JP4679951B2 - X-ray CT system - Google Patents

Description

  The present invention relates to an X-ray CT apparatus, and in particular, irradiates a subject with X-rays of a fan beam (fan-shaped beam) or cone beam (conical or pyramid-shaped beam) and detects X-rays transmitted through the subject. The present invention relates to a single-slice or multi-slice X-ray CT apparatus that obtains a tomographic image of a subject by measuring with a measuring instrument and backprojecting measurement data from multiple directions.

  In the multi-slice X-ray CT apparatus, as shown in FIG. 3, the subject 17 is irradiated with a cone beam, that is, a pyramid-shaped X-ray beam, from the X-ray tube 8, and the detection element 18 is arranged in a two-dimensional direction (channel direction and column). The X-rays transmitted through the subject 17 are measured by the detectors 11 arranged in the direction) to obtain projection data of the subject 17.

  In the single-slice X-ray CT apparatus, a detector 11 in which detector elements are arranged in one row, that is, in a one-dimensional direction (channel direction) is used, and a fan beam, that is, a fan-shaped X-ray beam is transmitted from the X-ray tube 8 to the subject 17. Irradiation and X-rays after passing through the subject 17 are measured to obtain projection data of the subject 17.

  In either case, the opposite X-ray tube 8 and detector 11 are rotated around the subject 17 to acquire projection data from multiple directions, and after performing reconstruction filter processing for blur correction, back projection is performed. Thus, a tomographic image of the subject 17 is reconstructed.

The projection data is acquired at discrete X-ray tube positions (hereinafter referred to as “views”), and the obtained projection data is referred to as “projection data in the corresponding view”. The number of views per revolution typically ranges from hundreds to thousands. The operation of acquiring projection data of the number of views necessary for reconstructing one CT image is called “scan”. The projection data for one view is composed of data corresponding to the number of channels of the detector 11 times the number of columns. (A single slice X-ray CT apparatus can be considered as the case where the number of columns = 1 as described above.)
Among such X-ray CT apparatuses, in Patent Document 1, an output value of an X-ray detector is compared with a predetermined determination threshold value, and a scanner is detected when the output value is outside the range defined by the determination threshold value. An X-ray CT apparatus that includes a determination circuit that outputs a scan end signal to the gantry control unit, and can prevent excessive X-ray exposure outside the examination target range even if the position of the subject is shifted during the scan execution. Proposed.
JP-A-9-75335

  However, in the above-mentioned Patent Document 1, since the output value of the X-ray detector does not take into consideration that the output value varies depending on the physical characteristics (for example, height and weight) of the subject, There is a problem that an appropriate operation cannot be performed on the subject.

  The present invention has been made in view of the above problems, and even with respect to an arbitrary subject, even if the subject is misaligned during the scan execution, the scan end position is appropriately determined during the scan, and the examination is performed. An object of the present invention is to provide an X-ray CT apparatus capable of preventing excessive X-ray exposure outside the target range.

In order to achieve the above object, the present invention provides an X-ray source for irradiating X-rays and an X-ray projection data arranged by facing the X-ray source across the subject and detecting X-rays. An X-ray detector for output, a rotating means capable of rotating by mounting the X-ray source and the X-ray detector, an image processing means for generating a tomographic image of the subject based on the X-ray projection data, A standard X-ray projection showing X-ray projection data obtained when a standard human body model is measured and photographed under an arbitrary measurement and photographing condition. Storage means for storing data, feature quantity input receiving means for receiving physical feature quantity input of the subject, and standard X-ray projection data stored in the storage means acquired by the feature quantity input receiving means To correct based on the physical features of the subject Ri, wherein an X-ray projection data is assumed to be obtained when the subject was measured captured at the arbitrary imaging condition, generating means for generating the subject assumes projection data containing information on the end position of the measuring shooting Whether or not the measurement imaging end position has been reached based on a comparison result between actual X-ray projection data obtained by measuring and imaging the subject under the arbitrary imaging conditions and the subject assumed projection data Determination means for determining whether or not.

