JP5484788B2 - X-ray CT system - Google Patents

X-ray CT system Download PDF

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JP5484788B2
JP5484788B2 JP2009124920A JP2009124920A JP5484788B2 JP 5484788 B2 JP5484788 B2 JP 5484788B2 JP 2009124920 A JP2009124920 A JP 2009124920A JP 2009124920 A JP2009124920 A JP 2009124920A JP 5484788 B2 JP5484788 B2 JP 5484788B2
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ray ct
exposure dose
image
exposure
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JP2010269048A (en
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勝 瀬戸
光彦 原
靖浩 今井
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ジーイー・メディカル・システムズ・グローバル・テクノロジー・カンパニー・エルエルシー
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Description

  The present invention relates to a user interface of an X-ray computed tomography system (X-ray CT).

  An X-ray CT apparatus that modulates the dose of an X-ray beam irradiated to a subject in the body axis direction or the rotation direction of the scan when the subject is scanned with an X-ray CT scan It is known (see, for example, Patent Document 1, Abstract, etc.). According to such an X-ray CT apparatus, the balance between the image quality of the reconstructed image and the exposure dose of the subject can be optimized according to the shape of the subject.

JP 2008-018044 A

  By the way, when the site | part with high radiation sensitivity is contained in the scanning range set to the body-axis direction of a subject, it is necessary to suppress the exposure dose of this site | part as much as possible.

  For that purpose, for example, it is conceivable to use a method of modulating the dose of the X-ray beam to be irradiated when scanning a range including a highly radiation-sensitive region.

  However, the conventional X-ray CT apparatus that modulates the tube current of the X-ray tube is designed for the purpose of optimizing the balance between the image quality of the reconstructed image and the exposure dose of the subject according to the shape of the subject. Is done. For this reason, it has been impossible to accurately and efficiently set scan conditions that reduce exposure of highly sensitive parts of the subject.

  In view of the above circumstances, an object of the present invention is to provide an X-ray CT apparatus capable of accurately and efficiently setting scan conditions for reducing exposure to highly radiation-sensitive parts.

  In a first aspect, the present invention displays an image of a subject and information indicating a predetermined position or range in the body axis direction of the subject in association with each other and the predetermined information in association with the information. A graphical user interface that supports an operation of inputting a relationship between a projection angle and a dose of an X-ray beam when an X-ray CT scan of the position or range of the image is input via the graphical user interface Provided is an X-ray CT apparatus including a scanning unit that performs X-ray CT scanning based on a relationship between a projection angle and an X-ray beam dose.

  Here, the “information indicating the predetermined position or range” is, for example, coordinates or image numbers indicating the predetermined position or range when an image of the subject is attached with coordinates, an image number, or the like. It can be an image number or the like.

  When the tube voltage of the X-ray tube is made constant, the dose of the X-ray beam can be increased or decreased by increasing or decreasing the tube current of the X-ray tube.

  In a second aspect, the present invention provides an image of the subject, an image obtained by scout scan of the subject, an image obtained by X-ray CT scan of the subject, or The X-ray CT apparatus according to the first aspect is an image obtained by imaging the subject with an optical imaging apparatus.

  The “scout scan” is a scan performed before the main scan in order to acquire an image used for the scan plan. In the “scout scan”, for example, an X-ray beam having a lower dose than the main scan is moved while moving the subject or the scanning gantry in the body axis direction while keeping the rotation angle position of the X-ray tube, that is, the projection angle constant. It is possible to consider a scan in which projection data is collected by irradiation. Further, for example, a helical scan using an X-ray beam having a dose much lower than that of the main scan can be considered.

  As the “image obtained by X-ray CT scan of a subject”, for example, an image obtained by a main scan performed in the past examination or immediately before the current scan can be considered.

  In addition, as an “image obtained by photographing with an optical photographing apparatus”, for example, an image obtained by a digital camera (digital camera) that receives reflected light from a subject and generates an image is considered. be able to.

  Note that these images may be two-dimensional images or three-dimensional images.

