JP7179497B2 - X-ray CT apparatus and image generation method - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to an X-ray CT apparatus and an image generation method .

Conventionally, in imaging using an X-ray CT apparatus (CT; Computed Tomography), a scan protocol for collecting data is set according to an examination site and examination contents. The scan protocol described above is set by selecting a scan protocol candidate suitable for the examination site and examination content from among a plurality of preset scan protocol candidates, and adjusting the preset conditions as appropriate. Here, each scan protocol candidate is classified according to, for example, physical characteristics such as age, adult/child, male/female, weight, and height, and inspection purpose. ) imaging range, scanning angle of the scan image, tube voltage and tube current when taking the positioning image, scanning method of main imaging (scanning) for collecting data used for diagnosis, scanning position, scanning range, scanning Various conditions such as the tube voltage and tube current when performing the above, the position and range of image reconstruction, etc. are set in advance.

An operator (for example, a technician) who operates the X-ray CT apparatus refers to the information of the subject to be examined, selects a scan protocol candidate to be executed from a plurality of scan protocol candidates, and selects the selected scan protocol. Various conditions included in the candidates are appropriately adjusted based on the physique, age, etc. of the subject, and the positioning image is captured. Based on the captured positioning image, the operator adjusts the scanning position and range of the main imaging (scanning), the position and range of image reconstruction, and the like, and executes the scanning.

JP-A-07-023946

A problem to be solved by the present invention is to provide an X-ray CT apparatus capable of efficiently generating an image suitable for diagnosis.

An X-ray CT apparatus according to an embodiment includes an acquisition unit, a first image reconstruction unit, a detection unit, and a second image reconstruction unit. The acquisition unit detects X-rays that have passed through the subject and acquires projection data. The first image reconstruction unit reconstructs first three-dimensional image data from the projection data. The detection unit detects a part of the subject included in the first three-dimensional image data. A second image reconstruction unit reconstructs second three-dimensional image data from the projection data for each part detected by the detection unit based on reconstruction conditions set for each part of the subject. do.

FIG. 1 is a diagram showing an example of the configuration of an X-ray CT apparatus according to the first embodiment. FIG. 2 is a diagram for explaining three-dimensional scanogram imaging by the scan control circuit according to the first embodiment. FIG. 3 is a diagram for explaining an example of part detection processing by the detection circuit according to the first embodiment. FIG. 4 is a diagram for explaining an example of part detection processing by the detection circuit according to the first embodiment. FIG. 5 is a diagram for explaining an example of part detection processing by the detection circuit according to the first embodiment. FIG. 6 is a diagram for explaining an example of reconstruction conditions according to the first embodiment. FIG. 7A is a diagram schematically showing information about reference lines according to the first embodiment; FIG. 7B is a diagram schematically showing information about reference lines according to the first embodiment; FIG. 7C is a diagram schematically showing information about reference lines according to the first embodiment; FIG. 8 is a diagram for explaining an example of display image generation by the second image reconstruction function according to the first embodiment. FIG. 9 is a diagram for explaining an example of display image generation by the second image reconstruction function according to the first embodiment. FIG. 10 is a flow chart showing the procedure of processing by the X-ray CT apparatus according to the first embodiment. FIG. 11 is a diagram schematically showing information about reference lines according to the second embodiment.

An embodiment of an X-ray CT (Computed Tomography) apparatus will be described in detail below with reference to the accompanying drawings.

(First embodiment)
First, the configuration of the X-ray CT apparatus 1 according to the first embodiment will be described. FIG. 1 is a diagram showing an example of the configuration of an X-ray CT apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus 1 according to the first embodiment has a gantry device 10, a bed device 20, and a console device 30. As shown in FIG. Here, the X-ray CT apparatus 1 is connected to other apparatuses via an in-hospital LAN (Local Area Network) installed in the hospital, for example, so that the X-ray CT apparatus 1 can directly or indirectly communicate with each other. . For example, the X-ray CT apparatus 1 includes a PACS (Picture Archiving and Communication System) server for storing and processing medical images, other medical image diagnostic apparatuses, and a device for the doctor in charge to refer to images. Connected to a terminal device or the like, each device mutually transmits and receives medical images and the like in accordance with, for example, the DICOM (Digital Imaging and Communications in Medicine) standard.

In addition, in a system having the devices described above, a HIS (Hospital Information System), a RIS (Radiology Information System), etc. are introduced to manage various types of information. For example, an examination order created by a terminal device by the system described above is transmitted to each medical image diagnostic device. Each medical image diagnostic apparatus acquires patient information from an examination order received directly from a terminal device or a patient list for each modality (modality worklist) created by a PACS server that has received an examination order.

The gantry device 10 is a device that irradiates the subject P with X-rays, detects the X-rays that have passed through the subject P, and outputs the X-rays to the console device 30, and includes an X-ray irradiation control circuit 11 and an X-ray generator. 12 , a detector 13 , a data acquisition circuit (DAS: Data Acquisition System) 14 , a rotating frame 15 , and a gantry drive circuit 16 .

The rotating frame 15 supports the X-ray generator 12 and the detector 13 so as to face each other with the subject P interposed therebetween, and is rotated at high speed in a circular orbit around the subject P by a gantry drive circuit 16, which will be described later. It is an annular frame that

The X-ray irradiation control circuit 11 is a device that supplies a high voltage to the X-ray tube 12a as a high voltage generator. generate lines. The X-ray irradiation control circuit 11 adjusts the X-ray dose with which the subject P is irradiated by adjusting the tube voltage and tube current supplied to the X-ray tube 12a.

