JP6524226B2 - X-ray CT system - Google Patents

Description

  The present invention relates to an X-ray CT apparatus and a control method thereof.

The X-ray CT apparatus comprises an X-ray irradiation unit including an X-ray tube and a scanner including an X-ray detection unit including an X-ray detector for detecting an X-ray transmitted through the patient around the subject Is rotated, and X-rays are emitted toward the subject placed near the rotation center, and X-rays transmitted through the subject are obtained at every predetermined rotation angle, and the test data is obtained from the obtained detection data Reconstruct the cross-sectional image of the person. Since the X-ray CT apparatus irradiates X-rays to a subject, the subject naturally comes with exposure. As indicators of exposure dose, there are CTDIvol, which is an indicator of exposure dose per unit length conventionally displayed on equipment, and DLP, which is an indicator of exposure dose of the whole inspection. The CTDIvol and DLP are obtained from the CTDI 100 in the central and peripheral portions of the 16 cm and 32 cm acrylic phantoms. The CTDI 100 is calculated according to the equation (1).

D (z) is the dose profile along a line perpendicular to the slice plane, N is the number of slices generated in one rotation of the radiation source, T is the nominal slice thickness, z is the axial distance of the subject Means The CTDIw weighted at the center and the periphery of the phantom is calculated according to equation (2).

The calculation method of CTDIvol is different depending on the scan method, and is calculated by Formula (3) in normal scan repeating scanning and bed movement, and Formula (4) in helical scan which continuously scans while moving the bed.

Δ d is the bed movement amount between normal scans, and BP is the bed movement amount per scanner rotation during scanning divided by the product of N and T. The DLP is obtained according to the equation (5) by the scanning method.

  D means the shooting range length. The X-ray CT system selects CTDIw of 16 cm regarded as equivalent to the head or 32 cm regarded as equivalent to the trunk according to the examination site, and CTDIvol and DLP are displayed from the imaging conditions, and the operator exposed the patient's exposure. It is a means to know the dose.

  Generally, small objects such as children use CTDIw of 16 cm regardless of the part, but neonates and infants may be smaller in size than 16 cm, and as a result, they may be underestimated. In addition, adult body trunks usually use CTDIw of 32 cm, but in the case of relatively thin test subjects, they are underestimated in the same manner as above, and the present method does not necessarily fit the size of the test subjects. The problem of not being able to get results has been addressed since before. Therefore, it is proposed from the AAPM (American Association of Physists in Medicine) to use SSDE as a method of determining a CTDIvol suitable for the size of a subject.

AAPM Report No. 204: Size-Specific Dose Estimates (SSDE) in Pediatric and Adult CT Examinations

  As described above, SSDE can take into account the physical form of the subject and has the effect of being able to grasp the exposure dose with high accuracy. However, no technology has been established that can accurately determine the size of a subject. Conventionally, various measurement methods have already been established if the size of the subject is simply measured. However, in the measurement of the subject size performed in the X-ray CT apparatus, a measurement method of a size suitable for the imaging state of the cross-sectional image is desired. Also in the configuration of the X-ray CT apparatus itself, it is necessary to take into account that the size of the subject is accurately measured. However, the measurement method of the size suitable for the imaging state of the cross-sectional image has not been studied, and the X-ray CT apparatus is not equipped with a configuration in consideration of the measurement of the size of the subject.

  For example, in Non-Patent Document 1, as a means for measuring the size of the subject in the PA direction or LAT direction before scanning, a method of physically measuring with a device such as a caliper, or a scanogram for setting a scan range A method of measuring with an image with a distance measuring function is disclosed. Moreover, also in the image after scanning, the measuring method is disclosed by the distance measuring function.

  However, measuring the size of the subject by the above-described physical method before scanning is not appropriate in terms of the fact that it takes time for the operator. Furthermore, it is desirable that the measured size and the size at the time of capturing the actual cross-sectional image be the same, but there is a problem that the form of the subject changes after setting the subject on the bed and after setting. .

  As described above, there is a problem in measurement accuracy, and as a result, there is a problem in the accuracy of exposure dose.

  Although a method has been proposed, such as SSDE, that accurately determines the exposure dose of the subject, there is a problem that the X-ray CT system itself does not cope with, and under the present circumstances, to grasp the exposure dose with high accuracy There is a problem. There is a need for an X-ray CT apparatus that can obtain exposure dose with higher accuracy.

  An object of the present invention is to obtain an X-ray CT apparatus capable of grasping the exposure dose of a subject with higher accuracy.

  An X-ray CT apparatus according to the present invention for solving the above problems has a scan gantry unit having a stationary X-ray CT scanner and a rotating X-ray CT scanner, a control device, a display device, and a bed. The rotation-side X-ray CT scanner includes an X-ray tube for emitting X-rays and an X-ray detector for detecting X-rays transmitted through the subject, and a measurement light projector for measuring the size of the subject is provided. And the size of the subject is calculated based on the measured value measured by the light projector for measurement, and based on the calculated size of the subject, an index related to the dose of the subject is calculated. An X-ray CT apparatus characterized in that

  According to the present invention, it is possible to obtain an X-ray CT apparatus capable of grasping the exposure dose of a subject with higher accuracy.

Explanatory drawing for demonstrating one Example of X-ray CT apparatus 100 to which this invention was applied. Explanatory drawing explaining body width size PA and body thickness size LAT and Deff of a subject Explanatory drawing explaining a conversion factor table An explanatory diagram for explaining the operation flow of the X-ray CT apparatus Flow chart for explaining the processing procedure of the first embodiment for measuring the size of the subject Explanatory drawing explaining measurement of body thickness size LAT and body width size PA in 1st Example Flow chart for explaining measurement of subject size before scanning in the second embodiment Explanatory drawing explaining measurement of body thickness size LAT in 2nd Example Explanatory drawing explaining measurement of the left end of body width size PA in the 2nd example Explanatory drawing explaining measurement of the right side end part of body width size PA in 2nd Example Flow chart for explaining the processing procedure of the third embodiment Explanatory drawing explaining measurement of body thickness size LAT at the time of using bed mat in 3rd Example Explanatory drawing explaining measurement of body thickness size LAT at the time of using accessories for children in 3rd Example Flow chart for explaining the processing procedure of the fourth embodiment Explanatory drawing explaining measurement of body thickness size PSLAT after a scan in 4th Example, and body width size PSPA after a scan Explanatory drawing explaining display of parameter | index SSDE in 4th Example Flow chart for explaining the processing procedure of the fifth embodiment Explanatory drawing explaining measurement of body thickness size PSLAT after a scan in 5th Example, and body width size PSPA after a scan

1. First, one mode for carrying out the invention (hereinafter referred to as an example) will be described with reference to the drawings.
Note that, in the drawings used for describing the embodiment, the substantially the same configuration is given the same reference numeral, and the description may be omitted for the configuration given the same reference numeral. The configurations given the same reference numerals perform substantially the same function and exhibit substantially the same effects, but in order to avoid complication due to the functions and effects, the repetition of the description may be omitted.

  The embodiment described below is not limited to the problems described in the problem column to be solved by the above-described invention, and it is possible to solve the problems different from the problems. The specific contents will be described in the description of the embodiment. In addition to the effects described in the column of the effects of the invention described above, various effects different from the effects can be achieved. The specific contents will be described in the description of the embodiment.

  In the present specification, not only mere algebraic calculations but also pre-recorded tables are searched for the concepts of the terms “calculation” and the terms “calculation” and “calculation”, respectively, and processing for selecting desired values or These terms are used as including also a process of obtaining a desired value from a parameter based on a predetermined functional relationship.