  In a third aspect, the present invention provides the first graphical user interface, wherein the graphical user interface displays a graphic indicating the predetermined position or range superimposed on the subject image or in the vicinity of the subject image. An X-ray CT apparatus according to a viewpoint or a second aspect is provided.

  As the “figure”, for example, an auxiliary line, an arrow, a frame, shading, and the like can be considered.

  In a fourth aspect, the present invention provides the graphical user interface according to the first aspect, wherein the graphical user interface further displays a graphic in which a range of a predetermined projection angle related to the input relationship is represented by a circular arc on a circumference. An X-ray CT apparatus according to any one of the third aspects is provided.

  In a fifth aspect, the present invention further comprises a predicted exposure dose calculation means for calculating a first predicted exposure dose of the subject when an X-ray CT scan is performed based on the input relationship, The X-ray CT apparatus according to any one of the first to fourth aspects, wherein the graphical user interface further displays the first predicted exposure dose.

  In a sixth aspect, the present invention relates to a case where the exposure predicted dose calculation means performs an X-ray CT scan based on a predetermined relationship between a projection angle and an X-ray beam dose, which is different from the input relationship. A second predicted exposure dose of the subject is further calculated, and the graphical user interface is configured to calculate the second predicted exposure dose or the difference between the first predicted exposure dose and the second predicted exposure dose. The X-ray CT apparatus of the said 5th viewpoint which displays further is provided.

  In a seventh aspect, according to the present invention, the predicted exposure dose calculation means calculates a predicted exposure dose at each spatial position of the subject, and the graphical user interface receives the predicted exposure dose at each position. The X-ray CT apparatus according to the fifth aspect of the present invention further displays a distribution map of the predicted exposure dose of the subject in the slice cross-sectional direction.

  In an eighth aspect, the present invention provides an exposure dose calculation means for calculating an exposure dose at each spatial position of the subject based on information obtained by an X-ray CT scan based on the input relationship. The X-ray CT apparatus according to any one of the first to seventh aspects, wherein the graphical user interface further displays a distribution map of the exposure dose at each position in the slice cross-sectional direction. provide.

  In a ninth aspect, the present invention provides a distribution map of a tomographic image obtained by an X-ray CT scan based on the input relationship and a radiation dose distribution of a subject portion corresponding to the tomographic image by the graphical user interface. An X-ray CT apparatus according to the eighth aspect is provided.

  According to the present invention, the X-ray CT apparatus displays an image of the subject and information indicating a predetermined position or range in the body axis direction of the subject in association with each other, and associates the information with the information. Since it has a graphical user interface that supports the operation of inputting the relationship between the projection angle and the dose of the X-ray beam when performing X-ray CT scan of a predetermined position or range, the X-ray CT scan of the subject is performed. The relationship between the projection angle and the X-ray beam dose can be set while intuitively grasping the scan position to which the relationship is applied. As a result, it is possible to accurately and efficiently set scan conditions for reducing exposure to highly radiation sensitive parts.

1 is a diagram schematically showing a configuration of an X-ray CT apparatus according to a first embodiment. It is a flowchart (flow chart) which shows the flow of the process which concerns on the X-ray CT apparatus of 1st embodiment. It is a figure for demonstrating a scout scan. It is a figure which shows an example of the scan plan screen displayed on a monitor (monitor). It is a figure which shows an example of the scan plan screen of the state which the tube current reduction setting window (window) opened. It is a figure which shows the example of a display of a tomographic image and distribution of the exposure dose corresponding to the tomography. It is a figure which shows an example of the scan plan screen by 2nd embodiment.

  Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited thereby.

(First embodiment)
FIG. 1 is a diagram schematically showing the configuration of the X-ray CT apparatus according to the first embodiment.

  The X-ray CT apparatus 100 includes an operation console 1, an imaging table 10, and a scanning gantry 20.

  The operation console 1 includes an input device 2 that receives input from an operator, a central processing unit 3 that performs control of each unit for imaging a subject, data processing for generating an image, and the like, and a scanning gantry 20. A data collection buffer (buffer) 5 that collects the acquired data, a monitor 6 that displays an image, and a storage device 7 that stores a program, data, and the like are provided.

