JP2015150208A - X-ray CT apparatus and imaging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus and an imaging method capable of controlling the imaging process by considering the effects of a plurality of different body motions in a comprehensive manner.SOLUTION: Body motion sensor 31, 32 are attached to different sites of a subject, to detect body motion waveform data T, S of the respective sites. A system control device 124 weight-adds the body motion waveform data T, S of the respective sites to calculates a composite waveform W in each imaging position. In addition, the system control device 124 controls imaging synchronously with the calculated the composite waveform W. The composite waveform W is calculated by weight-adding the body motion waveform data T, S output from the respective body motion sensors 31, 32, using a weighting coefficient corresponding to the relationship between the attached positions of the body motion sensors 31, 32 and the imaging positions.

Description

  The present invention relates to an X-ray CT apparatus and an imaging method, and more particularly to imaging control synchronized with body movement.

  Conventionally, when a moving part is imaged by an X-ray CT (Computed Tomography) apparatus, an artifact due to the movement occurs in the obtained tomographic image. In order to reduce this artifact, physiological movements are measured simultaneously with imaging using body motion sensors such as electrocardiographs and respiration sensors, and imaging is controlled using acquired measurement signals and images are processed. Or Patent Document 1 describes a method for determining a transition timing from a monitoring scan to a main scan in consideration of a change in CT value due to respiration in an examination using a contrast medium.

JP 2000-287965 A

  However, it may be affected by a plurality of body movements at the photographing position. In this case, there is a problem in applying the method of Patent Document 1 that controls imaging based on a waveform detected by one body motion sensor as it is. Specifically, for example, when imaging a plurality of parts continuously, in an organ (for example, lung) that is greatly affected by thorax motion during breathing and an organ (for example, liver) that is greatly affected by diaphragm motion, The magnitude (amplitude) and period of movement are different. Therefore, when imaging a region located in the middle of these organs, it is difficult to control imaging by comprehensively considering the influence of a plurality of body movements using a measurement signal from one body movement sensor. .

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an X-ray CT apparatus capable of controlling imaging while comprehensively considering the influence of a plurality of different body movements. And providing a photographing method.

  In order to achieve the above-described object, a first invention is an X-ray source that irradiates a subject with X-rays, and an X-ray detector that is disposed opposite to the X-ray source and detects X-rays transmitted through the subject. A body mounted with the X-ray source and the X-ray detector, rotating around the subject, and attached to a plurality of parts of the subject to detect body motion waveform data at each part A detector, weighted addition of body motion waveform data at each part, and a composite waveform calculation unit for calculating a composite waveform at each imaging position, and imaging control in synchronization with the composite waveform calculated by the composite waveform calculation unit An X-ray CT apparatus comprising: a synchronous imaging control unit configured to perform an image processing apparatus configured to reconstruct an image using transmission X-ray data detected by the X-ray detector.

  According to a second aspect of the present invention, the control device of the X-ray CT apparatus acquires the body motion waveform data detected by each body motion detector attached to a plurality of parts of the subject, An imaging method characterized by performing processing including a step of weighted addition of body motion waveform data to calculate a composite waveform at each imaging position and a step of controlling imaging in synchronization with the composite waveform.

  According to the present invention, it is possible to provide an X-ray CT apparatus and an imaging method capable of controlling imaging while comprehensively considering the influence of a plurality of different body movements.

Overall configuration diagram of X-ray CT apparatus 1 Mounting example of a plurality of body motion sensors 31, 32 Examples of body motion waveform data T and S obtained from the body motion sensors 31 and 32 Functional configuration diagram related to body motion synchronized shooting (A) The figure explaining the relationship between the attachment position of each body motion sensor 31, 32 and imaging | photography position, (b) Calculation of the weight coefficient data 41 according to the relationship between the attachment position of body motion sensor 31, 32 and imaging | photography position Example An example of body motion waveform data T and S obtained from each body motion sensor 31 and 32 and their weighted combined waveform W The flowchart explaining the procedure of the imaging | photography process which the system control apparatus 124 of this invention performs The flowchart explaining the procedure of the imaging | photography process which the system control apparatus 124 of this invention performs Functional configuration diagram according to the second embodiment of the present invention (a) Before contrast agent injection, (b) During monitoring scan Flow chart showing the procedure of CT value variation data calculation processing executed before contrast agent injection The flowchart which shows the procedure of the contrast agent inflow determination process performed at the time of contrast imaging

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First embodiment]
First, the overall configuration of the X-ray CT apparatus 1 will be described with reference to FIG.
As shown in FIG. 1, the X-ray CT apparatus 1 includes a scan gantry unit 100, a bed 105, an operation console 120, and first and second body motion sensors (body motion detectors) 31 and 32. The scan gantry unit 100 is an apparatus that irradiates the subject 3 with X-rays and detects X-rays transmitted through the subject. The console 120 is a device that controls each part of the scan gantry unit 100, acquires transmission X-ray data measured by the scan gantry unit 100, and generates and displays an image. The bed 105 is a device that places the subject 3 on the bed and carries the subject into and out of the X-ray irradiation range of the scan gantry unit 100. The body motion sensors 31 and 32 are devices that measure body motion waveform data representing the movement of a living body. For example, in the present embodiment, a respiration sensor that measures the movement of the subject 3 due to respiration is used.

