US-12622666-B2 - Calibration phantom

Abstract

A calibration phantom is configured to be difficult to deform and easy to handle. The calibration phantom can be used in a case of acquiring calibration data of a photon-counting type detector that outputs an electrical signal corresponding to photon energy of an incident X-ray. The calibration phantom includes first base substances and a second base substance which are known substances, the second base substance having an atomic number larger than an atomic number of the first base substances and being sandwiched between the first base substances.

Inventors

• Isao Takahashi
• Shinichi Kojima
• Kazuma Yokoi

Assignees

• FUJIFILM CORPORATION

Dates

Publication Date

20260512

Application Date

20240826

Priority Date

20230920

Claims (3)

1. 1 . A calibration phantom used in a case of acquiring calibration data of a photon-counting type detector that outputs an electrical signal corresponding to photon energy of an incident X-ray, the calibration phantom comprising: first base substances and a second base substance which are known substances, the second base substance having an atomic number larger than an atomic number of the first base substances and being sandwiched between the first base substances.
2. 2 . The calibration phantom according to claim 1 , wherein upper and lower thicknesses of the first base substances between which the second base substance is sandwiched are equal.
3. 3 . The calibration phantom according to claim 1 , wherein the second base substance is sandwiched between the first base substances and has a covered side surface.

Description

CROSS REFERENCE TO RELATED APPLICATION The present application claims priority from Japanese Patent Application JP 2023-151793 filed on Sep. 20, 2023, the content of which is hereby incorporated by reference into this application. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray computed tomography (CT) apparatus comprising a photon-counting type detector, and relates to a calibration phantom used for calibration of the photon-counting type detector. 2. Description of the Related Art The X-ray CT apparatus is an apparatus that generates a tomographic image of a subject by using a plurality of projection data acquired by executing irradiation of the subject with X-rays and detection of the X-rays transmitted through the subject at a plurality of projection angles. The generated tomographic image is used as a medical image for diagnosing the subject. In a photon-counting CT apparatus using the photon-counting type detector for the X-rays detection, a tomographic image decomposed into substances of different compositions, for example, tomographic images decomposed into an iodine contrast agent used in angiography and a soft tissue are obtained as medical images. In order to obtain the tomographic images decomposed into the substances, it is necessary to acquire, in advance, a relationship between output and photon energy in a case in which a phantom composed of a combination of a plurality of base substances, which are substances of which a composition and a thickness are known, is measured with the photon-counting type detector, as calibration data for each detection element. JP2013-146480A discloses that a two-dimensional map of acrylic thickness-iodine thickness is obtained as calibration data using a stepped phantom consisting of acrylic and iodine. SUMMARY OF THE INVENTION However, JP2013-146480A lacks consideration for handling the phantom. In the phantom composed of the combination of the plurality of base substances, a thickness of a base substance having a relatively large atomic number may be made extremely thin, for example, about 0.1 mm. The base substance having a thickness of about 0.1 mm is easily deformed, and in calibration data acquired using the phantom composed of the deformed base substance, an accuracy of discriminating the substance is lowered. An object of the present invention is to provide a calibration phantom that is difficult to be deformed and is easy to handle. In order to achieve the above object, according to the present invention, there is provided a calibration phantom used in a case of acquiring calibration data of a photon-counting type detector that outputs an electrical signal corresponding to photon energy of an incident X-ray, the calibration phantom comprising: first base substances and a second base substance which are known substances, the second base substance having an atomic number larger than an atomic number of the first base substances and being sandwiched between the first base substances. According to the present invention, it is possible to provide a calibration phantom that is difficult to be deformed and is easy to handle. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an overall configuration of a photon-counting CT apparatus. FIG. 2 is a diagram describing calibration data of a photon-counting type detector. FIG. 3 is a diagram showing a configuration example of a calibration phantom and an example of calibration data acquired using the calibration phantom. FIG. 4 is a diagram showing another configuration example of the calibration phantom. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a calibration phantom according to the present invention will be described with reference to the drawings. The calibration phantom according to the embodiment of the present invention is used in a photon-counting CT apparatus comprising a photon-counting type detector. In the following description and the accompanying drawings, components having the same functional configuration are designated by the same reference numerals, and duplicate description thereof will be omitted. Example 1 FIG. 1 shows an overall configuration diagram of a photon-counting CT apparatus 101. A horizontal direction of a paper surface is defined as an X axis, a vertical direction is defined as a Y axis, and a direction orthogonal to an XY plane is defined as a Z axis. The photon-counting CT apparatus 101 comprises a gantry 102, an X-ray tube 103, a bow tie filter 104, an examination table 105, a detector panel 107, a computing device 108, an input device 109, and a display device 110. A subject 106 is placed on the examination table 105 and is disposed in an opening portion 112 provided in the gantry 102. X-rays 111 radiated from the X-ray tube 103 is emitted to the subject 106 via the bow tie filter 104, are transmitted through the subject 106, and are then detected by the detector panel 107. The X-rays are for