JP2019000156A - X-ray CT apparatus, processing method, and program - Google Patents

Abstract

To provide an X-ray CT apparatus which prevents a contrast medium from overtaking and eliminates ineffective exposure caused by re-imaging.SOLUTION: A control part in the X-ray CT apparatus predicts the peak of a contrast effect based on an imaging condition and calculates and displays (steps S201-S202) a threshold prediction line, estimates (step S211) the measured value estimation line of a future CT value from a tomographic image of contrast imaging (steps S207-S208), compares (step S212) the threshold prediction line with the measured value estimation line, and changes (step S213) the imaging condition in accordance with a comparison result.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an X-ray CT (Computed Tomography) apparatus, and more particularly to a medical image photographing, creation, and management technique thereof.

  An X-ray CT apparatus is obtained by rotating an X-ray source that irradiates a subject with X-rays and an X-ray detector that detects an X-ray amount transmitted through the subject as projection data around the subject. A tomographic image of a subject is reconstructed using projection data from a plurality of angles, and the reconstructed tomographic image is displayed. The image displayed by the X-ray CT apparatus describes the shape of an organ in the subject and is used for image diagnosis.

  In a CT examination using an X-ray CT apparatus, a contrast CT examination is performed in which imaging is performed while injecting a contrast medium into a subject in order to perform a more accurate diagnosis. In contrast CT examination, a contrast medium injection device (injector) is used to inject a contrast medium into a subject. The injected contrast agent is carried to the whole body along the bloodstream, and CT imaging is performed when the concentration of the contrast agent in the blood is high.

  However, in contrast examinations from the chest to the lower limb, imaging may overtake the contrast agent. When overtaking, it is necessary to re-image the area, resulting in increased exposure and extended inspection time. In order to cope with contrast agent overtaking, in Patent Document 1, an operator sets a threshold value and a CT value measurement position during imaging, and adjusts the rotation speed and table movement speed of the scanner when the measured CT value exceeds the threshold value. A method has been proposed.

JP 2005-160784 A

  However, since the method of Patent Document 1 is a countermeasure after the threshold value is exceeded, the overtaking of the contrast agent itself cannot be avoided, and an important contrast effect peak cannot be maintained. The contrast effect means the contrast of the tomographic image after the injection with respect to the tomographic image before the injection of the contrast agent, that is, the difference between the CT values before and after the injection. An object of the present invention is to provide an X-ray CT apparatus, a processing method, and a program capable of preventing overtaking of a contrast agent and eliminating invalid exposure due to re-imaging.

  In order to achieve the above object, in the present invention, an X-ray CT apparatus, a threshold prediction line calculation unit that calculates a threshold prediction line by predicting a peak of a contrast effect at an imaging position based on imaging conditions; A projection data collection unit that collects projection data by irradiating the subject with X-rays, an image reconstruction unit that reconstructs an image based on the collected projection data, and an actual value estimation line for future CT values from the image An X-ray CT apparatus having a configuration including: an estimation unit that estimates a threshold value; and an imaging condition changing unit that compares a threshold prediction line and an actual measurement value estimation line and changes an imaging condition according to the comparison result.

  In order to achieve the above object, according to the present invention, a projection data collection unit that collects projection data by irradiating a subject with X-rays, and an image reconstruction that reconstructs an image based on the collected projection data. A processing method of an X-ray CT apparatus including a configuration unit and a control unit, wherein the control unit predicts a contrast effect peak based on imaging conditions, calculates a threshold prediction line, and calculates a future CT value from the image The X-ray CT apparatus is configured to estimate the actual measurement value estimation line, compare the threshold prediction line and the actual measurement value estimation line, and change the imaging conditions according to the comparison result.

  Furthermore, in order to achieve the above object, in the present invention, a projection data collection unit that collects projection data by irradiating a subject with X-rays, and an image that reconstructs an image based on the collected projection data A processing program for an X-ray CT apparatus including a reconstruction unit and a control unit, wherein the control unit predicts a contrast effect peak based on imaging conditions, calculates a threshold prediction line, and calculates a future CT from the image A processing program for an X-ray CT apparatus configured to operate by estimating a measured value estimation line of values, comparing a threshold prediction line and a measured value estimation line, and changing an imaging condition according to the comparison result is provided.

  According to the present invention, overtaking of a contrast agent can be prevented, and invalid exposure due to re-imaging can be eliminated.

