitted, and an X-ray image of the subject is recorded on the sheet 6B.

Therefore, the sheet 6A records mainly X-ray images of low-energy region X-rays, and the sheet 6B records X-ray images of high-energy region X-rays, and these X-ray images are photoelectrically recorded. After reading, it becomes possible to efficiently perform subtraction processing on the image signal.

Furthermore, as described above, the radiation generating sections 4A and 4B are arranged close to the upper wall of the cassette 5.

As shown in FIGS. 1 and 2, these radiation generating parts 4A and 4B include a cylindrical radiation shielding member with a hole bored inside and a radioactive isotope substance 8 fixed at the bottom of the hole. The radiation from this radioisotope substance 8 is emitted to the outside through the hole in the radiation shielding member. The radiation emitted from the radiation generating sections 4A, B in this manner passes through the earthen wall of the cassette 5 made of aluminum or the like and is irradiated onto predetermined positions of the stimulable phosphor sheets 6A, B. The above sheet 6A was formed by radiation irradiation.

The radiographic images accumulated and recorded in B cannot be seen as they are with the naked eye, but for convenience of explanation, in FIG. 3, marker images 9A and B formed on the sheet 6A by this radiation irradiation are conceptually shown. There is. That is, a marker image 9A is formed by the radiation from the radiation generating section 4A, and a marker image 9B is formed by the radiation from the radiation generating section 4B. Since these two marker images 9A and 9B are arranged at the two corner parts forming the sheet 6A, these two marker images 9A and B are also formed at the two corner parts forming diagonal positions on the sheet 6A. In this embodiment, the marker images 9A and 9B are formed at the corners of the sheet 6, so even if the irradiation field spreads over the entire surface of the sheet 6A, the marker images 9A and 9B are
There is little possibility that A and B will overlap with the main part of the subject in the Xi image. Further, the marker images 9A and 9B as described above are similarly formed on the sheet 6B, and this marker image 9
Since markers A and B are formed at corresponding positions on the two sheets 6A and B, after obtaining the image signal, these marker images 9A
, B, it becomes possible to perform relative alignment of the two X-ray images.

In addition, in FIG. 2, radiation is constantly emitted from the radiation generating parts 4A and 4B, but compared to the time when the sheets 6A and B are placed at a predetermined position in the cassette 5, this sheet In cases where it takes time to set the sheets 6A and 6B in the cassette 5, the sheets 6A and 6B may be placed in the cassette 5 while the sheets are being moved.

This radiation generating part 4A irradiates other parts of B.

Since the amount of radiation from B will increase, in order to eliminate this, a radiation shielding shutter is provided at the radiation exit portion of the radiation generating portions 4A and H, and this sheet 6A
It is desirable to control the radiation irradiation by performing an operation such as opening this shutter only for a predetermined time after , B are set.

Furthermore, the radioisotope substance 8 contained in the above-mentioned radiation generating sections 4A, B includes radiation that can pass through the upper wall of the case/note 5 and accumulate radioactive energy in the stimulable phosphor sheets 6A, B. For example, any substance containing a radioactive isotope that can emit X-rays, β-rays, γ-rays, etc. may be used. Examples of such radioactive isotopes include 3H,+4(,32p,
60 (0,90Sr, 226Ra, etc.)
In the embodiments described above, it is necessary to use radioactive isotopes that emit radiation in the energy range that is not screened by the energy separation filter.

The cassette 5A shown in FIG. 4 is the same as the cassette 5A shown in FIG.
It has almost the same structure as the cassette 5 shown in FIG. 3, but differs from the cassette 5 shown in FIG. There is. This is conveniently configured to mainly perform superimposition processing using image signals read from radiation images stored and recorded on these two sheets 6C and 6D. In this case as well, when photographing a subject, marker images 9AB are formed at two corresponding positions on the two stimulable phosphor sheets 6C and D by the radiation emitted from the radiation generating parts 4A and 4B, and an image signal is obtained. After that, the two X-ray images can be relatively aligned based on the marker images 9A and 9B.

FIG. 5 shows an embodiment in which the method of recording marker images for positioning of the present invention is applied to a built-in radiographic image recording/reading device in which a recording/reading image portion of radiographic image information is compactly incorporated. It is something. This built-in type device conveys the stimulable phosphor sheets 6E and F to the photographing section 5B by the roller IOA at the photographing entrance.
The photographing section 5B accumulates and records the subject X-ray images on the sheets 6E and F, and then the sheets 6E and F are stored in the photographing section 5B.
The sheets 6E and F are taken out from the image reading section B and conveyed toward the image reading section by rollers IOB at the photographing exit section.