2. Description of an example of the X-ray CT apparatus 100 to which the present invention is applied
2.1 Basic Structure of X-ray CT Apparatus 100 FIG. 1 is an explanatory diagram for describing an embodiment which is an example of the X-ray CT apparatus 100 to which the present invention is applied. A coordinate system 90 described in FIG. 1 shows an example of the definition of the direction in the X-ray CT apparatus 100. The X axis, the Y axis, and the Z axis of the coordinate system 90 are an example, and the present invention is not limited to this. For easy understanding in the following description, the X-axis, the Y-axis, and the Z-axis in the X-ray CT apparatus 100 are defined in the same direction in all the drawings. Incidentally, the Z axis is the body axis direction of the subject, the Y axis is the vertical direction of the subject, and the X axis is the left and right direction of the subject.

  The X-ray CT apparatus 100 has a scan gantry unit 110, an operation unit 140 for performing an operation for X-ray imaging, and a processing unit 160 for performing various processes including the process of the detection data. In addition, it does not matter in the implementation of the present invention to which part of the scan gantry unit 110, the operation unit 140, and the processing unit 160 each component of the X-ray CT apparatus 100 belongs to. This is an example for explaining the CT apparatus 100, and the application of the present invention is not affected by the division method of these parts or which part belongs to which part, even if different from the above.

  The scan gantry unit 110 has a function of irradiating the subject 12 placed on the bed 190 with X-rays, detecting X-rays transmitted through the subject 12, and outputting detection data. A stationary X-ray CT scanner 112 and a rotating X-ray CT scanner 120 are provided. The rotation-side X-ray CT scanner 120 determines the X-ray tube 122 for irradiating X-rays, the X-ray guarantee filter for adjusting the intensity distribution of X-rays irradiated from the X-ray tube 122, and the beam width of X-rays The X-ray detector 126 and the data acquisition device 128 are further provided. The X-ray detector 126 has a function of detecting X-rays transmitted through the subject 12, and has several hundreds to 1000 channels in the direction along the rotational surface and 1 to several hundreds in the Z axis direction. An X-ray detector 126 in the form of a two-dimensional matrix is provided in which the X-ray detector elements in a row are arranged.

  The X-rays transmitted through the subject 12 are converted by the X-ray detector 126 into electrical signals according to the X-ray intensity. The data acquisition device 128 acquires the electrical signal output from the X-ray detector 126 as detection data, converts it into a digital signal, and converts the digital signal into a communication interface (INTERFACE: I below) of the processing unit 160 described below. (Denoted as / F) 162 to the image processing apparatus 164.

  The rotation-side X-ray CT scanner 120 is rotated, and transmitted X-rays transmitted through the subject 12 at each predetermined rotation angle are detected by the X-ray detector 126, and the detection data is transmitted from the data acquisition device 128 to the image processing device 164. Sent to As described below, a cross-sectional image is generated by the image processing device 164 based on the detection data, and the generated cross-sectional image is displayed on the display device 168 described below or is stored in the recording device 166. .

The operation unit 140 includes an operation device 142, a control device 144, and a communication I / F 146.
The operating device 142 is used to input measurement conditions including a measurement schedule and to perform an operation for measurement. The control device 144 transmits a control command via the communication I / F 146 to control the rotation-side X-ray CT scanner 120, the bed 190, and the processing unit 160 according to the input measurement conditions, and also sends information Are received via the communication I / F 146.

  The control command to the rotation-side X-ray CT scanner 120 is sent from the communication I / F 146 to the stationary-side X-ray CT scanner 112 and is sent from the stationary-side X-ray CT scanner 112 to the rotation-side X-ray CT scanner 120 . The rotation-side X-ray CT scanner 120 that receives the control signal determines the X-ray tube 122 that emits X-rays, the X-ray compensation filter that adjusts the intensity distribution of X-rays, and the beam width of X-rays according to measurement conditions. A collimator unit 124 in which a collimator and the like are stored operates. The bed 190 simultaneously operates in accordance with the measurement condition, and the imaging operation of the cross-sectional image is performed in accordance with the measurement condition. Further, the X-ray detector 126 and the data acquisition device 128 operate according to the measurement conditions, the detection data is acquired, and is sent to the image processing device 164 as projection data by the communication I / F 162.

  The processing unit 160 holds a communication I / F 162 for transmitting and receiving information, an image processing apparatus 164 for performing processing for reconstructing an image, and holds measured projection data and data for performing arithmetic processing. The recording device 166, the display device 168 for displaying various information including images, the pre-scan SSDE processing device 172 for calculating the SSDE before the imaging operation, the body width size PA and the body thickness after the imaging operation is performed It has a post-scan measurement device 174 for measuring the size LAT, a post-scan SSDE processing device 176 after the photographing operation, and an SSDE recording device 178 for recording the obtained SSDE.

  When projection data is sent from the data acquisition device 128 to the image processing device 164, the image processing device 164 performs correction processing of the projection data, and raw data (Rawdata) after correction processing is created. Furthermore, a cross-sectional image is reconstructed based on the raw data. The raw data and the reconstructed cross-sectional image are recorded in the recording device 166. Further, information including a cross-sectional image reconstructed based on the operation is displayed on the display device 168.

2.2 Description of Measuring Means of Body Width Size PA and Body Thickness Size LAT of Subject In this embodiment, in order to grasp the exposure dose with higher accuracy, the scan gantry unit 110 further includes the subject of the subject. Measuring means for measuring the body width PA size and the body thickness size LAT are provided. The body width PA size and body thickness size LAT of the subject will be described with reference to FIG. In the cross section perpendicular to the body axis of the image measurement position of the subject 12, the size in the body thickness direction of the subject 12 is the body thickness size LAT, and the size in the body width direction of the subject 12 is the body width size PA It is. The effective size of the subject when the non-circular body width size PA and the body thickness size LAT of the subject are replaced with a circle is shown as Deff.

  An example of a specific configuration of the measuring means for measuring the body width size PA in the body width direction of the subject and the body thickness size LAT in the body thickness direction will be described with reference to FIG. In the present embodiment, a light projector 132 for measuring the body width size PA of the subject 12 placed on the bed 190 is provided in the scan gantry unit 110, and the body thickness size LAT of the subject 12 is further measured. A light projector 134 for measurement is provided. The measurement light projector 132 and the measurement light projector 134 may be provided in the stationary side X-ray CT scanner 112 or may be provided in the rotation side X-ray CT scanner 120.

  The light projector 132 for measurement is provided in the direction facing the bed 190, and emits light from the light projector 132 for measurement toward the bed 190 to measure the body width size PA. Although measurement may be performed by various methods, for example, when the measurement light projector 132 generates a light beam in the direction along the Y axis and operates the operation switch at the position of the light beam passing through the point P1 shown in FIG. The position of P1 is set, then the position of the light beam is moved along the X axis, and when the light beam operates the operation switch again at the position of point P2, the position of point P2 is set, and the position of point P1 and The body width size PA may be automatically measured by setting the position of the point P2.

  By doing this, it is possible to accurately measure the body width size PA without giving the subject 12 a burden such as exposure. Similarly, a light beam in a direction along the X axis is emitted from the measurement light projector 134, the position of the point T1 is set, and the position of the point T2 is set, so that the body thickness size LAT is measured. Also good. Like the measurement of the body width size PA, this method can accurately measure the body thickness size LAT without giving a load to the subject 12.

  A switch for operating the light projector 132 for measurement and the light projector 134 for measurement and the light control panel for measurement with the function of transmitting information of the measured body width size PA and body thickness size LAT to the pre-scan SSDE processing device 172 A cover 136 is provided on the cover of the stationary X-ray CT scanner 112 or the cover of the bed 190. Information of the measured body width size PA and body thickness size LAT is measured by the measurement light projector 132 and the measurement light projector 134, and information of the measured body width size PA and body thickness size LAT is the light projector control panel 136 for measurement Are sent to the pre-scan SSDE processor 172 via the communication I / F 162, and a more accurate exposure dose represented by the SSDE of the subject 12 is calculated.