It is a figure which shows an example of the whole structure of the X-ray CT apparatus which concerns on each Example. It is a figure which shows an example of the operation processing flow of the X-ray CT apparatus based on Example 1. FIG. It is a figure which shows an example of the tendency of HU (Hounsfield Unit) and each time in each imaging position at the time of inject | pouring a contrast agent based on Example 1. FIG. It is a figure for demonstrating the calculation method of the threshold prediction line based on Example 1. FIG. It is a figure which shows an example of the console display screen of the X-ray CT apparatus based on Example 1. FIG. It is a figure which shows an example of the stent and stenosis image which are image | photographed with the X-ray CT apparatus based on Example 1. FIG. It is a figure for demonstrating calculation of CT value of the X-ray CT apparatus based on Example 1. FIG. It is a figure which shows an example of the actual measurement line and threshold value prediction line which were displayed on the console display screen based on Example 1. FIG. It is a figure which shows an example of the actual value estimated line estimated from the actual value line for determination displayed on the console display screen based on Example 1. FIG. It is a figure which shows an example of the membership function of fuzzy logic based on Example 4. FIG. It is a figure which shows an example of the membership function by which the fuzzy logic was changed based on Example 4. FIG.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings. First, an example of the entire configuration of an X-ray CT apparatus that is commonly used in each embodiment will be described.

  FIG. 1 shows the overall configuration of an X-ray CT apparatus and a contrast medium injection apparatus. The X-ray CT apparatus includes an X-ray data acquisition unit 1 and a console 2. The X-ray data acquisition unit 1 includes a scan gantry unit 100 and a system control unit 120. The scan gantry unit 100 includes an X-ray tube 101, a rotating disk 102, an opening 104, a table, that is, a bed 105 on which a subject is placed, an X-ray detector 106, a data collection device 107, A line control device 108, a bed control device 111, and a gantry control device 112 are provided.

  The X-ray tube 101 is a device that irradiates a subject 103 placed on a bed 105 with X-rays. The rotating disk 102 includes an opening 104 into which a subject 103 placed on a bed 105 is inserted, and is mounted with an X-ray tube 101 and an X-ray detector 106 and rotates around the subject 103. . The X-ray detector 106 is a device that measures the spatial distribution of transmitted X-rays by detecting X-rays that are disposed opposite to the X-ray tube 101 and transmitted through the subject 103. The rotating disk 102 is arranged in the rotating direction, or the rotating disk 102 is arranged two-dimensionally in the rotating direction and the rotating shaft direction. The data collection device 107 is a device that collects the X-ray dose detected by the X-ray detector 106 as digital data. The X-ray control device 108 is a device that controls electric power input to the X-ray tube 101. The bed control device 111 is a device that controls the front, back, left, right, up and down movements of the bed 105. The gantry control device 112 is a device that controls the rotation of the rotary disk 102.

  The system control unit 120 includes a system control device 121, an image calculation device 122, and a storage device 123. The storage device 123 is a device that stores raw data (RawData) 124 collected by the data collection device 107, and is specifically an HDD (Hard Disk Drive) or the like. The image arithmetic device 122 is a device that performs arithmetic processing on RawData 124 stored in the storage device 123 to perform CT image reconstruction. The system control device 121 is a device that controls these devices and the X-ray control device 108, the bed control device 111, and the gantry control device 112.

  The console 2 includes a console display device 201, a console input device 202, a console control device 203, and a console storage device 204. The console storage device 204 is a storage device that stores the CT image 205 and base data created by the image calculation device 122. The console display device 201 is a device that displays a CT image 205 and an imaging plan screen, and is specifically a liquid crystal display or the like. The console input device 202 is a device for inputting a subject's name, examination date and time, imaging conditions, reconstruction conditions, and the like, and specifically, a keyboard and a pointing device.

  The X-ray control device 108 controls the power input to the X-ray tube 101 based on the imaging conditions input from the console input device 202, in particular, the X-ray tube voltage and the X-ray tube current. Irradiates the subject 103 with X-rays according to imaging conditions. The X-ray detector 106 detects X-rays irradiated from the X-ray tube 101 and transmitted through the subject 103 with a number of X-ray detection elements, and the data acquisition device 107 measures the distribution of transmitted X-rays.

  X-ray irradiation from the X-ray tube 101 and measurement of the transmitted X-ray distribution by the X-ray detector 106 are repeated along with the rotation of the rotating disk 102, whereby X-ray dose data from various angles is acquired. The acquired X-ray dose data from various angles is collected as RawData 124 and transmitted to the image calculation device 122. The image calculation device 122 reconstructs the CT image by performing back projection processing on the transmitted RawData 124 according to the reconstruction condition input by the console input device 202. The CT image obtained by the reconstruction is displayed on the console display device 201.