The X-ray irradiation control circuit 11 also switches the wedge 12b. Further, the X-ray irradiation control circuit 11 adjusts the X-ray irradiation range (fan angle and cone angle) by adjusting the aperture of the collimator 12c. Note that this embodiment may also be a case in which the operator manually switches between a plurality of types of wedges.

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

The X-ray tube 12a is a vacuum tube that irradiates the subject P with an X-ray beam using a high voltage supplied by a high voltage generator (not shown). irradiate against. The X-ray tube 12a produces an X-ray beam diverging with a fan angle and a cone angle. For example, under the control of the X-ray irradiation control circuit 11, the X-ray tube 12a continuously emits X-rays all around the subject P for full reconstruction, or half-reconfigurable exposure for half reconstruction. It is possible to continuously irradiate X-rays in an irradiation range (180 degrees + fan angle). Further, under the control of the X-ray irradiation control circuit 11, the X-ray tube 12a can intermittently emit X-rays (pulse X-rays) at a preset position (tube position). The X-ray irradiation control circuit 11 can also modulate the intensity of X-rays emitted from the X-ray tube 12a. For example, the X-ray irradiation control circuit 11 increases the intensity of the X-rays emitted from the X-ray tube 12a at a specific tube position, and increases the intensity of the X-rays emitted from the X-ray tube 12a at ranges other than the specific tube position. Decrease the intensity of the emitted X-rays.

The wedge 12b is an X-ray filter for adjusting the dose of X-rays emitted from the X-ray tube 12a. Specifically, the wedge 12b transmits X-rays emitted from the X-ray tube 12a so that the X-rays emitted from the X-ray tube 12a to the subject P have a predetermined distribution. It is an attenuating filter. For example, the wedge 12b is a filter made of aluminum so as to have a predetermined target angle and a predetermined thickness. A wedge is also called a wedge filter or a bow-tie filter.

The collimator 12c is a slit for narrowing down the X-ray irradiation range whose X-ray dose is adjusted by the wedge 12b under the control of the X-ray irradiation control circuit 11, which will be described later.

The gantry drive circuit 16 rotates the X-ray generator 12 and the detector 13 on a circular orbit centered on the subject P by rotationally driving the rotating frame 15 .

The detector 13 is a two-dimensional array type detector (area detector) that detects X-rays that have passed through the subject P. are arranged in a plurality of rows along the body axis direction (the Z-axis direction shown in FIG. 1). Specifically, the detector 13 in the first embodiment has X-ray detection elements arranged in multiple rows such as 320 rows along the body axis direction of the subject P. It is possible to detect X-rays that have passed through the subject P over a wide range, such as a range including the heart and heart.

The data acquisition circuit 14 is a DAS (Data Acquisition System) and acquires projection data from X-ray detection data detected by the detector 13 . For example, the data acquisition circuit 14 performs amplification processing, A/D conversion processing, inter-channel sensitivity correction processing, etc. on the X-ray intensity distribution data detected by the detector 13 to generate projection data. The projected data thus obtained is transmitted to the console device 30, which will be described later. For example, when X-rays are continuously emitted from the X-ray tube 12a while the rotating frame is rotating, the data acquisition circuit 14 acquires projection data groups for the entire circumference (360 degrees). The data acquisition circuit 14 also associates each acquired projection data with the tube position and transmits the data to the console device 30, which will be described later. The tube position is information indicating the projection direction of the projection data. Note that the sensitivity correction processing between channels may be performed by the preprocessing circuit 34, which will be described later. The data collection circuit 14 is also called a collection unit.

The bed device 20 is a device on which the subject P is placed, and has a bed driving device 21 and a tabletop 22 as shown in FIG. The bed driving device 21 moves the top plate 22 in the Z-axis direction to move the subject P into the rotating frame 15 . The top plate 22 is a plate on which the subject P is placed.

Note that the gantry device 10 performs helical scanning, for example, by rotating the rotation frame 15 while moving the table 22 to scan the subject P spirally. Alternatively, after moving the table 22, the gantry 10 rotates the rotation frame 15 while fixing the position of the subject P to perform conventional scanning in which the subject P is scanned in a circular orbit. Alternatively, the gantry device 10 performs a step-and-shoot method in which the position of the top board 22 is moved at regular intervals and conventional scanning is performed in a plurality of scan areas.

The console device 30 is a device that receives an operator's operation of the X-ray CT apparatus and reconstructs X-ray CT image data using the projection data acquired by the gantry device 10 . As shown in FIG. 1, the console device 30 includes an input circuit 31, a display 32, a scan control circuit 33, a preprocessing circuit 34, a projection data storage circuit 35, an image reconstruction circuit 36, and an image storage circuit. 37 , a detection circuit 38 and a control circuit 39 .

It should be noted that each function described below for each circuit described above is configured as a program and realized by the circuit executing the program. For example, the processing functions performed by the scan control circuit 33, the preprocessing circuit 34, the image reconstruction circuit 36, the detection circuit 38, and the control circuit 39 are stored in the image storage circuit in the form of a computer-executable program. 37. Each circuit reads a program from the image storage circuit 37 and executes it, thereby realizing a function corresponding to each program. Further, each processing function performed by the X-ray irradiation control circuit 11, the data acquisition circuit (DAS) 14, and the gantry drive circuit 16 is stored in the image storage circuit 37 in the form of a computer-executable program. be. Each circuit reads a program from the image storage circuit 37 and executes it, thereby realizing a function corresponding to each program.

Here, the circuit that performs each function may be a single circuit, or may be multiple circuits. That is, a single circuit may read a program corresponding to each function and implement the corresponding function, or a plurality of circuits may read programs corresponding to different functions and implement the corresponding functions. It may be realized. Further, each circuit described above is a processor that realizes a function corresponding to each program by reading the program from the image storage circuit 37 and executing the program.

