JP3446327B2 - Radiation imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation imaging apparatus for photographing a radiation image from radiation transmitted through a subject. 2. Description of the Related Art In recent years, as a radiation imaging apparatus for the chest, instead of a system in which an X-ray photographed image is obtained by directly irradiating a film with transmitted X-rays, a transmitted X-ray is converted into an electric signal by a semiconductor sensor. Accordingly, a method of obtaining an X-ray image has been developed. This sensor is usually configured as a line sensor in which individual X-ray detection sensors are arranged in a one-dimensional array, and a two-dimensional image is obtained by scanning this line sensor in the body axis direction of the subject. . FIG. 8 is a schematic diagram of an X-ray imaging apparatus which is one of the radiation imaging apparatuses using the line sensor. The X-ray tube 12 is movably disposed, and an X-ray tube 12 is disposed at an opposing position. Then, X-rays are emitted from the X-ray tube 12 to the subject B standing in front of the line sensor 10, and in this state, the X-ray is transmitted while moving the line sensor 10 downward, that is, in the body axis direction of the subject B. It is configured to obtain a two-dimensional X-ray image of the subject B by detecting a line. When the subject B is imaged by such an X-ray imaging apparatus, an X-ray absorptivity differs depending on the imaging site of the subject B, so that an image suitable for diagnosis can be obtained according to the purpose of each imaging. Therefore, the X-ray intensity at the time of imaging is variously changed. For example, in the mediastinum, abdominal area, and the like from the shoulder bone to the heart, where the X-ray absorption rate is very high, the X-ray intensity is sufficiently increased to image the subject. [0006] However, the X-ray detecting elements constituting the line sensor 10 each have individual detection characteristics, and each of the X-ray detecting elements has an X-ray intensity.
For example, it shows detection characteristics as shown in FIGS. That is,
In the example of FIG. 9A, the count value of the incident photons detected when the incident dose of X-rays exceeds IP rapidly decreases, and in the example of FIG. 9B, it is detected that the incident dose of X-rays exceeds IS. The incident photon count value becomes saturated. For this reason, it is not possible to distinguish between the case where the incident dose of X-ray is I1 and the case where it is I2 as shown in FIG. 9a, and in the case of FIG. Since the distinction cannot be made, when imaging the subject with sufficiently increased X-ray intensity or the like, a pseudo image or an artifact occurs in the captured image, which causes a problem that the diagnosis is hindered. Therefore, the present invention solves such a problem by providing a radiographic image which can obtain a good photographed image free from a pseudo image and an artifact even when the object is imaged by sufficiently increasing the X-ray intensity. It is intended to provide a device. [0009] In order to achieve the above object, the present invention provides a radiation imaging apparatus which detects radiation transmitted through a subject by a radiation sensor and processes an output of the radiation sensor to form an image. In the apparatus, the radiation sensor is configured by arranging a large number of radiation detection elements in a one-dimensional or two-dimensional array, and one of these detection elements is a guide detection element capable of detecting radiation that is sufficiently stronger than these elements.
Alternatively, it is characterized in that a plurality thereof are mixed. The operation of the present invention will be described with reference to the drawings.
The X-rays radiated and transmitted through the subject are detected by the line sensor 1, and the measured data of the detected X-rays are converted into data for image display by the correction means 4 via the buffer memory 2, and are displayed on the display means. 5 is displayed. At this time, as shown in FIGS. 2 and 4, the outputs of the guide sensors (guide detection elements) 1a, 1b,... Provided in the line sensor 1 are detected by the detection sensors (radiation detection elements). When the value exceeds a predetermined value YLk according to the characteristic, the calculating means 3 detects the detection sensors 1a ', 1b',.
.. Each output is, for example, a guide sensor output Y
Ri is calculated as a value obtained by applying the following arithmetic processing, Y = (YPk / YLk) · YRi, and the correction means 4 uses this as the measurement data of the detection sensors 1a ′, 1b ′,. The image is converted to display data and displayed. An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram of an X-ray imaging apparatus which is one of the radiation imaging apparatuses according to the present invention. In FIG. 1, reference numeral 1 denotes a line sensor for detecting X-rays transmitted through a subject, and a plurality of detection sensors are arranged in a straight line. 2
Is a buffer memory for temporarily storing measurement data of X-rays detected by the line sensor 1. 3 is a calculation means,
According to the measurement data of the X-ray detected by the guide sensor of the line sensor 1, the correction output of the detection sensor in the vicinity is calculated. Reference numeral 4 denotes a correction unit that calculates correction data for image display from measurement data of X-rays detected by the detection sensor. Reference numeral 5 denotes display means for displaying an image of a captured image based on the correction data output from the correction means 4. The line sensor 1 is, as shown in FIG.