  In addition, the determination unit may determine the end position of the measurement and imaging when an error between the assumed projection data of the object and actual X-ray projection data obtained by measuring and imaging the object is equal to or less than a predetermined threshold. It may be determined that has been reached.

  Further, the determination unit performs the measurement and imaging when it is determined that an error between the assumed projection data of the object and actual X-ray projection data obtained by measuring and imaging the object is a minimum value. It may be determined that the end position has been reached.

  Further, the image forming apparatus further includes setting means for setting a planned rotation speed for measurement imaging, and the determination means compares the actual X-ray projection data obtained by measuring and imaging the subject and the subject assumed projection data. As a result of determining whether or not the end position of the measurement imaging has been reached based on the above, even if it is determined that the end position has not yet been reached, the measurement imaging of the planned number of revolutions set by the setting means When the measurement is completed, the measurement imaging may be terminated.

  According to the present invention, in order to determine the imaging end position by comparing the object expected projection data generated corresponding to an arbitrary object and the actual X-ray projection data, the position of the object during the scan execution Even if the deviation occurs, an X-ray CT apparatus capable of preventing excessive X-ray exposure outside the inspection target range can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to embodiment shown below. A hardware configuration of an X-ray CT apparatus to which the present invention is applied will be described below with reference to FIGS. FIG. 1 is an overall overview diagram of an X-ray CT apparatus to which the present invention is applied, FIG. 2 is an overall configuration diagram of the X-ray CT apparatus of FIG. 1, and FIG. 3 is a configuration and X-ray irradiation of a detector of the X-ray CT apparatus. FIG. 4 is a diagram showing the relationship between the scanner of the X-ray CT apparatus, the patient table, and the subject from the side surface direction.

<Hardware configuration>
As shown in FIG. 1, the X-ray CT apparatus includes a scanner 1, a patient table 2, an operation console 3, a top 4 of the patient table 2, a display device 5, and an operation device 6.

  The scanner 1 has an X-ray tube 8 in which X-rays are controlled by an X-ray tube controller 7 as shown in FIG. The X-rays radiated from the X-ray tube 8 are converted into, for example, a pyramid-shaped X-ray beam, that is, a cone beam X-ray, by the collimator 10 controlled by the collimator control device 9, and irradiated to the subject 17. X-rays that have passed through the subject 17 enter the detector 11.

  As shown in FIG. 3, the detector 11 has a plurality of X-ray detection elements 18 that are two-dimensionally arranged in the channel direction and the column direction. The configuration of the detector 11 will be described later. A data collection device 12 is connected to the detector 11. The data collection device 12 collects detection data of individual X-ray detection elements 18 of the detector 11.

  The above components from the X-ray tube control device 7 to the data collection device 12 are mounted on the rotating plate 13 of the scanner 1. The rotating plate 13 is rotated by the driving force transmitted through the driving force transmission system 16 from the rotating plate driving device 15 controlled by the rotation control device 14.

  The detector 11 described above has a configuration in which a plurality of X-ray detection elements 18 are two-dimensionally arranged in the channel direction and the column direction as shown in FIG. The X-ray detection element 18 as a whole forms a cylindrical surface or an X-ray incident surface curved in a polygonal line shape with respect to the channel direction. The channel number i is, for example, about 1-1000, and the column number j is, for example, about 1-1000. It is. Further, the X-ray detection element 18 is constituted by a combination of a scintillator and a photodiode, for example. The cone beam X-ray spread angle in the channel direction of the detector 11 corresponding to the channel arrangement direction, that is, the fan angle is α, and the cone beam X-ray spread in the detector 11 corresponding to the column arrangement direction. The angle, i.e., the cone angle, is γ.

