JP2006034519A - Image photographing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image photographing system for adjusting an X-ray irradiation amount for each part of an examinee body and reducing the total X-ray exposure of the examinee body. <P>SOLUTION: This image photographing system is provided with a photographing device for detecting radiation emitted from a radiation generating substance present inside the examinee body and an X-ray CT apparatus for performing the X-ray tomography of the examinee body. The photographing device is provided with an information output part for outputting photographing data gathered by detecting the radiation for each part of the examinee body to the X-ray CT apparatus. The X-ray CT apparatus is provided with an information acquisition part for acquiring the photographing data, an X-ray irradiation condition setting part for setting an X-ray irradiation condition for stipulating the X-ray irradiation amount for each part of the examinee body on the basis of the photographing data, and an X-ray irradiation control part for performing irradiation with X-rays according to the X-ray irradiation condition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image capturing system, and more particularly to a technique for reducing an X-ray exposure dose of a subject when a positron CT apparatus and an X-ray CT apparatus are used in combination.

2. Description of the Related Art Conventionally, there is an image photographing system that photographs a subject by combining a positron CT (positron emission computed tomography, hereinafter referred to as “PET”) apparatus and an X-ray CT apparatus. In Patent Document 1, a PET apparatus and an X-ray CT apparatus are installed side by side, and PET / CT using X-ray data collected by the X-ray CT apparatus for γ-ray absorption correction processing indispensable for image configuration in the PET apparatus. A system is disclosed.
Japanese Patent Laid-Open No. 7-20245

  However, in the PET / CT system of Patent Document 1, when the X-ray CT apparatus collects X-ray data, the entire subject is irradiated with a certain amount of X-rays, or X-rays for each part of the subject are obtained. The X-ray dose was changed depending on the transmittance. Therefore, the amount of X-rays necessary for precise examination has been irradiated even on a site where there is no lesion candidate and precise examination is not necessary.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image capturing system that adjusts the X-ray irradiation amount for each part of the subject and reduces the total X-ray exposure amount of the subject. To do.

  In order to achieve the above object, an imaging system according to the present invention includes an imaging apparatus that detects radiation emitted from a radiation generating substance present in a subject, and an X-ray that performs X-ray tomography of the subject. An imaging system including a CT apparatus, wherein the imaging apparatus includes an information output unit that outputs imaging data collected by detecting the radiation for each part of the subject to the X-ray CT apparatus. The X-ray CT apparatus includes an information acquisition unit that acquires the imaging data, and an X-ray that sets an X-ray irradiation condition that defines an X-ray irradiation amount for each part of the subject based on the imaging data An irradiation condition setting unit and an X-ray irradiation control unit for irradiating X-rays according to the X-ray irradiation conditions are provided.

  Further, the radiation is γ-ray, and the imaging apparatus is a positron CT apparatus that detects the γ-ray for each tomographic plane of the subject, and the imaging data includes γ indicating the amount of the γ-ray. Contains line detection data.

  The X-ray CT apparatus further includes a scanogram processing unit that captures and displays a scanogram image, and the X-ray irradiation condition setting unit irradiates a portion of the subject corresponding to a predetermined region of the scanogram image. Correction for changing the X-ray dose is performed on the X-ray irradiation conditions.

  ADVANTAGE OF THE INVENTION According to this invention, the X-ray irradiation amount can be adjusted for every site | part of a subject, and the imaging system which reduces the total X-ray exposure amount of a subject can be provided.

  Hereinafter, preferred embodiments of an image photographing system according to the present invention will be described with reference to the accompanying drawings. The PET / CT system according to the present embodiment is an example in which the image capturing system according to the present invention is applied to a PET / CT system in which a PET apparatus and an X-ray CT apparatus are combined. This PET / CT system generates a γ-ray absorption correction function using the X-ray data collected by the X-ray CT apparatus, and uses this γ-ray absorption correction function to absorb the γ-ray detection data. To reconstruct the PET image. In X-ray CT imaging performed to collect this X-ray data, the X-ray irradiation dose is adjusted for each part of the subject, and as a result, the total X-ray exposure dose of the subject can be reduced. System.