Note that the term "processor" used in the above description is, for example, a CPU (central processing unit), a GPU (Graphics Processing Unit), or an application specific integrated circuit (ASIC)), a programmable logic device (For example, Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). The processor realizes its functions by reading and executing the programs stored in the memory circuit. It should be noted that instead of storing the program in the memory circuit, the program may be directly installed in the circuit of the processor. In this case, the processor implements its functions by reading and executing the program embedded in the circuit. Note that each processor of the present embodiment is not limited to being configured as a single circuit for each processor, and may be configured as one processor by combining a plurality of independent circuits to realize its function. good.

The input circuit 31 has a mouse, a keyboard, etc., which are used by the operator of the X-ray CT apparatus 1 to input various instructions and various settings, and transfers instructions and setting information received from the operator to the control circuit 39 . For example, the input circuit 31 receives, from the operator, imaging conditions for X-ray CT image data, reconstruction conditions for reconstructing X-ray CT image data, image processing conditions for X-ray CT image data, and the like. The input circuit 31 also receives an operation for selecting an examination for the subject.

The display 32 is a monitor that is referred to by the operator. Under the control of the control circuit 39, the display 32 displays X-ray CT image data to the operator, and receives various instructions and settings from the operator via the input circuit 31. It displays a GUI (Graphical User Interface) for accepting such as. Also, the display 32 displays a plan screen of a scan plan, a screen during scanning, and the like.

The scan control circuit 33 controls the operations of the X-ray irradiation control circuit 11, the gantry drive circuit 16, the data acquisition circuit 14, and the bed drive device 21 under the control of the control circuit 39, so that the projection data in the gantry device 10 is control the collection process. Specifically, the scan control circuit 33 controls acquisition processing of projection data in imaging for acquiring a positioning image (scano image) and main imaging (scanning) for acquiring an image used for diagnosis. Here, in the X-ray CT apparatus 1 according to the first embodiment, a two-dimensional scanogram and a three-dimensional scanogram can be taken.

For example, the scan control circuit 33 fixes the X-ray tube 12a at a position of 0 degrees (a position in the front direction with respect to the subject), and performs continuous imaging while moving the tabletop at a constant speed. Take a dimensional scanogram. Alternatively, the scan control circuit 33 fixes the X-ray tube 12a at a position of 0 degrees, intermittently moves the tabletop, and intermittently repeats imaging in synchronization with the movement of the tabletop. Take a scanogram. Here, the scan control circuit 33 can capture positioning images not only from the front direction of the subject, but also from any direction (for example, from the side direction).

In addition, the scan control circuit 33 captures a three-dimensional scanogram by acquiring projection data for the entire circumference of the subject when capturing a positioning image. FIG. 2 is a diagram for explaining three-dimensional scanogram imaging by the scan control circuit 33 according to the first embodiment. For example, as shown in FIG. 2, the scan control circuit 33 acquires projection data for the entire circumference of the subject by helical scanning or non-helical scanning. Here, the scan control circuit 33 executes helical scanning or non-helical scanning over a wide range of subjects such as the entire chest, the entire abdomen, the entire upper body, and the whole body at a dose lower than that of the actual imaging. As the non-helical scan, for example, the step-and-shoot scan described above is executed.

In this manner, the scan control circuit 33 collects the projection data for the entire circumference of the subject, and the image reconstruction circuit 36, which will be described later, reconstructs three-dimensional X-ray CT image data (volume data). As shown in FIG. 2, it is possible to generate a positioning image from an arbitrary direction using the reconstructed volume data. Here, whether the positioning image is captured two-dimensionally or three-dimensionally may be arbitrarily set by the operator, or may be set in advance according to the examination contents.

Returning to FIG. 1, the preprocessing circuit 34 performs logarithmic conversion processing and correction processing such as offset correction, sensitivity correction, and beam hardening correction on the projection data generated by the data acquisition circuit 14, Generate corrected projection data. Specifically, the preprocessing circuit 34 generates corrected projection data for each of the projection data of the positioning image generated by the data acquisition circuit 14 and the projection data acquired by the actual imaging, and stores the projection data. Stored in circuit 35 .

A projection data storage circuit 35 stores the projection data generated by the preprocessing circuit 34 . Specifically, the projection data storage circuit 35 stores the projection data of the positioning image generated by the preprocessing circuit 34 and the diagnostic projection data acquired by the main imaging.

As shown in FIG. 1, the image reconstruction circuit 36 executes a first image reconstruction function 36a and a second image reconstruction function 36b, and uses projection data stored in the projection data storage circuit 35. Reconstruct the X-ray CT image data. Specifically, the image reconstruction circuit 36 reconstructs X-ray CT image data from the projection data of the scouting image and the projection data of the image used for diagnosis. Processing by the first image reconstruction function 36a and the second image reconstruction function 36b will be described in detail later. Here, there are various reconstruction methods, for example, back projection processing. Further, as the back projection processing, for example, there is a back projection processing by the FBP (Filtered Back Projection) method. Alternatively, the image reconstruction circuit 36 may reconstruct the X-ray CT image data using a successive approximation method.

The image reconstruction circuit 36 also generates image data by performing various image processing on the X-ray CT image data. The image reconstruction circuit 36 stores the reconstructed X-ray CT image data and the image data generated by various image processing in the image storage circuit 37 . The image storage circuit 37 stores image data generated by the image reconstruction circuit 36 . Further, the image storage circuit 37 appropriately stores the results of processing by the detection circuit 38 and the control circuit 39, which will be described later. The results of processing by the detection circuit 38 and the control circuit 39 will be described later. The image reconstruction circuit 36 is also called an image reconstruction unit, the first image reconstruction function 36a is also called a first image reconstruction unit, and the second image reconstruction function 36b is called a second image reconstruction unit. is also called an image reconstruction unit.

