JP2011072502A - Radiographic apparatus - Google Patents

Abstract

In a radiographic apparatus that performs imaging while moving at least the radiation detection means, the influence of distortion generated in the radiation detection means during movement is reduced, and an accurate image can be acquired.
A plurality of laser displacement meters 52 detect distortion amounts generated on a detection surface of a solid detector 40 in a detection panel 11 at the time of photographing, and based on the results, PZT 51 is driven to detect distortion on the detection surface. to correct.
[Selection] Figure 2

Description

  The present invention relates to an improvement in imaging quality particularly in a radiation imaging apparatus that performs imaging while moving at least a radiation detection means.

  Conventionally, a radiation CT (Computed Tomography) apparatus for performing radiography is known. As such a radiation CT apparatus, a subject is placed on a rotation axis while rotating a radiographic source that emits radiation in a conical shape and an imaging unit in which a two-dimensional detection panel is disposed opposite to the rotation axis. There is known one that obtains a three-dimensional radiation CT image by continuously photographing a radiation image and further performing an image reconstruction calculation based on an image signal obtained by the continuous photographing (Patent Document 1).

  Such a radiation CT apparatus, like the apparatus described in Patent Document 1, lays the subject on the bed and moves the imaging unit in the vertical direction. The position and angle of the imaging unit can be adjusted freely, and the subject is standing upright as well as the mode in which the imaging unit is rotated in the vertical direction with the subject lying down. Thus, there has also been proposed an apparatus capable of performing various photographing such as an aspect of photographing while rotating the photographing unit in the horizontal direction.

JP 2005-058309 A JP 2007-000606 A

  The imaging section of the radiation CT apparatus as described above generally has a structure in which the radiation source and the detection panel are attached to both ends of the C-arm so as to face each other, and the radiation source and the detection panel rotate around the subject. Shooting is performed. In such an apparatus, if the positional relationship between the radiation source and the detection panel with respect to the subject changes due to vibration caused by rotation during imaging, an accurate image cannot be obtained. A method has been proposed in which a displacement is measured and a process for correcting an error caused by a positional deviation is performed (Patent Document 2).

  However, strictly speaking, not only the position of the detection panel moves, but also the detection surface of the panel itself may be deformed and distorted by vibration, and the detection surface of the panel may be distorted. If the projections and depressions occur, it becomes impossible to photograph the exact shape of the subject. In such a case, as described in Patent Document 2, it is not possible to obtain an accurate image only by correcting the error due to the positional deviation between the radiation source and the detection panel.

  Such a problem can occur in either a normal CT apparatus or a cone beam CT apparatus. However, in the apparatus using a flat panel detector in particular, the above-described problem occurs remarkably because the detection surface is easily distorted. In addition to the radiation CT apparatus, a radiation imaging apparatus that performs imaging while moving at least the detection panel, such as a tomosynthesis imaging apparatus, is a common problem.

  The present invention has been made in view of the above circumstances. In a radiation imaging apparatus that performs imaging while moving at least the radiation detection means, the influence of distortion generated in the radiation detection means during movement is reduced, and an accurate image is obtained. An object of the present invention is to provide a radiation imaging apparatus that can acquire the above.

  A radiation imaging apparatus according to the present invention includes a radiation source that emits radiation, a radiation detection unit that detects radiation, and a moving unit that moves at least the radiation detection unit, and at least performs radiography while moving the radiation detection unit. A distortion detection unit that detects a distortion amount generated on a detection surface of the radiation detection unit, a distortion correction unit that corrects distortion of the detection surface of the radiation detection unit, and a distortion amount detected by the distortion detection unit And a control means for controlling the correction amount of the distortion correction means.

  In the present invention, the strain correction means is preferably a piezoelectric element.

  Moreover, it is preferable that the distortion correction means is arranged at a plurality of positions corresponding to the detection surface of the radiation detection means.

  In this case, the control means may operate only the distortion correction means arranged at the position corresponding to the region of interest on the detection surface of the radiation detection means.

  Furthermore, the radiation detection means may be a solid detector formed on an organic substrate.

  According to the radiation imaging apparatus of the present invention, the radiation imaging apparatus includes a radiation source that emits radiation, a radiation detection unit that detects radiation, and a moving unit that moves at least the radiation detection unit, and performs imaging while moving at least the radiation detection unit. In the radiographic apparatus, a distortion detection unit that detects a distortion amount generated on a detection surface of the radiation detection unit, a distortion correction unit that corrects distortion of the detection surface of the radiation detection unit, and a distortion amount detected by the distortion detection unit And the control means for controlling the correction amount of the distortion correction means, the influence of the distortion generated in the radiation detection means during movement can be alleviated and an accurate image can be acquired.

  Here, if the distortion correcting means is a piezoelectric element having a high response speed, it is possible to more appropriately eliminate the influence of the distortion.

  Further, if the distortion correction means is arranged at a plurality of positions corresponding to the detection surface of the radiation detection means, it is possible to more appropriately eliminate the influence of distortion.