The scan gantry unit 100 includes an X-ray source 101, a turntable 102, a collimator 103, an X-ray detector 106, a data acquisition device 107, a gantry control device 108, a bed control device 109, and an X-ray control device 110.
The console 120 includes an input device 121, an image processing device 122, a storage device 123, a system control device 124, and a display device 125.

  An opening 104 is provided in the turntable 102 of the scan gantry unit 100, and the X-ray source 101 and the X-ray detector 106 are arranged to face each other through the opening 104. The subject 3 placed on the bed 105 is inserted into the opening 104. The turntable 102 rotates around the subject by a driving force transmitted from the turntable drive device through a drive transmission system. The turntable driving device is controlled by a gantry control device 108.

  The X-ray source 101 is controlled by the X-ray control device 110 to irradiate X-rays having a predetermined intensity continuously or intermittently. The X-ray controller 110 controls the X-ray tube voltage and the X-ray tube current applied or supplied to the X-ray source 101 according to the X-ray tube voltage and the X-ray tube current determined by the system controller 124 of the console 120. To do.

  A collimator 103 is provided at the X-ray irradiation port of the X-ray source 101. The collimator 103 limits the irradiation range of X-rays emitted from the X-ray source 101. For example, it is formed into a cone beam (conical or pyramidal beam). The opening width of the collimator 103 is controlled by the system controller 124.

  X-rays irradiated from the X-ray source 101, passing through the collimator 103, and passing through the subject 3 enter the X-ray detector 106.

  The X-ray detector 106 includes, for example, about 1000 X-ray detection element groups configured by a combination of a scintillator and a photodiode in the channel direction (circumferential direction), for example, about 1-320 in the column direction (body axis direction). It is an arrangement. The X-ray detector 106 is disposed so as to face the X-ray source 101 through the subject 3. The X-ray detector 106 detects the X-ray dose irradiated from the X-ray source 101 and transmitted through the subject 3 and outputs it to the data acquisition device 107.

  The data collection device 107 collects X-ray doses detected by individual X-ray detection elements of the X-ray detector 106, converts them into digital data, and sequentially outputs them to the image processing device 122 of the console 120 as transmitted X-ray data. To do.

  The image processing device 122 acquires the transmission X-ray data input from the data collection device 107, and performs preprocessing such as logarithmic conversion and sensitivity correction to create projection data necessary for image reconstruction. The image processing device 122 reconstructs an image such as a tomographic image using the generated projection data. The system control device 124 stores the image data reconstructed by the image processing device 122 in the storage device 123 and displays it on the display device 125.

  The system control device 124 is a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The system control device 124 performs body movement synchronization imaging processing according to the processing procedure shown in FIGS. Details of the body movement synchronization imaging process will be described later.

  The storage device 123 is a data recording device such as a hard disk, and stores programs, data, and the like for realizing the functions of the X-ray CT apparatus 1 in advance.

  The display device 125 includes a display device such as a liquid crystal panel and a CRT monitor, and a logic circuit for executing display processing in cooperation with the display device, and is connected to the system control device 124. The display device 125 displays the subject image output from the image processing device 122 and various information handled by the system control device 124.

  The input device 121 includes, for example, a keyboard, a pointing device such as a mouse, a numeric keypad, various switch buttons, and the like, and outputs various instructions and information input by an operator to the system control device 124. The operator operates the X-ray CT apparatus 1 interactively using the display device 125 and the input device 121. The input device 121 may be a touch panel type input device configured integrally with the display screen of the display device 125.

  The bed 105 includes a table on which a subject is placed, a vertical movement device, and a table driving device. The table height is raised and lowered under the control of the bed control device 109, and the body is moved back and forth in the body axis direction. Move left and right in the direction perpendicular to the axis and parallel to the floor (left and right direction). During imaging, the couch controller 109 moves the table at the couch moving speed and moving direction determined by the system controller 124.

  The first body motion sensor 31 and the second body motion sensor 32 are devices that measure data relating to the physiological movement of the subject. The movement of the subject includes, for example, thorax movement and diaphragm movement caused by respiration. When measuring movement due to respiration, respiration sensors are used as the body motion sensors 30 and 31.

  FIG. 2 is a diagram illustrating an example of attachment of the first and second body motion sensors 31 and 32. As shown in FIG. 2, the first body motion sensor 31 is attached to the first imaging region of the subject 3 and measures body motion waveform data in the first imaging region. The second body motion sensor 32 is attached to the second imaging region of the subject 3 and measures body motion waveform data at the second imaging region. Specifically, for example, the first body motion sensor 31 is attached to the chest of the subject 3 and measures body motion waveform data of thorax motion due to respiration. The second body motion sensor 32 is attached to the upper part of the abdomen of the subject 3 and measures body motion waveform data of diaphragm motion due to respiration.