A detection circuit 38 detects each of a plurality of sites in the subject included in the three-dimensional image data. Specifically, the detection circuit 38 detects parts such as organs included in the three-dimensional X-ray CT image data (volume data) reconstructed by the image reconstruction circuit 36 . For example, the detection circuit 38 detects parts such as organs based on anatomical landmarks in at least one of the volume data of the positioning image and the volume data of the image used for diagnosis. An anatomical feature point is a point that indicates a feature of a part such as a specific bone, organ, or lumen. An example of part detection by the detection circuit 38 will be described below. Note that the detection circuit 38 is also called a detection section.

For example, the detection circuit 38 extracts anatomical feature points from the voxel values included in the volume data of the positioning image or the volume data of the image used for diagnosis. Then, the detection function 37a compares the three-dimensional positions of the anatomical feature points in information such as textbooks with the positions of the feature points extracted from the volume data, thereby determining the position of the feature points extracted from the volume data. Optimize the positions of the feature points extracted from the volume data by removing inaccurate feature points from the inside. Thereby, the detection function 37a detects each part of the subject included in the volume data. For example, the detection circuit 38 first uses a supervised machine learning algorithm to extract anatomical feature points included in the volume data. Here, the supervised machine learning algorithm described above is constructed using a plurality of teacher images in which correct anatomical feature points are manually arranged. be done.

Then, the detection circuit 38 optimizes the extracted feature points by comparing the extracted feature points with a model indicating the three-dimensional positional relationship of the anatomical feature points on the body. Here, the model described above is constructed using the teacher image described above, and for example, a point distribution model or the like is used. That is, the detection circuit 38 generates a model in which the shape and positional relationship of a region, points specific to the region, etc. are defined from a plurality of teacher images in which correct anatomical feature points are manually arranged, and the extracted feature points. By comparing , the inaccurate feature points are removed and the feature points are optimized.

An example of the part detection processing by the detection circuit 38 will be described below with reference to FIGS. 3 to 5. FIG. 3 to 5 are diagrams for explaining an example of part detection processing by the detection circuit 38 according to the first embodiment. Although the feature points are arranged two-dimensionally in FIG. 3, the feature points are actually arranged three-dimensionally. For example, the detection circuit 38 applies a supervised machine learning algorithm to the volume data to extract voxels regarded as anatomical feature points as shown in FIG. black dots). Then, the detection circuit 38 fits the positions of the extracted voxels to a model in which the shape and positional relationship of the part, the points unique to the part, etc. are defined, so that the extracted voxels as shown in FIG. Inaccurate feature points are removed from the voxels obtained, and only voxels corresponding to more accurate feature points are extracted.

Here, the detection circuit 38 assigns an identification code for identifying the feature point indicating the feature of each part to the extracted feature points (voxels), and the identification code and the position (coordinate) information of each feature point. is attached to the image data and stored in the image storage circuit 37 . For example, the detection circuit 38 assigns identification codes such as C1, C2, and C3 to the extracted feature points (voxels), as shown in FIG. 3B. Here, the detection circuit 38 attaches an identification code to each data subjected to detection processing, and stores the data in the image storage circuit 37 . Specifically, the detection circuit 38 selects from at least one of the projection data of the positioning image, the projection data acquired under non-contrast enhancement, and the projection data acquired under contrast enhancement with a contrast agent. A part of the subject included in the reconstructed volume data is detected.

For example, as shown in FIG. 4, the detection circuit 38 attaches information in which an identification code is associated with the coordinates of each voxel detected from the volume data of the positioning image (positioning in the figure) to the volume data, and stores the information in the image storage circuit. 37. For example, the detection circuit 38 extracts the coordinates of the feature _points from the volume data of the positioning image, and obtains "identification code: C1, coordinates (x1, _y1 , _z1 )" as shown in FIG. , “identification code: C2, coordinates (x ₂ , y ₂ , z ₂ )” and the like are associated with the volume data and stored. Thereby, the detection circuit 38 can identify what kind of feature point is at what position in the volume data of the positioning image, and can detect each part such as an organ based on this information.

For example, as shown in FIG. 4, the detection circuit 38 attaches to the volume data information in which the identification code is associated with the coordinates of each voxel detected from the volume data of the diagnostic image (scan in the figure). is stored in the image storage circuit 37. Here, in the scan, the detection circuit 38 detects the feature from the volume data contrasted with the contrast agent (contrast phase in the figure) and the volume data not contrasted with the contrast agent (non-contrast phase in the figure). The coordinates of the points can be extracted and the identification code can be associated with the extracted coordinates.

For example, the detection circuit 38 extracts the coordinates of the feature points from the volume data of the non-contrast Phase among the volume data of the diagnostic image, and outputs "identification code: C1, coordinates (x' ₁ , y' ₁ , z' ₁ )", "identification code: C2, coordinates (x' ₂ , y' ₂ , z' ₂ )" and the like are stored in association with the volume data. Further, the detection circuit 38 extracts the coordinates of the feature points from the volume data of the contrast-enhanced _phase among the volume data of the diagnostic image, and, as shown in FIG. , y' ₁ , z' ₁ )", "identification code: C2, coordinates (x' ₂ , y' ₂ , z' ₂ )", etc. are stored in association with the volume data. Here, when extracting feature points from the volume data of the contrast-enhanced phase, feature points that can be extracted by being contrast-enhanced are included. For example, when extracting feature points from volume data in the contrast phase, the detection circuit 38 can extract a blood vessel or the like contrasted with a contrast agent. Therefore, in the _case of _contrast - _enhanced volume data, the detection circuit 38, as shown in FIG. Coordinates (x' ₃₄ , y' ₃₄ , z' ₃₄ ) and the like are associated with identification codes C31, C32, C33 and C34 and the like for identifying respective blood vessels.