  The imaging table 10 includes a cradle 12 on which the subject 40 is placed and put into and out of the opening B of the scanning gantry 20. The cradle 12 is moved up and down and horizontally moved by a motor built in the imaging table 10. Here, the body axis direction of the subject 40, that is, the horizontal linear movement direction of the cradle 12 is the z direction, the vertical direction is the y direction, and the horizontal direction perpendicular to the z direction and the y direction is the x direction.

  The scanning gantry 20 includes a rotating unit 15 and a main body 20a that rotatably supports the rotating unit 15. The rotating unit 15 includes an X-ray tube 21, an X-ray controller 22 that controls the X-ray tube 21, and a collimator (collimate) that shapes and collimates the X-ray beam Xb generated from the X-ray tube 21. collimator) 23, an X-ray detector 24 that detects an X-ray beam Xb that has passed through the subject 40, and a DAS (Data Acquisition System) that converts the output of the X-ray detector 24 into projection data and collects it (data acquisition) 25) and a rotating unit controller 26 that controls the X-ray controller 22, the collimator 23, and the DAS 25. The main body 20 a includes a control controller 29 that communicates control signals and the like with the operation console 1 and the imaging table 10. The rotating part 15 and the main body part 20 a are electrically connected via a slip ring 30.

  The central processing unit 3 is an example of a graphical user interface, exposure predicted dose calculation means, and exposure dose calculation means in the present invention, and functions as these means by executing a predetermined program. The scanning gantry 20 is an example of scanning means in the present invention.

  From this, the flow of the process which concerns on the X-ray CT apparatus of 1st embodiment is demonstrated.

  FIG. 2 is a flowchart showing a flow of processing according to the X-ray CT apparatus of the first embodiment.

  In step S1, a scout image of the subject 40 is acquired by performing a scout scan of the subject 40. The scout scan is, for example, by irradiating the subject 40 with an X-ray beam from the X-ray tube 21 while moving the cradle 12 on which the subject 40 is placed horizontally in the z direction while the rotating unit 15 is stationary. 40 projection data are obtained, and a scout image, which is a perspective image of the subject 40, is obtained based on the projection data. Thereby, a scout image obtained by projecting the subject 40 in one direction such as the x direction and the y direction is obtained. Note that a three-dimensional image that is CT volume data (volume data) of the subject 40 obtained by performing a helical scan with an ultra-low dose X-ray beam Xb, or this three-dimensional image is projected in the x and y directions. The image may be acquired as a scout image. In place of such a scout image, the subject 40 is imaged by an optical imaging device without using a three-dimensional image obtained by scanning the subject 40 during a past examination, a projection image thereof, or X-rays. You may acquire the image obtained by doing. That is, the image to be prepared in this step may be any image as long as it can be used for the scan plan in the next step.

  Here, as shown in FIG. 3, a first scout scan in which the X-ray tube 21 is positioned at a projection angle of 0 °, which is directly above the subject 40, and a projection in which the X-ray tube 21 is directly beside the subject 40. A second scout scan is performed at an angle of 90 ° to obtain two types of scout images.

  In step S2, a scan plan including tube current reduction is set. The scan plan is performed on a scan plan screen displayed on the monitor 6.

  FIG. 4 is a diagram illustrating an example of a scan plan screen displayed on the monitor. In the scan plan screen 51, a “start position” column 61, an “end position” column 62, a “slice thickness” column 63, a “tube voltage” column 64, and a “tube current” column 65 are displayed. The “start position” field 61 and the “end position” field 62 are fields for inputting the start position and the end position of the scan. The “slice thickness” column 63 is a column for inputting a slice thickness in scanning. The “tube voltage” column 64 and the “tube current” column 65 are columns for inputting a tube voltage and a tube current applied to the X-ray tube 21 at the time of scanning. Further, the scan plan screen has an image area 66, and one of the scout images acquired in step S1 is displayed here. The operator proceeds with the scan plan while viewing the scout image 81 displayed in the image area 66.