  An injection device 3 for injecting a contrast agent attached to the X-ray CT apparatus includes an operation input device 300 and a head unit 310. The operation input device 300 is a device through which an operator inputs conditions for injecting contrast medium or physiological saline. The head unit 310 includes an injection control device 311 and a chemical solution injection device 312. The injection control device 311 is a device for controlling the chemical solution injection device 312 based on the conditions input to the operation input device 300 and communicating with the system control device 121 of the X-ray data acquisition unit 1. The chemical solution injection device 312 is a device for injecting a contrast medium and physiological saline into a subject, and has respective cylinders for filling the contrast medium and physiological saline.

  The injection control device 311 controls the chemical solution injection device 312 according to the injection conditions received from the operation input device 300. The chemical injection device 312 uses power such as air pressure, motor, or hydraulic pressure according to preset contrast conditions (contrast medium injection amount, injection pressure (injection speed), etc.), and the contrast medium and physiological saline in the cylinder. Inject water into the subject.

  The first embodiment predicts a peak of contrast effect based on imaging conditions and calculates a threshold prediction line, and a projection data collection unit that collects projection data by irradiating a subject with X-rays An image reconstruction unit that reconstructs an image based on the collected projection data, an estimation unit that estimates a future CT value from the image as an actual value estimation line, and a threshold prediction line and an actual value estimation line This is an embodiment of an X-ray CT apparatus configured to include an imaging condition changing unit that changes imaging conditions according to a comparison result. An X-ray CT apparatus comprising: a projection data collection unit that collects projection data by irradiating a subject with X-rays; an image reconstruction unit that reconstructs an image based on the collected projection data; and a control unit The control unit predicts the contrast effect peak based on the imaging condition, calculates a threshold prediction line, estimates an actual value estimation line of a future CT value from the image, It is the Example of the processing method of the X-ray CT apparatus of a structure which compares an actual value estimated line, and changes an imaging condition according to a comparison result, and a processing program.

  FIG. 2 shows an example of an operation processing flow of the X-ray CT apparatus according to the present embodiment. This operation processing flow is realized by executing a program of a control device such as the system control device 121, the image calculation device 122, the console control device 203, and the injection control device 311. First, in step S <b> 201, positioning photographing for photographing a positioning image is performed, and the photographed positioning image is displayed on the console display device 201. The positioning image is an image obtained by taking an image while moving the bed 105 in the body axis direction of the subject while the rotating disk 102 is stopped, and is a so-called fluoroscopic image. Next, in step S202 constituting the threshold prediction line calculation unit, the contrast imaging range and the threshold prediction line are calculated and displayed. In the present embodiment, the threshold prediction line calculation unit realized by executing the program of the image arithmetic device 122 predicts the peak of the contrast effect at the imaging position based on the imaging conditions based on the acquired positioning image, A threshold prediction line is calculated using the peak value predicted at the photographing position. The threshold prediction line may be a line connecting predicted peak values or a line connecting a peak value multiplied by a predetermined coefficient. A method for predicting a threshold prediction line based on a captured positioning image in the threshold prediction line calculation unit will be described with reference to FIGS.

  FIG. 3 shows the trend of HU (Hounsfield Unit) and time at each imaging position (a), (b), and (c) when contrast medium is injected from the arm. As can be seen from the figure, the maximum value of HU, that is, the peak of the contrast effect decreases as the distance from the injection site increases. Therefore, when photographing from the chest toward the lower limbs, the maximum HU tends to decrease. The tendency of each part position and maximum HU is stored in the console storage device 204 in advance. Further, since the inclination increases as the height increases or the weight decreases and the volume decreases, the basic height and weight values are also stored in the console storage device 204 as base data. Note that the basic values of the imaging conditions and the contrast medium injection conditions may be stored in the console storage device 204 as base data as necessary. A part such as a chest and an abdomen is recognized from the positioning image obtained in step S201 this time, and the threshold prediction line calculation unit compares it with the base data stored in the console storage device 204 together with the height and weight values of the subject. Then, a threshold prediction line is calculated.

  As a schematic diagram for explaining an example of a method for calculating a threshold prediction line in the present embodiment in FIG. 4, a standard body model 401 and a dotted line graph 402 indicating the maximum HU tendency that is the peak of the contrast effect corresponding thereto, A positioning image 403 and the like are shown. Based on the dotted line graph 402 which is the tendency of each part section of the standard body model 401, a threshold prediction line 404 of the current positioning image 403 is calculated. The threshold prediction line displayed on the console display device 201 after the calculation is a thick line portion of the threshold prediction line 404 corresponding to the contrast imaging range 405. That is, the console display device 201 which is a display unit of the present embodiment displays the positioning image 403 on which the contrast imaging range 405 is superimposed together with the threshold prediction line 404.