As described above, the detection circuit 38 can identify what kind of feature point is at what position in the positioning image or the volume data of the image for diagnosis. Each site can be detected. For example, the detection circuit 38 detects the position of the target part using information on the anatomical positional relationship between the target part to be detected and the parts surrounding the target part. For example, if the target part is "lungs", the detection circuit 38 acquires coordinate information associated with the identification code indicating the characteristics of the lungs, and also acquires the coordinates of "ribs", "clavicle", and "heart". , "diaphragm", etc., to acquire coordinate information associated with an identification code indicating a region around the "lung". Then, the detection circuit 38 extracts the "lung" area in the volume data using the information of the anatomical positional relationship between the "lung" and the surrounding parts and the acquired coordinate information.

For example, the detection circuit 38 detects positional relationship information such as "apex of lung: 2 to 3 cm above clavicle" or "lower end of lung: height of seventh rib" and coordinate information of each part to determine , a region R1 corresponding to "lung" is extracted from the volume data. That is, the detection circuit 38 extracts the coordinate information of the region R1 in the volume data. The detection circuit 38 stores the extracted coordinate information in the image storage circuit 37 by associating the extracted coordinate information with the part information and attaching it to the volume data. Further, the detection circuit 38 appropriately sends the extracted coordinate information and part information to the control circuit 39 . Similarly, the detection circuit 38 can extract, for example, a region R2 corresponding to the "heart" in the volume data, as shown in FIG. Note that the detection circuit 38 can detect parts by various methods other than the method using the anatomical feature points described above. For example, the detection circuit 38 can detect a part included in the volume data by a voxel value-based region growing method or the like.

Returning to FIG. 1 , the control circuit 39 performs overall control of the X-ray CT apparatus 1 by controlling operations of the gantry device 10 , the bed device 20 and the console device 30 . Specifically, the control circuit 39 controls the CT scan performed by the gantry device 10 by controlling the scan control circuit 33 . The control circuit 39 also controls image reconstruction processing and image generation processing in the console device 30 by controlling the image reconstruction circuit 36 . The control circuit 39 also controls the display 32 to display various image data stored in the image storage circuit 37 .

The overall configuration of the X-ray CT apparatus 1 according to the first embodiment has been described above. With this configuration, the X-ray CT apparatus 1 according to the first embodiment can efficiently generate images suitable for diagnosis. As described above, in a conventional examination using an X-ray CT apparatus, a scan protocol for collecting data is set according to an examination site and examination contents, and scanning is performed. Here, an operator (for example, a technician) who operates the X-ray CT apparatus adjusts the scanning position and range of the main imaging (scanning), the position and range of image reconstruction, etc. based on the positioning image, Run a scan. Here, in the conventional X-ray CT apparatus, after adjusting various conditions based on the positioning image, if the position of the subject deviates due to body movement or the like before the scan is executed, the reconstructed X-ray The positional deviation of line CT image data was corrected manually. For example, the operator adjusts the position and range of image reconstruction, and reconstructs X-ray CT image data again from acquired projection data. As described above, in the conventional X-ray CT apparatus, there are cases where reconstruction adjustment is performed manually, which is time-consuming. Therefore, the X-ray CT apparatus 1 according to the first embodiment makes it possible to efficiently generate an image suitable for diagnosis by controlling the image reconstruction circuit 36, which will be described in detail below.

Specifically, in the X-ray CT apparatus 1 according to the first embodiment, volume data is reconstructed from the projection data acquired by the main scan, and the positions of parts included in the reconstructed volume data are detected. . Then, the X-ray CT apparatus 1 performs image reconstruction again using the optimum reconstruction conditions for each detected part. As a result, even if the subject moves before scanning, it is possible to automatically reconstruct the volume data at the optimal position, and to perform optimal image reconstruction for each part, making it suitable for diagnosis. It enables efficient generation of images with Details will be described below.

A first image reconstruction function 36a in the image reconstruction circuit 36 according to the first embodiment reconstructs first three-dimensional image data from projection data. Specifically, the first image reconstruction function 36a reconstructs volume data used for part detection from the projection data acquired by the main imaging. Here, the volume data reconstructed by the first image reconstruction function 36a may be image reconstruction with rough accuracy as long as the detection circuit 38 can detect the part. That is, since the volume data image-reconstructed by the first image reconstruction function 36a is used for detecting the part included in the volume data acquired by the actual imaging and the position of the part, the subsequent processing It is desirable that the image reconstruction by the first image reconstruction function 36a be executed at high speed in order to smoothly perform the above. Therefore, the first image reconstruction function 36a reads the projection data from the projection data storage circuit 35 each time the main imaging is executed and the projection data is stored in the projection data storage circuit 35, and performs volumetric reconstruction in real time in the background. Perform image reconstruction of the data.

The detection circuit 38 detects the parts of the subject included in the volume data reconstructed by the first image reconstruction function 36a. Specifically, the detection circuit 38 detects the site of the subject each time the volume data is reconstructed by the first image reconstruction function 36a. That is, the detection circuit 38 detects the position (coordinates) of each part of the subject in the volume data each time the volume data is generated.