A large number of X-ray detection sensors are arranged in an array, and guide sensors 1a, 1b,... Are provided for each of the four detection sensors. Here, four detection sensors 1a ′, 1b ′,... Adjacent to both sides of each guide sensor are assumed to be detection sensors near each guide sensor. As shown in FIG. 3, the guide sensors 1a, 1b,... Are made of an absorber 11a made of a material absorbing X-rays at an X-ray entrance of a semiconductor sensor of the same type as the detection sensor. 11b are arranged. In such a case, as shown in FIG. 4, the detection sensor output Yk starts to fall or saturate at the X-ray incident dose IP, whereas the guide sensor output YRi is changed by the absorbers 11a, 11b. As a result of the absorption of the line, the curve is gentler than that of a normal detection sensor, and the output does not decrease until the output reaches the count value YPk. Therefore, although the sensitivity is lower than that of a normal detection sensor, it is possible to identify and detect a very strong X-ray. Here, the absorbers 11a, 11b
・ ・ Because is usually formed by vapor deposition or plating, it is desirable that the substance be thin and well absorb X-rays.
Lead, gold, and the like are suitable as the material of the absorber. FIG. 5 is a flowchart showing the operation of one embodiment of the present invention. First, an X-ray of the subject is taken,
Measurement data of the X-ray transmitted through the subject detected by the line sensor 1 is obtained (S1). The calculating means 3 compares the measurement data YRi of the guide sensor 1a with a predetermined count value YLk, and when the measurement data YRi of the guide sensor 1a is larger than the predetermined count value YLk, the detection sensor is used. It is determined that strong X-rays that cannot be measured have entered, and the process proceeds to S3 to correct the measurement data of the nearby detection sensor 1a '. Otherwise, the measurement data is not corrected.
Proceed to S4. Here, the count value YLk to be compared with the measurement data YRi of the guide sensor 1a is, as shown in FIG. 4, the X value when the detection sensor output indicates the vicinity of the local maximum value YPk.
Assuming that the output value of the guide sensor 1a corresponding to the incident dose IP of the line is the incident dose of the X-ray within the range where the detection sensor operates normally with the output value YLk of the guide sensor as a boundary. Judgment is possible. Further, when the output of the sensor for detection shows a characteristic of being saturated at a predetermined X-ray intensity, the output value of the sensor for detection when saturation occurs may be set to YPk. In S2, when the measurement data YRi of the guide sensor 1a is larger than a predetermined count value YLk, the calculating means 3 sets the detection sensor 1 near the guide sensor 1a.
Correct the measurement data of a '. That is, in FIG. 4, when the detection sensor output YK is larger than YPK (X-ray incident dose is larger than IP), the correction output of the detection sensor is calculated by the following equation using the output YRi of the guide sensor. Calculate Y. Yk = (YPk / YLk) .YRi Here, k is a variable indicating the identification number of the sensor for detection, and i is a variable indicating the identification number of the sensor for guide. With this corrected output, the incident dose of X-rays becomes
If it is not less than P, the output value of the detection sensor becomes a value corresponding to the dotted line in FIG. 4 according to the incident dose. Note that the maximum value YPk of the output of the detection sensor differs depending on the individual characteristics of the detection sensor, and the value of YLk also differs depending on the individual characteristics of the individual detection sensor and the guide sensor. What is necessary is to gradually increase the intensity of the X-rays emitted in the absence of the subject, check the count values of all the detection sensors, and calculate the values of YPk and YLk for each of the detection sensors. Next, the correction means 4 calculates correction data for image display from the measurement data corrected or output as it is by the calculation means 3 (S4), and the display means 5 generates the correction data based on the correction data. An image is displayed (S5). Then, a series of these operations S2 to S5 are performed for all the guide sensors 1b, 1c,... Disposed in the line sensor 1 (S6). In the above-described embodiment, the correction output of the detection sensor is calculated using the output of the guide sensor in the vicinity thereof. However, the present invention is not limited to this.