2.3 Explanation of Calculation of Exposure Dose by SSDE Pre-Scan Processing Device 172 and Post-Scan SSDE Processing Device 176 Next, calculation of SSDE which is an exposure dose will be described next. When the measured information of body width size PA and body thickness size LAT is sent from measurement projector operating panel 136 to pre-scan SSDE processing device 172, the table shown in FIG. 3 recorded in advance is used to perform exposure The dose, SSDE, is calculated. The pre-scan SSDE processing device 172 uses the table information described in FIG. 3 recorded in the recording device 166. As an example, conversion coefficients from CTDIvol of two types of conversion coefficient tables shown in phantom size column 212 and phantom size column 214 are selected in conversion coefficient column 210 constituting the conversion coefficient table shown in FIG. The pre-scan SSDE, which is the pre-scan dose, is calculated from the region information of the subject 12. The calculated pre-scan dose is displayed on the display device 168.

  If there is no problem with the pre-scan dose, X-ray imaging of the subject 12 is performed, and the cross-sectional image is reconstructed by the image processing device 164 based on the obtained projection data, and the display device 168 as necessary. Is displayed on.

  The post-scan body width size PA and the body thickness size LAT are measured by the post-scan measurement device 174 from the reconstructed image, and the conversion factor fields constituting the conversion factor table shown in FIG. 3 recorded in the recording device 166 From the body width size PA measured after the scan 210 and the body thickness size LAT, the post-scan SSDE processing unit 176 calculates the SSDE which is the exposure dose. The calculated radiation dose, SSDE, is displayed on the display unit 168 as necessary, and the radiation dose calculated by the SSDE recorder 178 is recorded and accumulated.

3. Description of Operation Flow of X-ray CT Apparatus 100 The flow of the operation of the X-ray CT apparatus 100 including the calculation of the SSDE which is the exposure dose and the recording operation of the calculation result will be described using the flowchart shown in FIG. Note that this flowchart is executed by a computer, which is a control device included in the X-ray CT apparatus 100, according to an instruction of the operator or an input operation of information. The computer may be a single computer for controlling the entire X-ray CT apparatus 100, or a plurality of computers provided in the X-ray CT apparatus 100 may be executed in conjunction with one another. . In the present embodiment, the control device 144 provided in the operation unit 140 is described as executing the comprehensive control of the X-ray CT apparatus 100 described in FIG. 4, but the application of the present invention is not limited to this. Absent.

  The flow chart shown in FIG. 4 is roughly classified into a process of calculating exposure dose performed before an imaging operation by X-ray (referred to as a scan) and a process including a process for securing the safety regarding the dose. , Step S130 of actually performing a scan, and step S140 of performing, for example, calculation of an SSDE which is an exposure dose after the scan, recording results of the calculation, and the like.

  When the examination for the X-ray imaging of the subject 12 is started by the instruction of the operator or the like, the control device 144 starts the execution of step S100 of the examination start. Although illustration is omitted, the control device 144 is in an information input mode for inspection. In this information input mode, necessary information on the subject 12, information on the region to be imaged, information on the imaging schedule and imaging conditions are input. Next, in step S112, the control device 144 changes to a setting mode in which the subject 12 is set on the bed 190, and in the setting mode of the control device 144, the subject 12 is set on the bed 190. Of course, the display necessary for the setting mode or the display request for information input request or confirmation may be performed on the display device 168 by the control device 144.

  When the setting of the subject 12 on the bed 190 is completed, the execution of the control device 144 moves to step S114, and the LAT measurement mode for measuring the body thickness size LAT is set. In step S114, the body thickness size LAT of the subject 12 is measured using the measurement light projector 134 at a representative position of the examination range in the body axis direction of the subject 12. In this mode, measurement of basic data for measuring the body thickness size LAT is performed. The body thickness size LAT is calculated based on the measured basic data. When the calculation of the body thickness size LAT of the subject 12 is completed, the control device 144 then enters a mode for measuring the body width size PA (step S116). In this mode, basic data for measuring the body width size PA of the subject 12 using the measurement light projector 132 is measured at a representative position of the examination range in the body axis direction of the subject 12.

  The body width size PA is calculated based on the measured basic data. As described below, the measured basic data for calculating the body thickness size LAT and the body width size PA of the subject 12 from the measurement light projector 132 and the measurement light projector 134 via the measurement light projector control panel 136 The pre-scan SSDE processor 172 transmits the pre-scan SSDE processor 172 to calculate the body thickness LAT and the body width PA of the subject 12.

  Next, the control device 144 calculates a conversion coefficient described as AP + LAT or Deff described in the column 202 or the column 204 of FIG. 3 and further becomes a mode (step S118) of calculating the exposure dose. In step S118, the body thickness size LAT and body width size PA, which are the calculation results, are calculated by the pre-scan SSDE processing device 172 described below. In this embodiment, data measured by the measurement light projector 132 and the measurement light projector 134 is sent to the pre-scan SSDE processing device 172 via the measurement light projector operation panel 136 and held there each time. However, measurement results may be held in the measurement light projector 132, the measurement light projector 134, or the measurement light projector operation panel 136, and may be sent to the pre-scan SSDE processing device 172 when necessary.

  In step S118, a conversion factor for calculating the SSDE, which is an example of the exposure dose, is determined in accordance with the conversion table stored in the recording device 166 described in FIG. Next, in step S120, the control device 144 enters a scan condition setting mode. In this mode, scan conditions which are imaging conditions of the operation device 142 are input and set. The scan condition may be input at this time or may be input earlier. The controller 144 then enters the calculation mode of the SSDE, which is the dose. In this calculation mode, based on the instruction from the control device 144, the pre-scan SSDE processing device 172 calculates the SSDE which is the exposure amount from the conversion coefficient calculated in step S118 and the above-mentioned scan condition. The calculated exposure dose SSDE is displayed on the display device 168 based on the control command of the controller 144 (step S122).

  In the next step S124, the controller 144 enters a determination mode to determine whether the calculated exposure dose SSDE is in an excessive exposure state. The operator may determine the presence or absence of excessive exposure based on the SSDE displayed on the display device 168, and the determination result may be input in the form of an instruction, or the controller 144 may The presence or absence of overexposure may be determined by comparison with the threshold value. Even when the operator determines the presence or absence of overexposure, a display prompting the controller 144 to suggest the presence or absence of the overexposure to the operator is displayed together with the display on the SSDE, or the presence or absence of the overexposure is determined. A screen for inputting the result may be displayed on the display device 168 or the like. By displaying information for determining the presence or absence of excessive exposure on the image processing apparatus 164 in this manner, safety can be improved, such as preventing an erroneous determination.

  If the determination result in step S124 is excessive exposure, the controller 144 displays on the display device 168 a screen prompting a change of the scan condition or a screen for inputting a new scan condition. New scan conditions are input and set in step S120 based on these displays. Next, step S122 is executed again, and the pre-scan SSDE processing device 172 calculates SSDE which is an exposure amount again based on the new scan condition and the conversion coefficient calculated in step S118. If the calculated SSDE is in the state of overexposure, the determination of the presence or absence of the overexposure based on the scan condition changing operation and the calculated exposure amount is repeated. If it is determined in step S124 that the calculated SSDE is not excessive exposure, step S130 is executed, a scan as an imaging operation is performed, and a cross-sectional image is generated. The basic operation of this imaging operation is as described based on FIG. 1, and the detailed description is omitted.

  When a scan which is an imaging operation is performed and a cross-sectional image is generated, the control device 144 executes step S140 of calculating an exposure amount after the scan. In step S140, the post-scan body width size PSPA and the post-scan body thickness size PSLAT are measured from the reconstructed image (step S142), and the post-scan SSDE processor 176 measures the post-scan body width size PSPA and the post body thickness size PSLAT. The post-scan conversion factor described in FIG. 3 is calculated based on the above, and the post-scan SSDE is calculated from the scan conditions under which the scan is actually performed. Further, the execution of the control device 144 moves to step S144, the post-scan SSDE which is the calculated exposure amount is displayed on the display device 168, and the post-scan SSDE is recorded in the SSDE recording device 178.

