JP7238694B2 - Medical image processing device and program - Google Patents

Description

The present invention relates to a medical image processing apparatus and program.

In the medical field, modalities such as CT (Computed Tomography) devices are used. In the X-ray CT examination, the physique of the examinee affects the dose of X-rays to be applied to the examinee. Therefore, it is necessary to consider the physique of the subject when examining the appropriate exposure dose.

As a technique for radiation exposure dose management, for example, a measurement device has been proposed that obtains the radiation exposure dose for each organ based on the SUV value from a morphological image such as a CT image and a functional image such as a PET image (see Patent Document 1). .
In addition, a dose management system has been proposed that identifies the accumulated organ and accumulated amount of a radiopharmaceutical administered to a subject based on a nuclear medicine diagnostic image, and obtains the exposure dose of the organ of the subject (see Patent Document 2). ).

In addition, CTDI _vol is used as a general dose index for exposure dose management in X-ray CT examinations. However, CTDI _vol is an approximate value measured and calculated using a phantom, and does not reflect the body size of the subject.

Therefore, SSDE (Size Specific Dose Estimates) has been proposed as a dose index that takes into consideration the physique of a subject. The SSDE uses the waist circumference as an index representing the physique of the subject, approximates the subject area in the tomographic image having the maximum waist circumference among a plurality of tomographic images generated in the X-ray CT examination, and It is a dose index obtained by converting (correcting) CTDI _vol using a conversion coefficient determined based on the major axis and minor axis of the ellipse.

JP 2018-13419 A Japanese Patent Application Laid-Open No. 2017-67708

A tomographic image with the maximum abdominal circumference used for obtaining the SSDE is generally specified using a scout image taken during an X-ray CT examination. However, the scout image may not exist, and in this case, the operator has to manually search for the tomographic image with the maximum abdominal circumference from among the huge number of tomographic images generated in the X-ray CT examination. It was complicated and time consuming. There was also a problem with accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to enable efficient and accurate calculation of an index representing exposure dose in X-ray CT examination, taking into consideration the body size of an examinee, using a tomographic image generated in X-ray CT examination. is.

In order to solve the above problems, the medical image processing apparatus of the invention according to claim 1 comprises:
Extracting the contour of the subject region from each of a plurality of tomographic images of the abdomen of the subject generated in the X-ray CT examination of the subject, and based on the extracted contour, the area of the subject region or extracting means for calculating a contour length and extracting a maximum tomographic image having the maximum calculated area or the longest contour length;
approximation means for approximating the contour of the subject region in the maximum tomographic image with an ellipse to acquire the major and minor axes of the ellipse;
Radiation exposure for calculating an index representing the exposure dose in consideration of the body size of the subject in the X-ray CT examination based on the acquired major axis and minor axis and the dose information acquired during the X-ray CT examination. dose calculation means;
Prepare.

The invention according to claim 2 is the invention according to claim 1,
The approximation means selects arbitrary two points on the contour of the subject area in the maximum tomographic image, and passes through the selected two points and has a major axis of an ellipse having the same center of gravity as the center of the subject area. and the processing of calculating the minor axis is executed a plurality of times, and an elliptical shape that approximates the outline of the subject region is determined based on the obtained frequencies of the plurality of major and minor axes.

The program of the invention according to claim 3,
the computer,
Extracting the contour of the subject region from each of a plurality of tomographic images of the abdomen of the subject generated in the X-ray CT examination of the subject, and based on the extracted contour, the area of the subject region or Extraction means for calculating the contour length and extracting the maximum tomographic image in which the calculated area is the maximum or the contour length is the longest;
approximation means for approximating the contour of the subject region in the maximum tomographic image with an ellipse and acquiring the major and minor axes of the ellipse;
Radiation exposure for calculating an index representing the exposure dose in consideration of the body size of the subject in the X-ray CT examination based on the acquired major axis and minor axis and the dose information acquired during the X-ray CT examination. dose calculation means,
function as

Advantageous Effects of Invention According to the present invention, it is possible to efficiently and accurately calculate an index representing an exposure dose in X-ray CT examination considering the body size of an examinee using a tomographic image generated in X-ray CT examination. Become.