The second image reconstruction function 36b in the image reconstruction circuit 36 according to the first embodiment projects each part detected by the detection circuit 38 based on reconstruction conditions set for each part of the subject. Second three-dimensional image data is reconstructed from the data. Specifically, the second image reconstruction function 36b reads from the projection data storage circuit 35 the projection data used for reconstruction of the volume data in which the part of the subject is detected by the detection circuit 38, and reads the read projection data. Reconstruct volume data from data.

Here, the second image reconstruction function 36b sets the reconstruction position and range based on the position of the region detected by the detection circuit 38. FIG. Then, the second image reconstruction function 36b refers to reconstruction conditions set in advance for each part, and reconstructs volume data at the set position and range. That is, the second image reconstruction function 36b reconstructs volume data for a region that includes a predetermined site in the scan range under optimal reconstruction conditions for the predetermined site. As a result, the reconstructed volume data becomes optimal volume data for diagnosis.

Here, reconstruction conditions referred to by the second image reconstruction function 36b will be described. Such reconstruction conditions are arbitrarily set by the operator of the X-ray CT apparatus 1 and stored in the image storage circuit 37, a storage circuit (not shown), or the like. FIG. 6 is a diagram for explaining an example of reconstruction conditions according to the first embodiment. For example, as shown in FIG. 6, the reconstruction conditions referred to by the second image reconstruction function 36b are "reconstruction Conditions such as "method", "reconstruction function", and "slice thickness" are set.

For example, the FBP method or the iterative approximation method are set as the “reconstruction method” of the reconstruction condition. . In addition, in the "reconstruction function", a function with high spatial resolution (high resolution) is set for bones and lungs (lung fields), and soft tissue with low contrast resolution and high resolution is set for head and abdominal organs. function is set. The “slice thickness” is adjusted according to the size of the target site (or disease in the site).

Note that the reconstruction conditions shown in FIG. 6 are merely an example, and the embodiment is not limited to this. For example, reconstruction conditions may be set for various blood vessels imaged with a contrast agent. For example, conditions such as "reconstruction method", "reconstruction function", and "slice thickness" are set for each blood vessel.

The second image reconstruction function 36b is set as described above, refers to the reconstruction conditions stored in the image storage circuit 37, a storage circuit (not shown), or the like, and is set for each part detected in the scan range. The volume data are respectively reconstructed at the position and range determined. Then, the second image reconstruction function 36b generates image data along the reference line of the human body from the reconstructed volume data.

For example, the second image reconstruction function 36b generates a display image showing a cross section in a direction perpendicular to or parallel to the human body from reconstructed volume data. In such a case, first, the detection circuit 38 extracts the midline of the subject based on the site of the subject included in the volume data of the positioning image. Then, based on the midline extracted by the detection circuit 38, the second image reconstruction function 36b performs a body-axis section (axial plane), a sagittal section (sagittal plane), and a coronal section (coronal plane) of the subject. and a display image showing oblique planes (oblique planes). Also, the second image reconstruction function 36b generates a display image based on the reference line set for each part from the volume data reconstructed for each part. In one example, the second image reconstruction function 36b generates a display image showing cross-sections perpendicular to the reference line.

Information about such a reference line is arbitrarily set by the operator of the X-ray CT apparatus 1 and stored in the image storage circuit 37, a storage circuit (not shown), or the like. 7A to 7C are diagrams schematically showing information about reference lines according to the first embodiment. For example, as shown in FIG. 7A, a median line L1 is shown as information related to the reference line, and an axial plane 51 orthogonal to the median line L1 of the human body and a plane parallel to the median line L1 as a cross section of the displayed image are shown. Information indicating a sagittal plane 52 that divides the body into two and a coronal plane 53 that is parallel to the median line L1 and divides the body into ventral and dorsal sides is stored in the image storage circuit 37, a storage circuit (not shown), or the like.

Further, for example, as shown in FIG. 7B, as information related to the reference line of the head, a reference line L2 extending obliquely backward from the top of the head is shown, and a section 54 perpendicular to the reference line L2 is shown as a section of the display image. The information indicated is stored in the image storage circuit 37, a storage circuit (not shown), or the like. Further, for example, as shown in FIG. 7C, the long axis L3 of the heart is shown as the information about the reference line of the heart, and the information showing the cross section 55 orthogonal to the long axis L3 of the heart is stored as the cross section of the displayed image. It is stored in the circuit 37, a storage circuit (not shown), or the like.

The second image reconstruction function 36b generates image data by referring to the information about the reference line stored in the image storage circuit 37, a storage circuit (not shown), or the like. An example of display image generation will be described below with reference to FIGS. 8 and 9. FIG. 8 and 9 are diagrams for explaining an example of display image generation by the second image reconstruction function 36b according to the first embodiment. Here, FIG. 8 shows a case where a display image of an axial plane perpendicular to the midline of the human body is generated. Also, FIG. 9 shows a case where a display image of the head is generated.

For example, as shown in FIG. 8A, when scanning is performed in a scanning range R3 and the detection circuit 38 detects a “lung” region R4 from the reconstructed volume data, the second image reconstruction is performed. The function 36b first refers to the information on the reference line shown in FIG. 7A and reconstructs volume data from the projection data acquired in the main imaging of the scan range R3, using the region R4 as a reconstruction region. Here, as shown in FIG. 8A, since the orientation of the subject during scanning is not parallel to the z-axis of the gantry 10, reconstruction is performed in this state to display the display image of the axial plane. When generated, it becomes a cross section oblique to the midline of the subject.