  When values are input to the “start position” column 61 and the “end position” column 62, a line Za indicating the scan start position and a scan end position are displayed on the scout image 81 in the image area 66 based on the input values. The line Zb shown is displayed. Further, when a value is input to the “slice thickness” field 63, based on this input value, an image position that is the center position of each slice of the tomographic image to be imaged is calculated, and within the line Za-Zb interval. A line Zi indicating these image positions is displayed.

  When a line Zi indicating an image position on the scout image 81 is designated by the pointer 67 on the screen, a tube current reduction setting window is opened and displayed on the scan plan screen 51 based on this designation. In this tube current reduction setting window, the operator sets how much the tube current is reduced for which projection angle of which range of scans from the start position to the end position of the scan.

  Note that the position specified by the pointer 67 is an image position that intersects with a highly radiation-sensitive part of the subject 40, for example, the eyeball 41 including the lens, the thyroid gland 42, the mammary gland 43, and the like, and an image position in the vicinity thereof.

  The setting / display in the exposure reduction setting window will be described below.

  FIG. 5 is a diagram showing an example of a scan plan screen in a state where the exposure reduction setting window is opened. In the exposure reduction setting window 68 opened on the scan plan screen 52, an “exposure reduction scan range” column 69, a “tube current reference value” column 70, a “tube current reduction setting” column 71, and “expected exposure dose” are displayed. A column 72 is displayed. Further, in the exposure reduction setting window 68, a circular graph (graph) 73 representing the setting contents in the “tube current reduction setting” column 71 and a distribution map 75 of the predicted dose in the slice cross section are also displayed.

  The “exposure reduction scan range” column 69 is a column for setting and displaying a start position and an end position of a scan for reducing exposure, that is, a scan for reducing tube current. As the start position and the end position, the image position selected when the exposure reduction setting window 68 is opened is set as an initial setting. When the increase / decrease button displayed in this column 68 is pressed, the set value is changed by increasing / decreasing the start position and the end position. On the scout image 81 of the scan plan screen 52, a display indicating the range set in the “exposure reduction scan range” column 69 is made. In this example, this range is displayed by shading 76. When the set value of the scan range for reducing the tube current is changed, the display is updated almost in real time. Thus, the operator can intuitively understand which scan range in which the tube current is reduced is set corresponding to which range of the subject 40.

  In this example, the range in which the tube current is reduced is set in the scan range. However, as another setting method, for example, an image position included in the range in which the tube current is reduced may be set.

  The “tube current reference value” column 70 is a column for setting and displaying the reference value of the tube current to be given to the X-ray tube 21 when scanning the range set in the “exposure reduction scan range” column 69. The tube current reference value is initially set to the tube current input in the “tube current” column 65 of the scan plan screen 51. However, when the automatic exposure mechanism is used, the tube current set by this mechanism is set as the initial setting. When the increase / decrease button displayed in the “tube current reference value” column 70 is pressed, the set value is changed by increasing / decreasing the reference value of the tube current.

  The “tube current reduction setting” column 71 is a column for setting and displaying the correspondence between the projection angle in the scan and the reduction rate from the reference value of the tube current at the projection angle. Although the initial setting of this correspondence can be freely changed, in this example, the most standard correspondence is set as the initial setting. For example, a reduction rate of 50% for a projection angle range of −30 ° to + 30 °, a reduction rate of 30% for a range of + 30 ° to + 70 ° and a projection angle range of + 290 ° to + 330 °, and a projection angle of + 70 ° to The reduction rate is 0% with respect to the + 290 ° range. When the increase / decrease button (button) displayed in this column 71 is pressed, the set value is changed by increasing / decreasing the range of each projection angle and the reduction rate of the tube current.

  In this example, it is assumed that the tube current is reduced from the reference value for a predetermined projection angle, but the tube current may be increased from the reference value for a predetermined projection angle. For example, if the tube current is increased at the projection angle opposite to the projection angle at which the tube current should be reduced, the projection used for image reconstruction can be achieved while reducing the radiation exposure to highly sensitive parts. The dose of the X-ray beam Xb per data can be earned, and the image noise of the reconstructed image can be further reduced.

