JP5209175B2 - X-ray computed tomography apparatus and image processing apparatus - Google Patents

Description

  The present invention relates to an X-ray computed tomography apparatus and an image processing apparatus that generate tomographic image data based on projection data acquired by scanning a subject with X-rays.

  In recent X-ray computed tomography apparatuses, the practical use of volume scan (also called cone beam scan) accompanying the increase in the number of rows of helical scans or X-ray detectors has made it possible to collect a wide range of data in a short time. I came. In such a situation, instead of performing scanning with a scan range corresponding to a preset reconstruction range as in the past, there is a usage in which a reconstruction condition and a reconstruction range are set after scanning and an image is reconstructed. It is thought that it will increase. In this way, the process of setting the reconstruction condition and reconstruction range after scanning and reconstructing the image is scanned with the preset reconstruction condition and reconstruction range, and immediately reconstructing the image immediately after that. This is referred to as batch reconstruction processing. In the batch reconstruction process, an axial image is displayed together with a scanogram as shown in FIG. 8 in order to set a reconstruction range. A range in the body axis direction is designated on the scanogram, and a range in two directions orthogonal to the body axis is designated on the axial image.

  The scanogram is a projected image and the resolution is low, so the tissue structure is difficult to understand. Therefore, in order to finally determine the range in the body axis direction, confirmation is made with an axial image. The operator turns the axial image, that is, moves the cross-sectional position of the axial image along the body axis, confirms the tissue structure in detail on the axial image, and finally determines the range in the body axis direction. In this method, the operability is very poor, and it takes time to set the reconstruction range.

  An object of the present invention is to improve the operability of setting a reconstruction range for batch reconstruction processing in an X-ray computed tomography apparatus and an image processing apparatus.

One aspect of the invention, a scanning unit for scanning the three-dimensional region of the subject with X-ray, a storage unit for storing the projection data acquired by the scanning, the three-dimensional based on the stored projection data A volume data reconstruction unit that reconstructs volume data corresponding to a region, a cross-sectional image data generation unit that generates cross-sectional image data related to a cross section in a plurality of directions from the volume data, and the reconstructing range of the cross-sectional image data. A tomographic image data corresponding to the reconstruction range represented by the graphic element is reproduced based on the stored projection data, a display unit for displaying the graphic element together with the display unit, an operation unit for operating the graphic element, and the stored projection data. An X-ray computed tomography apparatus comprising a tomographic image reconstruction unit .

  ADVANTAGE OF THE INVENTION According to this invention, the operativity of the setting of the reconstruction range for batch reconstruction processing can be improved in an X-ray computed tomography apparatus and an image processing apparatus.

  Hereinafter, an image processing apparatus according to the present invention and an X-ray computed tomography apparatus including the same will be described with reference to embodiments. As is well known, an X-ray computed tomography apparatus has a rotation / rotation type in which an X-ray tube and an X-ray detector system are integrally rotated around a subject, and a large number of detection elements arrayed in a ring shape are fixed. There are various types such as a stationary / rotate type in which only the X-ray tube rotates around the subject, and the present invention can be applied to any type. Here, the rotation / rotation type that occupies the mainstream will be described. In addition to the current mainstream single tube system equipped with a pair of X-ray tube and detector system, a plurality of X-ray tubes and detector systems that have been developed for practical use in recent years, such as Although the present invention can be applied to a multi-tube system equipped with three pairs, a single-tube system will be described below for convenience. Furthermore, in order to reconstruct one tomographic image, projection data for about 360 degrees around the subject and projection data for about 360 degrees are required. In the half scan method, projection data for 180 degrees + fan angle is required. Although the present invention can also be applied to the above-described method, here, it is assumed that one tomographic image is reconstructed from the general projection data set of about 360 degrees.