1 is a system configuration diagram of a medical imaging system according to an embodiment of the present invention; FIG. FIG. 2 is a diagram for explaining a plurality of tomographic images generated by X-ray CT examination; 3 is a block diagram showing a functional configuration of an arithmetic device; FIG. FIG. 4 is a flowchart of correction dose calculation processing executed in the arithmetic unit of FIG. 3; FIG. FIG. 10 is a diagram for explaining a method of approximating a subject area with an ellipse in a maximum tomographic image;

An embodiment of a medical image processing apparatus according to the present invention will be described below. It should be noted that the present invention is not limited to the illustrated examples.

FIG. 1 shows an example system configuration of a medical imaging system 100 .
As shown in FIG. 1, a medical imaging system 100 includes a RIS (Radiology Information System) server 10, a CT device 20, an image storage device 30, an arithmetic device 40 as a medical image processing device, a dose management device 50, and the like. Each device is connected via a communication network N such as a LAN (Local Area Network) or a WAN (Wide Area Network) so as to be able to transmit and receive data. Each device constituting the medical imaging system 100 conforms to HL7 (Health Level Seven) and DICOM (Digital Image and Communications in Medicine) standards, and communication between each device is performed in accordance with HL7 and DICOM.

The RIS server 10 manages information within the radiology department, such as appointments for examinations and treatments using radiological equipment, examination results, and the like. The RIS server 10 manages examination order information and transmits the examination order information to modalities to be examined (CT apparatus 20, etc.).

The examination order information includes an examination requester (doctor), patient information, examination information, and the like.
Patient information is information about a patient (examinee). The patient information includes patient ID, patient name, date of birth, age, sex, height, weight, and the like.
Examination information is information about an examination. The examination information includes an examination ID, examination date and time, modality (CT, DR, CR, US, MRI, etc.), examination site, examination purpose, examination description, presence or absence of a contrast medium, and the like.

The CT apparatus 20 performs an X-ray CT examination on a subject and generates a plurality of tomographic images at intervals along a predetermined direction. FIG. 2 schematically shows a plurality of tomographic images generated by X-ray CT examination. In FIG. 2, a plurality of tomographic images (cross-sectional tomographic images) perpendicular to the body axis direction are generated at slice thickness intervals along the body axis direction. Note that the intervals between the plurality of tomographic images generated by the X-ray CT examination may be predetermined (constant) intervals, or may not be constant. The CT apparatus 20 can also generate a longitudinal cross-sectional tomographic image parallel to the body axis direction, in addition to the cross-sectional tomographic image.

In the CT apparatus 20, an examination technician sets an imaging protocol according to examination order information before imaging. The imaging protocol includes an imaging method, an imaging range (or information that can be converted into an imaging range), the presence or absence of a contrast medium, and the like.

The CT apparatus 20 attaches additional information to the CT image by writing the additional information in the header of the image file of the CT image (a plurality of tomographic images) in accordance with the DICOM standard. The incidental information includes patient information, examination information, series information, detailed image information, imaging protocol, and the like.
Series information is information about a series. Series information includes series number, series description, slice thickness, type of image (eg, transverse or longitudinal), and the like.
The image detail information is information about the image. The image detail information includes an image number, slice position, image generation time, and the like. The image number is a number indicating the imaging order of the tomographic images generated in one scan.

The CT apparatus 20 also outputs an RDSR (Radiation Dose Structured Report) together with the plurality of tomographic images. RDSR is information conforming to the DICOM standard, and is one of data formats representing dose information. In the RDSR, in addition to patient information and examination information, dose information (CTDI _vol ) for each scan in an X-ray CT examination is recorded in association with a sequence number that is information for identifying each scan.

The image storage device 30 stores and manages image data of medical images generated by modalities such as the CT device 20 for each patient. The image archiving device 30 is composed of a PACS (Picture Archiving and Communication System) or the like. For example, the image storage device 30 stores and manages a plurality of tomographic images generated by the CT device 20 for each patient and each examination. The image storage device 30 also stores the RDSR corresponding to each examination for each patient and each examination.

The calculation device 40 acquires, for example, a plurality of tomographic images and RDSR generated by the CT device 20 from the image storage device 30, calculates an index representing the exposure dose of the subject in the X-ray examination, and dose management device 50 output to

FIG. 3 shows the functional configuration of the computing device 40. As shown in FIG.
As shown in FIG. 3, the computing device 40 includes a control section 41, a communication section 42, a storage section 43, etc., and each section is connected by a bus.