  As shown in FIG. 5, the positioning image 403 and the threshold prediction line 404 are displayed on the console display device 201. The displayed threshold prediction line 404 can be freely changed by the operator using the console input device 202. When contrast imaging is performed a plurality of times, a threshold prediction line is displayed for each contrast imaging. In addition, the threshold prediction line may be used internally by the console control device 203 without displaying the threshold prediction line on the console display device 201 to proceed with the subsequent processing steps. The operator sets the contrast imaging position / range such as the contrast imaging range 405 and the imaging positions in steps S203 and S206 with the console input device 202.

  In step S203, simple imaging of the position where the contrast medium arrival is monitored is performed. This is imaging of a tomographic image used for designating a monitoring position in step S204, and a body axis position different from contrast imaging in step S207 can be designated. In addition, since it is sufficient to have a tomographic image for at least one section, it is not necessary to photograph a wide area. The taken tomographic image is displayed on the console display device 201.

  In step S204, the operator performs ROI (Region Of Interest) for monitoring whether the contrast agent has reached the tomographic image displayed in step S203, and CT imaging for CT imaging that is determined to have reached. A threshold, that is, a monitoring photographing threshold is set.

  Subsequently, in step S205, monitoring shooting is started. In step S206, the monitoring position is imaged, the tomographic image is reconstructed, and the CT value of the ROI is measured. It is determined whether the CT value of the ROI is higher than the monitoring imaging threshold set in step S204. If it is higher (Yes), the process goes to step S207. If not (No), the comparison with the monitoring imaging threshold in step S206 is repeated.

  In step S207, contrast imaging in the contrast imaging range set by the operator in step S202 is started. In step S208 constituting the image reconstruction unit, a tomographic image is reconstructed based on the collected projection data. This image reconstruction unit reconstructs a tomographic image at the current imaging position in real time. In step S209, a blood vessel is searched from the tomographic image created in step S208, and an average CT value in the blood vessel is calculated. That is, the average CT value in the blood vessel at each slice position is acquired from the tomographic image reconstructed in step S208 in step S209.

  In step S208 of this embodiment, template matching is used to search for blood vessels. When using template matching, a pattern of blood vessel position and blood vessel diameter features is stored in the console storage device 204 in advance. First, a bone region is extracted from the tomographic image created in step S208, and the tomographic image is rotated so as to be bilaterally symmetric. A Gabor filter effective for recognizing the position of an object in the image is applied to the rotated tomographic image, and features for each direction such as the direction of the blood vessel are extracted. A pattern most similar to the extracted feature for each direction is searched, and the blood vessel position is applied to the image. Thereafter, the rotated tomographic image is reversely rotated to obtain a blood vessel position.

  That is, the estimation unit of the present embodiment extracts a blood vessel position from a tomographic image acquired by contrast imaging using a previously stored blood vessel position and image feature pattern, and calculates an average CT value in the blood vessel. In particular, the estimation unit extracts a feature for each direction from the tomographic image, searches for a pattern most similar to the extracted feature, and applies the blood vessel position of the searched pattern to the tomographic image.

The blood vessel position is extracted in consideration of the blood vessel connection in consideration of the blood vessel position of the previous imaging position. If the blood vessel position does not change significantly from the blood vessel position at the previous imaging position, only the blood vessel position at the previous imaging position may be considered.
Since there is a possibility that the blood vessel has a stent or a stenosis, the CT value is calculated by excluding that. The image stent and stenosis pattern is, for example, as shown in FIG.

  A method for calculating the CT value of a blood vessel will be described with reference to FIG. Assume that a blood vessel having a stent and a stenosis as shown in FIG. A search is made for the presence of the stent by the stent width from the outer periphery of the blood vessel, and if it is found, the stent portion is removed as shown in FIG. Then, the non-contrast region caused by stenosis is excluded, and the average CT value of the remaining region shown in (c) of FIG. 7 is adopted.

  The threshold prediction line is adjusted only when the first scan of contrast imaging in step S207 is performed. In the first scan, the peak of the contrast effect is guaranteed in the monitoring imaging in step S206. Therefore, in order to reflect this peak value on the threshold prediction line, the entire threshold prediction line is moved up and down in the CT value direction based on the error of the first scan. Thereby, the influence of the fluctuation | variation of the prediction by an individual difference can be reduced.