  The above procedure shows an example, and various processes may be performed in addition to each procedure, and the execution order of the above procedure is not limited to this, and the execution order is partially You may replace it. For example, step S114 and step S116 do not have any problem whichever comes first. Step S114, step S116, and step S142 will be specifically described below.

Four. Explanation about measurement of size of subject 12
4.1 Description of the First Embodiment Regarding the Configurations and Operations of the Measurement Floodlight 132 and the Measurement Floodlight 134 A test using the measurement floodlight 132 and the measurement floodlight 134 executed in step S114 and step S116 described in FIG. 4 An example of measurement of the size of the person 12 will be described. FIG. 5 is a flowchart for explaining the operation, which is a detailed step of step S114 and step S116 described in FIG. Further, FIG. 6 shows an example of a specific configuration of the light projector 132 for measurement and the light projector 134 for measurement. The flow chart shown in FIG. 5 is executed by a control unit included in the X-ray CT apparatus 100. The control unit may be provided anywhere in the configuration shown in FIG. 1 but is executed by the control unit 144 as described above. Will be described below as

  When the execution of the control device 144 shifts from step S112 to step S114 described in FIG. 4, the execution of the control device 144 shifts to step S200 shown in FIG. 5, and then step S201 is executed. Since slack in the clothes of the subject is disturbed in the later measurement, in step S201, the belt is wound around the measurement points to prevent the slack of the clothes in order to bring the clothes into close contact with the body as preparation. This will be specifically described with reference to FIG. Since slack in the clothes of the subject 12 makes the measurement of the size of the subject 12 more likely to occur, the belt 303 is wound around the measurement point to make the clothes closely contact with the body as preparation in advance. Take preventive measures.

  Although such an operation is performed by the operator and does not seem to be related to the operation of the X-ray CT apparatus 100, in reality this is not the case. For example, when the execution moves to step S201, the command of the control device 144 The display of alerting is performed on the display device 168. The operator takes action to prevent the slack of the clothes by looking at the warning display.

  FIG. 6 shows a state in which a slack prevention belt 303 is wound around the subject 12 placed on the bed 190. The end portion in the X-axis direction for measuring the body width size PA of the subject 12 by using the belt 303 for suppressing slack, and the upper end portion in the Y-axis direction for measuring the body thickness size LAT Has the effect of making it easier to Next, by executing step S 202 of FIG. 5, the laser is emitted from the measurement light projector 134 for measuring the body thickness size LAT, and the light projector 304 until the laser hits the upper end portion of the subject 12 in the Y axis direction. To move. In step S203, the control panel 307 provided on the cover of the scan gantry unit 110 or the bed 190 is operated to acquire the body thickness size LAT of the subject 12 in the Y-axis direction.

Steps S202 and S203 will be described in more detail using FIG. The light projector for measurement 134 provided in the scan gantry unit 110 is provided with a light projector 304, a light projector guide 305 for moving the light projector 304 in the Y-axis direction, and a motor 306. The LAT measurement moving button provided on the operation panel 307 provided on the cover of the scan gantry unit 110 or the bed 190, the irradiation position of the laser 308 irradiated from the light projector 304 is the upper end in the Y-axis direction of the subject 12 While moving to the position Y _UP corresponding to the unit, the LAT measurement button on the operation panel 307 is operated. By operating the LAT measurement button on the operation panel 307, the position Y _UP can be transmitted to the pre-scan SSDE processing device 172 of FIG. 1 and recorded in the memory. As the lower end of the Y-axis direction of the examinee 12 is in contact with the upper surface of the top of the bed 190, before scanning SSDE processor 172, for example, from the reference plane 309 is a floor to the bed upper surface height H _Tb The body thickness size LAT of the subject 12 is determined from the height H _Y0 from the reference surface 309 to the reference position Yo of the light projector 134 for measurement and the recorded Y _{UP according} to the following equation (6).

  In order to make it easy to confirm that the laser 308 from the light projector 134 for measurement is in contact with the upper end of the subject 12 in the Y-axis direction, the belt 303 for slack suppression is a reflective material or a laser so that the color of the laser can be easily recognized. It is desirable that the color and contrast are easily attached.

Moreover, in FIG. 6, although the light projector 134 for measurement is provided in the right side of the subject 12, it is an example to this and you may be equipped in the left side or both of a figure. Returning to the flowchart of FIG. 5, in order to measure the body width size PA of the subject 12, steps S204 to S207 are performed. In step S204, laser from measuring projector 132 moves the light projector 310 to the laser hits the left end of the measurement site of a subject, operating the PA _L measurement button of the operation panel 307 in step S205. Following laser from the projector 310 in step S206 and moves the projector 310 to the laser hits the right end portion of the measurement portion of a subject 12, in step S207, the body operates the PA _R measurement button on the operation panel 307 Measure the width size PA.

A series of operations from step S204 to step S207 will be described using FIG.
The measurement light projector 132 provided in the stationary X-ray CT scanner 112 or the rotation side X-ray CT scanner 120 includes a light emitter 310, a light emitter guide 311 for moving the light emitter 310 in the X-axis direction, and a motor 312. It is done. Laser 313 from the projector 310 in the mobile button for PA measured at the control panel 307, is moved to the position X _L strikes the left end portion of the X-axis direction of the examinee 12, the PA _L measurement button on the operation panel 307 Manipulate. Position X _L by operating the PA _L measurement button on the operation panel 307 is recorded is transmitted to the pre-scan SSDE processing device 172 into the memory. Laser 313 from the projector 310 of the measurement projector 132 operates the PA _R measurement button on the operation panel 307 to move the projector 310 to the position X _R strikes the right end portion of the X-axis direction of the examinee 12. Position X _R by operating the PA _R measurement button on the operation panel 307 is recorded is transmitted to the pre-scan SSDE processing device 172 into the memory.

The pre-scan SSDE processor 172 calculates the body width size PA from the position X _L and the position X _R recorded in the memory according to the following equation (7).

  The measurement light projector 132 may move one light emitter 310 to measure the left and right ends, but using two light emitters enables more efficient work. In the measurement of the body thickness size LAT and the body width size PA, it may be confirmed visually that the laser is applied to the end of the measurement site, or the belt 303 for suppressing slack by an optical camera etc. near the light projector. The position of the end may be automatically measured and transmitted by regarding the position at which the reflected laser light reflected by or projected onto it can not be optically recognized, that is, the position beyond the end, as the end. Although in FIG. 6 there is a gap between the slack suppressing belt 303 and the body surface of the subject 12 for the sake of explanation, in practice the close contact as much as possible improves the accuracy.

  As described above, the conversion coefficient is calculated by referring to the data table of the conversion coefficient shown in FIG. 3 from the sum of the calculated body thickness size LAT and the body width size PA, and from the calculated conversion coefficient and scan conditions Calculate the SSDE. This point is as described in FIG.

4.2 Description of the Second Embodiment of Measurement of Body Width Size PA and Body Thickness Size LAT In this embodiment, the configurations of the light projector 132 for measurement and the light projector 134 for measurement are different from those of the first embodiment described above. Therefore, the specific part of the measurement method is different. When step S114 described in FIG. 4 is executed, execution of step S300 in FIG. 7 is started, and measurement of the body thickness size LAT and the body width size PA is started. Similar to step S201 of FIG. 5, in step S301 of FIG. 7, in order to bring the clothes of the subject 12 into close contact with the body as a preparation, the slack suppressing belt 303 is wound around the measurement point to prevent slack of the clothes. Next, in step S302, the bed 190 is moved in the Y-axis direction until the laser hits the top surface of the measurement region of the subject 12 from the light projector 304 fixed to the measurement light emitter 134. The body thickness size LAT is acquired by operating the LAT measurement button provided on the operation panel 307 in a state where the laser hits the upper surface of the measurement site of the subject 12 from the fixed light projector 304, as shown in step S303. .

