JP2000023955A - Radiograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To image good radiographs by detecting information about the relative localizations of a radiation source and a cassette, and performing always accurate alignment. SOLUTION: An engineer secures a cassette 11 to the shoulder joint of a patient in accordance with Johner's position imaging method. The engineer then displaces a radiation source 10 and starts alignment so that radiation is emitted perpendicular to the cassette 11 and toward the centerline of the cassette 11. Then a liquid crystal display means 13 provided on the radiation source 10 displays the relative positions of the radiation source 10 and the cassette 11, i.e., the state of alignment in real time. The engineer can easily achieve accurate alignment by checking the display of the state of alignment. The liquid-crystal display means 13 can display not only the relative positions but also the attitudes of the radiation source 10 and the cassette 11. Therefore, an operator can rapidly deal with the displacement of the already installed cassette 11 due to the movement of the patient, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiographic apparatus generally used in fields such as medical radiography and industrial nondestructive radiography.

[0002]

2. Description of the Related Art Conventionally, a radiographic apparatus is particularly called a cassette. A thin plate-shaped dark box including a phosphor for converting radiation into fluorescence and an image receiving means for receiving fluorescence in close contact with the phosphor, It is used for photography.

[0003] A cassette is generally light and portable and can be set up freely, so that it can be used for various photographing methods. In particular, when a cassette supporting device such as a standing stand and a lying table is used, the position where the cassette is to be loaded is clear in advance. Positioning and radiation source alignment can be performed. In addition, in order to vertically and horizontally load the cassette in the standing stand and the lying table, respectively, the inclination can be accurately set by fixing the radiation source at the click position of the angle adjustment mechanism.

FIG. 5 is a plan view of a conventional radiographic apparatus, in which a cassette 2 is arranged at a predetermined distance from a radiation source 1, and the cassette 2 is composed of a phosphor 3 and an image receiving means 4. I have. Generally, the phosphor 3 has CaWO
An intensifying screen obtained by coating ₄ or Gd ₂ O ₂ S: Tb on a support, or a phosphor crystal such as CsI is used, and has a property of emitting fluorescence having an intensity proportional to the radiation dose. Also,
The image receiving means 4 is a means for generating an image according to the amount of received light,
Generally, a film is used.

[0005] A grid 5 having a structure in which lead flakes and aluminum flakes are laminated is arranged on the front surface of the cassette 2.
Is located in front of the object T in the direction of the grid 5. When the subject T is irradiated with radiation emitted from the radiation source 1, the radiation is intensity-modulated and scattered according to the structure of the subject T due to interaction such as absorption and scattering by the subject T, and reaches the grid 5. The grid 5 removes scattered radiation by transmitting only radiation parallel to the lead strip and improves the contrast of the radiation image. When the thickness of the subject T is small and scattered radiation can be ignored, the grid 5 may not be used.

[0007] The radiation transmitted through the subject T is scattered by the grid 5 and is transmitted through the front plate of the cassette 2 to reach the phosphor 3 as a radiation image. The radiation image is converted into a visible light image by the phosphor 3, and the visible light image generated by the phosphor 3 becomes an image corresponding to the amount of light by the image receiving unit 4. The radiation image is recorded on a film as a latent image that gives a photographic density substantially proportional to the logarithm of the amount of fluorescence, is presented as a visible image after development processing, and is used for diagnosis, inspection, and the like.

Recently, a technique has been developed for acquiring a digital image by using a photoelectric conversion device in which pixels formed of minute photoelectric conversion elements, switching elements, and the like are arranged in a grid as the image receiving means 4. By using this photoelectric conversion device, an image can be obtained directly as digital data, thereby facilitating image processing, making it possible to easily correct improper photographing conditions and enhance an image of a region of interest. Become. In addition, by using image communication means using a large-capacity communication line or the like, a specialist in a large hospital can diagnose a patient in a remote place where the specialist is absent. Furthermore, if image digital data is stored on a magneto-optical disk or the like, the storage space can be significantly reduced as compared with storing the film, and past images can be easily searched. It is possible to present the reference image more easily than searching for.

[0008]

However, the radiation imaging apparatus using the conventional cassette 2 has the following problems. For example, when taking an oblique image of the clavicle, a cassette is provided at approximately 45 degrees along the back of the shoulder for a patient in the supine position, and at this time, the radiation source 1 also faces the cassette. Adjust the angle. Further, when photographing a front-back image and an oblique image of many parts, the radiation source 1 is arranged so as to irradiate the cassette 2 with radiation obliquely. In such photographing, the radiation source 1 and the cassette 2 are arranged.
It is difficult to obtain accurate alignment, and it is also difficult to set the cassette 2 at an accurate angle. In particular, in the case of the cassette 2 provided on the lower side of the patient, there is a problem that its position is difficult to confirm.