Therefore, as shown in FIG. 8B, the second image reconstruction function 36b projects the center line L1 of the subject detected by the detection circuit 38 so as to be parallel to the z-axis of the gantry device 10. After aligning the data, image reconstruction of region R4 is performed. That is, the second image reconstruction function 36b rotates (coordinates transforms) the acquired projection data so that the median line L1 of the subject is parallel to the z-axis of the gantry device 10, and the image of the region R4 is Perform a reconfiguration. Here, the second image reconstruction function 36b reconstructs the volume data of the region R4 by referring to the reconstruction conditions for the "lungs" stored in the image storage circuit 37 or a storage circuit (not shown). Then, as shown in FIG. 8B, the second image reconstruction function 36b uses the reconstructed volume data to generate a display image 56 of the axial plane. Thereby, the display image 56 of the axial plane orthogonal to the median line L1 of the subject can be generated.

Further, for example, when a scan is executed and the detection circuit 38 detects a "head" region from the reconstructed volume data, the second image reconstruction function 36b converts the information about the reference line shown in FIG. 7B into Based on this, the volume data of the “head” region is reconstructed from the projection data acquired by scanning. That is, the detection circuit 38 refers to the information on the reference line shown in FIG. 7B and further detects the reference line L2 from the detected head. The second image reconstruction function 36b aligns the projection data so that the reference line L2 detected by the detection circuit 38 is parallel to the z-axis of the gantry 10, and then reconstructs the volume data.

Here, the second image reconstruction function 36b reconstructs the volume data with reference to the reconstruction conditions for the "head". Then, the second image reconstruction function 36b uses the reconstructed volume data to generate a display image of the axial plane. This allows the second image reconstruction function 36b to generate a display image corresponding to the cross section 54 in FIG. 7B. That is, the second image reconstruction function 36b can automatically transform the cross-sectional image shown in FIG. 9A into the cross-sectional image shown in FIG. 9B.

Next, processing by the X-ray CT apparatus 1 according to the first embodiment will be described using FIG. FIG. 10 is a flow chart showing the procedure of processing by the X-ray CT apparatus 1 according to the first embodiment. Steps S101, S102, and S104 shown in FIG. 10 are steps executed by the scan control circuit 33 reading out a program corresponding to the processing function from the image storage circuit 37. FIG. In the X-ray CT apparatus 1 according to the first embodiment, as shown in FIG. 10, when an examination is started (Yes in step S101), the scan control circuit 33 controls to acquire positioning images (step S102).

Step S<b>103 in FIG. 10 is a step executed by the input circuit 31 . After the positioning image is collected, the input circuit 31 receives an input operation for setting the scanning range based on the positioning image (step S103). Then, the scan control circuit 33 executes scanning based on the set scanning range (step S104), and the first image reconstruction function 36a executes image reconstruction using the projection data acquired by the scanning. (step S105). Note that the image reconstruction performed here may be performed with coarse accuracy. Steps S105, S107 and S108 shown in FIG. 10 are steps executed by the image reconstruction circuit 36 reading out a program corresponding to the processing function from the image storage circuit 37. FIG.

Step S106 shown in FIG. 10 is a step in which the detection circuit 38 reads a program corresponding to the processing function from the image storage circuit 37 and executes it. When the volume data is reconstructed by image reconstruction by the first image reconstruction function 36a, the detection circuit 38 detects the parts included in the volume data (step S106). Then, the second image reconstruction function 36b arranges the reconstruction range for each part (step S107), sets the reconstruction conditions for each part, and sets the projection data acquired in the scan in step S104. is used to perform image reconstruction (step S108).

After that, the second image reconstruction function 36b generates a display image based on the reference line for each part from the reconstructed volume data, and the control circuit 39 causes the display 32 to display the generated display image (step S109). . Note that step S109 shown in FIG. 10 is a step in which the control circuit 39 reads a program corresponding to the processing function from the image storage circuit 37 and executes it.

As described above, according to the first embodiment, the data acquisition circuit 14 acquires projection data by detecting X-rays that have passed through the subject. A first image reconstruction function 36a reconstructs volume data from the projection data. A detection circuit 38 detects a part of the subject included in the volume data. The second image reconstruction function 36b reconstructs volume data from projection data for each part detected by the detection circuit 38 based on reconstruction conditions set for each part of the subject. Therefore, the X-ray CT apparatus 1 according to the first embodiment can automatically generate an optimal image for each part, and can efficiently generate an image suitable for diagnosis.

Further, according to the first embodiment, the second image reconstruction function 36b generates a display image based on the reference line set for each part from the volume data reconstructed for each part. Therefore, the X-ray CT apparatus 1 according to the first embodiment makes it possible to generate a display image suitable for diagnosis for each part.

Also, according to the first embodiment, the second image reconstruction function 36b generates a display image showing a cross section perpendicular to the reference line. Therefore, the X-ray CT apparatus 1 according to the first embodiment makes it possible to generate display images that are more suitable for diagnosis.

Further, according to the first embodiment, the detection circuit 38 extracts the midline of the subject based on the region of the subject included in the volume data. The second image reconstruction function 36b generates display images showing axial, sagittal, coronal and oblique slices of the subject based on the midline extracted by the detection circuit 38. FIG. Therefore, the X-ray CT apparatus 1 according to the first embodiment generates a display image on a plane perpendicular to or parallel to the median line of the subject regardless of the state of the subject during scanning. make it possible.

(Second embodiment)
Now, although the first embodiment has been described so far, it may be implemented in various different forms other than the above-described first embodiment.