The operations of step S302 and step S303 will be described using FIG. The bed on which the subject is placed is provided with a motor 315 for moving the bed along the Y-axis direction. The bed 190 is moved in the Y-axis direction to a position where the laser 308 from the light-emitter 304 fixed to the measurement light-emitter 134 hits the upper surface end of the subject 12 in the Y-axis direction. By operating the operating means such as a button provided on the operation panel 307 records, for example, from the reference plane 309 such as a floor surface height H _Tb to the bed upper surface is transmitted to the pre-scan SSDE processor 172 memory Be done. As Y-axis direction lower end of the subject 12 is in contact with the bed upper surface, before scanning SSDE processing apparatus 172 and the height H _Y0 from the reference plane 309 to the projector 304 of the measuring light projector 134, from the recorded H _Tb The body thickness size LAT is calculated by the following equation (8).

  As in the first embodiment, in order to make it easy to confirm that the laser 308 from the light emitter 304 is in contact with the upper end of the subject 12, the belt 303 for slack suppression is a reflective material so that the color of the laser can be easily recognized. It is desirable that the color and contrast of the laser and the color of the laser are easy. Further, the light projector 134 for measurement may be provided on either side of the subject 12 or may be provided on both sides.

Returning to the flowchart of FIG. 7, in step S304, the bed 190 is moved along the X-axis until the laser from the light emitter 318 fixed to the measurement light emitter 132 hits the left end of the measurement region of the subject 12. Laser 319 from the projector 318 in a state which corresponds to the left end portion of the measurement portion of the subject 12, operating the PA _L measurement button on the operation panel 307 (step S305). By this operation, the position of the left end of the measurement site of the subject 12 is measured. Subsequently, in step S306, the bed is moved until the laser 321 from the light projector 320 hits the right end of the measurement site of the subject 12, and the operation is performed with the laser 321 hitting the right end of the measurement site of the subject 12 to manipulate the PA _R measurement button of the board 307 (step S307). By this operation, the position of the right end of the measurement site of the subject 12 is measured.

  The body width size PA is obtained based on the measured position of the left end and the position of the right end of the measurement site of the subject 12.

An example of the operation from step S304 to step S307 in FIG. 7 will be described using FIG. 9 and FIG. In order to measure the positions of the left end and the right end of the measurement site of the subject 12 in the present embodiment, it is necessary to move the bed 190 along the X axis, and in order to move the bed 190 in the X direction Motor 316 is provided. In addition, a projector 318 fixed at a distance of D / 2 in the left direction from the center 317 of the bed 190 in the X direction is provided, and the bed 190 is placed so that the laser 319 from the projector 318 hits the left end of the subject 12 X-axis direction to move TbX _L manipulating PA _L measurement button on the operation panel 307. By operating the PA _L measurement button provided on the operation panel 307 transmits the moving direction and distance TbX _L in the X-axis direction of the bed 190 to the scan pre SSDE processing apparatus 172 is recorded in the memory.

The operations of step S306 and step S307 described in FIG. 7 will be described using FIG.
A projector 320 is provided, which is fixed at a distance of D / 2 in the right direction from the center 317 in the X-axis direction. Laser 321 from the projector 320 operates the PA _R measurement button that in the state in which the bed 190 is moved in the X-axis direction by TbX _R provided operation panel 307 to strike the right end portion of the subject 12. By operating the PA _R measurement button provided on the operation panel 307, the moving direction and distance TbX _R in the X direction of the bed 190 is recorded in the memory is transmitted to the pre-scan SSDE processor 172. Here, the direction of movement of the bed 190 can be represented, for example, by making the right direction positive with respect to the center 317 in the X-axis direction and making the left direction negative. Of course, other methods may be used. The pre-scan SSDE processing device 172 can obtain the body width size PA from the recorded TbX _L and TbX _{R according} to the following equation (9).

  As in the first embodiment, both of the body thickness size LAT and the body width size PA may visually confirm that the laser has hit the end of the measurement site of the subject 12, or it may be optically It may be detected.

  For example, the position where the laser light reflected or projected onto the belt 303 for suppressing slack by an optical camera or the like in the vicinity of the light projector can not be optically recognized, that is, the position immediately after passing the end It may be regarded as a part, and measurement of the end part concerning the light projector 132 for measurement or the light projector 134 for measurement may be automatically performed, and the position of the measured end part may be transmitted.

  By accurately measuring the body thickness size LAT and the body width size PA as described above, the conversion coefficient shown in FIG. 3 is calculated with high accuracy from the sum of the body thickness size LAT and the body width size PA obtained. It becomes possible. The pre-scan SSDE, which is the exposure dose before the scan, can be calculated with high accuracy from the calculated conversion coefficient and scan condition. Furthermore, the above-described method is excellent in workability and has an effect of reducing the burden on the operator.

4.3 Description of Third Embodiment of Measurement of Body Width Size PA and Body Thickness Size LAT This embodiment is the body thickness size when a bed accessory is used in the above-mentioned first embodiment and second embodiment. The measurement of LAT will be described. In the first embodiment and the second embodiment, measurement of the body thickness size LAT in a state where the subject 12 is directly placed on the bed 190 will be described. However, for example, the patient may be placed on the relatively soft bed mat 322 because the bed 190 is hard. Furthermore, in the case where the subject 12 is a child, it may be put on a bed accessory exclusively for children. In such a case, the height of the bed can not be treated as the lower end of the subject 12. Therefore, in the present embodiment, the presence or absence of a bed accessory is considered in the measurement of the body thickness size LAT of the subject 12 and will be specifically described below.

  The present embodiment relates to Step S202 and Step S203 described in FIG. 5 or Step S302 and Step S303 described in FIG. 7, and the body thickness size is accurate even in a state where a bed accessory is used in these processes. It enables measurement of LAT. FIG. 11 describes a flowchart of the present embodiment that enables accurate measurement even in the state of using a bed accessory. The flowchart shown in FIG. 11 corresponds to an error in the Y-axis direction by the bed accessory, and will be described in a form limited to the measurement of the body thickness size LAT.

  When the measurement process of the body thickness size LAT is started in step S400, the control device 144 determines in step S401 whether or not the bed accessory is used. For example, the controller 144 displays on the display 168 a question regarding the use of the bed accessory. When the operator inputs the use condition of the bed accessory from the operation device 142 in response to the inquiry of the control device 144, the control device 144 determines the use / nonuse of the bed accessory according to the input contents. Of course, the presence or absence of use of the sleeper accessory may be determined by another method.

  If the bed accessory is not used, execution proceeds to step S402 after step S401, and measurement of the body thickness size LAT is performed by the method already described in the first embodiment or the second embodiment, and the processing of the calculation described above Thus, the body thickness size LAT is calculated and held in the memory of the pre-scan SSDE processor 172. Detailed explanation about this is omitted.

  On the other hand, when using a bed accessory, the operator reads the information on the bed accessory to be used from the recording device 166 shown in FIG. 1 in step S403, or the operator based on the request display of the information displayed on the display device 168. Information is input from the operation device 142, and information on these bed accessories is sent to the pre-scan SSDE processing device 172 and held in the memory of the pre-scan SSDE processing device 172.

Next, step S404 is carried out to measure the position Y _UP of the upper end portion of the subject 12 in the Y-axis direction. The method of the first embodiment or the second embodiment described above can be used to measure the position Y _UP of the upper end portion in step S404. As described above in these embodiments, the light emitter 304 of the measurement light emitter 134 is moved by the motor 306 in step S404. The LAT measurement button provided on the operation panel 307 is operated in a state where the laser 308 emitted by the light projector 304 hits the upper end portion of the subject 12 in the Y-axis direction. By this operation, the position Y _UP of the upper end portion of the subject 12 in the Y-axis direction can be measured. Of course, the position Y _{UP of the} upper end may be measured, or the position Y _{UP of the} upper end may be measured as a distance from a predetermined reference position.