  The average CT value obtained in step S209 is displayed on the console display device 201 as an actual measurement value of the imaging position. As an example of the display, FIG. 8 shows a threshold prediction line 404 and an actual measurement value line 803 that is a line connecting actual measurement values from the contrast imaging start position to the current imaging position 802. When there are a plurality of blood vessels in one image, each value and position are stored in the console storage device 204, and the highest CT value is displayed. When there are a plurality of blood vessels and there is a blood vessel to which no contrast agent has come, it may be notified to the operator. For example, the color of a point on the actual measurement value line 803 can be changed, or a character can be displayed next to the actual measurement value line 803. Thereby, it is possible to determine the embolism during contrast imaging.

  In step S210, it is determined whether contrast imaging is completed at the current imaging position. If it is the last imaging position (Yes), the process ends. If not (No), Step S211 is performed to estimate an actually measured value estimated value that is a CT value in the subsequent imaging. This step S211 constitutes an estimation unit that estimates a future CT value as a measured value estimation line from a tomographic image obtained by contrast imaging. In step S211, which constitutes the estimation unit, a weighted moving average is first taken to remove noise included in the blood vessel average CT value of the tomographic image at each imaging position. The value of a certain photographing position is a value weighted to the actual measurement values up to several places. This is used as an actually measured value for determination. Note that the weight is increased as the position is closer to a certain photographing position. Since noise increases when mAs or kV is low, the average number may be increased. Further, instead of the weighted moving average, another smoothing process such as a simple moving average may be used.

  In step S212, it is determined whether the actual measurement value estimation line for determination is below the threshold prediction line in future contrast imaging. As shown in FIG. 9, the measured actual measurement value line 901 is extrapolated and the actual measurement value estimation line 902 is drawn. That is, the console display device 201 as a display unit displays the determination actual measurement value line 901 and the actual measurement value estimation line 902 calculated based on the captured tomographic image, together with the threshold prediction line 404. When the actual measurement value estimation line 902 may fall below the threshold prediction line 404, step S213 for changing the imaging condition is performed. Otherwise, step S208 is performed.

  Step S213 constitutes an imaging condition changing unit that changes the imaging condition in accordance with a comparison result obtained by comparing the threshold prediction line and the actual value estimation line. In addition, when the CT value becomes low, the imaging condition changing unit determines whether the imaging has been performed since the imaging of the peak of the contrast agent is low or the peak of the contrast agent is earlier than the imaging position. To do. Therefore, the determination is made based on the relationship between the imaging conditions changed in the previous S213 and the CT value behavior of the subsequent imaging. For example, if the CT value is smaller than the previous photographing position in the photographing immediately after the pitch is reduced in S213, it can be determined that the peak is ahead of the photographing position. Note that the table may be reconstructed at a plurality of locations such as the front, center, and rear with respect to the table traveling direction, and determination may be made by a method of which is the highest CT value.

  In step S213, there is a possibility that the actually measured value estimation line may fall below the threshold prediction line, and if the image is taken ahead of the peak, the pitch is reduced. Since the inclination of the actually measured value estimation line becomes gentler by the pitch after the change / the pitch before the change, the pitch is reduced to an inclination that does not fall below. The changed pitch value is changed not immediately before the threshold prediction line, but when it is determined to be lower, and the contrast imaging in step S208 is continued under the changed imaging conditions. As a result, contrast imaging can be performed without the actual measurement value falling below the threshold prediction line.

  If the actual measurement value falls below the threshold prediction line even if the shooting condition is changed, a notification such as whether to re-shoot or pause, or an option operator may be presented. Moreover, you may display the probability which falls for every imaging | photography position. In the case of temporary stop, the contrast imaging is temporarily stopped, and the table on which the subject is placed is controlled by the bed control device 111 as needed, and the imaging is resumed after a while.

  Note that a margin may be given to the threshold prediction line. Further, steps may be provided such as a threshold prediction line as a warning line as a trigger for changing the shooting condition and a threshold prediction line as a lowest line for stopping shooting.

  Also, if the pitch is lowered, the exposure at the photographing position increases, so the photographing conditions are adjusted to reduce the dose. Lowering kV results in insufficient dose in bone-rich areas, so lower mA. However, since noise increases when mA is reduced too much, noise reduction processing such as successive approximation reconstruction may be performed only for the photographing position for the final image. If there is no problem in processing time, processing may be performed by reconstruction of tomographic images for display on the console display device 201 during contrast imaging.

