JP5677723B2 - X-ray computed tomography apparatus and imaging control program - Google Patents

Description

  The present invention relates to an X-ray computed tomography apparatus and an imaging control program.

  Conventionally, imaging using a contrast medium (contrast medium imaging) is performed in imaging by an X-ray computed tomography apparatus (hereinafter referred to as an X-ray CT apparatus, CT; Computed Tomography). Contrast agent imaging is a method in which a contrast medium is administered to a subject and then an X-ray is irradiated to image the affected area. In the CT image reconstructed from the data obtained by this, the CT image is specified by the contrast medium. Therefore, a highly accurate image diagnosis is possible.

  Here, in contrast agent imaging using an X-ray CT apparatus, it is important to start a scan for imaging CT images (hereinafter referred to as a main scan) when the contrast agent administered to the subject flows into the imaging region. is there. For this reason, a technique is known in which a main scan is automatically started by performing a preliminary scan (hereinafter referred to as “preliminary scan”) and detecting the inflow of contrast medium before the main scan (for example, Patent Documents). 1).

  In such a technique, a preliminary scan in which an X-ray having a lower dose than the main scan is exposed to the subject and a CT image are reconstructed from projection data obtained by the preliminary scan are repeatedly performed. Each time a CT image is reconstructed, a contrast value is determined by extracting a pixel value (CT value) in a region of interest (ROI), and a CT value in the region of interest is set in advance. When the time exceeds, the preliminary scan is stopped and the main scan is started. Here, in the preliminary scanning, “continuous scanning” in which scanning is performed by continuously irradiating X-rays until the CT value in the region of interest reaches the threshold value, and constant until the CT value in the region of interest reaches the threshold value. There is an “intermittent scan” in which X-rays are emitted at intervals to scan. Further, when the preliminary scan is executed, X-rays are usually irradiated with a thinner slice thickness along the body axis direction of the subject than when the main scan is executed.

  For example, in recent years, an X-ray detector in which a plurality of rows of X-ray detection elements are arranged along the body axis direction of a subject (for example, a surface detector in which X-ray detection elements are arranged over 160 mm in the body axis direction). Has entered the stage of practical application. When such an X-ray detector is used, at the time of executing the preliminary scan, the X-ray is irradiated only to the X-ray detection element array corresponding to a slice thickness (for example, 2 mm) thinner than that at the time of executing the main scan, and CT is performed. The image is reconstructed.

JP 2003-245275 A

  By the way, the above-described conventional technique has a problem in that it is necessary to repeatedly reconstruct a CT image at the time of performing a preliminary scan, so that the processing load required for analyzing the contrast agent concentration increases.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an X-ray computed tomography apparatus capable of reducing the processing load required for analyzing the contrast agent concentration and An object is to provide a shooting control program.

In order to solve the above-described problems and achieve the object, the present invention provides an X-ray tube that emits X-rays and a detection element array including a plurality of channels of X-ray detection elements. An X-ray detector that is arranged in a plurality of rows along the body axis direction and that is exposed from the X-ray tube and transmits the subject, and an X-ray detected by the X-ray detector The same data collected by the data collecting means in the data collecting means for collecting projection data for performing the back projection process and the preliminary photographing performed before the main photographing for photographing the subject to which the contrast medium is administered. Analyzing the projection data corresponding to the projection direction to determine whether or not the contrast agent concentration, which is the concentration of the contrast agent in the region of interest, is a predetermined condition; and It is determined that the predetermined conditions are met. At the time, the photographing transition control means for controlling to shift to the main photographing, and the projection data collected by the data collecting means after the transition from the preliminary photographing to the main photographing by the photographing transition control means is reversed. Image reconstruction means for reconstructing an image by performing projection processing.

In addition, the present invention is an imaging control for analyzing a contrast agent concentration, which is a concentration in a region of interest of a contrast agent administered to a subject by preliminary imaging, and starting main imaging when the contrast agent concentration reaches a predetermined condition. An imaging control program for causing a computer to execute a method, wherein an X-ray detector includes a plurality of rows of X-ray detector elements arranged along a body axis direction of the subject. A data collection procedure for collecting projection data for performing back projection processing from X-rays transmitted through the detected subject, and projection data corresponding to the same projection direction collected by the data collection procedure in the preliminary imaging And determining whether or not the contrast agent concentration, which is the concentration of the contrast agent in the region of interest, satisfies the predetermined condition, and the contrast agent according to the determination procedure When it is determined that the degree has become the predetermined condition, a shooting transition control procedure for controlling to shift to the main shooting, and after the transition from the preliminary shooting to the main shooting by the shooting shift control procedure, An image reconstruction procedure for reconstructing an image by performing a back projection process on the projection data collected by the data collection procedure is executed by a computer.

According to the present invention, it is possible to reduce the processing load required to analyze the contrast agent concentration.