Next, in step S405, the thickness of the bed accessory is corrected with respect to the measurement value of the position Y _UP of the upper end portion to calculate a correct body thickness size LAT.

  The measurement method of the body thickness size LAT in consideration of the bed accessories such as the bed mat 322 and the children's accessory 324 will be described with reference to FIG. 12 and FIG. The example described in FIG. 12 is the case where the subject 12 is an adult. Measurement of body thickness size LAT when using a relatively soft bed mattress 322 placed between the subject 12 and the bed 190 when photographing an adult trunk using FIG. 12 Will be explained. The basic idea is as described in the first embodiment, and the basic measurement method in the Y-axis direction is the same as in the first embodiment.

The laser 308 emitted from the light projector 304 provided in the measurement light projector 134 is provided on the control panel 307 in a state where the light projector 304 is moved to a position Y _UP which hits the upper end portion of the subject 12 in the Y axis direction. Operate the LAT measurement button. The difference from the first embodiment is that the thickness TH _Ac of the bed mat 322 in the Y-axis direction is read out from the information of the bed mat 322 transmitted to the SSDE processing device 172 before scanning and corrected. Specifically, the body thickness size LAT is calculated by the following equation (10).

FIG. 13 is an explanatory view for explaining the case where the children's accessory 324 is used. The basic configuration and the basic processing method are similar to the configuration and the processing method described with reference to FIG. If the subject 12 is a child, a dedicated pediatric accessory 324 is used to keep her small and stationary during the scan. As in the case of using the bed mat 322 of FIG. 12, information on the thickness TH _{Ac in} the Y-axis direction of the pediatric accessory 324 is transmitted to the pre-scan SSDE processing device 172 and held in the memory. The thickness TH _Ac of the children's accessory 324 may be read out in advance from the information held in the recording device 166 and transmitted to the pre-scan SSDE processing device 172 or may be newly input from the operation device 142 etc. .

The position Y _UP of the upper end portion of the subject 12 in the Y-axis direction is measured by the method described above. Using the measured position Y _UP of the upper end portion of the subject 12 and the thickness TH _Ac of the accessory for children 324, the pre-scan SSDE processing device 172 calculates the body thickness size LAT by the above equation (10). Although the contents described above with reference to FIGS. 12 and 13 are based on the first embodiment, this is merely an example, and processing may be performed based on the configuration and processing method of the second embodiment. In this case, it is possible to obtain the body thickness size LAT by the following equation (11).

In addition, even if the thickness TH _{Ac of} the bed accessory in the Y-axis direction changes in the Z-axis direction, if the positional relationship between the bed 190 and the bed accessory can be defined in the Z-axis direction, SSDE processing before scanning The table of positions z and TH _Ac (Z) of the bed accessory in the Z-axis direction is recorded in advance in the recording device 166 in the device 172, and information is received from the recording device 166 to measure the size in the Y-axis direction. TH _Ac (Z) can be determined from the position in the Z-axis direction of the bed, and the body thickness size LAT can be determined using Equation (10) or Equation (11).

As described above, the measurement and calculation of the body thickness size LAT in the case of using the bed accessory based on the equation (10) or the equation (11) is an example, and the basic technical concept behind these is is important. For example, a measurement value representing the position Y _UP of the upper end in the Y-axis direction of the subject 12 is acquired, and based on the use of the bed accessory, in the case of using the bed accessory, the measurement representing the position Y _UP It is important to correct the values based on the information of the bed accessory thickness. The measurement value representing the position Y _UP is, for example, a measurement result in which a relationship of a predetermined function exists between the position Y _UP and the measurement value.

Five. Explanation of measurement of body width size PSPA after scan and body thickness size PSLAT after scan from reconstructed image after scan
5.1 Description of the Fourth Embodiment Regarding Measurement of Body Width Size PSPA After Scan and Body Thickness Size PSLAT After Scan The configuration shown in FIG. 14 is the configuration and operation of the after-scan SSDE processing device 176 shown in FIG. It is a flowchart for demonstrating. Further, in the present embodiment, the measurement of the body width size PA and the body thickness size LAT from the reconstructed image after scanning, which is the specific processing contents of the step S142 and the step S144 configuring the step S140 described in FIG. It is an example of the structure for displaying the radiation dose based on the measurement result and the measurement result, and keeping it and its processing method. These are described below. Although the flowchart of FIG. 14 is shown as an example of the detailed flowchart of step S142 and step S144 described in FIG. 4, the flowchart of FIG. 14 is merely an example, and the present invention is not limited to this.

  The execution of the scan in step S130 described in FIG. 4 generates a cross-sectional image. After the cross-sectional image is generated, step S500 shown in FIG. 14 is executed, and the execution of the flowchart for calculating the post-scan SSDE is started. In the next step S501, the image is based on the slice thickness input by the operator under the condition of the largest reconstruction FOV in terms of specification, in order to use for measurement of body width size PSPA and body thickness size PSLAT after scanning. The processor 164 reconstructs a cross-sectional image. The reconstructed image is sent to the measuring device 174 after scanning.

  In addition, since this reconstructed image is not used for diagnosis, in principle, it is not necessary to display it on the display device 168. The reason for reconstruction with the maximum FOV is to fit the entire cross section of the subject 12 in an image of the number of pixels of M × M [pix]. Since the post-scan SSDE is calculated in each image, the slice thickness is the display pitch of the SSDE in the body axis direction (Z direction) to be displayed later. If it is desired to check finely, a thin slice thickness may be used, and if coarseness is sufficient, a thick slice thickness may be used. Since the human body does not change rapidly in the axial direction, for example, if it has a slice thickness of about 5 mm to 10 mm, it may be used to measure the body width size PA or body thickness size LAT after scanning. Sufficient accuracy can be secured.

  In step S502, in order to extract the cross-sectional portion of the examinee of the reconstructed image, binarization is performed to set all pixel values of the predetermined threshold Th or more to "1" and all pixel values smaller than the predetermined threshold Th to "0". Perform the process. The sleeper accessories such as the sleeper 190 and the sleeper mat 322 can be easily removed since the material having a small attenuation of the X-ray dose which does not originally affect the X-ray imaging is used. The removal of the bed 190 and the bed accessories is not limited to this, and may be removed by another method. In addition, there are substances close to air in areas such as lungs and intestines in the human body, but after binarization, all "0" pixel values in the part surrounded by "1" pixels are replaced with "1". Perform the process. In this manner, the cross section of the subject can be set to “1” and the others can be set to “0”, and an image with a clear contour can be generated.

Next, in step S503, profiles of pixel values in the X-axis direction and the Y-axis direction are acquired in an image of the number of pixels of M × M [pix] after binarization. Acquisition of the profile in step S503 will be described using FIG. Reference numeral 351 is a cross-sectional image of M × M [pix] of the subject 12 after binarization, and a dot-displayed part is a cross-sectional image part 352 of the subject 12. Respectively to obtain the profile of the Y-axis direction in each column of X _M-1 column from X ₀ row on the image. Originally the M profile is acquired at predetermined intervals, in order to avoid the 15 complexity, and X _A -X _A column profile 353 or, X _B -X _B column profile 354, X The three Y axis direction profiles of the profile 355 in the _{C 1} -X _C column are shown.

Subsequently, to obtain the profile of the X-axis direction in the Y _M-1 rows each of the Y ₀ rows. Like the Y-axis direction profile, in order to avoid the 15 complexity, and Y _A -Y _A row of profile 356, and Y _B -Y _B line of profile 357, the Y _C -Y _C line of profile 358 Three X-axis direction profiles are shown as an example. In step S504 described in FIG. 14, the body thickness size PSLAT after scanning is acquired by selecting the largest size profile from the profiles in the Y-axis direction.