  In the following description, as shown in FIG. 2, the body motion waveform of the chest is measured by the first body motion sensor 31, and the body motion waveform of the upper abdomen (diaphragm) is measured by the second body motion sensor 32. As will be described, the present invention may be directed to the movement of other parts. In addition, the subject 3 is carried into the scan gantry unit 100 from the head side, and imaging is performed in order from the head side. However, the present invention is not limited thereto, and imaging is performed in order from the leg side. Is also applicable. Further, the number of body motion sensors attached is not limited to two, but may be attached to three or more parts, and the body motion waveform data in each part may be measured. Each body motion sensor may measure the same type of body motion, or may measure another type of body motion. For example, a body motion sensor that detects different types of body motion waveforms, such as a breathing sensor on one side and a heart rate monitor on the other side, may be used.

  The first and second body motion sensors 31 and 32 sequentially send the measured body motion waveform data to the system control device 124, respectively. The system controller 124 controls imaging based on body motion waveform data (first body motion waveform data S and second body motion waveform data T) acquired from the first and second body motion sensors 31 and 32. Details of the shooting control method will be described later.

  3A shows an example of the first body motion waveform data T acquired from the first body motion sensor 31, and FIG. 3B shows the second body motion waveform data S acquired from the second body motion sensor 32. It is an example. In the graph showing the waveform in FIG. 3, the horizontal axis indicates time, and the vertical axis indicates the magnitude of movement. The first body motion waveform data T and the second body motion waveform data S have different motion cycles and motion magnitudes.

  In synchronous imaging with body motion, generally, when the upper peak Ta1, Ta2, Ta3, Ta4,... Of the measured body motion waveform is used as a trigger (inhalation phase trigger in the case of respiration), the waveform down-peak Tb1, There are cases where Tb2, Tb3, Tb4,... Are used as a trigger (expiratory phase trigger in the case of respiration). The user can arbitrarily set which phase is a trigger.

Next, with reference to FIG. 4, a functional configuration relating to body motion synchronization imaging according to the present invention will be described.
The system control device 124 includes a body motion waveform data acquisition unit 21, a combined waveform calculation unit 22, a synchronous imaging control unit 23, and a table position monitoring unit 26 as a functional configuration related to body motion synchronization imaging.

  The body motion waveform data acquisition unit 21 includes first body motion waveform data T and second body motion waveform data measured by the first body motion sensor 31 and the second body motion sensor 32 attached to each part of the subject 3. Get S. The acquired first and second body motion waveform data T and S are output to the combined waveform calculation unit 22 and the synchronous imaging control unit 23.

  The table position monitoring unit 26 monitors the current table position (shooting position) and outputs the shooting position information to the combined waveform calculation unit 22 and the synchronous shooting control unit 23.

  The composite waveform calculation unit 22 performs weighted addition of the body motion waveform data T and S acquired from the body motion sensors 31 and 32, and calculates a composite waveform at each imaging position. When calculating the composite waveform, the composite waveform calculation unit 22 uses the weighting coefficient corresponding to the relationship between the attachment positions of the body motion sensors 31 and 32 and the imaging positions, and uses the first and second body motion waveform data T, S is weighted.

Here, the weighting coefficient used when calculating the composite waveform will be described.
As shown in FIG. 5A, the distance between the mounting position of the first body motion sensor 31 and the mounting position of the second body motion sensor 32 is L, and the shooting position is the first body motion sensor 31 and the second body motion sensor. When the body motion sensor 32 is located at a position X away from the attachment position of the first body motion sensor 31, the weight coefficients W1 and W2 multiplied by the body motion waveform data T and S are, for example, FIG. It is desirable to calculate as shown in the weight coefficient data 41 (b) (the following formulas (1) and (2)).

  This weighting factor is for the case where the imaging progress direction proceeds from the attachment position side of the first body motion sensor 31 to the attachment position side of the second body motion sensor 32.

A composite waveform W calculated using such weighting factors W1 and W2 is shown in the middle of FIG.
The weighted composite waveform W is obtained by weight-adding the first body motion waveform data T and the second body motion waveform data S using the weighting factors W1 and W2 as shown in the above formulas (1) and (2). It is.

  The synchronous imaging control unit 23 monitors the table position (current imaging position) in the actual imaging, and if the current imaging position is between the first body motion sensor 31 and the second body motion sensor 32, the composite waveform Imaging is controlled so as to be synchronized with the combined waveform W calculated by the calculation unit 22. The synchronous imaging control unit 23 includes a scan speed calculation unit 24 and a trigger detection unit 25.

  The scan speed calculation unit 24 calculates the rotation speed (scan speed) of the turntable 102 at each imaging position so as to be synchronized with the wavelength of the composite waveform W calculated by the composite waveform calculation unit 22. The trigger detection unit 25 detects an imaging start trigger from the combined waveform W of the body motion waveform data T and S at the current imaging position in the main imaging. Whether the imaging start trigger is the inspiratory phase Wa or the expiratory phase Wb is set in advance via the input device 121 or the like. When the synchronous imaging control unit 23 detects the imaging start trigger of the composite waveform W, the synchronous imaging control unit 23 sends a control signal to the scan gantry unit 100 so as to start imaging at the scan speed calculated by the scan speed calculation unit 24.