The control unit 41 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like, and controls the processing operations of each unit of the arithmetic unit 40 in an integrated manner. Specifically, the CPU reads various processing programs stored in the ROM, develops them in the RAM, and performs various processing in cooperation with the programs. The control unit 41 functions as extraction means, approximation means, and dose calculation means.

The communication unit 42 is configured by a network interface or the like, and transmits and receives data to and from an external device connected via the communication network N. For example, the communication unit 42 receives CT images (a plurality of tomographic images) and RDSR from the CT device 20 or the image storage device 30 .

The storage unit 43 is configured by an HDD (Hard Disk Drive), a nonvolatile memory, or the like, and stores various data.
For example, the storage unit 43 stores a transform coefficient table 431 . The conversion coefficient table 431 contains the major axis and minor axis (or major axis + minor axis) obtained from the approximate ellipse of the subject area in the tomographic image of the subject's maximum abdominal circumference, and the conversion for converting CTDI _vol into SSDE. It is a table in which coefficients and are associated with each other. SSDE is a dose index obtained by correcting CTDI _vol in consideration of the physique of the subject, and was proposed by AAPM (American Associations of Physicist in Medicine).

The storage unit 43 also stores image data of a plurality of tomographic images generated in each X-ray CT examination.

The dose management device 50 stores the index indicating the exposure dose of the subject transmitted from the arithmetic device 40 in a database in association with patient information and examination information, and manages the exposure dose for each patient (subject). .

Next, the operation of arithmetic unit 40 will be described.
FIG. 4 is a flow chart showing the correction dose calculation process executed by the computing device 40. As shown in FIG. This processing is implemented by software processing in cooperation with the CPU of the control unit 41 and the programs stored in the ROM.

First, the control unit 41 acquires a plurality of tomographic images and RDSR generated by X-ray CT examination (step S1).
For example, the control unit 41 inquires of the image storage device 30 to obtain a plurality of X-ray CT examination tomographic images including the abdomen and the RDSR generated in the CT device 20 and stored in the image storage device 30 . Alternatively, when a plurality of tomographic images of an X-ray CT examination including the abdomen and RDSR are transmitted from the CT apparatus 20 to the image storage device 30, the image storage device 30 may transfer these data to the arithmetic device 40. good. Alternatively, a plurality of tomographic images and RDSR generated in an X-ray CT examination including the abdomen may be transmitted directly from the CT device 20 to the arithmetic device 40 .

Next, the control unit 41 specifies and acquires a series of cross-sectional tomographic images (a plurality of tomographic images) from the acquired plurality of tomographic images (step S2).
A series of cross-sectional tomographic images can be specified, for example, by series information included in the supplementary information of each tomographic image.

Next, the control unit 41 specifies the range of the tomographic image of the abdomen from the plurality of acquired tomographic images of the cross section, and acquires the tomographic image of the abdomen (step S3).
Here, the imaging range may include a plurality of regions such as chest to abdomen, chest to waist, head to waist, and the like. Therefore, for example, the control unit 41 identifies the part imaged in each scan from the information of the imaging range of the imaging protocol included in the incidental information, and determines the ratio of the length of each part in the body axis direction of the human body to the subject. A tomographic image range of the abdomen is specified from the imaging range based on the height of the person, etc., and a plurality of tomographic images in the specified range are acquired.

Next, the control unit 41 extracts the contour of the subject region from each abdominal tomographic image (step S4).
For example, the signal value (CT value) of each tomographic image is binarized by a predetermined threshold, and the boundary between 1 and 0 is extracted as the contour of the subject area.

Next, the control unit 41 obtains the area of the subject region based on the extracted outline in each of the tomographic images of the abdomen, and selects the tomographic image having the largest area of the subject region from among the plurality of tomographic images of the abdomen. is extracted as the maximum tomographic image (step S5)
Among the multiple tomographic images of the abdomen, the maximum tomographic image is the tomographic image of the maximum abdominal circumference. The area of the subject area can be obtained, for example, by counting the number of pixels in the area surrounded by the outline of the extracted subject area.
Note that the contour length of the subject region may be used instead of the area of the subject region, and the tomographic image having the longest contour length may be set as the maximum tomographic image.