  As shown in FIG. 4, after the subject 17 placed on the top 4 of the patient table 2 is carried into the opening of the scanner 1, the cone beam X-ray whose cone angle γ is adjusted by the opening width of the collimator 10 is taken. When the specimen 17 is irradiated, an image of the subject 17 irradiated with the cone beam X-ray is projected onto the detector 11, and the X-ray transmitted through the subject 17 is detected by the detector 11.

  The patient table 2 shown in FIG. 1 controls the patient table vertical movement device 21 by the patient table control device 20 to an appropriate table height, and controls the top plate driving device 22 by the patient table control device 20 to adjust the table. The plate 4 is moved back and forth so that the subject 17 is carried into and out of the X-ray irradiation space of the scanner 1.

  The console 3 shown in FIG. 1 has a system control device 19. The scanner 1 and the patient table 2 are connected to the system control device 19.

  More specifically, the X-ray tube control device 7, the collimator control device 9, the data collection device 12, and the rotation control device 14 in the scanner 1 are controlled by the system control device 19. The patient table control device 20 in the patient table 2 is controlled by the system control device 19.

  Data collected by the data collection device 12 in the scanner 1 is input to the image reconstruction device 23 under the control of the system control device 19.

  The image reconstruction device 23 creates a scanogram image using the scanogram projection data (subject fluoroscopy data) collected by the data collection device 12 at the time of scanogram imaging, and the projection data of a plurality of views collected by the data collection device 12 at the time of scanning. Use to perform CT image reconstruction.

  A storage device connected to the system control device 19 includes a scanogram image generated by the image reconstruction device 23, a reconstructed CT image, various data, a program for realizing the functions of the X-ray CT apparatus, and the like. 24.

  The system controller 19 is also connected to the display device 5 and the operation device 6. The display device 5 displays the reconstructed image output from the image reconstruction device 23 and various information handled by the system control device 19. The operation device 6 is operated by an operator and inputs various instructions and information to the system control device 19. An operator interactively operates the X-ray CT apparatus using the display device 5 and the operation device 6.

  A scan planning device 25 is also connected to the system control device 19, and a scan condition pre-plan is created using an instruction input by the operator using the operation device 6 and a scanogram image read from the storage device 24. It can be carried out. That is, the scanogram image read from the storage device 24 is displayed on the display device 5, and the operator designates the coordinates of the scan start position using the operation device 6 on the displayed scanogram image of the subject. A scan start position can be planned.

  In the X-ray CT apparatus according to the present invention, various preparation operations are performed in order to set imaging conditions before a scan for acquiring a CT image of a subject. As this preparatory operation, scanning of a scanogram image for setting the scan start position of the subject, setting of the scan start position based on the scanogram image, input of physical feature data of the subject, based on physical feature data of the subject The generation of the scan end position determination condition is performed under the control of the system control device 19. In particular, the generation of the scan end position determination condition based on the physical feature data of the subject is an important function of the scan planning device 25 connected to the system control device 19.

  As main components involved in these preparation operations, the system control device 19, the scan planning device 25, the operation device 6, the display device 5, the X-ray tube 8, and the detector 11 in FIG. Etc.

  In this preparatory operation, the operation device 6 mainly inputs X-ray conditions such as an X-ray tube voltage and an X-ray tube current set value and physical characteristic data of the subject to the system. In the present embodiment, the physical feature data of the subject is the height and weight of the subject.

  The X-ray tube 8 and the detector 11 move the table 2 and the rotating plate 13 along the body axis of the subject 17 without rotating the rotating plate 13 to take a scanogram image, and scanogram image data. Is stored in the storage device 24. In the present embodiment, scanogram imaging may be performed limited to the range necessary for setting the scan start position.

  The scan planning device 25 sets the scan start position as described above, and sets the conditions for determining the scan end position during the scan based on the height and weight of the subject and the scan target part.

  Although the gantry type X-ray CT apparatus has been described above, a C-arm type X-ray CT apparatus may be used.

<Preparation process flow>
Next, a preparation operation in the X-ray CT apparatus according to the present embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing the flow of the preparatory operation process prior to the scan of the X-ray CT apparatus. FIG. 6 is a diagram for explaining the creation of subject projection data. After this preparation operation, measurement photographing is started. In the following, description will be given along the order of steps in FIG.