  In addition, there is a possibility that the value falls below the threshold prediction line, and the pitch is increased when photographing behind the peak. The collimator may be narrowed according to the pitch. In the scan after the pitch change, if a margin appears on the actual value estimation line rather than the threshold prediction line, the pitch may be returned to the original value. Also, the imaging speed may be slowed so as not to overtake the contrast agent under imaging conditions other than the pitch. In order to make the pitch constant, the rotation speed of the scanner and the table moving speed may be changed.

  Furthermore, in the present embodiment, it is assumed that one tomographic image is reconstructed per scan in step S208, but there are a plurality of locations such as front, center, and rear with respect to the table traveling direction. Reconfiguration may be performed for subsequent processing. Depending on the pitch, a wide width may be imaged by one rotation, so that by increasing the sampling for measuring the actual measurement value, it is possible to improve the determination accuracy such that the blood vessel CT value is high in the rear but low in the front.

  In the X-ray CT apparatus of the present embodiment, by resetting the imaging conditions so that the CT value acquired from the projection data being imaged does not exceed the threshold prediction line set based on the imaging conditions, At the time of contrast imaging, it is possible to prevent overtaking of the contrast agent, and it is possible to eliminate invalid exposure due to re-imaging. Furthermore, since it is possible to continue photographing at the peak of the contrast effect, an effective image can be obtained by diagnosis.

  In step S211 of the first embodiment, the actual value estimation line of the future, that is, after that is calculated by the moving average. However, in the second embodiment, information obtained from the tomographic image reconstructed in step S208 in the estimation unit is also obtained. This is an example of a configuration in which the estimation accuracy of the actual value estimation line is increased by calculating the actual value estimation line in consideration.

  Depending on the blood vessel diameter, the number of branches, and the like, the blood flow velocity further decreases from the contrast agent injection start position, and the peak of the contrast effect becomes lower. Therefore, the CT value calculated in S209 decreases as the blood vessel diameter extracted in step S208 is thinner than the previous imaging position. In addition, the CT value decreases as the number of blood vessels in one image increases. Furthermore, the CT value decreases as the distance from the imaging start position of contrast imaging increases. From the above points, in the present embodiment, the CT value of the future contrast imaging is estimated by taking into account information on the size and number of blood vessels obtained from these tomographic images reconstructed in step S208. Therefore, it is possible to increase the estimation accuracy of the CT value.

  Example 3 is an example of a configuration in which an estimation unit extracts a blood vessel route from a tomographic image and estimates an actual measurement value estimation line according to a comparison result between the extracted blood vessel route and a stored blood vessel route model. .

  In step S212 of the first embodiment, the subsequent actual measurement value estimation line is calculated by the moving average. However, in the third embodiment, the calculation is performed by adding information obtained from all the tomographic images reconstructed so far in step S208. Since the blood flow velocity depends on the blood vessel curve, it can be estimated that the CT value becomes low at the blood vessel curve portion where the flow velocity decreases. Therefore, in this embodiment, a 3D model of only a blood vessel is created from all the reconstructed tomographic images, thereby identifying a blood vessel curve location and estimating a CT value at the curve location low.

  In addition, by preparing a general blood vessel model of the human body in the console storage device 204 in advance and matching it with a blood vessel model created during contrast imaging, a blood vessel model ahead can be assumed. As a result, since a change in blood flow can be predicted therefrom, the CT value estimation accuracy can be made higher than that in the first embodiment. The model may be a 2D model as well as a 3D model. Furthermore, the configurations of the first to third embodiments can be applied depending on the inclination value of the threshold prediction line.

  In step S213, which constitutes an imaging condition changing unit that changes the imaging condition in accordance with the comparison result obtained by comparing the threshold prediction line and the actual value estimation line in the first embodiment, the actual value estimation line and the threshold prediction line are compared and imaged. The condition has been changed. In the fourth embodiment, the shooting condition changing unit determines the change value of the shooting condition using fuzzy logic from the situation and shooting conditions at that time. Then, the imaging condition changing unit uses the number of scans until the measured value estimation line falls below the threshold prediction line, the rotation speed, and the magnitude of the pre-change pitch as fuzzy logic rules, and the membership function shown in FIG. In this way, the margin until the actually measured value estimation line falls below the threshold prediction line is defined.

  When changing the shooting conditions, there is a difference in the margin for subsequent re-establishment when changing just before the threshold prediction line is changed and when changing with a margin. For this reason, the change value varies depending on the number of scans until it falls below. Further, when the rotation speed of the scanner is high, even if the pitch is reduced, the extension of the time until it falls below the threshold prediction line is reduced. When the pitch before the change is originally small, the time extension is small even if the pitch is changed.