For example, a linear approximation at a predetermined angle whose initial value is the count value YPk may be used. As described above, according to the present invention, even when strong X-rays that cannot be detected by the detection sensor enter, the measurement data of the X-rays detected by the guide sensor in the vicinity can be used. Since the correction output of the detection sensor is calculated and the image is displayed using the correction output, there is no adverse effect on the captured image due to a sudden decrease or saturation of the output of the detection sensor as in the related art, and the captured image with few artifacts Can be obtained. FIG. 6 is a flowchart showing the operation of another embodiment of the present invention. In this embodiment, the line sensor 1
The two-dimensional image is displayed in the same manner as in the related art without correcting the measurement data, and at the same time, in accordance with the X-ray measurement data detected by the guide sensor, the detection is performed by the detection sensor in the vicinity. The case where the correction of the measured data of the X-ray is performed will be described. First, an X-ray image of the subject is taken, and measurement data of the X-ray transmitted through the subject detected by the line sensor 1 is obtained (S11). 1. A two-dimensional image is displayed on the display unit 5 via the correction unit 4 (S12). In parallel with this, the calculation means 3 reads the guide sensor 1 read from the buffer memory 2 in the same manner as in steps S2 and S3 in the flowchart shown in FIG.
The measured data YRi of a is compared with a predetermined count value YLk (S13), and the measured data Y
If Ri is larger than the predetermined count value YLk, the measurement data of the detection sensor 1a 'near the guide sensor is further read from the buffer memory 2, the corrected output is calculated, and stored in the buffer memory 2 again. Yes (S1
4). When the measurement data YRi of the guide sensor 1a is smaller than the predetermined count value YLk or equal,
The process directly proceeds to S15 without correcting the measurement data (S15).
13). Then, a series of these operations S13 to S1
4 is a sensor 1 for all guides disposed on the line sensor 1
.. (S15), the correction means 4 reads the measured data from the buffer memory 2, calculates correction data for image display (S16), and re-displays the already displayed image. It is displayed (S17). As described above, according to the second embodiment of the present invention, the photographed image can be observed immediately after photographing, the whole photographed image can be quickly grasped, and there is no corrected artifact slightly later. Since a good photographed image is displayed, there is an advantage that the diagnosis of details is not hindered. In the above-described embodiment, a line sensor is used as an array sensor, but a two-dimensional sensor may be used, and a case where the most typical X-ray is used as radiation has been described. , Other radiation, such as gamma rays,
Positrons (positrons), photons (photons), or the like may be used. Further, in the above-described embodiment, as a guide sensor, a structure in which an absorber made of a material that absorbs radiation such as lead is provided in a normal detection sensor is shown. However, as shown in FIG. The output of the normal detection sensor may be counted by the ultra-high-speed amplifier 11b.
This is based on the assumption that an amplifier capable of counting the number of photons with sufficient linearity even if strong X-rays are incident will be developed in the future.
By using a small number of expensive ultra-high-speed amplifiers as guide sensors, good images can be obtained, and an inexpensive system can be provided. According to the present invention, even when strong X-rays that cannot be detected accurately by the detection sensor are incident, the measurement data of the X-rays detected by the guide sensor in the vicinity thereof can be used. Since it is desired to display an image using the data corrected by using the method, there is no adverse effect on the captured image due to a sudden decrease in the output of the detection sensor or saturation as in the related art, and the X-ray intensity is sufficiently increased to obtain the object. Thus, a captured image with few pseudo images and artifacts can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a radiation imaging apparatus according to the present invention. FIG. 2 is a diagram showing details of a line sensor according to the present invention. FIG. 3 is a view showing a guide sensor according to the present invention. FIG. 4 is a diagram showing a relationship between an incident dose of X-rays and an output in a detection sensor and a guide sensor. FIG. 5 is a flowchart showing the operation of the present invention. FIG. 6 is a flowchart showing the operation of the present invention. FIG. 7 is a diagram showing another configuration example of the guide sensor according to the present invention. FIG. 8 is a schematic diagram of a radiation imaging apparatus. FIG. 9 is a diagram showing the relationship between the incident dose of X-rays and the output in the X-ray detection sensor. [Description of Signs] 1 ... Line sensor 2 ... Buffer memory 3 ... Calculation means 4 ... Correction means 5 ... Display means

Claims (1)

(57) [Claim 1] In a radiation imaging apparatus that detects radiation transmitted through a subject with a radiation sensor and processes an output thereof to form an image, the radiation sensor includes a plurality of radiation sensors. A radiation detecting element is arranged in a one-dimensional or two-dimensional array, and a plurality of guiding detecting elements capable of detecting radiation that is stronger than radiation within a range where these elements operate normally are included in these detecting elements. Further, by comparing the output of the guide detecting element with a predetermined output predetermined according to the detection characteristics of the detecting sensor, the incident radiation dose falls within the normal operating range of each detecting element. Calculating means for determining whether or not the incident radiation amount is within the normal operating range; and The radiation imaging device for a correcting means for correcting the output of each detector element by comparison with the force, comprising the.