  In the scanogram imaging process of step S100, a scanogram image of the subject 17 near the planned scan start position is captured. In the conventional CT apparatus, it was necessary to capture a scanogram image that covers the entire scan range. However, in the X-ray CT apparatus according to the present embodiment, it is sufficient to capture a scanogram image near the scan start scheduled position. X-ray exposure associated with can be reduced. In step S100, the scanogram projection data is obtained by irradiating the subject 17 with X-rays from a certain direction, for example, the back direction, without rotating the rotating plate 13, and capturing the detection data by the detector 11. This scanogram projection data is sent from the detector 11 to the image reconstruction device 23 via the system control device 19, and a scanogram image is created in the image reconstruction device 23.

  The scanogram image obtained at this time is an image of X-rays transmitted from a front direction from a certain direction, for example, from the back to the front. This scanogram image is used for setting the start slice position (CT image reconstruction start position) of the subject 17 at the time of scanning.

  In step S110, the operator selects a scan protocol suitable for the site to be scanned from the scan protocol data stored in the storage device 24.

  In step S120, the operator inputs a scan start position from the operating device 6 with reference to the scanogram image.

  In step S130, the operator confirms the input result of step S120 on the display device 5 and proceeds to step S140 if the scan start position is determined to be appropriate. If it is determined that the scan start position is inappropriate, the process returns to step S120 and the scan start position is input again.

  In step S140, the setting value of the protocol selected by the operator in step S110 (for example, X-ray tube voltage, X-ray tube current, etc.) is changed as necessary.

  In step S150, the operator confirms the protocol data whose settings have been changed in step S140 on the display device 5, and if it is determined that the protocol is appropriate, the process proceeds to step S160. If it is determined that the protocol is inappropriate, the process returns to step S140 and the protocol setting value is input again.

  In step S160, the operator inputs the height and weight of the subject from the operation device 6.

  In step S170, the scan planning device 25 reads out standard X-ray projection data in a range corresponding to the protocol selected in step S110 from the storage device 24. The standard X-ray projection data here refers to a standard human body model, for example, a male with a height of 173 cm and a weight of 65 kg for an adult male and a female with a weight of 158 cm and a weight of 50 kg for an adult female. Projection data obtained or assumed to be obtained when X-rays are irradiated on a human body model based on a certain protocol (X-ray tube voltage value, slice thickness, etc.). The standard human body model is changed according to gender in the above example, but may be further defined in detail according to age. Furthermore, as a physical feature value that defines a standard human body model, a physical feature value such as head circumference, chest circumference, abdominal circumference, and sitting height may be used in addition to height and weight. In addition, the protocol changed the protocol, that is, the X-ray irradiation conditions such as the X-ray tube voltage value and the slice thickness for one standard human body model (for example, an adult male having a height of 173 cm and a weight of 65 kg). Multiple protocols may be prepared. Thereby, standard X-ray projection data corresponding to a plurality of protocols can be generated for one standard human body model.

  Standard X-ray projection data for the entire measurement range may be used, or standard X-ray projection data corresponding to the end position of the scan target region associated with the protocol is known in advance from the protocol selected in step S110. Only the standard X-ray projection data corresponding to the end position may be read from the storage device 24. Further, it may be standard X-ray projection data included in a range before and after the body axis direction including the end position.

  In step S180, the scan planning apparatus 25 calculates subject projection data using the height and weight values input in step S160 and the standard X-ray projection data read in step S170. An example of this calculation method is as described below. First, the height ratio α between the subject and the standard human body is calculated by the following equation.