Two stimulable phosphor sheets 6 arranged in this photographing section 5B
Similarly to the two stimulable phosphor sheets 6A and B stored in the cassette 5 shown in FIG.
An energy separation filter 7 is disposed between them for convenience in making subsequent subtraction processing more efficient. In this case as well, the radiation emitted from the radiation generating parts 4A and 4B causes the two stimulable phosphor sheets 6E to
, F are formed at two corresponding positions, and after obtaining an image signal, relative alignment of the two X-ray images can be performed based on the marker images 9A, H. .

It should be noted that the alignment marker image recording method, radiation image recording device, and cassette of the present invention are not limited to those of the above-described embodiment, and various changes can be made to the configuration of this embodiment. For example, the shape of the radiation generating portion does not have to be cylindrical, but may be any shape that can efficiently emit radiation toward the stimulable phosphor sheet. Further, a member such as a ring capable of shielding radiation is arranged at a predetermined position between the radiation generating part and the stimulable phosphor sheet, and a non-irradiation region in the shape of this member is formed on the sheet. It is also possible to record marker images. Furthermore, the number of radiation generating parts is not limited to two, and the number of radiation generating parts may be one if even one marker image formed can function as a reference point or reference line. Of course, it is also possible to provide three or more of these. Further, the arrangement position may be any position that can form a predetermined marker image on a plurality of stimulable phosphor sheets to be subjected to superimposition processing or subtraction processing, and it is also possible to arrange it inside a cassette, for example. be. Note that the number of stimulable phosphor sheets on which marker images are to be formed simultaneously is not limited to two, and may be three or more.

In addition, although the above-mentioned embodiment shows a case in which radiographic images are simultaneously stored and recorded with stacked stimulable phosphor sheets, the stimulable phosphor sheets are continuously put in and taken out of the imaging unit, and the radiographic images are successively recorded. It is also possible to apply the present invention to the case of storing and recording.

Note that the method for recording alignment marker images, the radiation image recording device, and the cassette of the present invention are not limited to recording target tissues of the human body, and can be used, for example, to analyze the internal structure of industrial products or archaeological objects. Of course, it is also possible to record these structures when recording.

(Effects of the Invention) As explained above, according to the alignment marker image recording method, radiation image recording device, and cassette of the present invention, a radiation source for marker image recording that is different from a radiation source for recording an object is used. Therefore, the marker image is recorded on the stimulable phosphor sheet when recording the subject image, and the marker image can be reliably recorded on the stimulable phosphor sheet regardless of the width or narrowness of the irradiation field. A plurality of radiation images can be reliably aligned in superposition processing or subtraction processing without considering the relationship between the recording position and this irradiation field.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing an embodiment of the method for recording alignment marker images of the present invention, FIG. 2 is a cross-sectional view taken along line X-X of the cassette shown in FIG. 1, and FIG. A schematic diagram conceptually showing a marker image recorded on a phosphor sheet, FIG. 4 is a sectional view showing a cassette partially different from FIG. 1, and FIG. 5 is a recording of a marker image for alignment according to the present invention. FIG. 2 is a schematic cross-sectional view showing an example of an imaging unit when the method is applied to a built-in radiographic image recording/reading device. 1...Subject 2...Photography stand 3...X
Radiation source 4A, B...Radiation generating part 5...
Cassette 6A, B, C, D, E, F...Stormable phosphor sheet 7
...Energy separation filter 8...Radioisotope substance 9A, B...Marker image Fig.

Claims (3)

[Claims] (1) When recording a radiation image of a subject on a stimulable phosphor sheet using radiation from the main radiation source, the radiation from the radiation source for recording marker images is used to mark reference points or reference points on the sheet. A method for recording marker images for alignment, comprising recording marker images forming a line. (2) a main radiation source that generates radiation; a subject placement section where a subject is placed; and a radiation image of the subject placed in a position facing the main radiation source with the subject placement section sandwiched between them. a stimulable phosphor sheet; and a marker image recording radiation source disposed at a position facing the stimulable phosphor sheet and recording a marker image constituting a reference point or a reference line on the sheet. A radiation image recording device characterized by: (3) A cassette body capable of storing a stimulable phosphor sheet on which a radiation image is recorded; and a cassette body disposed in a position facing the sheet stored in the cassette body, and forming a reference point or a reference line on the sheet. A cassette comprising a marker image recording radiation source for recording a marker image.