  In this case, if the control means operates only the distortion correction means arranged at the position corresponding to the region of interest on the detection surface of the radiation detection means, the processing amount of the control means can be reduced. Can be realized easily.

  Furthermore, if the radiation detection means is a solid detector formed on an organic substrate having low hardness, the distortion can be easily corrected by the distortion correction means, so that the influence of the distortion can be more appropriately eliminated. .

1 is a schematic configuration diagram of a radiation CT apparatus according to an embodiment of a radiation imaging apparatus of the present invention. Configuration diagram of the detection panel of the radiation CT apparatus The top view which shows the arrangement | positioning state of the distortion detection means and distortion correction means in the detection panel of the said radiation CT apparatus Timing chart during operation of the radiation CT apparatus Timing chart during operation of radiation CT apparatus according to other embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a radiation CT apparatus according to a first embodiment of the radiation imaging apparatus of the present invention.

  As shown in FIG. 1, the radiation CT apparatus 1 is connected to an imaging apparatus that captures a radiographic image, a bed 22 that is a support for supporting a subject P, and an imaging apparatus. The computer 30 which processes the image obtained by this, and the monitor 31 connected to this computer 30 are comprised.

  The imaging apparatus includes a radiation source 10 that emits conical radiation (hereinafter also referred to as conical radiation), a detection panel 11 that detects radiation emitted from the radiation source 10, and a C-arm that holds the radiation source 10 and the detection panel 11. The imaging unit 2 includes 12, a driving unit 15 that rotates the imaging unit 2, and an arm 20 that holds the driving unit 15.

  The imaging unit 2 can rotate 360 ° around the rotation axis C. In addition, the arm 20 including the movable portion 20a is held by a base 21 that is movably attached to the ceiling, and can be moved to a wide range of positions in the photographing room, and the rotation direction of the photographing portion 2 ( The rotation axis angle) can also be changed.

  The radiation source 10 and the detection panel 11 are arranged to face each other with the rotation axis C interposed therebetween. When performing radiation CT imaging with the radiation CT apparatus 1, the rotation axis C, the radiation source 10, and the detection panel 11 are positioned relative to each other. The relationship is fixed. The detection surface on which the detection pixels constituting the detection panel 11 are arranged may be a flat surface or a curved surface.

  Here, the configuration of the detection panel 11 will be described in detail with reference to the drawings. As shown in FIG. 2, a solid detector 40 is accommodated in the detection panel 11.

  The solid state detector 40 includes a first conductive layer 44 made of an a-Si TFT on a plastic substrate 45, a photoconductive layer 43 that generates electric charges when irradiated with radiation, and a second conductive layer. The layer 42 and the insulating layer 41 are laminated in this order.

  The first conductive layer 44 is formed with a TFT corresponding to each pixel, the output of each TFT is connected to an IC chip 46, and the IC chip 46 is connected to an image signal processing unit (not shown). .

  When the solid state detector 40 irradiates the photoconductive layer 43 with radiation when an electric field is formed between the first conductive layer 44 and the second conductive layer 42, the solid state detector 40 enters the photoconductive layer 43. Charge pairs are generated, and latent image charges corresponding to the amount of the charge pairs are accumulated in the first conductive layer 44. When reading the accumulated latent image charge, the TFTs of the first conductive layer 44 are sequentially driven to output an analog signal corresponding to the latent image charge corresponding to each pixel, and this analog signal is processed by image signal processing. The detection is performed for each pixel in the unit, and the analog signals detected for each pixel are combined in the pixel arrangement order. The combined analog signal is AD converted by an AD converter (not shown) to generate a digital image signal. The generated digital image signal is transmitted from the image signal processing unit to the computer 30 via the memory.

  The solid state detector 40 is mounted on a solid metal base 50 via a plurality of PZTs 51. The PZT 51 also functions as a distortion correction unit that corrects the distortion of the detection surface of the solid state detector 40. Further, for each PZT 51, a laser displacement meter 52 for measuring the displacement between the substrate 50 and the solid state detector 40 is provided adjacently. The laser displacement meter 52 functions as a strain detection unit that detects the amount of strain generated on the detection surface of the solid state detector 40.

  The vertical height of the PZT 51 is changed by applying a voltage in the vertical direction in FIG. Therefore, if the PZT 51 is driven so as to cancel the displacement measured by the laser displacement meter 52, the height of the detection surface of the solid state detector 40 can always be kept constant with respect to the substrate 50.

  As shown in FIG. 3, a set of the PZT 51 and the laser displacement meter 52 is arranged at a plurality of positions corresponding to the detection surface of the solid state detector 40.

  The strain correction means is not limited to PZT, and other piezoelectric elements may be used, or a mechanism other than the piezoelectric elements may be provided. The strain detection means is not limited to the laser displacement meter, and other means such as a strain gauge may be used.

  The computer 30 includes a central processing unit (CPU) (not shown) as control means, a storage device (not shown) such as HDD and SSD, and operation input means such as a mouse and keyboard (not shown).