FIG. 1 is a diagram for explaining the configuration of the X-ray CT apparatus in the present embodiment. FIG. 2 is a diagram for explaining data to be analyzed for the contrast agent concentration when the preliminary scan is executed. FIG. 3 is a diagram for explaining the configuration of the system control unit in the present embodiment. FIG. 4 is a diagram for explaining a region of interest and transition condition setting GUI. FIG. 5 is a diagram for explaining the contrast effect in the heart region and the contrast effect in the lung field region. FIG. 6 is a diagram for explaining the preliminary scan in the present embodiment. FIG. 7 is a diagram for explaining the threshold determination unit. FIG. 8 is a diagram for explaining the collimator adjustment unit. FIG. 9 is a diagram for explaining processing of the X-ray CT apparatus in the present embodiment. FIG. 10 is a diagram for explaining the first modification. FIG. 11 is a diagram for explaining a second modification.

  Exemplary embodiments of an X-ray computed tomography apparatus and an image reconstruction method according to the present invention will be described below in detail with reference to the accompanying drawings. In the following description, the X-ray computed tomography apparatus is abbreviated as an X-ray CT apparatus (CT; Computed Tomography).

  First, the structure of the X-ray CT apparatus in a present Example is demonstrated using FIG. FIG. 1 is a diagram for explaining the configuration of the X-ray CT apparatus in the present embodiment. As shown in FIG. 1, the X-ray CT apparatus in the present embodiment includes a gantry device 10, a couch device 20, and a console device 30.

  The gantry device 10 is a device that collects projection data by irradiating the subject P with X-rays. The gantry controller 11, the X-ray generator 12, the X-ray detector 13, the data collector 14, The rotating frame 15 and the gantry control unit 11 are included.

  The rotating frame 15 supports the X-ray generator 12 and the X-ray detector 13 so as to face each other with the subject P interposed therebetween, and is fast at a circular orbit centering on the subject P by a gantry driving unit 11c described later. It is a rotating annular frame.

  The X-ray generator 12 is an apparatus that irradiates the subject P with X-rays, and includes an X-ray tube 12a, a wedge 12b, and a collimator 12c.

  The X-ray tube 12a has a conical shape and a pyramid shape along the body axis direction (Z-axis direction shown in FIG. 1) of the subject P by a high voltage supplied from a high voltage generator 11a described later. It is a vacuum tube that generates an X-ray beam (cone beam) having a shape-like spread, and the cone beam is exposed to the subject P as the rotating frame 15 rotates.

  The wedge 12b is an X-ray filter for adjusting the X-ray dose of X-rays emitted from the X-ray tube 12a.

  The collimator 12c is a slit for narrowing down the X-ray irradiation range in which the X-ray dose is adjusted by the wedge 12b under the control of a collimator adjustment unit 11b described later.

  The X-ray detector 13 is a two-dimensional array type detector (surface detector) that detects X-ray intensity distribution data indicating the intensity distribution of X-rays irradiated from the X-ray generator 12 and transmitted through the subject P. A plurality of detection element arrays, which are X-ray detection elements arranged in the channel direction (Y-axis direction shown in FIG. 1), are arranged along the body axis direction (Z-axis direction shown in FIG. 1) of the subject P. . For example, in this embodiment, the X-ray detector 13 has detection element rows arranged in 320 rows along the body axis direction of the subject P, and a wide range of X-ray intensity distribution data transmitted through the subject P. To detect.

  The data acquisition unit 14 is a data acquisition system (DAS), and performs projection processing and A / D conversion processing on the X-ray intensity distribution data detected by the X-ray detector 13 to generate projection data. The generated projection data is transmitted to the console device 30 described later.

  The gantry control unit 11 is a device that controls the operations of the X-ray generation device 12 and the rotating frame 15 under the control of a scan control unit 33 described later, and includes a high voltage generation unit 11a, a collimator adjustment unit 11b, a gantry And a drive unit 11c.

  The high voltage generating unit 11 is a device that supplies a high voltage to the X-ray tube 12a, and the collimator adjusting unit 11b is adjusted from the X-ray generating device 12 to the subject P by adjusting the aperture and position of the collimator 12c. It is an apparatus for adjusting the irradiation range of X-rays to be irradiated. For example, the collimator adjustment unit 11b irradiates the subject P with X-rays by adjusting the aperture of the collimator 12c to narrow the X-ray irradiation range (cone angle).

  The gantry drive unit 11 c rotates the X-ray generator 12 and the X-ray detector 13 on a circular orbit around the subject P by rotating the rotary frame 15.

  The couch device 20 is a device on which the subject P is placed, and includes a couchtop 22 and a couch driving device 21. The top plate 22 is a plate on which the subject P is placed, and the couch driving device 21 moves the top plate 22 in the Z-axis direction under the control of the scan control unit 33 to be described later. P is moved into the rotating frame 15.

  The console device 30 is a device that accepts the operation of the X-ray CT apparatus by the operator and reconstructs a CT image representing the internal form of the subject P from the projection data collected by the gantry device 10. A display device 32, a scan control unit 33, a preprocessing unit 34, a projection data storage unit 35, an image reconstruction processing unit 36, an image storage unit 37, and a system control unit 38.