Method of acquiring body thickness size PSLAT after scanning is described with reference to X _A -X _A column profile 353 or, X _B -X _B column profiles 354, X _C -X _C column profile 355 of FIG. 15 . For example, the number of pixels of “1” is counted from each rectangular profile. X _A -X _A number of pixels "1" of the profile 353 of the column pixel count of _{NV1_X A [pix] 359, "} 1" of X _B -X _B column profiles 354 _{NV1_X B [pix] 360, X} C The number of “1” pixels of the profile 355 in the column X _C is NV 1 _X _C [pix] 361. Each of them is compared, a profile in which the number of pixels of “1” is the largest is searched, and the number of pixels of “1” in the largest profile is converted into a distance to obtain a post-scan body thickness size PSLAT.

In FIG. 15, since NV1_X _B [pix] 360 of profile 354 in column X _B- X _B corresponds to the maximum, NV1_X _B [pix] 360 is Max_LAT [pix], and the following (12) from Max_LAT [pix] The body thickness size PSLAT after scanning can be determined by the equation.

Here, DFOV means the reconstruction FOV [mm] of the reconstruction image 351, and M means the number of pixels on one side of the reconstruction image 351 as described above.

In the flowchart shown in FIG. 14, in step S505, a post-scan body width size PSPA is acquired from the profile in the X-axis direction shown in FIG. Method of acquiring the scan after the body width size PSPA, will be described with reference to Y _A -Y _A row of profile 356, Y _B -Y _B line of profile 357, X _C -X _C line of the profile 358 of Figure 15. The number of pixels of "1" is counted from the profile on each rectangle. The number of pixels of “1” of the profile 356 in the Y _A -Y _A row is NV1_YA _A [pix] 362 and the number of pixels of “1” of the profile 357 in the Y _B -Y _B row is NV1_Y _B [pix] 363, Y _C -Y number of pixels _C "1" row of profile 358 becomes NV1_Y _C [pix] 364. Each of them is compared, a profile in which the number of pixels of “1” is the largest is searched, and the number of pixels of “1” in the largest profile is converted into a distance to obtain a body width size PSPA after scan.

In Figure 15, Y _B -Y for NV1_Y _B [pix] 363 of _B line of profile 357 corresponds to the maximum, the NV1_Y _B [pix] 363 and Max_PA [pix], Max_PA following formula from [pix] (13 Body width size PSPA can be calculated after scanning.

  In step S506 of the flowchart shown in FIG. 14, the post-scan body thickness size PSLAT and the post-scan body width size PSPA calculated by the equations (12) and (13) after the post-scan SSDE processing device shown in FIG. Send to 176 to calculate the post-scan SSDE. In step S507, it is determined whether the processing described in step S502 to step S506 has been performed on all the images transmitted to the measuring device 174 after scanning. If there is an image for which the process described in step S502 to step S506 is not performed, the execution transitions from step S507 to step S502, and the process of step S502 to step S506 is performed again.

  When the processing from step S502 to step S506 is completed for all the images transmitted to the measuring device 174 after scanning, the execution proceeds from step S507 to step S508, and the post-scan SSDE is displayed in step S508. , Also recorded. By the above process, it becomes possible to obtain the post-scan SSDE at each position of the scanned subject 12 in the Z-axis direction.

  As a display method, for example, it may be added to the information column of each axial image to display the SSDE after scanning. Alternatively, it may be as shown in FIG. A graph 402 indicating the change in the post-scan SSDE, which is the exposure dose, is displayed along the Z direction so as to align with the MPR image (sagittal image) 401 in the Z direction created from the scanned image. Furthermore, it is possible to display a table 403 representing the maximum value, the minimum value, the average value, and the like in the scanned range. By recording such information, it is possible to use it for the exposure control of the subject 12 (step S509).

  According to the fourth embodiment, since the MPR image 401, the graph 402 indicating the change in SSDE after scanning, and the table 403 such as the maximum value, the minimum value, and the average value can be freely displayed by the instruction of the operator, It becomes possible to confirm the actual radiation dose with simple operation. In addition, since it is possible to display a graph 402 indicating changes in SSDE after scanning for all captured MPR images 401 and a table 403 that displays maximum value, minimum value, average value, etc. The exposure dose of the subject 12 who has been exposed to Since these pieces of information shown in FIG. 16 are recorded and stored in the SSDE recording device 178 or the like, when the subject 12 receives a plurality of examinations by the X-ray CT apparatus within a predetermined period such as half a year, the past Can be easily confirmed, and it has excellent effects in terms of safety.

5.2 Description of Fifth Example Regarding Measurement of Body Width Size PSPA After Scan and Body Thickness Size PSLAT After Scan A fifth example regarding acquisition of the post-scan SSDE described in FIG. 4 will be described next. Similar to the fourth embodiment, measurement of a post-scan body width size PSPA and a post-scan body thickness size PSLAT from the reconstructed image after scan related to the processing of step S142 and step S144 described in FIG. 4 and a post-scan SSDE based thereon Calculation and display of However, the specific processing method is different from the fifth embodiment and the fourth embodiment. The fifth embodiment will be described in accordance with the flowchart shown in FIG.

  Steps S500 to S502 have already been described using FIG. 14 in the description of the fourth embodiment, and the description will be omitted. In step S603, the barycentric pixel position (XG, YG) of the binarized image is calculated. As a calculation method, it is possible to use a known method which is already known, and the description is omitted. In step S604, a profile of pixel values on a straight line passing through the gravity center pixel position is acquired, and a profile at each angle is acquired for each predetermined angle while rotating in the rotational direction with the gravity center pixel position as the rotation center. In step S605, a post-scan body thickness size PSLAT and a post-scan body width size PSPA are acquired from the acquired profile.

  The processes of steps S603 to S605 will be described with reference to FIG. The reference numeral 501 in FIG. 18 is a cross-sectional image of M × M [pix] of the subject 12 after binarization, and the part 502 described by dots is a cross-sectional image part of the subject 12. In the fifth embodiment, it is possible to accurately measure the post-scan body thickness size PSLAT and the post-scan body width size PSPA without any problem even if the subject 12 is inclined. The example shown in FIG. 18 shows the subject 12 being placed on the bed 190 with a slight inclination. Such a case can not actually lie on the bed due to the condition of the subject 12 and may occur when scanning with a towel or the like sandwiched between the backs and in an inclined state.

A radial RR profile passing through the barycentric pixel position 503 is acquired with respect to the cross-sectional image 501 after binarization at predetermined angles. When the rotation angle is a predetermined angle θ, it is possible to obtain an R _θ −R _θ profile 504 at a predetermined angle θ. For the R _θ -R _θ profile 504 at a predetermined angle θ, as in the fourth embodiment, the number of pixels of “1” is counted from the rectangular profiles of “0” and “1”, and NV1_R (angle θ ) [Pix] 505 can be obtained.

By rotating the angle θ from, for example, 0 ° to 180 °, the R ₀ -R ₀ profile 506 with θ of ₀ ° to the R ₁₈₀ -R ₁₈₀ profile 507 with 180 ° is acquired for each predetermined angle. Obtain NV1_R (0 degrees) to NV1_R (180 degrees) from the profile at each angle. A graph 508 shows the state of change from NV1_R (0 degree) to NV1_R (180 degree) in which θ is rotated from 0 degree to 180 degrees. The profile of the minimum value is searched from the NV1_R (θ) [pix] of the graph 508, and the number of pixels of “1” is converted into a distance to obtain a post-scan body thickness size PSLAT of the subject.