[0009] Therefore, if the center of the radiation irradiation and the center of the cassette 2 are first shifted due to the inaccurate alignment, a desired radiation image will be located outside the cassette range. Next, when the cassette 2 is installed at an unexpected angle with respect to the radiation source 1, the radiation image projected on the cassette 2 may be distorted or the radiation intensity at one end and the other end of the cassette 2 may be reduced. Unlikely, shading occurs.

When the cassette 2 and the grid 5 are photographed in combination, the grid 5 has a strong directivity, so that shading occurs and the radiation intensity of the entire surface of the cassette 2 decreases. . In general, the grid 5 is a one-dimensional grid, but as a result of the rotation of the grid 5, the alignment between the one-dimensional grid of the grid 5 and the radiation source 1 becomes inaccurate. Similarly, shading occurs or the entire surface of the cassette 2 is changed. A phenomenon occurs in which the radiation intensity decreases. For this reason, there arises a problem that a skilled technique of a technician is essential for cassette photographing.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a radiation imaging apparatus that always performs accurate alignment between a radiation source and an imaging unit and realizes good radiation imaging.

[0012]

According to the present invention, there is provided a radiation imaging apparatus comprising: a radiation source for generating radiation; and imaging means for responding to radiation generated from the radiation source. At least one of the radiation source or the imaging unit is movable, and in a radiation imaging apparatus that irradiates a subject with radiation to capture an image, the position or orientation of at least one of the radiation source or the imaging unit is detectable. It is characterized by the following.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a structural view of a radiation imaging apparatus according to a first embodiment, in which a shoulder S of a human body as a subject is placed between a radiation source 10 for generating radiation and a cassette 11.
Is arranged. The radiation source 10 is provided with a posture sensor 12 for detecting its posture and a liquid crystal display 13 for displaying an alignment state. The cassette 11 is provided with a posture sensor 14 for detecting its posture.
The output of the radiation generating means 15 for driving the radiation source 10 is connected to the radiation source 10.

A control means 16 is provided for controlling the operation of the entire radiation detection system.
The output of 6 is connected to attitude sensors 12 and 14 and radiation generating means 15 via a bus line 17 for transmitting a signal. Further, the bus line 17 is connected to outputs of a display means 18 for displaying a radiation image, an image processing means 19 for calculating a radiation image, and an external storage means 20 for storing a radiation image.

The attitude sensors 12 and 14 are acceleration sensors for detecting acceleration or angular acceleration, and integrate the obtained acceleration and angular acceleration to detect the velocity and angular velocity, respectively.
Further, the position and the rotation angle are detected by integrating the velocity and the angular velocity, respectively. Acceleration sensors have been put to practical use for automatic piloting of aircraft, position recognition of automobiles, and the like, and can accurately know the position of the acceleration sensor itself. When an absolute position or the like is required, the absolute zero velocity and the zero angular velocity, the zero position and the zero angle must be input in advance in principle, but the radiation source 10 and the cassette 11 are fixed at their respective home positions. Thus, it is possible to input the absolute zero speed and the zero angular speed, the zero position and the zero angle.

In this case, the photographing is performed by the Jonner position photographing method for photographing the incision direction image of the shoulder joint. Cassette 11
Is behind the patient's shoulder S on the table, from the outside to the inside 2
It is set at 0 degree and 20 degrees from the hip side to the head side direction. The radiation source 10 is aligned so as to emit radiation perpendicular to the cassette 11 and toward the center line of the cassette 11.

The attitude sensor 14 built in the cassette 11 and the attitude sensor 12 built in the radiation source 10 always detect the position and the angle from the home position, and the detection signal is changed as needed. And cassette 1
1 is input to the control means 16 through the bus line 17, and the control means 16 calculates the relative positions of the two from the signals of the attitude sensors 12 and 14. Here, the relative positions of the two are the distance between the center of the radiation source 10 and the center of the cassette 11, the distance between the irradiation center of the radiation source 10 and the center of the cassette 11, the irradiation direction of the radiation source 10, and the inclination of the normal line of the cassette 11. , At least one of the rotations of the cassette 11 in the plane.

