US-12622654-B2 - Computed tomography apparatus

US12622654B2US 12622654 B2US12622654 B2US 12622654B2US-12622654-B2

Abstract

A radiation source includes a radiation tube having a cathode which is a cold cathode. An imaging control unit directs the radiation source to intermittently and alternately emit the first radiation having a first energy distribution and the second radiation having a second energy distribution different from the first energy distribution whenever a rotation mechanism rotates the radiation source and a radiation detector by a preset angle. The imaging control unit directs the radiation detector to output a first projection image based on the first radiation and a second projection image based on the second radiation which are obtained by the intermittent emission of the first radiation and the second radiation. An image processing unit generates a tomographic image on the basis of the first projection image and the second projection image.

Inventors

Sho SHIMIZUKAWA
Tatsuya Taneichi
Takashi Tajima
Naoyuki Nishino
Hisatsugu Horiuchi

Assignees

FUJIFILM CORPORATION

Dates

Publication Date: 20260512
Application Date: 20230814
Priority Date: 20220823

Claims (8)

1 . A computed tomography apparatus comprising: a radiation source that emits radiation having a pyramid shape to a subject positioned in either a standing posture or a sitting posture and that includes a radiation tube having a cold cathode; a radiation detector in which a plurality of pixels detecting the radiation transmitted through the subject are two-dimensionally arranged and which outputs a projection image of the subject; a rotation mechanism that rotates the radiation source and the radiation detector around a body axis of the subject; a plurality of imaging units each of which is composed of a set of the radiation source and the radiation detector and which have different phases in a rotation direction; a displacement mechanism that changes an interval between the plurality of imaging units in a rotation axis direction; and a processor that controls operations of the radiation source, the radiation detector, and the rotation mechanism, wherein the processor directs the radiation source to intermittently and alternately emit first radiation having a first energy distribution and second radiation having a second energy distribution different from the first energy distribution whenever the rotation mechanism rotates the radiation source and the radiation detector by a preset angle, directs the radiation detector to output a first projection image based on the first radiation and a second projection image based on the second radiation which are obtained by the intermittent emission of the first radiation and the second radiation, and generates a tomographic image on the basis of the first projection image and the second projection image.
2 . The computed tomography apparatus according to claim 1 , wherein the cold cathode is a field emission type having an electron emission source that emits an electron beam using a field emission phenomenon.
3 . The computed tomography apparatus according to claim 1 , wherein the processor sets the interval such that an overlapping imaging range occurs between the projection images obtained by the imaging units adjacent to each other in a case in which an imaging range that exceeds a width of a detection surface for the radiation in the radiation detector is imaged, performs a reconstruction process on the projection images obtained from each of the plurality of imaging units to generate a plurality of the tomographic images for each of the plurality of imaging units, and registers the plurality of tomographic images on the basis of the overlapping imaging range to combine the plurality of tomographic images.
4 . The computed tomography apparatus according to claim 1 , wherein the radiation detector has a configuration in which a plurality of detection units for the radiation are arranged along a direction orthogonal to a rotation axis direction of the radiation source and the radiation detector.
5 . The computed tomography apparatus according to claim 1 , wherein the radiation detector is disposed at an offset position that is separated from a reference position facing the radiation source by a preset angle as viewed from a rotation axis direction of the radiation source and the radiation detector.
6 . The computed tomography apparatus according to claim 1 , wherein the radiation source and the radiation detector are held in a frame, the subject is positioned in the frame, and the radiation source is disposed outside the frame, and the radiation detector is disposed inside the frame as viewed from a rotation axis direction of the radiation source and the radiation detector.
7 . The computed tomography apparatus according to claim 1 , wherein the processor uses a compression sensing method in a case in which a reconstruction process is performed on the projection images to generate the tomographic image.
8 . The computed tomography apparatus according to claim 1 , wherein a width of a detection surface for the radiation in the radiation detector is equal to or greater than 300 mm.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2022-132603, filed on Aug. 23, 2022. The above application is hereby expressly incorporated by reference, in its entirety, into the present application. BACKGROUND 1. Technical Field The technology of the present disclosure relates to a computed tomography apparatus. 2. Description of the Related Art JP2006-346011A discloses a computed tomography apparatus (hereinafter, referred to as a CT apparatus) that images a subject in a decubitus posture or a sitting posture and comprises two imaging units each of which is composed of a radiation source that emits radiation to the subject and a radiation detector that detects the radiation transmitted through the subject and outputs a projection image. The two imaging units are disposed at an interval of 90° in a gantry that is rotated around a body axis of the subject. The radiation source emits a cone beam, and the radiation detector has a configuration in which a plurality of pixels are arranged in a two-dimensional matrix. In JP2006-346011A, one of the two imaging units emits first radiation having a first energy distribution, and the other emits second radiation having a second energy distribution different from the first energy distribution. The two imaging units irradiate the subject with the first radiation and the second radiation at the same time whenever the gantry is rotated by a preset angle. Therefore, a first projection image and a second projection image of the subject irradiated with the radiation components having different energy levels are obtained. In JP2006-346011A, an energy subtraction (hereinafter, referred to as ES) process is performed on the first projection image and the second projection image to generate an ES image in which a specific biological tissue has been highlighted. Specifically, the ES image is generated from the first projection image and the second projection image obtained at the same rotation position. Then, a reconstruction process is performed on the ES images at each rotation position to generate a tomographic image. The specific biological tissue is a bone tissue, such as a rib or a backbone, or a soft tissue, such as a lung or a stomach. SUMMARY In the CT apparatus described in JP2006-346011A, since the two imaging units are disposed at an interval of 90°, the imaging angles of the subject in the first projection image and the second projection images obtained at the same time are different. Therefore, it is not possible to generate the ES image from the first projection image and the second projection image obtained at the same time. Therefore, it is considered that the ES image is generated from the first projection image and the second projection image obtained at the same rotation position, for example, the first projection image obtained in a case in which one of the imaging units is at a position of 0° and the second projection image obtained in a case in which the other imaging unit is rotated by 90° and reaches the position of 0°. However, in this method, a time lag occurs between the acquisition time of the first projection image and the acquisition time of the second projection image, and imaging is greatly affected by the body movement of the subject. The inventors have conceived a CT apparatus for obtaining a tomographic image of a subject in a standing posture or a sitting posture. Further, in order to solve the above-described problems of the CT apparatus described in JP2006-346011A, a configuration is considered in which one radiation source continuously emits the first radiation and the second radiation to obtain the first and second projection images, in which the imaging angles of the subject are almost the same, substantially at the same time at each rotation position. However, in this case, it is necessary to speed up the switching between the emission of the first radiation and the emission of the second radiation in order to secure the synchronism of the first projection image and the second projection image. In addition, in order to generate a tomographic image having reasonable quality, it is better to obtain a larger number of first and second projection images at a preset rotation speed. For that purpose, it is necessary to speed up the switching between the emission of the first radiation and the emission of the second radiation. Further, a subject in the standing posture or the sitting posture is more unstable and is more likely to make a body movement than a subject in a decubitus posture. From this point of view, it is also necessary to speed up the switching between the emission of the first radiation and the emission of the second radiation. One embodiment according to the technology of the present disclosure provides a computed tomography apparatus that can speed up switching between the emission of first radiation and the emission of second radiation