  Here, volume data is handled. The volume data is defined as a data set representing a three-dimensional distribution of CT values corresponding to a three-dimensional region of the subject, and is actually a collection over a plurality of slices of tomographic images as a collection of a plurality of pixels having CT values. As a multi-slice format, or a voxel format as a collection of a plurality of voxels having CT values. As a scan for obtaining volume data, a helical scan method or a cone beam scan method is adopted. As is well known, in the helical scan method, the X-ray tube and the X-ray detector continuously rotate around the subject, and the top plate on which the subject is placed moves at a constant speed along the rotation axis. The collection is repeated, and the cone beam scanning method is a method in which a large number of detection element arrays are arranged over a width of, for example, 30 cm in the slice direction (parallel to the rotation axis), which is also called a surface detector, two-dimensional array detector, or multi-row detector. By adopting an arrayed X-ray detector and a cone beam X-ray tube that generates a pyramidal X-ray, this is a method of collecting data in a three-dimensional region while the top is stopped.

  FIG. 1 is a block diagram showing the configuration of a computed tomography apparatus according to this embodiment. The scan gantry 100 includes an annular gantry rotating unit 2 that is rotatably held by the bed gantry mechanism unit 3. The rotation of the gantry rotating unit 2 by the bed gantry mechanism unit 3 is controlled by the mechanism control unit 4. The mechanism control unit 4 is under the control of the system control unit 11.

  An X-ray tube 13 and an X-ray detector 16 are mounted on the gantry rotating unit 2 so as to face each other across the rotation center axis. A subject 30 placed on the bed 1 is disposed in the vicinity of the rotation center axis. The X-ray tube 13 generates X-rays when a high voltage is applied from the high-voltage generator 12 via the slip ring 15 and a filament current is supplied. An X-ray restrictor 14 is attached to the X-ray emission window of the X-ray tube 13 in order to shape the X-ray into a predetermined pyramid shape. The X-ray tube 13 constitutes the X-ray generator 5 together with the high voltage generator 12, the slip ring 15 and the X-ray restrictor 14.

  The X-ray detector 16 has a plurality of detection elements arrayed in a one-dimensional or two-dimensional manner for converting X-rays transmitted through the subject 30 into a number of charges corresponding to the intensity. One or a predetermined number of detection elements constitute one electrically separated channel. Here, for convenience of explanation, it is assumed that one element constitutes one channel. A data acquisition system (DAS) 18 is connected to the X-ray detector 16 via a switch group 17. The data acquisition system 18 includes an IV converter that converts a current signal of the X-ray detector 16 into a voltage, an integrator that periodically integrates the voltage signal in synchronization with an X-ray exposure period, An amplifier for amplifying the output signal of the integrator and an analog / digital converter for converting the output signal of the preamplifier into a digital signal are provided for each channel. Data (projection data) output from the data collection system 18 is sent to the image data generation unit 7 via a non-contact type data transmission circuit 19 using light or magnetism. The X-ray detector 16 constitutes the projection data collection unit 6 together with the switch group 17, the data collection system 18 and the data transmission circuit 19. The projection data collection operation of the projection data collection unit 6 is under the control of the system control unit 11.

  The image data generation unit 7 includes a projection data storage circuit 20 for storing projection data output from the projection data collection unit 6, a reconstruction calculation circuit 21, a reconstruction processing control circuit 23, a volume data storage circuit 22, and an MPR process. A circuit 24 is included. The reconstruction calculation circuit 21 is equipped with a cone beam reconstruction method, a multi-slice reconstruction method, and an enlargement reconstruction method that can be selected. As is well known, the cone beam reconstruction method is a process in which a voxel aggregate is back-projected to an oblique ray according to the cone angle, and the enlarged reconstruction method limits the reconstruction range to a part of the scan range. This is a process for reconstructing a high-resolution image (an image with a high spatial resolution).

  Based on the projection data stored in the projection data storage circuit 20, the reconstruction calculation circuit 21 generates volume data under control according to the reconstruction condition by the reconstruction processing control circuit 23. The volume data is typically generated by interpolating the reconstructed multi-slice tomographic image data in the slice direction. The reconstruction conditions include a reconstruction method, a reconstruction range, a reconstruction function, a full reconstruction / half reconstruction, a reconstruction slice thickness, a line-of-sight direction, the number of stacks, a filter presence / absence, and the like via the input unit 10 It is set and supplied from the system control unit 11 to the reconfiguration processing control circuit 23.