In the above-described embodiment, the case where the reference line is a straight line has been described, but the embodiment is not limited to this, and the reference line may be a curved line. In such a case, for example, the second image reconstruction function 36b extracts the core line of the part of the subject from the volume data reconstructed for each part, and displays a cross section normal to the extracted core line. Generate an image. FIG. 11 is a diagram schematically showing information about reference lines according to the second embodiment.

For example, as shown in FIG. 11A, when scanning is performed with the subject bending, the second image reconstruction function 36b according to the second embodiment reconstructs each site. A core line of the part of the subject is extracted from the configured volume data, and a display image showing a cross section in a direction normal to the extracted core line is generated. As an example, when generating display images for regions included in the chest and abdomen, the second image reconstruction function 36b, as shown in FIG. are extracted, and the core line L4 of the extracted spine is extracted.

Then, the second image reconstruction function 36b uses the extracted core line L4 as a reference line to generate a display image showing a cross section 57 in the direction normal to the core line L4. At this time, the control circuit 39 controls to display information indicating the actual state of the spine together with the generated display image. The example described above is merely an example, and the region from which the core line is extracted is not limited to the spine. For example, a display image may be generated in which a core line is extracted from a hollow organ or the like in the body, and the inside of the hollow organ is shown in a cross section normal to the extracted core line. Note that the core line extraction described above is performed by a Bessel tracking method or a method for thinning the internal region.

Moreover, the reference line described above can be arbitrarily set by the operator. In such a case, the input circuit 31 receives an input operation of inputting an arbitrary reference line for generating a display image for each site of the subject. Then, the second image reconstruction function 36b generates a display image based on an arbitrary reference line for which an input operation is received from the volume data reconstructed for each part. For example, the second image reconstruction function 36b generates a display image showing a cross-section perpendicular to an arbitrary reference line for which an input operation has been received.

Also, each component of each device illustrated in the first embodiment is functionally conceptual, and does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution and integration of each device is not limited to the one shown in the figure, and all or part of them can be functionally or physically distributed and integrated in arbitrary units according to various loads and usage conditions. Can be integrated and configured. Further, each processing function performed by each device may be implemented in whole or in part by a CPU and a program analyzed and executed by the CPU, or implemented as hardware based on wired logic.

Also, the control method described in the first embodiment can be realized by executing a prepared control program on a computer such as a personal computer or a work station. This control program can be distributed via a network such as the Internet. In addition, this control program is recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, DVD, etc., and can be executed by being read from the recording medium by a computer.

As described above, according to each embodiment, it is possible to efficiently generate an image suitable for diagnosis.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 X-ray CT apparatus 14 data acquisition circuit 36a first image reconstruction function 36b second image reconstruction function 38 detection circuit

Claims (9)

an acquisition unit that acquires projection data by detecting X-rays that have passed through a subject;
a first image reconstruction unit that reconstructs first three-dimensional image data from the projection data;
a detection unit that detects a part of the subject included in the first three-dimensional image data;
second three-dimensional image data is reconstructed from the projection data for each part detected by the detection unit based on the reconstruction condition set for each part of the subject; a second image reconstruction unit that generates a display image based on the reference line from the second three-dimensional image data reconstructed for each part;
with
The second image reconstruction unit aligns the projection data based on the reference line of the part and the axial direction in the imaging space, and generates the second three-dimensional image data from the aligned projection data. A reconstructing X-ray CT apparatus. 2. The X-ray CT apparatus according to claim 1, wherein said second image reconstruction unit generates a display image based on a reference line set for said part according to the shape of said part. The second image reconstruction unit performs coordinate transformation of the projection data so that the reference line of the part is parallel to the axial direction in the imaging space, and based on the reconstruction conditions set for each part, 3. The X-ray CT apparatus according to claim 1, wherein said second three-dimensional image data is reconstructed from projection data after coordinate transformation. 4. The X-ray CT apparatus according to any one of claims 1 to 3, wherein said second image reconstruction unit generates a display image showing a cross section perpendicular to said reference line. The second image reconstruction unit extracts a core line of the part of the subject from the second three-dimensional image data reconstructed for each part, and displays a cross section normal to the extracted core line. The X-ray CT apparatus according to any one of claims 1 to 4, which produces an image. The detection unit extracts a midline of the subject based on the part of the subject included in the first three-dimensional image data,
3. The second image reconstructing unit generates a display image showing a body axial section, a sagittal section, a coronal section and an oblique section of the subject based on the midline extracted by the detecting section. 6. The X-ray CT apparatus according to any one of 1 to 5. further comprising a reception unit that receives an input operation for inputting an arbitrary reference line for generating a display image for each part of the subject;
7. The second image reconstruction unit according to any one of claims 1 to 6, wherein the second image reconstruction unit generates a display image based on an arbitrary reference line for which an input operation is accepted from the second three-dimensional image data reconstructed for each part. The X-ray CT apparatus according to item 1. The detection unit reconstructs from at least one of the projection data of the positioning image, the projection data acquired under non-contrast enhancement, and the projection data acquired under contrast enhancement with a contrast agent. 8. The X-ray CT apparatus according to any one of claims 1 to 7, wherein the part of said subject included in the first three-dimensional image data is detected. detecting X-rays that have passed through a subject to collect projection data;
reconstructing first three-dimensional image data from the projection data;
detecting a site of the subject included in the first three-dimensional image data;
Second three-dimensional image data is reconstructed from the projection data for each detected part based on reconstruction conditions set for each part of the subject, and based on the reference line set for each part. generating a display image from the second three-dimensional image data reconstructed for each part;
including
aligning the projection data based on the reference line of the part and the axial direction in the imaging space, and reconstructing the second three-dimensional image data from the aligned projection data;
A method of generating an image , further comprising :

Images