  The input device 31 includes a mouse and a keyboard used by the operator of the X-ray CT apparatus to input various instructions and various settings, and transfers instructions and setting information received from the operator to the system control unit 38.

  Specifically, when contrast medium imaging is performed using the X-ray CT apparatus according to the present embodiment, the input device 31 performs “preliminary scan for analyzing the concentration of contrast medium administered to the subject P”. Accepts the setting of the region of interest to be analyzed during execution. Further, the input device 31 accepts a setting of a transition condition for shifting from the preliminary scan to “a main scan for reconstructing the CT image of the subject P in which the contrast medium has flowed into the imaging region”. Note that the input device 31 may also receive a main scan end condition (for example, the main scan ends when the number of projection data collected by the gantry device 10 reaches a predetermined number), from the operator. Accept.

  The display device 32 is a monitor referred to by the operator, and displays a CT image or the like to the operator under the control of the system control unit 38 or accepts various settings from the operator via the input device 31. The GUI (Graphical User Interface) is displayed.

  Specifically, in the present embodiment, the display device 32 is a GUI for the operator to input the setting of the region of interest for analyzing the contrast agent concentration and the setting of the transition condition for shifting from the preliminary scan to the main scan. Is displayed.

  The preprocessing unit 34 performs correction processing such as logarithmic conversion processing, offset correction, sensitivity correction, and beam hardening correction on the projection data generated by the data collection unit 14.

  The projection data storage unit 35 stores the projection data corrected by the preprocessing unit 34. Hereinafter, “corrected projection data” stored in the projection data storage unit 35 is referred to as “corrected projection data”.

  The image reconstruction processing unit 36 reconstructs a CT image by performing back projection processing on the corrected projection data stored in the projection data storage unit 35.

  The image storage unit 37 stores the CT image reconstructed by the image reconstruction processing unit 36.

  The scan control unit 33 controls the operations of the gantry control unit 11, the data collection unit 14, and the bed driving device 21 under the system control unit 38. Specifically, the scan control unit 33 controls the gantry control unit 11 under the system control unit 38 to rotate the rotating frame 15 or to capture the X-ray tube 12a when imaging the subject P. X-rays are emitted from the light source, and the aperture and position of the collimator 12c are adjusted. More specifically, the scan control unit 33 controls the gantry control unit 11 under the system control unit 38 to control the preliminary scan and the main scan in contrast medium imaging, which will be described in detail later. .

  Further, the scan control unit 33 controls the amplification processing and A / D conversion processing of the data collection unit 14 under the system control unit 38. In addition, the scan control unit 33 moves the top 22 by controlling the bed driving device 21 during imaging of the subject P under the system control unit 38.

  The system control unit 38 performs overall control of the X-ray CT apparatus by controlling the operations of the gantry device 10, the couch device 20, and the console device 30. Specifically, the system control unit 39 controls the scan control unit 33 to execute the preliminary scan and the main scan, and collects projection data from the gantry device 10. Further, the system control unit 38 controls the image processing in the console device 30 by controlling the preprocessing unit 34 and the image reconstruction processing unit 36. Further, the system control unit 38 controls the display device 32 to display the corrected projection data stored in the projection data storage unit 35 and the CT image stored in the image storage unit 37.

  Here, the X-ray CT apparatus in this embodiment analyzes the concentration (contrast agent concentration) in the region of interest of the contrast agent administered to the subject by the preliminary scan, and the main scan is performed when the contrast agent concentration becomes the setting condition. The main feature is that it is possible to reduce the processing load required to analyze the contrast agent concentration. Hereinafter, this main feature will be described with reference to FIGS. FIG. 2 is a diagram for explaining data to be analyzed for the contrast medium concentration during the preliminary scan, and FIG. 3 is a diagram for explaining the configuration of the system control unit in the present embodiment. 4 is a diagram for explaining a GUI for setting a region of interest and a transition condition, and FIG. 5 is a diagram for explaining a contrast effect in a heart region and a contrast effect in a lung field region. These are the figures for demonstrating the preliminary scan in a present Example, FIG. 7 is a figure for demonstrating a threshold value determination part, FIG. 8 is a figure for demonstrating a collimator adjustment part.

  First, the X-ray CT apparatus according to the present embodiment uses the corrected projection data stored in the projection data storage unit 35 as data to be analyzed for the contrast agent concentration when the preliminary scan is executed. Specifically, the X-ray CT apparatus in the present embodiment analyzes the contrast agent concentration using corrected projection data corresponding to the same projection direction. More specifically, the X-ray CT apparatus in the present embodiment is a correction generated from detection data of X-rays exposed when the X-ray tube 12a is in a specific phase when the rotary frame 15 is rotated. The contrast agent concentration is analyzed using the already-projected data.

  For example, as shown in FIG. 2, the X-ray CT apparatus in the present embodiment detects X-rays detected by the X-ray detector 13 when the X-ray tube 12a emits X-rays from the back side of the subject P. Then, the contrast agent concentration is analyzed using the corrected projection data generated by the data collection unit 14 and the preprocessing unit 34. Here, since the X-ray detector 13 is a surface detector having a width along the body axis direction of the subject P, the corrected projection data has a wide range in the body axis direction as shown in FIG. The contrast state of the subject P can be confirmed.