  The volume data is stored in the volume data storage circuit 22. The MPR processing circuit 24 generates tomographic image data of an arbitrary cross section from the volume data stored in the volume data storage circuit 22 by MPR processing (cross section conversion processing).

  The GUI screen generation circuit 26 is a graphical user interface screen (GUI screen) including tomographic image data together with various operation buttons according to various stages such as a scan planning stage and a reconstruction condition setting stage of batch reconstruction processing such as enlargement reconstruction. Is provided to generate The generated GUI screen is scan-converted by the conversion circuit 27 and displayed on the monitor 28.

  As shown in FIG. 2, the overall operation procedure according to the present embodiment is as follows. First, according to the scan condition set at the time of the scan plan, the three-dimensional region of the subject 30 is converted into a helical scan method or a volume scan method (cone beam scan method). (S1). Thereby, a projection data set relating to the three-dimensional region is collected and stored in the projection data storage circuit 20. After the scanning is completed, the CT value distribution in the three-dimensional region is immediately determined by the cone beam reconstruction method or the multi-slice reconstruction method based on the stored projection data set according to the reconstruction condition set at the time of the scan planning. As volume data is reconfigured (S2). The volume data is stored in the volume data storage circuit 22. Typically, the volume data reconstruction condition is initially set according to the imaging region.

  After S2, when the execution of, for example, the enlargement reconstruction process as a batch process with a reconstruction condition different from the reconstruction condition for the immediate reconstruction process set at the time of the scan planning is instructed, the system control unit 10 enlarges Start the expert system for the reconstruction process. Under the expert system, as a series of the flow of the enlargement reconstruction process, an enlargement reconstruction condition setting stage (S3), an enlargement reconstruction process stage (S4), and a display stage of the enlarged and reconstructed high-resolution tomographic image Move in order.

  In this embodiment, as shown in FIG. 3, in order to set, for example, an enlarged reconstruction range as a reconstruction condition, an axial image, a sagittal image, an orthogonal triaxial image of a coronal image from volume data, and further tilted as necessary. It is characterized by generating and displaying images (oblique images) and enabling so-called image turning that arbitrarily moves the cross-sectional position of each image, so that three-dimensional information can be seen at a glance. Thus, a wide expansion reconstruction range can be set accurately, finely and quickly.

  FIG. 4 shows the processing procedure for setting the expanded reconstruction range in S3 of FIG. When an enlargement reconstruction process is requested here as a batch process via the input unit 10, the system control unit 11 first starts from the volume data corresponding to the three-dimensional area of the subject 30, in the initial three-dimensional area. The MPR processing circuit 24 is instructed to generate an axial image, a sagittal image, and a coronal image as cross-sectional images in three directions orthogonal at the center. Note that a cross-sectional image generated (reconstructed) from volume data is referred to as a “cross-sectional image”, and a cross-sectional image reconstructed from projection data is referred to as a “tomographic image” to facilitate distinction between the two. In accordance with a command from the system control unit 11, the MPR processing circuit 24 generates a cross-sectional image related to a cross section in three directions from the volume data (S11). The cross-sectional images related to cross-sections in different three directions are typically an axial image, a sagittal image, and a coronal image that are orthogonal at the center of the three-dimensional region. The cross-sectional image has a pixel size of, for example, 512 × 512.

  As shown in FIG. 5, the GUI screen generation circuit 26 controls the axial image (XY plane), sagittal image (XZ plane), and coronal image (YZ plane) generated in S11 under the control of the system control unit 11. Are the graphic elements (marks) R1, R2, R3 representing the enlarged reconstruction range, the cross-section lines (Inter Section Line) ISL1, ISL2, ISL3 representing the cross-sectional positions, and the frame SR representing the scan range where the projection data is collected. And a GUI screen including the reconstruction condition in the lower right column of the screen is generated. Note that, on the GUI screen, as shown in FIG. 7, scanograms taken at the time of scan planning may be displayed together with marks R2 and R3.