First, the technician fixes the cassette 11 to the patient's shoulder joint based on the Johnner image capturing method. Next, the radiation source 10 is moved so as to irradiate the radiation perpendicular to the cassette 11 and toward the center line of the cassette 11,
Start alignment. At this time, the liquid crystal display means 13 provided on the radiation source 10 displays the relative position between the radiation source 10 and the cassette 11, that is, the alignment state in real time. The technician can easily perform accurate alignment by checking the display of the alignment state. Further, the liquid crystal display means 13 can display not only the relative position but also the attitude of the radiation source 10 and the cassette 11. Therefore, the technician can quickly respond even when the already installed cassette 11 moves due to the patient's movement or the like.

As described above, the radiation source 10 and the cassette 1
By providing the attitude sensors 12 and 14 in the camera 1 and displaying the relative positions of the two, accurate shooting based on a predetermined shooting method can be performed. In FIG. 1, the attitude sensors 12 and 14 are connected to the bus line 17 by signal lines. However, the attitude sensors 12 and 14 may transmit signals by wireless communication using radio waves or light, and may omit the signal lines.

Further, in the present embodiment, the attitude sensor 12,
Although the acceleration sensor is used for 14, the other methods can be applied as long as the sensor is suitable for detecting the posture and the position. Further, as in the case of the radiation source 10, a display means may be provided on the cassette 11 so that the position and angle of the cassette 11 are always displayed. For example, in the Johnner position image capturing method, the cassette 11 is installed at an angle of 20 degrees with respect to the vertical line of the photographing table.
The technician can easily install the cassette 11.
At this time, it is preferable to display an appropriate angle and a displacement from the appropriate angle in accordance with the imaging method.

FIG. 2 shows a display image of the second embodiment, in which relative position information of the radiation source 10 and the cassette 11 is displayed on the film F in addition to the radiation image. Radiation source 1
Distance FFD between 0 and cassette 11, irradiation center and cassette 1
The distance D of one center, the rotation angles θ and φ in the horizontal and vertical directions of the cassette 11, and the rotation angle ω about a line connecting the radiation source 10 and the center of the cassette 11 are displayed as display information.

In FIG. 1, a radiation source 10 and a cassette 1
The first posture information is detected by the control means 16 using the posture sensors 12 and 14 through the bus line 17 in synchronization with the generation of radiation from the radiation source 10. The control means 16 calculates the relative position of the distance between the radiation source 10 and the cassette 11, the amount of parallel movement, the inclination, and the rotation angle from the respective pieces of posture information.

The distance is the distance between the radiation source 10 and the center of the cassette 11, and the translation amount is the point where the irradiation center line of the radiation source 10 and the plane formed by the cassette 11 intersect, that is, the irradiation center on the cassette 11 and the cassette. 11 is the distance from the center of the light receiving unit. The distance may be displayed as an XY component as needed. The inclination is the angle between the irradiation center line of the radiation source 10 and the normal line of the cassette 11. This is the angle formed by the reference axis.

The control means 16 calculates the relative position at the time of imaging, and adds the calculated value to the radiation image information. As an additional method, a method of providing data imprinting means in the cassette 11 and optically recording on a film loaded in the cassette 11 can be considered. When the solid-state imaging device is loaded in the cassette 11, the image information is digitized. Therefore, the image information is stored in the external storage unit 20 together with the image information as a part of the header of the image information. You may. Further, after that, the radiation image is displayed on the display unit 1.
8, the relative position can be displayed at a position that does not hinder the diagnosis.

Since the technician can check the relative position information between the radiation source 10 and the cassette 11 while viewing the radiographed image as shown in FIG. 2, it is possible to know whether or not the radiographing has been performed with the desired alignment. it can. In addition, since the imaging direction can be confirmed, a doctor can relatively easily make a diagnosis even when the bones are overlapped and imaged.

FIGS. 3 and 4 show a third embodiment, which is a schematic view of a radiation image in which the image is distorted, shaded, and rotated due to an incorrect alignment between the radiation source 10 and the cassette 11 in joint imaging. . Diagnosis is possible with this image, but a doctor must perform operations such as holding the film obliquely and consciously correcting distortion and shading at the time of diagnosis.

In this embodiment, the radiation source 10 and the cassette 1
When the alignment of radiation source 1 was not accurate,
Based on the relative position information of the cassette 0 and the cassette 11, image processing is performed on the photographed image as shown in FIG. 3 to obtain an image equivalent to an image photographed with accurate alignment as shown in FIG. it can.

Although radiography is performed using the same apparatus as that shown in FIG. 1, the cassette 11 uses a solid contact element as an image receiving means, and transmits a radiographic image through a bus line 17 to a control means 16.
Transfer to The control means 16 digitizes the image and performs various kinds of image processing using the image processing means 19. In addition, the attitude information of the radiation source 10 and the cassette 11 at the time of imaging is similarly transferred to the control means 16 via the bus line 17.