  Therefore, in order to analyze the contrast agent concentration using the corrected projection data, the system control unit 38 in the present embodiment, as shown in FIG. 3, displays a display control unit 38a, a setting information storage unit 38b, and a threshold determination. A unit 38c and a scan transition control unit 38d.

  The display control unit 38b displays the GUI for the operator to input the setting of the region of interest for analyzing the contrast agent concentration in the preliminary scan and the setting of the transition condition for shifting from the preliminary scan to the main scan. Control to display with. For example, the display device 32 displays a “region of interest and transition condition setting GUI” as shown in FIG. 4 under the control of the display control unit 38b.

  Here, in the “region of interest and transition condition setting GUI”, a “reference image display region” for displaying corrected projection data (reference image) referred to in order to receive the region of interest from the operator (see FIG. 4 (see (1)), there is a “transition condition setting area” (see (2) in FIG. 4) for accepting the setting of the transition condition from the operator, and the corrected projection data generated after the start of the preliminary scan There is a “plot display area” (see (3) in FIG. 4) that displays a plot of the average luminance value in the region of interest.

  For example, the operator has corrected the reference image by moving the X-ray tube 12b at the position shown in FIG. 2 and exposing the subject P to the subject P before administration of the contrast agent. Projection data is generated. Then, the display control unit 38a reads the corrected projection data generated as the reference image from the projection data storage unit 35 and displays it in the “reference image display area”.

  Alternatively, the operator images the subject P and reconstructs the CT image before administering the contrast agent. The display control unit 38a then uses a specific phase (for example, a phase in which the X-ray tube 12a is behind the subject P) in the corrected projection data used when the CT image is reconstructed. The generated corrected projection data is read from the projection data storage unit 35 and displayed in the “reference image display area”.

  Then, the operator refers to the reference image displayed in the “reference image display area”, and uses the input device 31 (for example, a mouse) to set a region of interest for observing the contrast effect. For example, when the blood flow dynamics in the heart and lung fields are to be observed, the operator sets a region of interest “ROI-1” for observing the contrast effect of the heart region as shown in FIG. A region of interest “ROI-2” for observing the contrast effect of the field region is set.

  Then, the operator who sets the region of interest sets the transition condition in the “transition condition setting region”.

  Here, in the present embodiment, a value based on the luminance value of the corrected projection data sequentially generated along the time series in the preliminary scan is used as a value for analyzing the contrast agent concentration. For example, when the average value (average luminance value) of all the luminance values in the region of interest of the corrected projection data is used as a value for analyzing the contrast effect, the contrast effect in the heart region (ROI-1) and the lung field region ( The contrast effect of ROI-2) is considered to be expressed as a change in average luminance value shown in FIG. That is, the contrast agent reaches the lung field after passing through the right heart system, and then passes through the left heart system. Therefore, the average luminance value of the heart region (ROI-1) gradually increases from the right heart system passage to the left heart system passage (see the solid line in FIG. 5). Further, the average luminance value of the lung field region (ROI-2) rapidly increases when reaching the lung field (see the dotted line in FIG. 5).

  For this reason, for example, in the “transition condition setting area”, as shown in FIG. 4, “text” is input in order to input a threshold value as a transition condition for each of the set regions of interest (ROI-1 and ROI-2). Box "is arranged. In addition, as shown in FIG. 4, whether “average luminance value” or “average luminance value change (change in average luminance value per unit time)” is used as the threshold for the “transition condition setting area”. A “radio button” for selecting is arranged. Further, as shown in FIG. 4, a “text box” for inputting a delay time is arranged in the “migration condition setting area”.

  For example, in consideration of the difference between the average luminance value of the heart region and the average luminance value of the lung field region and the degree of increase, in the example shown in FIG. : 100 ”,“ threshold: 110 ”is set for the average luminance value in ROI-2, and the delay time and“ 0 second ”are set.

  Accordingly, in the example shown in FIG. 4, in the preliminary scan executed by administering the contrast medium to the subject P, the “specific phase corrected projection data sequentially generated in time series” in ROI-1 From the time when the average luminance value becomes “100” or higher, or from the time when the average luminance value in ROI-2 of “specific phase-corrected projection data sequentially generated in time series” becomes “200” or higher. This means that the transition condition “immediately shift to main scan” is set. When the delay time is set as “10 seconds”, “at the time when“ 10 seconds ”has elapsed since either of the average luminance values in ROI-1 or ROI-2 became equal to or greater than the corresponding threshold value. Thus, the transition condition “transition to main scan” is set.

  When the operator selects “change in average luminance value” and sets a threshold value for each of ROI-1 and ROI-2, the transition condition is either “change in average luminance value in ROI-1 or ROI-2” When the set delay time has elapsed from when the current value becomes equal to or greater than the corresponding threshold value, the process proceeds to “main scan”.