Further, the profile having the maximum value is searched from each profile of NV1_R (θ) [pix] of the graph 508, and the number of pixels of “1” is converted into the distance to obtain the body width size PSPLAT after scan of the subject. . In this embodiment, the pixel number NV1_R (θmin) 509 of “1” of the angle θmin at which NV1_R (θ) [pix] is minimum is MIN_R [pix], and the body thickness size PSLAT after scan according to the following equation (14). Can be calculated.

Here, DFOV and M are as described in the fourth embodiment. On the other hand, with the pixel number NV1_R (θmax) 510 of “1” of the angle θmax at which NV1_R (θ) [pix] becomes maximum, MAX_R [pix], the post-scan body width size PSPA is calculated by the following equation (15) Can.

  As described above, it is possible to calculate the body thickness size after scan PSLAT and the body width size after scan PSPA with high accuracy even when the subject 12 is not in contact with the bed. In step S606 of the flowchart shown in FIG. 17, the post-scan body thickness size PSLAT and the post-scan body width size PSPA calculated are transmitted to the post-scan SSDE processor 176 to calculate the post-scan SSDE. In the flowchart of FIG. 17, step S507, step S508, and step S509 have already been described with reference to the flowchart of FIG.

  According to the embodiment described above, it becomes possible for the operator to grasp SSDE which is an index of exposure dose accurately correlated with the size of the subject 12 before and after scanning. As a result, it is possible to set the scan conditions more accurately before the scan. This leads to overexposure prevention. Also, after the scan, it will be possible to contribute to the detailed control of exposure.

  According to the embodiment described above, the X-ray CT apparatus 100 can detect the exposure dose more accurately.

  In the above embodiment, a laser is used as an example for measurement. The laser has good convergence and can concentrate light energy in a narrow area, which is advantageous for improving measurement accuracy. However, the application of the present invention is not limited to the laser, and even for general light other than the laser, measurement accuracy can be obtained by using a lens or a slit to form irradiation light with a small diameter or a narrow width. Can be improved.

  In the configuration of the above-described embodiment, it has been described that the operation panel 307 has buttons for various operations in order to avoid the complexity of the description. This does not mean that the application of the present invention is limited to the button type switch, but it means that it may be, for example, a button type switch. The control panel 307 may have a function of receiving an instruction of the operator, and may be, for example, a touch panel, or may be various other types of input means.

  12 subject, 90 coordinate system, 100 X-ray CT apparatus, 110 scan gantry, 112 stationary side X-ray CT scanner, 120 rotational side X-ray CT scanner, 122 X-ray tube, 124 collimator unit, 126 X-ray detector , 128 data acquisition device, 132 measurement light projector, 134 measurement light projector, 136 measurement light projector operation panel, 140 operation unit, 142 operation device, 144 control device, 146 communication I / F, 160 processing unit, 162 communication I / F 164 image processing apparatus 166 recording apparatus 168 display apparatus 172 pre-scan SSDE processing apparatus 174 post-scan measuring apparatus 176 post-scan SSDE processing apparatus 178 SSDE recording apparatus 210 conversion factor column 303 belt 304 projector 305 projector guide, 306 motor, 307 control panel, 308 laser, 309 reference plane, 310 projector, 311 projector guide, 313 laser, 316 motor, 318 projector, 320 projector, 322 bed mat, 324 children's accessories, 401 MPR picture , 402 graphs, 403 tables, 501 cross-sectional images, 503 the centroid pixel position

Claims (5)

A scan gantry unit having a stationary X-ray CT scanner and a rotational X-ray CT scanner, a control device, a display device, and a bed,
The rotation-side X-ray CT scanner includes an X-ray tube for irradiating X-rays, and an X-ray detector for detecting X-rays transmitted through a subject.
A light projector for measuring the size of the subject is provided.
The size of the subject is calculated based on the measured value measured by the light projector for measurement, and an index related to the dose of the subject is calculated based on the calculated size of the subject,
A first measurement light projector and a second measurement light projector are provided as the measurement light projectors,
The first measurement light projector emits a first light for measuring the body width size of the subject,
The second light projector for measurement emits a second light for measuring the body thickness size of the subject,
The first measurement light projector and the second measurement light projector are disposed such that the first light and the second light are in a relation orthogonal to each other,
The control device determines whether a bed accessory is provided, and when it is determined that the bed accessory is provided, the control device uses the thickness information of the bed accessory to determine the subject's X-ray CT apparatus characterized by calculating body thickness size. A scan gantry unit having a stationary X-ray CT scanner and a rotational X-ray CT scanner, a control device, a display device, and a bed,
The rotation-side X-ray CT scanner includes an X-ray tube for irradiating X-rays, and an X-ray detector for detecting X-rays transmitted through a subject.
A light projector for measuring the size of the subject is provided.
The size of the subject is calculated based on the measured value measured by the light projector for measurement, and an index related to the dose of the subject is calculated based on the calculated size of the subject,
A first measurement light projector and a second measurement light projector are provided as the measurement light projectors,
The first measurement light projector emits a first light for measuring the body width size of the subject,
The second light projector for measurement emits a second light for measuring the body thickness size of the subject,
The first measurement light projector and the second measurement light projector are disposed such that the first light and the second light are in a relation orthogonal to each other,
The bed comprises means for moving the subject in a direction of a body width size of the subject,
The movement distance of the bed until one end of the subject is the irradiation position of the first light, and the other end of the subject is the irradiation of the other first light The X-ray CT apparatus, wherein the body width size of the subject is calculated based on the movement distance of the bed up to the position. In the X-ray CT apparatus according to claim 2 ,
The bed comprises means for moving the subject upwards;
On the basis of the moving distance to the upper end of the subject reaches the second light, the body thickness size of the subject is calculated, X-rays CT apparatus characterized by. A scan gantry unit having a stationary X-ray CT scanner and a rotational X-ray CT scanner, a control device, a display device, and a bed,
The rotation-side X-ray CT scanner includes an X-ray tube for irradiating X-rays, and an X-ray detector for detecting X-rays transmitted through a subject.
A light projector for measuring the size of the subject is provided.
The size of the subject is calculated based on the measured value measured by the light projector for measurement, and an index related to the dose of the subject is calculated based on the calculated size of the subject,
A post-scan processing device for calculating a body width size of the subject after scanning and a body thickness size of the subject after scanning based on the cross-sectional image reconstructed by X-ray imaging;
Based on the calculated body width size of the subject after the scan and the body thickness size of the subject, an index relating to the exposure dose after the scan is calculated,
A plurality of profiles of pixel values in a predetermined direction on the reconstructed cross-sectional image are created at predetermined intervals, and a body width size of the subject and a body thickness size of the subject are determined from the plurality of profiles. The profile for calculation is selected, and the body width size of the subject and the body thickness size of the subject after the scan are calculated from the selected profile,
An indicator related to the exposure dose of the subject after scanning calculated based on the body width size of the subject and the body thickness size of the subject is displayed on the display device. X-ray CT system. A scan gantry unit having a stationary X-ray CT scanner and a rotational X-ray CT scanner, a control device, a display device, and a bed,
The rotation-side X-ray CT scanner includes an X-ray tube for irradiating X-rays, and an X-ray detector for detecting X-rays transmitted through a subject.
A light projector for measuring the size of the subject is provided.
The size of the subject is calculated based on the measured value measured by the light projector for measurement, and an index related to the dose of the subject is calculated based on the calculated size of the subject,
A post-scan processing device for calculating a body width size of the subject after scanning and a body thickness size of the subject after scanning based on the cross-sectional image reconstructed by X-ray imaging;
Based on the calculated body width size of the subject after the scan and the body thickness size of the subject, an index relating to the exposure dose after the scan is calculated,
A centroid pixel position is calculated from the reconstructed cross-sectional image,
A plurality of profiles of pixel values on a straight line rotating about the center-of-gravity pixel position are acquired for each predetermined rotation angle,
An X-ray CT in which a body width size of the subject and a body thickness size of the subject after the scan are calculated based on a profile selected from the plurality of acquired profiles. apparatus.

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