  The “expected exposure dose” column 72 is a column for displaying the predicted exposure dose at the time of scanning for the subject portion within the range set in the “exposure reduction scan range” column 69.

  First, a predicted exposure dose is calculated by a known calculation method for each of the three-dimensional positions of the subject portion to be processed. Thereafter, the sum is calculated. The predicted exposure dose is calculated and displayed for two cases, when there is no tube current reduction setting and when there is tube current reduction setting. Thereby, the operator can confirm quantitatively the effect of the exposure reduction by tube current reduction setting.

  The predicted exposure dose is calculated by simulating based on the phantom measurement data acquired in advance and the setting contents in the “tube current reduction setting” column 71, for example. Instead of or in addition to the phantom measurement data, simulation may be performed using a scout image of the subject 40, a tomographic image acquired in the past of the subject 40, or model data (model data). . As a highly accurate simulation method, for example, a physical calculation method based on a Monte Carlo method employed in a simulation program such as EGS4 or GEANT4 can be considered. These methods have been developed by the High Energy Accelerator Research Organization (KEK), the Stanford Linear Accelerator Center (SLAC), and the like. In these methods, an X-ray level electromagnetic wave is considered as a particle, and the destination of the particle is calculated according to the physical law for each locus of the particle. If it is determined that the particles remain in the body, the energy of the particles at the remaining points becomes the final absorbed energy, which is repeatedly calculated by millions to hundreds of millions, and is statistically answered.

  The circular graph 73 is a graph that visually represents the correspondence between the projection angle range set in the “tube current reduction setting” column 71 and the reduction rate of the tube current in that range. In this circular graph 73, the projection angle is represented by a position on the circumference, and each range of the projection angle is represented by an arc on the circumference. A color is assigned to each range of the projection angle set in the “tube current reduction setting” column 71, and an arc representing each range of the projection angle in the circular graph 73 is a color assigned to the range. Is displayed. When the set value of the projection angle range in the “tube current reduction setting” column 71 is changed, the display of the circular graph 73 is updated almost in real time. Further, the boundary 74 between the arcs of the circular graph 73 corresponding to the boundary between the projection angle ranges can be moved by using the pointer 67 on the screen 52, and “ The boundary between the ranges of the projection angles set in the “tube current reduction setting” column 71 is also changed. Thus, the operator can intuitively set and understand the correspondence between the projection angle range and the tube current reduction rate in the range.

  The distribution diagram 75 of the predicted exposure dose in the slice cross-sectional direction is a distribution diagram in the slice cross-sectional direction of the three-dimensional predicted exposure dose for the subject portion within the range set in the “exposure reduction scan range” column 69. This distribution map 75 is created based on the previously calculated three-dimensional exposure predicted dose when tube current reduction is set. In the distribution map 75, for example, the predicted exposure dose at each position is displayed in a color (color) representing the tone according to the magnitude of the value. Thereby, the operator can intuitively confirm how the exposure reduction of the subject 40 is performed spatially.

  Estimated exposure doses are more easily prepared in advance by obtaining simulation results under some setting conditions in advance, and the simulation results determined to be closest to the current set conditions are approximated as predicted exposure doses. May be required. In addition, with regard to the distribution map 75 in the slice cross-sectional direction of the predicted exposure dose, several distribution maps corresponding to the simulation results obtained in advance are prepared in a simplified manner and approximated based on the present setting conditions. A distribution map corresponding to the simulation result obtained in (1) may be obtained as the distribution map 75 described above.

  The above is the description of the setting / display in the exposure reduction setting window 68. When tube current reduction setting is to be performed for a plurality of positions or ranges within the set scan range, the above setting process is performed in the range. Repeat as many times as

  In step S3, scanning is performed according to scanning conditions including tube current reduction set by the scanning plan in step S2, and projection data of the subject 40 is collected.