  Note that the transition condition using the threshold is “the main scan at the time when the set delay time has elapsed since both the values based on the luminance values in ROI-1 and ROI-2 became equal to or greater than the corresponding threshold. It may be a case of “transition to”.

  In this embodiment, the case where the average luminance value or the average luminance value change is used as the value based on the luminance value of the corrected projection data in order to analyze the contrast effect has been described. However, the present invention is not limited to this. For example, the maximum luminance value in the region of interest or the maximum luminance value change in the region of interest may be used as a value based on the luminance value of the corrected projection data. In this case, the operator sets a maximum brightness value and a threshold value corresponding to the maximum brightness value change.

  In this embodiment, the case where two regions of interest for analyzing the contrast effect are set has been described. However, the present invention is not limited to this. For example, when only one region of interest is set. Alternatively, three or more regions of interest may be set. In addition, the threshold may be set for only a part of the region of interest even when a plurality of regions of interest are set.

  The display control unit 38a stores the information on the region of interest (specifically, the coordinate data on the corrected projection data) and the transition condition information set by the operator in the setting information storage unit 38b shown in FIG. .

  The setting information storage unit 38b stores the information on the above-described region of interest and information on the transition condition (average luminance value or threshold value set for average luminance value change). Further, the setting information storage unit 38b also receives and stores the specific phase (described above) of the X-ray tube 12a for setting corrected projection data to be analyzed in the preliminary scan from the operator via the input device 31. To do. For example, in the present embodiment, the setting information storage unit 38b stores the phase on the back side of the subject P due to the rotation of the X-ray tube 12a as the specific phase.

  After the region of interest and the transition condition are stored in the setting information storage unit 38b, upon receiving a preliminary scan start instruction from the operator via the input device 31, the system control unit 38 controls the scan control unit 33. The preliminary scanning is started by the gantry device 10.

  Here, as shown in FIG. 6, the high voltage generator 11 a emits X-rays to the X-ray tube 12 a only when the X-ray tube 12 a reaches a specific phase due to the rotation of the rotating frame 15. Supply high voltage to generate. That is, in the preliminary scan in the present embodiment, as shown in FIG. 6, only when the X-ray tube 12a is in a specific phase (back side) due to the rotation of the rotary frame 15 (clockwise in the figure), X-rays are emitted. As a result, the X-ray detector 13 detects X-rays only when the X-ray tube 12a reaches a specific phase during the preliminary scan, and the data collection unit 14 generates only projection data at the specific phase. Then, the preprocessing unit 34 generates only the corrected projection data in the specific phase and stores it in the projection data storage unit 35.

  Returning to FIG. 3, the threshold determination unit 38 c reads “corrected projection data in a specific phase” stored in the projection data storage unit 35. Then, the threshold determination unit 38c identifies the region of interest of “corrected projection data in a specific phase” with reference to the coordinates of the region of interest stored in the setting information storage unit 38b, and is based on the luminance value of the identified region of interest. Calculate the value.

For example, as illustrated in FIG. 7A, the threshold determination unit 38 c generates “corrected in a specific phase” that is generated by detecting the X-rays that the X-ray tube 12 a has exposed from the back side of the subject P. In “projection data”, “average luminance value of ROI-1” and “average luminance value of ROI-2” are calculated.
The display control unit 38a displays “corrected projection data in a specific phase” in the above-described “reference image display area” (see (1) in FIG. 4). Further, the display control unit 38a displays the average luminance value calculated by the threshold determination unit 38c in the “plot display area” (see (3) in FIG. 4).

  Then, the threshold determination unit 38c determines whether or not the average luminance value has become a transition condition.

  That is, the threshold determination unit 38c refers to the transition conditions (“ROI-1 threshold: 100, ROI-2 threshold: 110, delay time: 0 seconds”) stored in the setting information storage unit 38b. To do. For example, as illustrated in FIG. 7B, the threshold determination unit 38c sets the average luminance value of ROI-2 to “threshold: 110” before the average luminance value of ROI-1 reaches “threshold: 100”. Is determined as the time when the transition condition is met.

  Returning to FIG. 3, the scan shift control unit 38 d controls the scan control unit 33 to shift to the main scan when it is determined by the threshold determination unit 38 c that the shift condition is satisfied. Specifically, the scan control unit 33 controls the gantry control unit 11 so that the X-ray exposure from the X-ray tube 12a is executed even in a phase other than the specific phase when the main scan is executed.

  The scan control unit 33 accepts setting information input by the operator using the input device 31 via the system control unit 38, and adjusts the opening degree and position of the collimator 12c in the preliminary scan and the main scan. Alternatively, the collimator adjustment unit 11b may be controlled. For example, the operator sets the X-ray irradiation range of the preliminary scan with respect to the center position (Mid plane) in the body axis direction in the imaging region of the main scan.