  The X-ray control device 110 controls the power input to the X-ray source 101 according to the tube current and tube voltage instructed from the system control device 124 (synchronous imaging control unit 23). The gantry control device 108 controls the drive system of the turntable 102 according to the rotation speed calculated by the synchronous imaging control unit 23 to rotate the turntable 102. The bed control device 109 moves the bed 105 to a predetermined shooting start position, and moves the table of the bed 105 at a predetermined movement interval during shooting.

  In addition, in the actual photographing, when the current photographing position is not between the first body motion sensor 31 and the second body motion sensor 32, the synchronous photographing control unit 23 obtains a body obtained from a body motion sensor close to the photographing position. It is assumed that shooting is performed in synchronization with moving waveform data. For example, when the first and second body motion sensors 31 and 32 are attached to the subject 3 as shown in FIG. 2, the first body motion sensor from the imaging start position (the head side in the example of FIG. 2). The imaging section up to 31 performs imaging in synchronization with the first body motion waveform data T. In addition, in the imaging section from the second body motion sensor 32 to the imaging end position, imaging is performed in synchronization with the second body motion waveform data S.

Next, the operation of the X-ray CT apparatus 1 will be described with reference to FIGS.
The system control device 124 of the X-ray CT apparatus 1 executes body movement synchronization imaging processing according to the procedure shown in the flowcharts of FIGS. That is, the system control device 124 reads a program and data related to the body movement synchronization imaging process from the storage device 123, and executes a process based on the program and data.

  The X-ray CT apparatus 1 first measures the attachment positions of the body motion sensors 31 and 32 (step S101). For example, the attachment positions of the body motion sensors 31 and 32 are measured using a positioning laser marker or the like provided around the opening of the scan gantry unit 100. The system control device 124 holds the attachment positions of the measured body motion sensors 31 and 32 in a RAM or the like. In addition, the measuring method of the attachment position of the body motion sensors 31 and 32 is not limited to the illustrated method, Other methods may be used.

  Next, the X-ray CT apparatus 1 performs trigger setting for body motion synchronization imaging (step S102). In step S102, the system control device 124 sets which phase in the body motion waveform is to be a trigger. For example, the system control device 124 may display a setting screen that allows the display device 125 to select either the expiration phase or the inspiration phase as a trigger and allow the operator to select the setting screen.

  When an instruction to start actual photographing is input, the system control device 124 moves the table of the bed 105 to the photographing start position (step S103). The table position is constantly monitored by the table position monitoring unit 26 of the system control device 124.

  The system control device 124 determines whether or not the table position of the bed 105 has reached the first imaging region (step S104). The first imaging region is a range from the imaging start position to the attachment position of the first body motion sensor 31. When the table position reaches the imaging start position (first imaging region) (step S104; Yes), the system controller 124 monitors the first body motion waveform data measured by the first body motion sensor 31, and the step It waits for the detection of the phase set as the trigger set in S102. When the trigger phase of the first body motion waveform data T is detected (step S105), the system control device 124 performs imaging at a scan speed synchronized with the cycle of the first body motion waveform data T (step S106).

  Next, the system control device 124 moves the table of the bed 105 by a predetermined table movement distance (step S107), and determines whether or not the first imaging region is finished (step S108). When the imaging position is in the first imaging region (step S108; No), the process returns to step S105, and synchronous imaging based on the first body motion waveform data T is repeatedly performed. Steps S105 to S108 are repeated until the first imaging region is exceeded.

  When the first imaging region is exceeded (step S108; Yes), the imaging position is between the attachment position of the first body motion sensor 31 and the attachment position of the second body motion sensor 32. In this section, the system control device 124 acquires body motion waveform data T and S from the first and second body motion sensors 31 and 32, respectively (step S109). Then, the system controller 124 multiplies the body movement waveform data T and S by weighting factors W1 and W2 (see the above formulas (1) and (2)) corresponding to the current photographing position, and adds the weighting factors. A composite waveform is calculated (step S110). The system control device 124 calculates a scan speed according to the combined waveform W at the current imaging position (step S111).

  The system control device 124 waits for detection of the phase set as the trigger set in step S102. When the trigger phase is detected from the composite waveform data W calculated in step S110 (step S112), the system control device 124 performs imaging at a scan speed synchronized with the composite waveform data W (scan speed calculated in step S111) ( Step S113).

  Next, the system control device 124 moves the table of the bed 105 by a predetermined table moving distance (step S114), and determines whether or not the next imaging position has reached the second imaging region (step S115). If the imaging position is between the first imaging region and the second imaging region (step S115; No), the process returns to step S109.

  The system control device 124 acquires body motion waveform data T and S from each of the body motion sensors 31 and 32 even at the next imaging position, calculates a weighted composite waveform W corresponding to the imaging position, and corresponds to the weighted composite waveform W. Calculate the scan speed. When a phase that is a trigger for starting imaging is detected from the weighted combined waveform, imaging is performed at a scan speed synchronized with the cycle of the combined waveform data W. Thereafter, the system control device 124 moves the table of the bed 105 by a predetermined table moving distance and determines whether or not the second imaging region has been reached (steps S109 to S115). Steps S109 to S115 are repeated until the second imaging region is reached.