  FIG. 1 is a block diagram showing a hardware configuration of a PET / CT system 1 according to the present embodiment. The PET / CT system 1 in FIG. 1 includes an X-ray CT apparatus 10, a PET apparatus 20, a common bed 30 shared by the X-ray CT apparatus 10 and the PET apparatus 20, and a common bed that moves the common bed 30 in the Z direction. A couch moving device 31, a control device 40, and a display device 41 including a CRT device or a liquid crystal display device for displaying a PET image, an X-ray CT image, or the like are provided. The X-ray CT apparatus 10 and the PET apparatus 20 are installed side by side in the Z direction in FIG. The control device 40 is connected to the X-ray CT apparatus 10, the PET apparatus 20, the common couch moving apparatus 31, and the display apparatus 41, and controls these components.

  The X-ray CT apparatus 10 includes an X-ray tube 11 that emits X-rays, and an X-ray detector 12 that is provided at a position facing the X-ray tube 11 and detects X-rays transmitted through the subject 50. Prepare.

  The PET apparatus 20 includes a γ-ray detector 22 arranged in an annular shape around the body axis position of the subject 50 placed on the common bed 30 in order to detect γ-rays emitted from the subject 50. Prepare.

  Next, the control device 40 will be described with reference to FIG.

  The control device 40 includes a PET processing unit 60 that performs processing of the PET apparatus 20 and an X-ray CT processing unit 70 that performs processing of the X-ray CT apparatus 10. The control device 40 also includes an image composition unit 80 configured to superimpose the PET image and the X-ray CT image output from the PET processing unit 60 and the X-ray CT processing unit 70 to form a composite image, and a PET image and an X-ray CT image. And an image display unit 81 for displaying a composite image or the like on the display device 41. Furthermore, the control device 40 includes a common bed control unit 90 that controls the common bed moving device 31.

  The PET processing unit 60 includes a PET device control unit 61 that controls the PET device 20, a PET data collection unit 62 that collects γ-ray detection data output from the γ-ray detector 22 for each tomographic plane of the subject 50, and A PET data calculation unit 63 is provided that rearranges the collected γ-ray detection data for each tomographic plane in the height direction of the subject 50 and generates γ-ray distribution data in the height direction. The PET data calculation unit 63 outputs the above-described γ-ray distribution data in the height direction to the X-ray CT processing unit 70. Furthermore, the PET processing unit 60 includes a PET image reconstruction unit 64 that performs γ-ray absorption correction processing on the γ-ray detection data to reconstruct a PET image. The PET image reconstruction unit 64 outputs the reconstructed PET image to the image composition unit 80 and the image display unit 81.

  The X-ray CT processing unit 70 generates an X-ray irradiation condition, performs X-ray irradiation control based on the X-ray irradiation condition, and performs other control related to the X-ray CT apparatus 10. 71, an X-ray CT data collection unit 72 that collects X-ray data output from the X-ray detector 12, and an X-ray CT image reconstruction unit 74 that reconstructs an X-ray CT image based on the X-ray data. Prepare. The X-ray CT data collection unit 72 outputs the X-ray data to the X-ray CT image reconstruction unit 74 and the PET image reconstruction unit 64. The PET image reconstruction unit 64 uses this X-ray data to generate a γ-ray absorption correction function.

  The common bed control unit 90 outputs the position information of the common bed 30 to the PET device control unit 61, the X-ray CT device control unit 71, and the common bed moving device 31, and controls the common bed moving device 31 to thereby share the common bed. Move 30. The PET apparatus control unit 61 and the X-ray CT apparatus control unit 71 perform PET measurement and X-ray CT imaging while referring to the position information.

  Next, the operation procedure of the PET / CT system 1 and the relationship between the γ dose and the X-ray dose will be described with reference to FIGS.

  FIG. 3 is a flowchart showing an operation procedure of the PET / CT system 1. FIG. 4 is a schematic diagram illustrating a relationship between the γ-ray distribution and the X-ray irradiation amount, and an example of a PET image after back projection.