ここで算出された拡大率γを用い、図６に示すように標準Ｘ線投影データ（図６で点線表示されたデータ）を検出器チャネル範囲方向および投影値についてγ倍に拡大した投影データを算出し、これを被検体想定投影データ（図６で実線表示されたデータ）とする。 [Equation 1]
α = height of the subject / height of the standard human body or the weight ratio β between the subject and the standard human body is calculated by the following equation
[Equation 2]
β = weight of the subject / weight of the standard human body and the projection data enlargement rate γ are calculated by the following equation.

Using the magnification γ calculated here, projection data obtained by enlarging the standard X-ray projection data (data indicated by the dotted line in FIG. 6) to the detector channel range direction and the projection value by γ times as shown in FIG. This is calculated and assumed to be subject projection data (data indicated by a solid line in FIG. 6).

  This completes the scan preparation operation. Subsequently, measurement photography is performed.

<First embodiment>
Next, the flow of scan processing according to the first embodiment will be described with reference to FIGS. FIG. 7 is a flowchart showing the flow of scan processing according to the first embodiment. FIG. 8 is an explanatory diagram of the projection data centroid alignment process. Hereinafter, description will be made along the order of steps in FIG.

  First, in step S200, scanning for one rotation is performed.

  Next, in step S210, the projection data of the subject actually measured in step S200 (hereinafter referred to as “subject actual measurement projection data”) and the assumed subject projection data calculated in step S180 of FIG. 5 (solid line in FIG. 6). Compare the data shown in Here, the system control device 19 calculates, for example, a root mean square error between the subject actual measurement projection data and the subject assumed projection data, and the determination threshold value stored in the storage device 24 and the root mean square error are calculated. Make a comparison. However, before calculating the mean square error, the mean square error is calculated after moving the projection data so that the center of gravity of the subject actual measurement projection data and the subject assumed projection data coincide as shown in FIG. To do.

In step S220, it is determined whether or not the scan end position has been reached.
For example, the scan end determination is made by determining that the end position of the scan target part has been reached when the mean square error between the estimated object projection data calculated in step S210 and the measured object projection data is equal to or less than the determination threshold. Also good. Further, the mean square error is plotted in the body axis direction, and a curve for interpolating the plotted points is obtained. Then, when a minimum point is detected on the curve indicating the mean square error, it may be determined that the end position of the scan target portion has been reached. If it is determined that the end position of the scan target part has been reached, the scan is terminated. Otherwise, the process proceeds to step S230.

  In step S230, the top plate is moved to the next scan position. Thereafter, the process returns to step S200, and scanning for the next one rotation is performed.

  According to the present embodiment, scanogram imaging performed when making a scan plan only needs to be performed in the vicinity of the scan start position, and the exposure dose in the subject is reduced compared to the conventional scanogram imaging for the entire scan target region. can do. Furthermore, even if a situation occurs such that the subject moves during scanning and the end position is reached before the scheduled number of scans is completed, the scan can be automatically terminated and Exposure to a part can be prevented.

<Second embodiment>
Next, a flow of scan processing according to the second embodiment will be described with reference to FIG. FIG. 9 is a flowchart showing a flow of scan processing according to the second embodiment. In the present embodiment, a condition for determining whether or not the scan for the scheduled number of rotations has been completed is added before step S220 of the first embodiment. The scan in this embodiment is performed after the preparation operation shown in FIG. 5 is completed, as in the first embodiment. In the following, description will be given in the order of steps in FIG.

  In step S300, similarly to step S200, scanning for one rotation is performed.

  In step S310, similarly to step S210, the projection data of the subject actually measured in step S300 is compared with the assumed subject projection data calculated in step S180 of FIG.

  In step S320, the scan corresponding to the planned number of rotations determined by the scan protocol selected in step S110 of FIG. 5 or the scan protocol corrected and determined in step S150 of FIG. 5 is completed. Determine whether or not. If scanning for the planned number of rotations has been completed, the process proceeds to step S330. If scanning for the planned number of rotations has not been completed, the process proceeds to step S340.

  In step S330, as in step S220, it is determined whether the scan end position has been reached based on the comparison result in step S310. If it is determined that the scan end position has been reached, the scan ends. If it is determined that the scan end position has not been reached, the process proceeds to step S340.