  When the second imaging region is reached (step S115; Yes), the imaging position is in the vicinity of the attachment position of the second body motion sensor 32. Turning now to FIG. In this section, the system control device 124 acquires the body motion waveform data S from the second body motion sensor 32 and performs synchronous imaging based on the body motion waveform data S. That is, when the system control device 124 detects the trigger phase set in step S102 from the second body motion waveform data S acquired from the second body motion sensor 32 (step S116), the cycle of the second body motion waveform data S is detected. Shooting is performed at a scanning speed synchronized with (step S117).

  Thereafter, the system control device 124 moves the table of the bed 105 by a predetermined table movement distance, and determines whether or not the second imaging region has ended (step S119). If the imaging position is in the second imaging region (step S119; No). The process returns to step S116. Steps S116 to S119 are repeated until the second imaging region is completed. When the second imaging region ends (step S119; Yes), a series of imaging processing ends.

  The transmitted X-ray data measured at each imaging position is sent to the image processing device 122 by the data collection device 107. The image processing device 122 acquires transmission X-ray data from the data acquisition device 107 and performs tomographic image reconstruction processing using the acquired transmission X-ray data. The system control device 124 stores the reconstructed image in the storage device 123 and displays it on the display device 125.

As described above, the X-ray CT apparatus 1 of the present invention acquires body motion waveform data T and S at each part from the body motion sensors 31 and 32 attached to a plurality of parts of the subject 3, and the body In the imaging section between the attachment positions of the motion sensors 31 and 32, a combined waveform W obtained by weighted addition of the body motion waveform data T and S is calculated, and imaging synchronized with the combined waveform is executed.
Accordingly, even when a plurality of parts are continuously photographed, optimal body motion synchronized photographing can be performed at each photographing position, so that an image with few motion artifacts can be continuously photographed. For example, if the imaging process of this embodiment is applied to imaging using a contrast agent, a plurality of sites can be continuously imaged with a single injection of the contrast agent, which is preferable.

  The synthesized waveform is weighted and added to each body motion waveform data T, S obtained by each body motion sensor 31, 32 using a weighting coefficient corresponding to the relationship between the attachment position of the body motion sensors 31, 32 and the imaging position. Is required. For this reason, the influence of the body movement at each photographing position can be acquired more accurately.

  In addition, although this Embodiment showed the example applied about the body motion which arises by respiration, body motion waveform data are not limited to the body motion which arises by respiration. For example, body motion data representing a heartbeat may be used. Also. The body motion data based on respiration and the body motion data based on heartbeat may be measured together, and the synchronized imaging according to the present embodiment may be performed based on the combined waveform data obtained by combining these.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS.

  Conventionally, in an examination using a contrast agent, a monitoring scan is performed, and the main imaging is performed at the timing when the contrast agent reaches a desired imaging region. In the monitoring scan, the X-ray CT apparatus 1 images the inflow site of the contrast agent with a dose lower than that in the main imaging, and reconstructs a tomographic image in real time using the projection data obtained by the monitoring scan. Then, it is determined whether or not the contrast agent has reached using a CT value (for example, an average CT value) in a predetermined monitoring region set in the reconstructed image. When the average CT value becomes larger than a predetermined threshold, the main scan is started after elapse of a predetermined time (time when the contrast medium is predicted to reach the imaging region).

  However, it is known that the average CT value of the image obtained by the monitoring scan varies depending on the respiration (body motion) of the subject. This variation is called CT value variation. In contrast imaging, because of this CT value variation, there is a risk that the average CT value in the monitoring area will exceed the threshold before the contrast agent reaches the imaging region sufficiently. For this reason, it is necessary to correct the influence of the CT value variation due to respiration (body motion) and accurately determine the start timing of the main imaging.

  Therefore, in the second embodiment, in the case where a monitoring scan is performed with a portion affected by body motion at a plurality of locations as a monitoring position, the contrast agent inflow determination is performed in consideration of the CT value variation caused by the body motion.

  Therefore, the X-ray CT apparatus 1 according to the second embodiment includes (A) combined waveform data W obtained by synthesizing body motion waveform data T and S measured at a plurality of locations and CT value fluctuations in advance of a monitoring scan. Seeking the relationship. In addition, (B) in the monitoring scan, an average CT value in the monitoring region is acquired together with the composite waveform indicating the body movement, and the CT value variation in each phase of the composite waveform is corrected by subtracting it from the actual average CT value. . Then, the contrast medium inflow determination is performed using the corrected average CT value.

First, the configuration of the X-ray CT apparatus 1 according to the second embodiment will be described.
The hardware configuration of the X-ray CT apparatus 1 of the second embodiment is the same as that of FIG. 1 (first embodiment). Similarly to the first embodiment, body motion sensors (first and second body motion sensors 31 and 32) are provided at a plurality of locations on the subject 3. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

The X-ray CT apparatus 1 of the second embodiment has a functional configuration shown in FIG. 9 in addition to the functional configuration of the X-ray CT apparatus 1 of the first embodiment shown in FIG.
In the second embodiment, the X-ray CT apparatus 1 performs a pre-scan prior to the monitoring scan, obtains CT value variation data, and stores it in the storage unit 51. For this reason, the image processing apparatus 122 is similar to the image processing apparatus 122a illustrated in FIG. 9A. The storage unit 51, the combined waveform acquisition unit 52, the reconstruction calculation unit 53, the CT value acquisition unit 54, and the variation data calculation unit. 55.