(Step S301)
First, a radiopharmaceutical is administered to the subject 50, and preparations for imaging such as placing on the common bed 30 are made (S301).

(Step S302)
Next, PET measurement is performed by the PET apparatus 20 (S302). In the PET measurement, the γ-ray detector 22 detects γ-rays for each slice position at each slice position of the subject 50, for example, the a-1 position and the b-1 position in FIG. By moving the common bed 30 by the width of the γ-ray detector 22 in the Z direction on FIG. 4A, γ-rays can be detected for the whole body of the subject 50.

(Step S303)
The PET data collection unit 62 collects γ-ray detection data for the number of slices (S303) and outputs the collected data to the PET data calculation unit 63.

(Step S304)
The PET data calculation unit 63 calculates the γ dose for each slice based on the γ-ray detection data (S304). The γ dose here includes the total number of detected γ rays and the γ ray density.

  In malignant tumors, radiopharmaceuticals administered in the body accumulate at high concentrations. Therefore, by measuring the amount of γ dose, it is possible to identify a site (hereinafter referred to as “lesion candidate site”) that is likely to have a malignant tumor. FIG. 4B is an I-arrow gamma ray distribution diagram showing the X-direction gamma ray distribution state viewed from the I direction at each of the positions a-1 and b-1. At the a-1 position, there is no portion where the γ dose is prominent. On the other hand, at the b-1 position, there is a part where the γ dose is prominently higher than other parts. A portion where the γ dose is prominently large can be estimated as a lesion candidate site. The lesion candidate site at the position b-1 corresponds to the site where the malignant tumor i existing in the chest of the subject 50 shown in FIG.

(Step S305)
Next, the PET data calculation unit 63 rearranges the calculation results of the γ dose calculated for each slice in the height direction of the subject 50, and generates γ-ray distribution data in the height direction (S305).

(Step S306)
Next, the height direction γ-ray distribution data generated in step S305 is output to the X-ray CT apparatus control unit 71 (S306).

(Step S307)
The X-ray CT apparatus control unit 71 refers to the height direction γ-ray distribution data, calculates which part in the height direction has the lesion candidate part, and defines the X-ray dose for each part of the subject 50. X-ray irradiation conditions are set (S307).

  Specifically, the γ dose at each part in the height direction is compared with a preset reference γ dose. When the γ dose at each part is equal to or higher than the reference γ dose, an X-ray irradiation condition is set such that X-rays are irradiated with a tube current value sufficient to image a lesion candidate part. On the other hand, when the γ dose is lower than the reference γ dose, an X-ray irradiation condition is set such that X-ray irradiation is performed with a value smaller than the above tube current value. This small value includes the case where the tube current value is zero. In this case, X-rays are not irradiated.

  In addition to setting the X-ray irradiation dose condition by performing the above threshold processing, the X-ray irradiation dose corresponding to the γ dose and the γ dose may be set, for example, in a proportional relationship.

  FIG. 4-3 is a schematic diagram showing the relationship between the γ dose and the X-ray dose. The X-ray dose to be irradiated is increased for a lesion candidate site (b-1 position), and the X-ray dose to be irradiated to a site (a-1 position) that is not a lesion candidate site.

(Step S308)
The X-ray CT apparatus controller 71 irradiates the subject 50 with X-rays based on the X-ray irradiation conditions set above, and performs X-ray CT imaging (S308). The X-ray CT apparatus control unit 71 acquires the position information of the common bed 30 from the common bed control unit 90. With reference to the position information and the X-ray irradiation conditions, the X-ray tube 11 is irradiated with a necessary amount of X-rays for imaging a lesion candidate at the lesion candidate site. Further, the X-ray tube 11 is irradiated with a smaller amount of X-rays at a site that is not a lesion candidate site.

(Step S309)
The X-ray detector 12 outputs X-ray data indicating the X-ray absorption amount for each slice position of the subject 50. Then, the X-ray CT data collection unit 72 collects X-ray data for the number of slices and outputs it to the PET image reconstruction unit 64 and the X-ray CT image reconstruction unit 74 (S309).