As an example of the image processing performed here, there is a process of obtaining a displacement of a photographed image from a normal position and moving the photographed image in parallel and rotationally. First, the displacement from the normal position is obtained from the attitude information of the radiation source 10 and the cassette 11 and the imaging method information at the time of imaging. The displacement amount to be output is a distance, a translation amount, a tilt, a rotation angle, or a difference between each displacement amount and a normal value determined by an imaging method.

Next, the captured image is translated and rotated by two-dimensional affine transformation based on the translation amount and the rotation angle among the obtained displacement amounts. The two-dimensional affine transformation is a transformation method used for coordinate transformation in a two-dimensional space.
It is represented by a × 3 matrix.

[0031]

(Equation 1)

The enlargement, reduction, and inversion around the origin are a,
d, rotation about the origin is a = cos
is performed by substituting θ, b = −sin θ, and d = cos θ, and the translation is performed by t _x and t _y .

Further, distortion correction is performed using the inclination, which is one of the displacement amounts obtained as required. The following equation is generally used for distortion correction. However, the coefficients A _ij and B _ij can be obtained from the slope.

X = ΣΣA _ij X ⁱ Y ^j Y = ΣΣB _ij X ⁱ Y ^j

Further, shading correction is performed as required. This shading correction is performed using the inclination, distance, and shading characteristics, which are one of the displacement amounts to be obtained. The shading characteristic is a two-dimensional radiation intensity distribution on the cassette 11 using the inclination and the distance as variables. Since the shading characteristics differ depending on the presence or absence of a grid and the type of grid, it is necessary to know the shading characteristics in each case in advance.

As a result of performing the image processing as described above, FIG.
Is obtained. As described above, an image position shift due to an alignment error between the radiation source 10 and the cassette 11,
Rotation, distortion, and shading are corrected, and an image that can be easily diagnosed can be provided.

[0037]

As described above, the radiation imaging apparatus according to the present invention can detect the position or orientation of at least one of the radiation source and the imaging means, thereby aligning the radiation source with the imaging means. The alignment can be easily performed, and the alignment state at the time of photographing can be accurately known. As a result, it is possible to avoid image distortion, shading, and imaging failure due to an insufficient alignment between the radiation source and the imaging unit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a Johner position image capturing method according to a first embodiment.

FIG. 2 is an explanatory diagram of relative position information attached to image information according to a second embodiment.

FIG. 3 is an explanatory diagram of an alignment failure image according to a third embodiment.

FIG. 4 is an explanatory diagram of a corrected image.

FIG. 5 is a configuration diagram of a conventional cassette photographing method.

[Explanation of symbols]

 Reference Signs List 10 radiation source 11 cassette 12, 14 attitude sensor 13 liquid crystal display means 15 radiation generation means 16 control means 17 bus line 18 display means 19 image processing means 20 external storage means T subject

Claims (9)

[Claims] 1. A radiation source for generating radiation, and imaging means responsive to radiation generated from the radiation source,
At least one of the radiation source or the imaging unit is movable, and in a radiation imaging apparatus that irradiates a subject with radiation to capture an image, the position or orientation of at least one of the radiation source or the imaging unit is detectable. A radiographic apparatus characterized by the above-mentioned. 2. A camera according to claim 1, wherein said photographing means is a cassette.
A radiation imaging apparatus according to claim 1. 3. The radiation imaging apparatus according to claim 1, wherein a relative position between the radiation source and the imaging unit can be detected. 4. The relative position includes a distance between a center of the radiation source and a center of the imaging unit, an irradiation center of the radiation source and a center distance of the imaging unit, an irradiation direction of the radiation source, and a 4. The radiation imaging apparatus according to claim 3, wherein at least one of a rotation about a tilt of a normal line and a line connecting a center of the radiation source and a center of the imaging unit is used as an axis. 5. The radiation imaging apparatus according to claim 3, further comprising at least one of an output function of the relative position, a display function, and a function attached to image information. 6. The radiographic apparatus according to claim 3, wherein the detection and output of the relative position are performed at any time regardless of whether or not radiography is performed. 7. The radiation imaging apparatus according to claim 3, wherein the relative position is detected in synchronization with radiation generation. 8. The radiation imaging apparatus according to claim 3, wherein image processing is performed based on the relative position information. 9. The radiation imaging apparatus according to claim 8, wherein the image processing is at least one of translation, rotation, distortion correction, and shading correction.