  The pre-scan is performed at a predetermined time interval at a low dose with respect to a position where the inflow of the contrast medium is monitored. In the pre-scan, the acquisition of body motion waveform data T and S from the body motion sensors 31 and 32 and the calculation of the composite waveform W by the composite waveform calculation unit 22 are simultaneously performed. The acquisition of the body motion waveform data T and S and the calculation of the composite waveform W are the same as in the first embodiment.

  The composite waveform acquisition unit 52 performs weighted addition of the first and second body motion waveform data T and S measured during the execution of the pre-scan according to the distance from the body motion sensors 31 and 32 to the contrast agent monitoring position. The composite waveform W is acquired and output to the fluctuation data calculation unit 55.

  The reconstruction calculation unit 53 reconstructs the tomographic image of each time phase using the transmission X-ray data obtained by the pre-scan.

  The CT value acquisition unit 54 acquires the CT value of each pixel in a predetermined ROI (hereinafter referred to as monitoring ROI) set in the reconstructed tomographic image, calculates the average CT value in the monitoring ROI, and changes the fluctuation data It outputs to the calculation part 55.

  The variation data calculation unit 55 obtains CT value variation data from the combined waveform W acquired by the combined waveform acquisition unit 52 and the average CT value in the monitoring ROI of each time phase acquired by the CT value acquisition unit 54. The CT value variation data is data indicating the relationship between the synthesized waveform and the variation of the average CT value, and specifically, data representing the variation of the CT value in each phase of the synthesized waveform. For example, the variation of the average CT value at the upper peak (inspiratory phase) of the composite waveform and the variation of the average CT value at the down peak (expiratory phase), respectively, the variation of the CT value for each phase of the composite waveform. Is required. The CT value variation is a difference value between the reference CT value and the average CT value with the most frequent CT value obtained in a state where no contrast medium is injected as a reference CT value.

  The CT value fluctuation data can be obtained from, for example, a CT value fluctuation graph as disclosed in FIG. 4 of JP-A-2000-287965. The CT value variation graph is a graph in which the horizontal axis is the time axis and the vertical axis is the average CT value in the monitoring ROI. The fluctuation data calculation unit 55 creates a CT value fluctuation graph from the average CT value in the monitoring ROI obtained by the pre-scan. The synthesized waveform is superimposed on the time axis of the CT value fluctuation graph, and the CT value fluctuation for each phase of the synthesized waveform is obtained.

  The CT value variation data calculated by the variation data calculation unit 55 is stored in the storage unit 51 and is referred to in the monitoring scan using the contrast agent.

  In the monitoring scan, the image processing apparatus 122 has the functional configuration of the image processing apparatus 122b shown in FIG. The image processing apparatus 122b includes a storage unit 51, a combined waveform acquisition unit 52, a reconstruction calculation unit 53, a CT value acquisition unit 54, a difference unit 56, and a contrast agent inflow determination unit 57.

The combined waveform acquisition unit 52 calculates a combined waveform W based on the first and second body motion waveform data T and S measured during the monitoring scan, and sends the combined waveform W to the difference unit 56.
The reconstruction calculation unit 53 reconstructs a tomographic image at each time phase using transmission X-ray data obtained by the monitoring scan. The CT value acquisition unit 54 acquires the CT value of each pixel in the monitoring ROI from the reconstructed tomographic image, and calculates the average CT value in the monitoring ROI. The CT value acquisition unit 54 sends the calculated average CT value (actual measurement value) to the difference unit 56.

  The difference unit 56 is measured during the monitoring scan, acquires the obtained combined waveform data W, and acquires the average CT value in the monitoring ROI of the image obtained by the monitoring scan. Further, the difference unit 56 acquires CT value variation data stored in the storage unit 51. Then, the difference unit 56 outputs a difference CT value obtained by subtracting the CT value variation obtained in advance from the average CT value (actually measured value) in the monitoring ROI obtained by the monitoring scan to the contrast agent inflow determination unit 57.

The contrast agent inflow determination unit 57 compares the difference CT value corrected for the CT value variation due to respiration (body movement) by the difference unit 56 with a predetermined threshold value. Thereby, it is determined whether or not the contrast medium has reached the monitoring ROI. The contrast agent inflow determination unit 57 notifies the determination result to the system control unit 124. When notified of the arrival of the contrast agent at the monitoring ROI, the system control unit 124 is timed in consideration of the arrival time of the contrast agent at the imaging region and body movement (obtained from each of the body movement sensors 31 and 32). An imaging start signal is sent to the scan gantry unit 100 in synchronization with the body motion waveform data T, S or their combined waveform data W).
The scan gantry unit 100 performs main imaging according to the imaging start signal from the system control unit 124.