  In addition, the GUI screen includes scan conditions (upper left column) and icon sets (lower left column). The icon set includes a “raw data selection” button for instructing which batch processing (in this case, enlargement reconstruction processing) is to be performed using raw data (or projection data) collected by scanning, and a section line “Oblique display” button for instructing generation and display of a cross-sectional image (oblique image) inclined to at least one of the XYZ axes corresponding to ISL4, and selection / non-display of the cross-sectional lines ISL1 to ISL4 An “Inter Section display” button for resetting, an “range reset” button for resetting the enlarged reconstruction range, and a “reconfiguration execution” button for starting the reconstruction execution. The generated GUI screen is displayed on the monitor 28.

  In order to set the enlarged reconstruction range, the sections of the axial image, the sagittal image, and the coronal image can be moved by moving the corresponding section lines ISL3, ISL2, and ISL1 (S13). The movement of the section lines ISL3, ISL2, and ISL1 is performed by an alternative operation of a mouse wheel rotation operation included in the input device 10 and a drag-and-drop operation of the section lines ISL3, ISL2, and ISL1. In the case of a mouse wheel rotation operation, the wheel is rotated with the pointer placed on the image to be moved.

  When the cross section line is moved, the MPR processing circuit 24 generates a cross section image corresponding to the cross section passing through the cross section line ISL1, ISL2 or ISL3 after the movement from the volume data, and switches and displays it (S14). When the “oblique display” button is clicked (S15), a sectional image of the oblique section corresponding to the position and direction of the oblique section line ISL4 arbitrarily designated on the axial image, sagittal image or coronal image is generated from the volume data. Then, as shown in FIG. 6, the display is switched from the reconstruction condition to the lower right column (S17).

  The operator operates the mouse to move the cross-sectional positions of the axial image, sagittal image, and coronal image, and to display the oblique cross-sectional image at an arbitrary position and direction, and to enlarge and reconstruct the cross-sectional image on the cross-sectional image. The target part is confirmed, and the marks R1, R2, and R3 representing the enlarged reconstruction range are enlarged, reduced, rotated, and moved so as to appropriately include the target part of the enlarged reconstruction (S18). Under the control of the system control unit 11, the marks R1, R2, and R3 are enlarged, reduced, rotated, and moved in relation to each other.

  In addition, the operator operates the mouse to select a reconstruction function for the expanded reconstruction range, full reconstruction / half reconstruction, reconstruction slice thickness, and line-of-sight direction as reconstruction conditions for the expanded reconstruction process. The number of stacks, filter presence / absence, etc. are arbitrarily set (S19). The reconstruction condition for the expansion reconstruction process is not limited by the volume data reconstruction condition. The reconstruction conditions for the enlargement reconstruction process may be the same as the volume data reconstruction conditions, or some or all items may be different.

  When the enlargement reconstruction range and the reconstruction conditions are set, the set enlargement reconstruction is performed from the system control unit 11 to the reconstruction processing control circuit 23 in response to the click (S20) of the “execute reconstruction” button. The configuration range and the reconstruction conditions are transmitted to 23 (S21). The reconstruction processing control circuit 23 controls the reconstruction calculation circuit 20 so that the tomographic image data corresponding to the transmitted enlarged reconstruction range and reconstruction condition is reconstructed from the projection data in the projection data storage circuit 20. The enlarged and reconstructed tomographic image has, for example, the same 512 × 512 pixel size as the cross-sectional image.

  In the above description, the tomographic image is reconstructed limited to the enlarged reconstruction range, but the entire scan range is reconstructed according to a specific item such as the reconstruction function of the reconstruction condition in S21 to generate volume data, You may make it produce | generate the tomographic image of the expansion reconstruction range from the volume data by MPR.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