  In step S4, an image is reconstructed based on the collected projection data, and a tomographic image of the subject 40 is obtained.

  In step S5, based on the scout image 81 of the subject 40, the set scan conditions, projection data, etc., three-dimensional dose data representing the dose at each three-dimensional position of the subject 40 is generated. Specifically, for example, the projection angle and the dose (tube voltage and tube current) of the X-ray beam irradiated at the projection angle, the exposure dose CTDIcenter at the center in the imaging space of the scanning gantry 20 and the exposure dose CTDIperi at the periphery Based on the above, the exposure dose at each three-dimensional position of the subject 40 is calculated.

  The generated three-dimensional exposure dose data of the subject 40 is stored in the storage device 7 and sent to and stored in a database (not shown) connected to the X-ray CT apparatus 100. In addition, you may memorize | store in storage media, such as CD-ROM, DVD, USB memory. The database stores and manages all the three-dimensional exposure dose data of the subject 40 generated so far for each subject.

  In step S <b> 6, the reconstructed tomographic image and the dose distribution map corresponding to the tomographic image are displayed on the monitor 6.

  FIG. 6 is a diagram illustrating a display example of a tomographic image and a distribution diagram of exposure dose corresponding to the tomographic image. For example, for a plurality of slices of the subject 40, as shown in FIG. 6, the tomographic images 82a to 84a of the slices SL1 to SL3, and the distribution of the exposure dose corresponding to the tomograms of these tomographic images 82a to 84a in the slice cross-sectional direction. 82b to 84b are displayed side by side. Furthermore, the superimposed images 82c to 84c of the tomographic images 82a to 84a and the distribution maps 82b to 84b of the exposure dose, and the superimposition of the tomographic image images 82a to 84a and the distribution map representing the exposure dose as an effective dose for each organ. The image images 82d to 84d may be displayed. Thus, if the tomographic image and the distribution map of the exposure dose are superimposed and displayed, the exposure dose of the organ of interest can be directly confirmed.

  Note that the display of the distribution chart of the exposure dose is preferably, for example, a color distribution display in which the difference in the exposure dose is represented by a difference in color tone.

  The effective dose for each organ is determined, for example, by identifying each organ included in the tomography based on the CT value of the tomographic image, and for each identified organ, the tissue load coefficient specific to the organ Multiply The tissue weighting factor for each organ is defined by the International Commission on Radiological Protection (ICRP).

  Further, the exposure dose may be expressed by cumulatively adding not only the exposure dose due to the current imaging but also the past imaging. For example, the 3D exposure dose data for the past imaging related to the subject 40 is read from the database, and this and the 3D exposure data for the current imaging are cumulatively added to obtain the 3D total exposure dose data. . Then, based on the three-dimensional total dose data, a dose distribution corresponding to the tomographic image tomography is obtained.

  The target for calculating the exposure dose is not limited to the tomographic image, but may be a predetermined organ of the subject 40. For example, the CT image of the subject 40 is displayed in 3D or MPR based on the CT volume data of the subject 40 obtained by imaging. The operator designates a three-dimensional region including the target organ on these display surfaces. The target organ is extracted based on the CT value of each pixel in the designated three-dimensional area. Then, the extracted exposure dose of the target organ is calculated based on the three-dimensional exposure dose data.

  According to such a first embodiment, the X-ray CT apparatus 100 displays an image of the subject 40 in association with information indicating a predetermined position or range of the subject 40 in the body axis direction, Corresponding to this information, a graphical user interface that supports an operation for inputting the relationship between the projection angle and the dose of the X-ray beam Xb when performing the X-ray CT scan of the predetermined position or range is provided. The relationship between the projection angle and the dose of the X-ray beam Xb when the specimen 40 is X-ray CT scanned can be set while intuitively grasping the scan position to which the relationship is applied. As a result, it is possible to accurately and efficiently set scan conditions for reducing exposure to highly radiation sensitive parts.