  Based on the above conditions, in this embodiment, the membership function is defined as shown in FIG. Further, as a rule for the above combination, the number of scans until the actual value estimation line falls below the threshold prediction line, the rotation speed, and the magnitude of the pitch before change are defined as shown in FIG. The membership function of the consequent part is shown in FIG. The membership function of the consequent part represents the pitch after changing the horizontal axis in stages, and it is considered that there is not much change in a little pitch change, so that it has a width as it is, and even if it is lowered, it will not drop rapidly Since there is no triangle, the center is the starting point.

  If it is determined in step S212 in FIG. 2, the membership function and rules are applied, fuzzy inference is performed by the MIN-MAX centroid method, and the changed pitch is calculated. In another example of FIG. 11, the membership function of the consequent part is lowered by two steps from the center of gravity. If the threshold prediction line is not exceeded, the pitch can be changed to a large value by separately preparing a rule and a membership function of the consequent part.

  With the configuration of this embodiment, fuzzy inference can be used, and the pitch can be changed based on an intuitive control rule according to the threshold prediction line and the actual measurement value estimation line. Changes can be made.

  In this embodiment, the estimation unit acquires a CT value at each slice position by taking a difference between a tomographic image acquired by simple imaging and a tomographic image acquired by contrast imaging. . That is, in step S209 of the first embodiment, the blood vessel stent is analyzed and determined. However, in the fifth embodiment, simple imaging of the whole body of the subject is performed in the same range as the contrast imaging, and in step S209. The stent or blood vessel position is determined by taking the difference between the tomographic image of simple imaging and the tomographic image of contrast imaging in real time.

  The image interval of simple imaging is matched with contrast imaging, and the difference in body movement is aligned by non-rigid registration, and the activation of the tube is also adjusted. In step S209, a difference is obtained by matching the edge of the human body on the image with the simple captured image at the same position. Thereby, a CT value can be calculated by removing the stent and calcification. It can also be determined not to use CT values near blood vessels with much calcification as measured values.

  In step S202 in the first embodiment, the threshold prediction line is calculated mainly using the information of the positioning image, but in this embodiment, the calculation is performed using machine learning using only the subject information and the imaging conditions. To do. The threshold prediction line calculation unit of the present embodiment calculates a threshold prediction line by machine learning using subject information and imaging conditions.

  Therefore, the threshold prediction line calculation unit preliminarily includes subject information such as height and weight, imaging conditions such as kV, mA, and pitch that affect the contrast effect, and blood vessel CT values at each imaging position when imaging is performed under those conditions. Machine learning based on this tendency. At the time of examination, the trend line of the CT value applicable from the subject information and the imaging conditions input by the operator is called and displayed on the console display device 201. As a result, the prediction line can be calculated without taking a positioning image.

  Note that a learning method may be used in which imaging conditions are determined in accordance with a threshold prediction line input by an operator and subject information. In this case, the injection condition is instructed to the injection control device 311 according to the imaging condition.

  In step 209 in the first embodiment, pattern matching is used for searching for a blood vessel position. In this embodiment, machine learning is used. That is, since the estimation unit of the present embodiment extracts a blood vessel position from a tomographic image and calculates an average CT value in the blood vessel, where the blood vessel exists on the tomographic image based on the tomographic image and the learning data of the blood vessel position. In this embodiment, the network of machine learning results is stored, an image is input to the network, and the blood vessel position is specified from the output result of the network.

  In this embodiment, machine learning is performed in advance. As learning data, a tomographic image obtained by contrast imaging and a blood vessel position corresponding thereto are used. Since it is necessary to learn and output the blood vessel position on the tomographic image and there are cases where there are a plurality of blood vessels in one image, the node of the output layer is the number of pixels of the tomographic image. Learning is performed so that the probability of whether a blood vessel exists in each pixel is output from each node.

  In step 209, the tomographic image created in step S208 is input to the learned network, so that the blood vessel is output with a probability in the tomographic image. In this embodiment, the blood vessel position in the tomographic image can be specified with high accuracy by machine learning.

  The present invention is not limited to the various embodiments described above, and includes various modifications. For example, the above-described embodiments have been described in detail for better understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  Furthermore, the control units such as the above-described configurations, functions, and system control units have been described as examples of creating a program that realizes some or all of them. However, some or all of them are designed with, for example, an integrated circuit. Needless to say, it may be realized by hardware. That is, all or a part of the functions of the control unit may be realized by an integrated circuit such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA) instead of the program.