  The collimator adjusting unit 11b described above adjusts the collimator 12c, and as shown in FIG. 8A, the X-ray dose is adjusted from the focus of the X-ray tube 12a and the X-ray dose is adjusted by the wedge 12b. The X-ray detection range by the X-ray detector 13 is adjusted by adjusting the irradiation range. That is, the operator sets the X-ray detection range in the body axis direction of the X-ray detector 13 in the preliminary scan by setting the X-ray irradiation range in the preliminary scan.

  For example, when the operator sets the X-ray irradiation range to be the same in the preliminary scan and the main scan (see FIG. 8B), the collimator adjustment unit 11b does not perform the adjustment process of the collimator 12c. .

  Further, when the operator sets the X-ray irradiation range of the preliminary scan to be narrowed around the mid plane in the preliminary scan and the main scan (see FIG. 8C), the collimator adjustment unit 11b While the position of the collimator 12c is fixed, the opening degree of the collimator 12c is adjusted to be small when the preliminary scan is executed, and the opening degree of the collimator 12c is adjusted to be large when the main scan is executed. As a result, the X-ray detector 13 causes the X-ray detection range to be, for example, 120 columns when the preliminary scan is executed, and 320 columns when the main scan is executed.

  In addition, when the operator sets the X-ray irradiation range of the preliminary scan to be narrowed and moves around the mid plane in the preliminary scan and the main scan (see FIG. 8D), the collimator The adjustment unit 11b adjusts the collimator 12c so that the opening degree of the collimator 12c is reduced and the position of the collimator 12c is moved from the mid plane during the preliminary scan. Further, the collimator adjustment unit 11b increases the opening degree of the collimator 12c during the main scan execution and adjusts the position of the collimator 12c to return to the mid plane. Accordingly, the X-ray detection range by the X-ray detector 13 is, for example, 120 columns for only one of the mid planes when the preliminary scan is executed, and 320 columns when the main scan is executed.

  Then, at the time of executing the main scan, the image reconstruction processing unit 36 reconstructs a CT image by back projection processing from corrected projection data stored in the projection data storage unit 35 from all projection directions, and reconstructs the CT image. Is stored in the image storage unit 37. The display control unit 38a controls the display device 32 to display the CT image stored in the image storage unit 37.

  Next, a processing flow of the X-ray CT apparatus in the present embodiment will be described with reference to FIG. FIG. 9 is a diagram for explaining processing of the X-ray CT apparatus in the present embodiment.

  As shown in FIG. 9, the X-ray CT apparatus according to the present embodiment starts the preliminary scan after receiving from the operator the region of interest to be analyzed for the contrast agent concentration and the transition condition for shifting to the main scan. When receiving the request (Yes at Step S101), the scan control unit 33 starts a preliminary scan under the control of the system control unit 38 (Step S102).

  Then, under the control of the scan control unit 33, the X-ray tube 12a emits X-rays at a specific phase, and the preprocessing unit 34 generates corrected projection data at the specific phase (step S103).

  Subsequently, the threshold determination unit 38c calculates an average luminance value in the region of interest of the corrected projection data (step S104), and determines whether or not the calculated average luminance value becomes a transition condition (step S105).

  If the average luminance value is not the transition condition (No at Step S105), the process returns to Step S103, and the preliminary scan is continued under the control of the scan control unit 33.

  On the other hand, when the average luminance value becomes the transition condition (Yes at Step S105), the scan transition control unit 38d performs control so as to shift to the main scan via the scan control unit 33 (Step S106). When the delay time is set, the threshold value determination unit 38c determines the time point when the set delay time has elapsed since the average luminance value reaches the threshold value as the time point when the transition condition is met.

  Then, the scan transition control unit 38d determines whether or not the main scan end condition is satisfied (step S107).

  If the main scan end condition is not satisfied (No at Step S107), the scan transition control unit 38d controls to continue the main scan and waits until a main scan end request is received.

  On the other hand, the scan transition control unit 38d ends the process when the end condition of the main scan is reached (Yes at Step S107).

  As described above, in the present embodiment, the display control unit 38a sets the GUI for setting “the region of interest for analyzing the contrast agent concentration” and “the transition condition for shifting to the main scan” to the display device 32. The information on the region of interest and the transition condition input by the operator is displayed and stored in the setting information storage unit 38b. Then, at the time of performing the preliminary scan, the threshold determination unit 38c calculates an average luminance value in the region of interest of the “specific phase corrected projection data” generated at the time of performing the preliminary scan, and the projection data storage unit 35 stores it. It is determined whether or not the transition condition is met. Then, the scan shift control unit 38d controls the scan control unit 33 to shift to the main scan when the shift condition is met.

  Therefore, in this embodiment, the preliminary scan can be executed with the “corrected projection data” without reconstructing the CT image, and, as described above, the processing load required for analyzing the contrast agent concentration Can be reduced.

  Further, in this embodiment, since X-rays are irradiated only in a specific phase in the preliminary scan, the exposure amount can be reduced, and the back side having low sensitivity to exposure is directed to the X-ray irradiation direction. The influence of exposure on the specimen P can be reduced.