FIG. 1 is a configuration diagram showing an X-ray computed tomography apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart showing a flow of processing from scanning to completion of an enlargement reconstruction process according to the embodiment. FIG. 3 is a diagram showing an overview of the process of S3 of FIG. FIG. 4 is a flowchart showing a detailed processing flow of S3 of FIG. FIG. 5 is a diagram showing an example of a display screen in S12 of FIG. 6 is a diagram showing an example of a display screen in S17 of FIG. FIG. 7 is a view showing another display screen example of S12 of FIG. FIG. 8 is a diagram showing an outline of processing for setting a conventional enlarged reconstruction range.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Scan gantry, 3 ... Sleeper stand mechanism part, 2 ... Stand rotation part, 4 ... Mechanism control part, 5 ... X-ray generation part, 6 ... Projection data collection part, 7 ... Image data generation part, 10 ... Input part, DESCRIPTION OF SYMBOLS 11 ... System control part, 12 ... High voltage generator, 13 ... X-ray tube, 14 ... X-ray restrictor, 15 ... Slip ring, 16 ... X-ray detector, 17 ... Switch group, 18 ... Data acquisition system (DAS) , 19 ... Data transmission circuit, 20 ... Projection data storage circuit, 21 ... Reconstruction calculation circuit, 22 ... Volume data storage circuit, 23 ... Reconstruction processing control circuit, 24 ... MPR processing circuit, 26 ... GUI screen generation circuit, 27: Conversion circuit, 28 ... Monitor, 30 ... Subject.

Claims (12)

A scanning unit that scans a three-dimensional region of the subject with X-rays;
A storage unit for storing projection data collected by the scanning;
A volume data reconstruction unit for reconstructing volume data corresponding to the three-dimensional region based on the stored projection data;
A cross-sectional image data generating unit for generating cross-sectional image data relating to an orthogonal cross-section and oblique image data relating to one oblique cross-section from the volume data;
In accordance with an operator instruction, a display unit for displaying a screen including the orthogonal cross-sectional image and the oblique image together with a graphic element representing an enlarged reconstruction range;
An operation unit for operating the graphic element to set the enlarged reconstruction range ;
An X-ray computed tomography apparatus comprising: a tomographic image reconstruction unit that reconstructs tomographic image data corresponding to the enlarged reconstruction range based on the stored projection data.   The X-ray computed tomography apparatus according to claim 1, wherein a cross-sectional line corresponding to another cross-section is displayed in each cross-sectional image.   The X-ray computed tomography apparatus according to claim 2, wherein the position of each cross section is moved by the movement of the cross section line.   The X-ray computed tomography apparatus according to claim 1, wherein the operation unit includes a wheel mouse, and the position of each cross-section is moved by a rotation operation of a wheel of the wheel mouse.   2. The X-ray computed tomography apparatus according to claim 1, wherein the plurality of cross sections are set to axial, sagittal, and coronal.   2. The X-ray computed tomography apparatus according to claim 1, wherein a cross-sectional image relating to the oblique cross-section is generated from the stored volume data together with a cross-sectional image relating to the cross-section in the plurality of directions.   The X-ray computed tomography apparatus according to claim 1, wherein the graphic element has a rectangular shape. The X-ray computed tomography apparatus according to claim 1, wherein the tomographic image reconstruction unit generates tomographic image data corresponding to an enlarged reconstruction range represented by the graphic element by enlargement reconstruction.   2. The X-ray computed tomography apparatus according to claim 1, wherein the reconstruction condition of the tomographic image data is set independently of the reconstruction condition of the volume data.   The X-ray computed tomography apparatus according to claim 1, wherein the reconstruction condition of the tomographic image data is different from the reconstruction condition of the volume data.   The X-ray computed tomography apparatus according to claim 1, wherein the display unit displays the cross-sectional image data together with other graphic elements representing the scanned three-dimensional area. A storage unit for storing projection data relating to a three-dimensional region of the subject;
A volume data reconstruction unit for reconstructing volume data corresponding to the three-dimensional region based on the stored projection data;
A cross-sectional image data generating unit for generating , from the volume data , data of three cross-sectional images related to three orthogonal cross-sections and oblique image data related to one oblique cross-section ;
Switching between a screen including three cross-sectional images related to the three orthogonal cross sections with a graphic element representing an enlarged reconstruction range, and a screen including the cross-sectional image related to the three orthogonal cross-sections and the oblique image together with the graphic element according to an operator instruction. a display unit that displays Te,
An operation unit for operating the graphic element to set the enlarged reconstruction range ;
An image processing apparatus comprising: a tomographic image reconstruction unit that reconstructs tomographic image data corresponding to the enlarged reconstruction range based on the stored projection data.

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