(Step S310)
The PET image reconstruction unit 64 generates a γ-ray absorption correction function using the X-ray data, performs an absorption correction process on the γ-ray detection data using the γ-ray absorption correction function, and FIG. The back-projected PET image shown is reconstructed. The X-ray CT image reconstruction unit 74 reconstructs an X-ray CT image using the X-ray data (S310). The malignant tumor i is imaged in the PET image corresponding to the position b-1 among the PET images viewed from the arrow I in FIG. 4-4.

(Step S311)
The PET image reconstruction unit 64 and the X-ray CT image reconstruction unit 74 output the configured PET image and X-ray CT image to the image composition unit 80 (S311).

(Step S312)
The image composition unit 80 generates a composite image by superimposing the PET image and the X-ray CT image (S312).

(Step S313)
Thereafter, the image display unit 81 displays the composite image on the display device 41 (S313).

  Next, another embodiment will be described with reference to FIG. FIG. 5 shows a procedure in which the X-ray CT apparatus 10 captures a scanogram image before performing X-ray CT imaging, and the operator changes the X-ray irradiation conditions using the scanogram image.

  It is known that the γ dose detected by the PET apparatus 20 increases at a site (for example, brain, heart, etc.) or an excretory organ (for example, kidney, bladder) in the subject 50. Therefore, among the sites with a large γ dose, a lesion candidate site is distinguished from a site with a large blood flow rate and a site of excretory organs, and a necessary amount of X-ray irradiation is performed only on the lesion candidate site.

(Steps S501 to S507)
Specifically, according to the same procedure as in steps S301 to S307 in FIG. 3, the γ-ray detection data is collected by the PET apparatus 20, and the X-ray irradiation conditions are set (S501 to S507).

(Step S508)
Next, scanogram imaging is performed by the X-ray CT apparatus 10 (S508). In this scanogram imaging, the X-ray tube 11 and the X-ray detector 12 are stationary, the X-ray imaging is performed by moving only the common bed 30, and the plane perspective image of the subject 50 placed on the common bed 30. Is to shoot.

(Step S509)
Based on the scanogram image, the X-ray irradiation conditions are manually changed (S509). The PET / CT system 1 displays the captured scanogram image on the display device 41. An operator who operates the PET / CT system 1 looks at the display screen of the scanogram image and designates a region where the blood flow is high, such as the brain and the heart, or a display area of excretory organs such as the kidney and the bladder. The operator then gives a change instruction to the X-ray CT apparatus control unit 71 to reduce the X-ray irradiation amount of the part of the subject 50 corresponding to the display area. The X-ray CT apparatus control unit 71 performs X-ray irradiation condition change processing in accordance with this change instruction. Similarly, the operator designates a display area of a part having a large influence of X-ray exposure, such as a crystalline lens or a genital organ, and issues a change instruction to further reduce the X-ray irradiation amount of the part corresponding to the display area. The X-ray CT apparatus control unit 71 performs X-ray irradiation condition change processing in accordance with this change instruction. The change instruction for further reducing the X-ray irradiation amount includes a change content that makes the X-ray irradiation amount zero, that is, does not perform X-ray irradiation.

(Steps S510 to S515)
Based on the X-ray irradiation conditions changed in step S509, the X-ray CT apparatus 10 performs X-ray CT imaging (S510). Then, a combined image of the PET image and the X-ray CT image is generated and displayed on the display device 41 by the same procedure as in steps S309 to S313 in FIG. 3 (S511 to S515).

  The PET apparatus 20 of the above embodiment uses the all-round PET apparatus 20 in which the γ-ray detector 22 is annularly arranged as an image capturing apparatus, but instead of the all-round PET apparatus 20, opposing γ-rays are used. Even if an imaging device such as a PET device, a single photon emission computed tomography (hereinafter referred to as “SPECT”) device, a scintillation camera or the like is used, the detector 22 is partially reduced. Good.