  In step S340, after the top plate is moved to the next scan position, the process returns to step S300 to scan for the next one rotation.

  According to the present embodiment, even when the scan for the scheduled number of rotations determined by the scan protocol is finished, the end position is further determined based on the comparison result between the measured object projection data and the estimated object projection data, Decide whether to end the scan. Therefore, even if a situation occurs in which the subject does not reach the end position even if the scan is completed a predetermined number of times due to movement of the subject during the scan, the scan can be continued to the end position.

  Note that even if the order of step S310 and step S320 in FIG. That is, in step S300, scanning is performed for one rotation, and it is then determined whether the same processing as in step S320, that is, scanning for the planned number of rotations is completed. If scanning for the predetermined number of times is not completed, the process proceeds to step S340 and the top plate is moved. When the scheduled number of scans have been completed, the same processing as in step S310, that is, the comparison processing between the actual measured projection data and the estimated subject projection data is performed. Based on the comparison result, the same processing as step S330 may be performed. By switching the order of step S310 and step S320 in FIG. 9, the process of step S310 is performed only after the scan for the predetermined number of rotations is completed, and the process associated with step S310 can be reduced.

<Third embodiment>
Next, the flow of scan processing according to the third embodiment will be described based on FIG. FIG. 10 is a flowchart showing the flow of scan processing according to the third embodiment. In the present embodiment, a condition for determining whether or not the scan for the predetermined number of rotations has been completed after step S220 in the first embodiment is added. The scan in this embodiment is performed after the preparation operation shown in FIG. 5 is completed, as in the first embodiment. In the following, description will be given in the order of steps in FIG.

  In step S400, a scan for one rotation is performed as in step S200.

  In step S410, similarly to step S210, the projection data of the subject actually measured in step S400 is compared with the assumed subject projection data calculated in step S180 of FIG.

  In step S420, as in step S220, it is determined whether the scan end position has been reached based on the comparison result in step S410. If it is determined that the scan end position has been reached, the scan ends. If it is determined that the scan end position has not been reached, the process proceeds to step S430.

  In step S430, the scan corresponding to the planned number of rotations determined by the scan protocol selected in step S110 of FIG. 5 or the scan protocol corrected and confirmed in step S150 of FIG. Determine whether or not. If the scan for the planned number of rotations has been completed, the scan is terminated. If scanning for the planned number of rotations has not been completed, the process proceeds to step S440.

  In step S440, the top plate is moved to the next scan position, and then the process returns to step S400 to scan for the next one rotation.

  According to the present embodiment, even when the end position is determined based on the comparison result between the measured object projection data and the estimated object projection data, even if the scan does not end, the scan corresponding to the scheduled number of rotations determined by the scan protocol is performed. The scan can be forcibly terminated. For example, if the body fat percentage of the subject is greatly deviated from the value of the standard human body model, or if there is a skeletal abnormality of the subject, the error between the subject projection data and the subject actual measurement data is more than expected. It can grow. For this reason, even if the end position cannot be determined with the expected accuracy based on these comparison results, according to the present embodiment, no more scans than the scheduled number of rotations are performed. As a result, the amount of X-ray exposure in the subject can be prevented from becoming unnecessarily large due to the planned number of rotations at the maximum.