  The CPU serves as various operation control means such as operation control of the radiation source 10, control of the detection operation of the detection panel 11 and image signal readout operation, rotation control of the imaging unit 2 by the drive unit 15, drive control of the arm 20 and the base 21. In addition to the above function, a function as image processing means for obtaining a three-dimensional radiation CT image of a subject by performing image reconstruction calculation on a plurality of image signals obtained by continuous imaging, and each laser displacement meter 52 (distortion It also has a function as a control means for controlling the correction amount of each PZT 51 (distortion correction means) based on the distortion amount detected by the detection means).

  Hereinafter, the operation of the radiation CT apparatus 1 will be described.

  First, the subject P is laid on the bed 22, and the radiation source 10 and the detection panel 11 are arranged at symmetrical positions with the rotational axis C being the approximate center of the subject P's body. Then, the photographing unit 2 is positioned. The photographing unit 2 is moved based on the operation of the computer 30 by the photographer.

  When imaging is started, exposure of the cone-shaped radiation emitted from the radiation source 10 and passing through the subject P to the detection panel 11 at every predetermined angle while rotating the imaging unit 2 and an image recorded on the detection panel 11 A radiological image representing the subject P is continuously acquired by repeating signal readout a plurality of times. That is, for each shooting in the continuous shooting, the image signal recorded on the detection panel 11 is read out, input to the computer 30, and stored in the storage device.

  At this time, if the distortion of the detection surface of the solid state detector 40 is corrected by driving the PZT 51 during the radiation exposure, the amount of charge generated in the solid state detector 40 changes. Therefore, as shown in the timing chart of FIG. Prior to the exposure of the conical radiation to the detection panel 11, the amount of distortion generated on the detection surface of the solid state detector 40 in the detection panel 11 is detected by a plurality of laser displacement meters 52, and based on this result. The PZT 51 is driven to correct the detection surface distortion. Thereafter, the conical radiation is exposed to the detection panel 11 to read the image signal.

  The above process is repeatedly executed, and the continuous shooting with the subject P as the subject is completed.

  After completion of the continuous imaging, the CPU generates a three-dimensional radiation CT image by performing an image reconstruction calculation based on a plurality of image signals stored in the storage device, and displays it on the monitor 31.

  These series of processes are all performed based on control from the CPU in the computer 30.

  The radiation imaging apparatus of the present invention has been described in detail above, but the present invention is not limited to the above embodiment.

  For example, the correction timing of the distortion generated on the detection surface of the solid state detector 40 in the detection panel 11 is not limited to the aspect of the above embodiment, and may be the aspect shown in the timing chart of FIG. That is, the time for one cycle may be shortened by detecting the distortion of the detection surface of the solid state detector 40 during image reading.

  Detection and correction of the distortion of the detection surface of the solid state detector 40 may be performed every time radiation irradiation is performed, or may be performed once every several times or just before a series of moving image capturing.

  Further, the distortion may be corrected only for the region of interest (for example, the region I in FIG. 3) on the detection surface, instead of correcting the distortion for the entire detection surface.

  In addition, the apparatus configuration of the above embodiment is a relatively large apparatus capable of photographing the subject's chest and limbs. However, the present invention is not limited to such a mode. For example, the imaging unit rotates around the breast. Any device configuration may be used, such as a relatively small device that performs the above.

  In addition, the present invention can be applied to any apparatus as long as it is an imaging apparatus that performs imaging while moving at least the detection panel, such as a tomosynthesis imaging apparatus, as well as a radiation CT apparatus.

  Furthermore, it goes without saying that various improvements and modifications other than those described above may be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Radiation CT apparatus 2 Imaging part 10 Radiation source 11 Detection panel 12 C arm 15 Driving part 20 Arm 21 Base part 22 Bed 23 Balancer weight 24 Vibration detection sensor 30 Computer 31 Monitor 40 Solid state detector 50 Substrate 51 PZT
52 Laser displacement meter C Rotating axis P Subject

Claims (5)

A radiation imaging apparatus, comprising: a radiation source that emits radiation; a radiation detection unit that detects the radiation; and a moving unit that moves at least the radiation detection unit, and performing imaging while moving at least the radiation detection unit,
Strain detection means for detecting the amount of strain generated on the detection surface of the radiation detection means;
Distortion correcting means for correcting distortion of the detection surface of the radiation detecting means;
A radiation imaging apparatus comprising: a control unit that controls a correction amount of the distortion correction unit based on a distortion amount detected by the distortion detection unit.   The radiographic apparatus according to claim 1, wherein the distortion correcting unit is a piezoelectric element.   The radiation imaging apparatus according to claim 1, wherein the distortion correction unit is disposed at a plurality of positions corresponding to detection surfaces of the radiation detection unit.   4. The radiation imaging apparatus according to claim 3, wherein the control means operates only the distortion correction means arranged at a position corresponding to a region of interest on a detection surface of the radiation detection means.   The radiation imaging apparatus according to any one of claims 1 to 4, wherein the radiation detection means is a solid state detector formed on an organic substrate.

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