In the above embodiment, the PET apparatus 20 and the X-ray CT apparatus 10 formed separately from the PET apparatus 20 are used in combination, but the X-ray data for collecting X-ray data in the PET apparatus 20 is used. You may form the apparatus carrying a tube. Then, the γ-ray detection data collected from the PET apparatus 20 may be used to control the X-ray irradiation amount irradiated from the X-ray tube. Further, the PET apparatus 20, the SPECT apparatus, the scintillation camera, and the like, and the X-ray CT apparatus 10 may be configured as a single unit formed in a single unit.
Further, in the above embodiment, the X-ray CT control device 71 calculates where the lesion candidate site is in the subject 50, but this calculation may be performed by the PET data calculation unit 63. That is, the PET data calculation unit 63 compares the γ dose at each site in the height direction with the reference γ dose, and identifies where the lesion candidate site is in the height direction. Then, the position data specifying the position of the lesion candidate site is output to the X-ray CT control unit 71. Then, the X-ray CT control unit 71 may set an X-ray irradiation condition that defines an X-ray irradiation amount for each part of the subject based on this position data.

  In the above embodiment, the X-ray CT apparatus 10 controls the X-ray dose to be irradiated by increasing or decreasing the tube current value. However, the X-ray CT apparatus 10 increases or decreases the tube voltage value or changes the slice width of the X-ray CT apparatus 10. Or, the X-ray irradiation dose may be controlled.

  In the above embodiment, as the setting order of the X-ray irradiation conditions, first, the X-ray irradiation conditions are set so that a necessary amount of X-rays are irradiated to the lesion candidate site, and the site that is not the lesion candidate site or X The X-ray irradiation conditions are changed so that the X-ray irradiation dose smaller than the required dose is applied to the site that is easily affected by the radiation exposure. However, the X-ray dose lower than the required dose is applied to all the portions of the subject 50. An X-ray irradiation condition of irradiation may be set, and a modification may be performed on the X-ray irradiation condition by increasing the X-ray irradiation amount only to a lesion candidate site and irradiating a required amount of X-rays.

FIG. 1 is a block diagram showing a hardware configuration of a PET / CT system according to the present invention. FIG. 2 is a block diagram showing the configuration of the control device. FIG. 3 is a flowchart showing an operation procedure of the PET / CT system according to the present invention. FIG. 4 is a schematic diagram showing a relationship between the γ-ray distribution and the X irradiation amount, and an example of a PET image after back projection. FIG. 5 is a flowchart showing another operation procedure of the PET / CT system according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... PET / CT system 10 ... X-ray CT apparatus 11 ... X-ray tube 12 ... X-ray detector 20 ... PET apparatus 22 ... γ-ray detector 30 ... Common bed 31 ... Common bed moving device 40 ... Control device 41 ... Display Apparatus 50 ... Subject

Claims (3)

An imaging system comprising: an imaging device that detects radiation emitted from a radiation generating substance present in a subject; and an X-ray CT device that performs X-ray tomography of the subject,
The imaging device
An information output unit that outputs imaging data collected by detecting the radiation for each part of the subject to the X-ray CT apparatus;
The X-ray CT apparatus
An information acquisition unit for acquiring the photographing data;
An X-ray irradiation condition setting unit for setting an X-ray irradiation condition for defining an X-ray irradiation amount for each part of the subject based on the imaging data;
An X-ray irradiation control unit that irradiates X-rays according to the X-ray irradiation conditions;
An image photographing system comprising: The radiation is gamma rays,
The imaging apparatus is a positron CT apparatus that detects the γ-ray for each tomographic plane of the subject,
The imaging data includes γ-ray detection data indicating the amount of γ-rays.
The image photographing system according to claim 1. The X-ray CT apparatus further includes a scanogram processing unit that captures and displays a scanogram image,
The X-ray irradiation condition setting unit performs correction on the X-ray irradiation condition to change an X-ray dose irradiated to a part of the subject corresponding to a predetermined region of the scanogram image.
The image photographing system according to claim 1 or 2, wherein

Images