  In the difference unit 56, when the CT value variation is subtracted from the average CT value (actually measured value) obtained during the monitoring scan, the difference is calculated at the same phase of the combined waveform W. From the relationship between the composite waveform obtained before contrast agent injection (pre-scan) and the CT value fluctuation, the effect of the CT value fluctuation is obtained on the phase of the composite waveform whose amplitude may fluctuate. Therefore, the correction is performed by subtracting the CT value variation in a specific phase from this relationship. As a result, the contrast agent inflow determination can be performed using the average CT value that does not vary due to respiration (body motion).

The operation of the X-ray CT apparatus 1 in the second embodiment will be described with reference to FIGS.
Before contrast imaging (before contrast agent injection), the system control device 124 of the X-ray CT apparatus 1 performs a pre-scan of the monitoring ROI according to the procedure shown in the flowchart of FIG. 10 to obtain CT value variation data. That is, the system control device 124 reads the program and data related to the pre-scan shown in FIG. 10 from the storage device 123, and executes processing based on the program and data.

  The X-ray CT apparatus 1 measures and holds the attachment positions of the body motion sensors 31 and 32 in advance (step S201). In addition, the timing of the body motion waveform data is set as the imaging start trigger (step S202). The processing of step S201 to step S202 is the same as that of step S101 to step S102 in the first embodiment (see FIG. 7).

  Thereafter, the system control device 124 moves the table of the bed 105 to the contrast agent monitoring position (step S203). In the present embodiment, it is assumed that the contrast medium monitoring position is between the attachment positions of the first and second body motion sensors 31 and 32.

  When the table position reaches the contrast medium monitoring position, the system control device 124 acquires the first and second body motion waveform data T and S measured by the body motion sensors 31 and 32, respectively (step S204). The system control device 124 calculates a weighted composite waveform W from the acquired first and second body motion waveform data T and S and the positional relationship between the sensor attachment position and the contrast agent monitoring position (step S205). The calculation of the composite waveform W is the same as in the first embodiment.

  The system controller 124 scans with a low-dose X-ray at the monitoring position (step S206). In the image processing apparatus 122a, the system control apparatus 124 acquires the transmission X-ray data detected in step S206, and reconstructs a tomographic image. The scan in step S206 and the image reconstruction process in step S207 are executed a plurality of times at predetermined time intervals. Also, the composite waveform calculation processing in steps S204 to S205 is performed simultaneously during scanning.

  The image processing device 122a calculates an average CT value in the monitoring ROI set in each time phase image reconstructed in step S207. Then, the average CT value of each time phase is graphed along the time axis. From the relationship between the CT value variation graph and the synthesized waveform W, the CT value variation for each phase of the synthesized waveform W is calculated (step S208). The image processing apparatus 122a stores the calculated CT value variation in each phase of the combined waveform W in the storage unit 51 as CT value variation data (step S209).

  At the time of contrast imaging (during contrast medium injection), the system control device 124 of the X-ray CT apparatus 1 executes a monitoring scan of the contrast medium monitoring position according to the procedure shown in the flowchart of FIG. An arrival determination process is performed. The system control device 124 reads the program and data related to the monitoring scan shown in FIG. 11 from the storage device 123, and executes processing based on the program and data.

  The system control device 124 of the X-ray CT apparatus 1 moves the table of the bed 105 to the contrast agent monitoring position (step S301). The contrast agent monitoring position is the same position as the pre-scan monitoring position in FIG.

  When the table position reaches the monitoring position, the system control device 124 acquires the first and second body motion waveform data T and S measured by the body motion sensors 31 and 32, respectively (step S302). The system control device 124 calculates a weighted composite waveform W from the acquired first and second body motion waveform data T and S, and the positional relationship between the sensor attachment position and the contrast agent monitoring position (step S303). The weighting coefficient used when calculating the composite waveform W is obtained from the relationship between the contrast agent monitoring position (imaging position) and the attachment position of the body motion sensor, as in the first embodiment.

  The system controller 124 starts the injection of the contrast agent and performs a monitoring scan on the contrast agent monitoring position (step S304). The surveillance scan should be performed at a low dose as in the pre-scan. In the image processing apparatus 122a, the system control apparatus 124 acquires transmission X-ray data detected by the monitoring scan in step S304, and reconstructs a tomographic image. The scan in step S304 and the image reconstruction process in step S305 are executed a plurality of times at predetermined time intervals. In addition, the body motion waveform data acquisition process and the composite waveform calculation process in steps S302 to S303 are performed simultaneously and continuously during the monitoring scan.

  The image processing device 122b calculates an average CT value in the monitoring ROI set in the image reconstructed in step S305 (step S306). The image processing device 122b subtracts the CT value variation corresponding to the phase of the combined waveform when the image is scanned from the calculated average CT value (step S307). The CT value variation for each phase is stored in advance in the storage unit 51.

  Based on the average CT value after the difference, the image processing device 122b determines whether the contrast agent has flowed into the contrast agent monitoring position (step S308). The determination as to whether or not the contrast agent has flowed is performed by, for example, comparison with a predetermined threshold value.