  Further, in the preliminary scan for reconstructing a conventional CT image, X-rays are continuously emitted to a thin slice. In this embodiment, the body axis is detected by the X-ray detector 13 as a surface detector. Since the preliminary scan is performed in a wide range along the direction, the X-ray exposure to the subject P can be dispersed.

  Also, in the conventional preliminary scan and main scan, if the center position of the region of interest for analyzing the contrast agent concentration in the preliminary scan is different from the center position of the imaging region of the main scan, the top 22 needs to be moved. Therefore, there are cases where it is not possible to quickly shift to the main scan. However, in this embodiment, the corrected projection data generated by using the X-ray detector 13 as a surface detector is set as an analysis target, so that the contrast state can be set in a wide range in the body axis direction of the subject P. In addition, since it is not necessary to move the positions of the preliminary scan, the main scan, and the subject P, it is possible to quickly move to the main scan.

  Note that the scan control unit 33 may control the bed driving control device 21 so that the position of the top plate 22 cannot be moved at the time of shifting to the main scan. This also allows a quick transition from the preliminary scan to the main scan.

  Further, in this embodiment, since the contrast effect can be analyzed in a wide range in the body axis direction, the opening degree and position of the collimator 12c are adjusted by the preliminary scan and the main scan to reduce the exposure to the subject P. In addition, the contrast agent concentration analysis region can be set with a high degree of freedom.

  In this embodiment, since CT reconstruction is not performed, the contrast agent concentration in the region of interest can be quickly analyzed. For example, the operator needs to set the delay time by adjusting the threshold value. Disappears.

  In the above-described embodiment, the case where there is one pair of the X-ray tube and the X-ray detector has been described. However, the present invention is not limited to this, and the X-ray tube and the X-ray detector are not limited thereto. There may be a plurality of pairs. This will be described with reference to FIG. In addition, FIG. 10 is a figure for demonstrating a 1st modification.

  For example, as shown in FIG. 10A, the X-ray CT apparatus has two pairs of X-ray tube and X-ray detector (system 1 and system 2), and the specific phase is the back of the subject P. When the rotation frame rotates 90 degrees clockwise after the system 1 X-ray tube reaches a specific phase, the system 2 X-ray tube enters a specific phase.

  Therefore, in the first modification, as shown in FIG. 10B, control is performed so that X-rays are exposed when the X-ray tubes of the system 1 and the system 2 are in a specific phase. . As a result, the number of corrected projection data generated per unit time can be increased, and as a result, changes in the contrast agent concentration along the time axis can be analyzed in more detail.

  In the above-described embodiment, the case where the contrast medium concentration is analyzed using one corrected projection data has been described. However, the present invention is not limited to this, and a plurality of corrected projection data is used. It may be a case where the contrast agent concentration is analyzed. This will be described with reference to FIG. In addition, FIG. 11 is a figure for demonstrating a 2nd modification.

  In the second modification, addition data obtained by adding a plurality of corrected projection data of a specific phase generated by the preprocessing unit 34 in a predetermined period is set as an analysis target for analyzing the contrast agent concentration. Specifically, in the second modification, addition data obtained by adding “a plurality of consecutive corrected projection data near a specific phase” is set as an analysis target for analyzing the contrast agent concentration. For example, when one rotation of the rotary frame 15 is divided into “1000” and the specific phase is “position: 500”, in the second modified example, as shown in FIG. And 501 ”, the added data obtained by adding the“ three corrected projection data in the vicinity of the specific phase ”generated by the preprocessing unit 34 by the X-ray exposure is analyzed to analyze the contrast agent concentration. set to target. That is, in the second modification, the addition data is set as an analysis target, whereby the resolution as an image can be improved, and the contrast agent concentration can be analyzed more accurately. In addition, since it is not necessary to change the tube current significantly between the preliminary scan and the main scan, X-ray control in the X-ray CT apparatus can be simplified. Note that the number of corrected projection data added in the second modification can be arbitrarily changed according to the rotation speed of the rotating frame 15 as long as it is a period in which no blur due to the movement of the subject P occurs. .

  In the above-described embodiment, the case where the contrast medium concentration is analyzed using the corrected projection data generated by the preprocessing unit 34 has been described. However, the present invention is not limited to this, and for example, the channel If the projection data has been subjected to the sensitivity correction processing in between, the contrast agent concentration may be analyzed using the projection data generated by the data collection unit 14.

  In the above-described embodiment, the case where the number of detection element rows of the X-ray detector 13 is 320 has been described. However, the present invention can be applied to the X-ray detector 13 as a surface detector having a width capable of collecting contrast effect information along the body axis direction.

  As described above, the X-ray computed tomography apparatus and the imaging control program according to the present invention analyze the contrast agent concentration which is the concentration in the region of interest of the contrast agent administered to the subject by the preliminary scan, and the contrast agent concentration is predetermined. This is useful when starting a main scan when the above condition is met, and is particularly suitable for reducing the processing load required to analyze the contrast agent concentration.