In addition, according to the first embodiment, since the three-dimensional exposure dose data of the subject 40 is generated, stored, and managed, when the next scan is performed, the appropriate exposure dose is managed from the previous exposure dose. Can be done. Such three-dimensional exposure data of the subject 40 is generated, stored, and managed not only by the X-ray CT apparatus but also by PET (Positron
Emission Tomography (SPECT) (Single Photon Emission Computed)
The present invention can also be applied to other imaging apparatuses that involve exposure, such as Tomography apparatus.

  In addition, according to the first embodiment, since the distribution map of the exposure dose is displayed after the scan is performed, it is possible to spatially grasp the degree of the exposure of the subject 40 by the scan. And it can be confirmed whether desired exposure reduction was able to be performed.

(Second embodiment)
In the second embodiment, some settings in the “tube current reduction setting” column 71 are preset in advance, and the tube current reduction is set using these settings.

  FIG. 7 is a diagram illustrating an example of a scan plan screen according to the second embodiment. In the second embodiment, several presets of correspondence relationships between the range of the projection angle in the scan and the reduction rate of the tube current in the range are prepared in advance. Then, for example, as shown in FIG. 7, each preset is converted into an icon (77 to 79) and included in the scan plan screen 53 and displayed. As the preset for the exposure reduction setting, it is preferable to prepare a preset suitable for each type of region having high radiation sensitivity. For example, as a preset suitable for reducing exposure of a crystalline lens or the like, a preset is prepared with a tube current reduction rate of −30% with respect to a projection angle range of −50 ° to + 50 °. Further, for example, as a preset suitable for exposure reduction of the thyroid gland, a preset is prepared with a tube current reduction rate of −50% with respect to a projection angle range of −30 ° to + 30 °.

  The operator first selects a desired tube current reduction setting preset by pressing one of the icons 77 to 79 with the pointer 67. Next, on the scout image 81, a scan range to which the preset is to be applied is designated by drawing a frame or the like with the pointer 67. Then, the preset of the tube current reduction setting selected previously is applied to the designated scan range. In the example of FIG. 7, the icon 77 is pressed to select a preset suitable for the lens, and a frame 77k is drawn on the scout image 81 so as to surround the eyeball 41 including the lens, and the range to which this preset is applied is specified. Yes. Further, a preset suitable for the thyroid gland is selected by pressing the icon 78, and a frame 78 k is drawn on the scout image 81 so as to surround the thyroid gland 42 to specify a range to which this preset is applied. In addition, a preset suitable for the mammary gland is selected by pressing the icon 79, and a frame 79k is drawn on the scout image 81 so as to surround the mammary gland 43 to designate a range to which this preset is applied. It should be noted that the applied tube current reduction setting can be adjusted manually.

  According to the second embodiment, since several tube current reduction settings are preset in advance and the tube current reduction is set using the presetting, it is possible to efficiently set the scan condition including the tube current reduction. Can be done.

  In this example, the scan range for reducing the tube current is specified after selecting the preset for the tube current reduction setting. Conversely, after specifying the scan range for reducing the tube current, the tube current is reduced. A reduction setting preset may be selected.

  In this example, the selection of the preset for the tube current reduction setting and the designation of the scan range to which this is applied are performed by the operator, but this may be performed automatically. For example, analysis processing based on the contour shape and pixel values in the image of the subject used for the scan plan such as a scout image, and the like is highly sensitive to radiation such as an eyeball including a crystalline lens, a neck including a thyroid gland, and a breast including a mammary gland. A range including a region may be specified, and an optimum tube current reduction setting preset associated with each tissue type may be applied. This reduces the burden on the operator.

  Moreover, it is preferable that the simulation (simulation) of the predicted exposure dose described in the first embodiment can be performed at a time other than the scan planning time. In this case, the tube current reduction setting window is opened to enable setting and display of conditions, simulation of predicted exposure dose based on phantom and sample data, and display of calculated values and distribution maps. . This allows the operator to simulate the predicted exposure dose before examining the actual scan plan, and examine and set the presets that should be prepared for each type of highly radiation-sensitive part and the desired presets. Can do.