  When it is determined that the contrast agent has not yet reached the contrast agent monitoring position (step S309; No), the image processing device 122b repeats the processing of step S302 to step S308. That is, body motion waveform data acquisition, composite waveform calculation, monitoring scan is performed, the average CT value of the monitoring ROI in the reconstructed image is obtained, and the variation corresponding to the phase of the composite image at the time of scanning is differentiated, The inflow of the contrast agent is determined based on the CT value after the difference.

  When it is determined that the contrast medium has reached the contrast medium monitoring position (step S309; Yes), the image processing apparatus 122b notifies the system control apparatus 124 of the determination result. The system control device 124 predicts the time until the contrast agent reaches the imaging region, and outputs a start instruction for main imaging to the scan gantry unit 100 after the predicted time has elapsed (step S310).

  In the main photographing, the system control device 124 performs photographing in synchronism with the composite waveform W as in the photographing processing of the first embodiment.

As described above, the X-ray CT apparatus 1 according to the second embodiment uses the CT value obtained by subtracting the CT value variation caused by body movement (respiration) in the monitoring scan of the contrast agent in the monitoring ROI. Determine arrival of contrast agent.
Since contrast medium inflow is determined based on CT values that do not change due to body movement (breathing), it is not necessary to set a margin for CT value fluctuation in the threshold used for determination of contrast medium inflow, and accurate determination results Can be obtained. In addition, since an accurate determination result can be obtained, it is not necessary to perform test injection, and main imaging can be started immediately in response to the start of inflow of contrast medium.

  The preferred embodiment of the X-ray CT apparatus according to the present invention has been described above, but the present invention is not limited to the above-described embodiment. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

1 ......... X-ray CT apparatus 100 ......... Scan gantry section 101 ......... X-ray source 102 ......... Rotary panel 106 ......... X-ray detector 120 ......... Operation console 121 ......... Input device 122... Image processing device 123... Storage device 124... System control device 125... Display device 21 ....... Body motion waveform data acquisition unit 22. ... Synchronous imaging control unit 24 ………… Scan speed calculation unit 25 ………… Trigger detection unit 26 ………… Table position monitoring unit 31 ………… First body motion sensor 32 ………… Second body motion Sensor 41 ………… Weighting factor data 51 ………… Storage unit 52 ………… Composite waveform acquisition unit 53 ………… Reconstruction calculation unit 54 ………… CT value acquisition unit 55 ………… Variation data Calculation unit 56 ………… Difference unit 57 ………… Contrast medium inflow Tough T ............... first body motion waveform data S ............... second body motion waveform data W ............... weighted synthesized waveform

Claims (6)

An X-ray source for irradiating the subject with X-rays;
An X-ray detector arranged to face the X-ray source and detecting X-rays transmitted through the subject;
A rotary disk that is mounted with the X-ray source and the X-ray detector and rotates around the subject;
A body motion detector that is attached to a plurality of regions of the subject and detects body motion waveform data in each region;
Weighted addition of body movement waveform data in each part, a combined waveform calculation unit for calculating a combined waveform at each imaging position;
A synchronous imaging control unit that controls imaging in synchronization with the composite waveform calculated by the composite waveform calculation unit;
An image processing device for reconstructing an image using transmission X-ray data detected by the X-ray detector;
An X-ray CT apparatus comprising: The composite waveform calculation unit
The body motion waveform data obtained by each body motion detector is weighted and added using a weighting factor corresponding to the relationship between the attachment position of the body motion detector and the imaging position. X-ray CT system.   The X-ray CT apparatus according to claim 1, wherein the body motion detector is a respiration sensor that detects body motion due to respiration. The synchronous photographing control unit is configured to perform main photographing.
If the current imaging position is not between the mounting positions of the plurality of body motion detectors, the body motion waveform data obtained from the body motion detector close to the imaging position among the plurality of body motion detectors is synchronized. Take a picture,
The control is performed so that imaging is performed in synchronization with the composite waveform calculated by the composite waveform calculation unit when a current imaging position is between the attachment positions of the plurality of body motion detectors. The X-ray CT apparatus according to 1. In advance of contrast imaging, a variation data calculation unit that calculates in advance CT value variation data indicating the relationship between the combined waveform and the CT value variation at the contrast agent monitoring position;
A storage unit for holding the CT value variation data;
In a monitoring scan for monitoring the inflow of contrast agent, the composite waveform and CT value at the contrast agent monitoring position are acquired, and the CT value variation data is acquired from the storage unit, and the CT value variation is obtained from the acquired CT value. A difference part that is different, and
A contrast agent inflow determination unit that determines whether or not a contrast agent has flowed into the contrast medium monitoring position based on the difference CT value that has been differentiated by the difference unit;
The X-ray CT apparatus according to claim 1, further comprising: The control device of the X-ray CT apparatus is
Obtaining each body motion waveform data detected by a body motion detector attached to a plurality of parts of the subject;
A weighted addition of body motion waveform data at each acquired part, and calculating a composite waveform at each imaging position;
Controlling imaging in synchronization with the synthesized waveform;
An imaging method characterized by performing a process including:

Images