1 is an overall overview diagram of an X-ray CT apparatus. 1 is an overall configuration diagram of an X-ray CT apparatus. The schematic diagram explaining the relationship with the structure of the detector of X-ray CT apparatus, and X-ray irradiation. The figure which shows the relationship of the scanner of X-ray CT apparatus, a patient table, and a subject from a side surface direction. The flowchart which shows the flow of the process of the preparation operation prior to the scan of an X-ray CT apparatus. Explanatory drawing of object subject projection data creation. 6 is a flowchart showing a flow of scan processing according to the first embodiment. Explanatory drawing of a projection data gravity center alignment process. 9 is a flowchart showing a flow of scan processing according to the second embodiment. 10 is a flowchart showing a flow of scan processing according to the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Scanner, 2 ... Patient table, 3 ... Console, 4 ... Top plate, 5 ... Display apparatus, 6 ... Operation apparatus, 7 ... X-ray tube control apparatus, 8 ... X-ray tube, 9 ... Collimator control apparatus, 10 DESCRIPTION OF SYMBOLS ... Collimator, 11 ... Detector, 12 ... Data acquisition device, 13 ... Rotating plate, 14 ... Rotation control device, 15 ... Rotating plate drive device, 16 ... Driving force transmission system, 17 ... Subject, 18 ... X-ray detection element , 19 ... System control device, 20 ... Patient table control device, 21 ... Patient table vertical movement device, 22 ... Top plate drive device, 23 ... Image reconstruction device, 24 ... Storage device, 25 ... Scan planning device

Claims (5)

An X-ray source that emits X-rays;
An X-ray detector disposed opposite to the X-ray source across the subject, detecting X-rays and outputting X-ray projection data;
Rotating means capable of rotating by mounting the X-ray source and the X-ray detector;
Image processing means for generating a tomographic image of the subject based on the X-ray projection data;
Display means for displaying the tomographic image;
An X-ray CT apparatus comprising:
Storage means for storing standard X-ray projection data indicating X-ray projection data obtained when a standard human body model is measured and photographed under arbitrary measurement and imaging conditions;
Feature quantity input receiving means for receiving an input of a physical feature quantity of the subject;
The standard X-ray projection data stored in the storage unit is corrected based on the physical feature amount of the subject acquired by the feature amount input receiving unit, thereby measuring and photographing the subject under the arbitrary photographing conditions. X-ray projection data that is assumed to be obtained at the time of generation, and generating means for generating subject projection data including information related to the end position of measurement imaging ,
Whether or not the measurement imaging end position has been reached based on a comparison result between actual X-ray projection data obtained by measuring and imaging the subject under the arbitrary imaging conditions and the subject assumed projection data Determination means for determining;
An X-ray CT apparatus comprising: The determination means performs the measurement when an error between the subject assumed projection data and actual X-ray projection data obtained by measuring and photographing the subject under the arbitrary photographing conditions is equal to or less than a predetermined threshold. It is determined that the shooting end position has been reached,
The X-ray CT apparatus according to claim 1. The determination unit determines that an error between the subject assumed projection data and the actual X-ray projection data obtained by measuring and photographing the subject under the arbitrary photographing conditions is a minimum value. It is determined that the measurement photographing end position has been reached,
The X-ray CT apparatus according to claim 1. It further comprises a setting means for setting the planned rotation speed of measurement photography,
The determination means reaches the end position of the measurement imaging based on a comparison result between actual X-ray projection data obtained by measuring and imaging the subject under the arbitrary imaging conditions and the assumed projection data of the subject. Even if it is determined that the end position has not yet been reached as a result of determining whether or not the measurement has been completed, the measurement imaging is terminated when the measurement imaging of the planned rotation speed set by the setting unit is completed. Let
The X-ray CT apparatus according to any one of claims 1 to 3. The feature amount input receiving means acquires the height and weight of the subject as physical feature amounts,
The generation means calculates a height ratio calculating means for calculating a height ratio that is a ratio between the height of the subject acquired by the feature amount input receiving means and the height of the standard human body model;
A body weight ratio calculating unit that calculates a body weight ratio that is a ratio between the body weight of the subject acquired by the feature amount input receiving unit and the body weight of the standard human body model;
An enlargement ratio calculating means for calculating a projection data enlargement ratio based on the height ratio calculated by the height ratio calculating means and the weight ratio calculated by the weight ratio calculating means;
Means for generating the assumed object projection data by enlarging the standard X-ray data stored in the storage means by the projection data enlargement ratio calculated by the enlargement ratio calculation means;
5. The X-ray CT apparatus according to claim 1, comprising:

Images