  In each of the above-described embodiments, the tube current of the X-ray tube 21 is changed according to the projection angle in the scan in order to reduce the radiation dose at a highly radiation-sensitive part. May be. For example, the tube voltage of the X-ray tube 21 may be changed according to the projection angle. Further, for example, a filter having a variable X-ray absorption rate may be installed on the path of the X-ray beam Xb, and this filter may be controlled to change the dose of the X-ray beam Xb.

  The above embodiments are all related to the X-ray CT apparatus, but the present invention is also applicable to a PET-CT apparatus, a SPECT-CT apparatus, or the like that combines the X-ray CT apparatus and PET or SPECT. Is possible.

DESCRIPTION OF SYMBOLS 1 Operation console 2 Input device 3 Central processing unit 5 Data collection buffer 6 Monitor 7 Storage device 10 Imaging table 12 Cradle 15 Rotating part 20 Scanning gantry 21 X-ray tube 22 X-ray controller 23 Collimator 24 X-ray detector 25 DAS
26 Rotating unit controller 29 Control controller 30 Slip ring 40 Subject 100 X-ray CT apparatus

Claims (10)

  1. In association with the image of the subject, in the body axis direction of the subject, a range including a region where the subject is highly sensitive is set and displayed as an exposure reduction range, and the exposure reduction range is displayed by an X-ray CT scan. to assist the operation of inputting the relationship between the reduction rate from the reference value of the tube current is an initial set value of the set tube current by an automatic exposure mechanism prior to the projection angle between the exposure reduction range of settings when A graphical user interface to display in

    An X-ray CT apparatus comprising: a scanning unit that performs X-ray CT scanning based on a relationship between a projection angle input via the graphical user interface and an X-ray beam dose.
  2. The X-ray CT apparatus according to claim 1, wherein the graphical user interface is capable of adjusting a range of the projection angle.
  3. The image of the subject is an image obtained by performing a scout scan of the subject, an image obtained by performing an X-ray CT scan of the subject, or by photographing the subject with an optical imaging device. The X-ray CT apparatus according to claim 1 , wherein the X-ray CT apparatus is an obtained image.
  4. Said graphical user interface, the figure indicating the exposure reduction range, according the to any one of claims 1 to 3 to be displayed in the vicinity of the image overlaid or analyte to the subject of the image X Line CT device.
  5. Said graphical user interface, according to any one of claims 1 to 4, the range of a predetermined projection angle according to the input relationship further displays a graphic represented by an arc on the circumference X Line CT device.
  6. Further comprising an exposure predicted dose calculation means for calculating a first predicted exposure dose of the subject when an X-ray CT scan is performed based on the input relationship;

    It said graphical user interface, X-rays CT apparatus according to any one of claims 1 to 5 which further displays the first exposure prediction dose.
  7. The predicted exposure dose calculation unit calculates a second predicted exposure dose of the subject when an X-ray CT scan is performed based on a predetermined relationship between a projection angle and an X-ray beam dose, which is different from the input relationship. Is further calculated,

    The X-ray CT apparatus according to claim 6 , wherein the graphical user interface further displays the second predicted exposure dose or a difference between the first predicted exposure dose and the second predicted exposure dose.
  8. The predicted exposure dose calculation means calculates a predicted exposure dose at each spatial position of the subject,
    The X-ray CT apparatus according to claim 6 , wherein the graphical user interface further displays a distribution map in the slice cross-sectional direction of the predicted exposure dose of the subject based on the predicted exposure dose at each position.
  9. Further comprising an exposure dose calculating means for calculating an exposure dose at each spatial position of the subject based on information obtained by an X-ray CT scan based on the input relationship;

    The X-ray CT apparatus according to any one of claims 1 to 8 , wherein the graphical user interface further displays a distribution map of the exposure dose at each position in a slice cross-sectional direction.
  10. It said graphical user interface, to claim 9 for displaying overlapping the tomographic image obtained by the X-ray CT scan based on the input relationship, and a distribution diagram of the exposure dose of the subject portion corresponding to the tomographic image The X-ray CT apparatus described.
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