DESCRIPTION OF SYMBOLS 10 Mount apparatus 11 Mount control part 11a High voltage generation part 11b Collimator adjustment part 11c Mount drive part 12 X-ray generator 12a X-ray tube 12b Wedge 12c Collimator 13 X-ray detector 14 Data collection part 20 Bed apparatus 21 Bed drive apparatus 22 Top plate 30 Console device 31 Input device 32 Display device 33 Scan control unit 34 Preprocessing unit 35 Projection data storage unit 36 Image reconstruction processing unit 37 Image storage unit 38 System control unit 38a Display control unit 38b Setting information storage unit 38c Threshold Judgment unit 38d Scan transfer control unit

Claims (9)

An X-ray tube that emits X-rays;
A plurality of rows of X-ray detection elements arranged for X-ray detection elements are arranged along the body axis direction of the subject, and X-rays that have been exposed from the X-ray tube and transmitted through the subject are detected. An X-ray detector to detect;
Data collection means for collecting projection data for performing a back projection process from the X-rays detected by the X-ray detector;
In preliminary imaging performed before the main imaging for imaging a subject to which a contrast medium has been administered , the X-ray tube is in a specific phase while the X-ray tube and the X-ray detector are rotating. X-ray control means for controlling to emit X-rays from the X-ray tube at the time,
In the preliminary imaging, the determination unit that analyzes the projection data in the specific phase collected by the data collection unit and determines whether or not the contrast agent concentration that is the concentration of the contrast agent in the region of interest is a predetermined condition. When,
Photographing transition control means for controlling to shift to the main photographing at a time when the contrast medium concentration is determined to be the predetermined condition by the judging means;
Image reconstructing means for reconstructing an image by backprojecting the projection data collected by the data collecting means after the photographing transition control means has shifted from the preliminary photographing to the main photographing;
An X-ray computed tomography apparatus comprising: When having a plurality of tube detector pairs that are pairs of the X-ray tube and the X-ray detector,
In the preliminary imaging, the X-ray control means is configured to emit X-rays from the X-ray tube when any of the X-ray tubes of the tube detector pair reaches the specific phase. The X-ray computed tomography apparatus according to claim 1 , wherein the X-ray computed tomography apparatus is controlled. The determination unit calculates a value based on a luminance value of the projection data in the region of interest as a value corresponding to the contrast agent concentration, and compares the calculated value with a threshold set as the predetermined condition. it is, X-rays computed tomography system according to claim 1 or 2, wherein the contrast agent concentration and judging whether or not a predetermined condition. The determination means calculates, as a value based on the luminance value, an average value of luminance values of the projection data in the region of interest, a maximum value of luminance values, an average value of luminance value changes, or a maximum value of luminance value changes. The X-ray computed tomography apparatus according to claim 3 . When a plurality of the regions of interest are set,
The determination unit compares a value based on a luminance value of the projection data in each of a plurality of regions of interest with a threshold set in each of the plurality of regions of interest as the predetermined condition. The X-ray computed tomography apparatus according to 3 or 4 . The X-ray control means controls the X-ray tube to emit X-rays from the X-ray tube in a predetermined period from the time when the X-ray tube is close to the specific phase,
Said determining means, X-rays according to any one of claims 1-5, characterized in that analyzing the summed data obtained by adding a plurality of projection data acquired in the predetermined period by the data collecting means Computer tomography equipment. Control is performed to change the aperture and / or position of a collimator that narrows down the X-rays exposed from the X-ray tube when the imaging transition control means shifts from the preliminary imaging to the main imaging. X-ray computer tomography apparatus according to any one of claims 1-6, characterized in further comprising a collimator control means. At the time when the transition to the main photographing from the preliminary imaging by the imaging transfer controlling means, according to claim 1-7, characterized in that the subject is further provided with a couch control unit to unmovable position of the bed to be lying An X-ray computed tomography apparatus according to any one of the above. Analyzing the contrast agent concentration, which is the concentration in the region of interest of the contrast agent administered to the subject by preliminary imaging, and causing the computer to execute an imaging control method for starting the main imaging when the contrast agent concentration reaches a predetermined condition A shooting control program,
A detection element array in which X-ray detection elements for a plurality of channels are arranged is reversed from the X-ray transmitted through the subject detected by the X-ray detector arranged in a plurality of rows along the body axis direction of the subject. A data collection procedure for collecting projection data for performing projection processing;
In the preliminary imaging, when the X-ray tube enters a specific phase during the rotation of the X-ray tube and the X-ray detector, the X-ray tube is exposed to X-rays. X-ray control procedure for controlling to radiate,
In the preliminary imaging, the projection data at the specific phase collected by the data collection procedure is analyzed to determine whether or not the contrast agent concentration that is the concentration of the contrast agent in the region of interest is the predetermined condition. Procedure and
An imaging transition control procedure for controlling to shift to the main imaging when it is determined by the determination procedure that the contrast medium concentration has reached the predetermined condition;
An image reconstruction procedure for reconstructing an image by performing a back projection process on the projection data collected by the data collection procedure after shifting from the preliminary photographing to the main photographing by the photographing transition control procedure;
An imaging control program that causes a computer to execute the above.

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