DESCRIPTION OF SYMBOLS 1 X-ray data acquisition part 100 Scan gantry part 101 X-ray tube 102 Rotating disk 103 Subject 104 Opening part 105 Bed 106 X-ray detector 107 Data acquisition apparatus 108 X-ray control apparatus 111 Bed control apparatus 112 Gantry control apparatus 120 System control Unit 121 System control device 122 Image calculation device 123 Storage device 124 RawData
2 console 201 console display device 202 console input device 203 console control device 204 console storage device 205 CT image 3 injection device 300 operation input device 310 head unit 311 injection control device 312 chemical solution injection device 401 standard body model 402 dotted line Graph 403 Positioning image 404 Threshold prediction line 405 Contrast imaging range 802 Current imaging position 803 Actual value line 901 Determination actual value line 902 Actual value estimation line

Claims (15)

An X-ray CT apparatus,
A threshold prediction line calculation unit that calculates a threshold prediction line by predicting the peak of the contrast effect based on the imaging conditions;
A projection data collection unit that collects projection data by irradiating the subject with X-rays;
An image reconstruction unit for reconstructing a tomographic image based on the collected projection data;
An estimation unit that estimates an actual value estimation line of a future CT value from the tomographic image;
An imaging condition changing unit that compares the threshold prediction line and the actual measurement value estimation line and changes the imaging condition according to a comparison result;
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
A display unit for displaying the threshold prediction line;
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The threshold prediction line calculation unit
Predicting the peak based on the obtained positioning image;
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The estimation unit includes
Extracting the blood vessel position from the tomographic image acquired by contrast imaging using the previously stored blood vessel position and the tomographic image feature pattern, and calculating the average CT value in the blood vessel,
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 4,
The estimation unit includes
Extracting a feature for each direction from the tomographic image, searching for the pattern most similar to the extracted feature, and applying a blood vessel position of the searched pattern to the tomographic image;
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The estimation unit includes
Using the tomographic image reconstructed by the image reconstruction unit, the actual measurement value estimation line is estimated,
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 6,
The estimation unit includes
Extracting a blood vessel route from the tomographic image, and estimating the measured value estimation line according to a comparison result between the extracted blood vessel route and a stored blood vessel route model,
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The photographing condition changing unit
Determining a change value of the shooting condition using fuzzy logic based on a fuzzy rule and a membership function;
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 8,
The photographing condition changing unit
As a rule of the fuzzy logic, a margin until the measured value estimation line falls below the threshold prediction line is used.
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The estimation unit includes
Obtain the CT value of each slice position by taking the difference between the tomographic image acquired by simple imaging and the tomographic image acquired by contrast imaging,
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The threshold prediction line calculation unit
Calculating the threshold prediction line using subject information and imaging conditions;
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 1,
The estimation unit includes
Extracting a blood vessel position from the tomographic image,
Based on the tomographic image and the learning data of the blood vessel position, memorize the network of the result of machine learning where the blood vessel exists on the tomographic image,
Input the tomographic image of contrast imaging to the network, and specify the blood vessel position from the output result of the network,
An X-ray CT apparatus characterized by that. The X-ray CT apparatus according to claim 2,
The display unit
Along with the threshold prediction line, a positioning image in which a contrast imaging range is superimposed, a determination actual value line calculated based on the tomographic image, and the actual value estimation line are displayed.
An X-ray CT apparatus characterized by that. An X-ray CT apparatus comprising: a projection data collection unit that collects projection data by irradiating a subject with X-rays; an image reconstruction unit that reconstructs a tomographic image based on the collected projection data; and a control unit Processing method,
The controller is
Predict the contrast effect peak based on the imaging conditions and calculate the threshold prediction line;
Estimating the actual value estimation line of the future CT value from the tomographic image,
Compare the threshold prediction line and the measured value estimation line, and change the shooting conditions according to the comparison result,
A processing method characterized by the above. An X-ray CT apparatus comprising: a projection data collection unit that collects projection data by irradiating a subject with X-rays; an image reconstruction unit that reconstructs a tomographic image based on the collected projection data; and a control unit A processing program of
The control unit is
Predict the contrast effect peak based on the imaging conditions and calculate the threshold prediction line;
Estimating the actual value estimation line of the future CT value from the tomographic image,
Compare the threshold prediction line and the measured value estimation line, and change the shooting conditions according to the comparison result,
A processing program characterized by that.

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