Next, the control unit 41 approximates the subject area in the extracted maximum tomographic image with an ellipse and obtains its major axis and minor axis according to the procedure shown in FIG.
First, the control unit 41 calculates the center of gravity G of the maximum tomographic image (step S6).

Next, the control unit 41 selects any two points on the contour extracted in step S4 in the maximum tomographic image, and obtains an ellipse passing through the selected two points and having the center of gravity G obtained in step S6. The process of obtaining and storing (storing in the RAM) the major axis and minor axis of the ellipse obtained is executed a plurality of times (step S7).
It is preferable that the number of executions of the process in step S7 is as large as possible because an accurate approximate ellipse can be obtained.

Next, the control unit 41 determines the approximate ellipse of the subject region in the maximum tomographic image based on the accumulated frequencies of the major axis and minor axis, and acquires the major axis and radius of the approximate ellipse (step S8).
Here, an ellipse passing through arbitrary two points on the contour of the subject area in the maximum tomographic image and having the center of gravity G calculated in step S6 is repeatedly obtained, and its major axis and minor axis are accumulated. Data are concentrated on the major and minor axes of the ellipse near the examiner's area. Therefore, the approximate ellipse of the subject area is determined based on the accumulated frequencies of the major axis and minor axis, and the major axis and minor axis are acquired.
For example, as shown in FIG. 5, for each of the accumulated major diameters and minor diameters, the distribution of diameter lengths was obtained by plotting on a graph in which the horizontal axis is the length of the diameter and the vertical axis is the frequency. An ellipse whose major and minor axes are the average value of the diameters within a predetermined range R based on the length of the diameter at which the frequency peaks in the distribution diagram is determined as an approximate ellipse, and its major and minor axes are determined. to get
As for R, for example, when the width of the bottom of the distribution map is 1, it is preferable to set R to a range of 0.5 or less centering on the peak. It is more preferably 0.3 or less, still more preferably 0.1 or less.

Conventionally, when approximating a subject area of a tomographic image having the maximum abdominal circumference with an ellipse, the approximation ellipse was drawn manually, and there was a problem that the approximation could not be performed with high accuracy. Since the contour is automatically extracted and the automatically extracted contour is approximated with an ellipse, the subject area can be approximated with an ellipse with high accuracy. Further, by approximating the subject area with an ellipse by the method described in step S8 using the automatically extracted contour, it is possible to obtain an ellipse closer to the subject area with higher accuracy. As a result, it is possible to calculate an index representing an appropriate exposure dose for the subject, and contribute to appropriate radiography.

Next, the control unit 41 refers to the conversion coefficient table 431 to obtain conversion coefficients corresponding to the major axis and minor axis of the approximate ellipse (step S9).

Next, the control unit 41 corrects the CTDI _vol recorded in the RDSR acquired in step S1 using the acquired conversion coefficient, and calculates an index representing the exposure dose of the subject (step S10).
In step S10, the control unit 41 multiplies the CTDI _vol for each scan recorded in the RDSR by the conversion coefficient, thereby calculating the SSDE, which is an index of exposure dose corrected in consideration of the physique of the subject, for each scan. , and the calculated SSDE is multiplied by the length of the scanned range (imaging range) to calculate an index representing the exposure dose of the subject for each scan.

Then, the control unit 41 associates the index representing the calculated exposure dose with the patient information, examination information, etc., and transmits the index to the dose management apparatus 50 via the communication unit 42 (step S11), and ends the correction dose calculation process.

Upon receiving the index representing the exposure dose, the dose management device 50 associates the received index representing the exposure dose with the patient information and examination information and accumulates it in a database, aggregates the exposure dose for each subject (patient), to manage.

As described above, according to the arithmetic device 40 of the present embodiment, the control unit 41 first determines the region of the subject from each of a plurality of tomographic images of the abdomen of the subject generated in the X-ray CT examination. The contour is extracted, the area of the subject region is calculated based on the extracted contour, and the tomographic image with the maximum calculated area or the longest contour length is extracted as the maximum tomographic image. Next, the outline of the subject area in the maximum tomographic image is approximated by an ellipse, and the major and minor axes of the ellipse are obtained. Then, based on the obtained major axis and minor axis and the dose information obtained during the X-ray CT examination, an index representing the exposure dose in consideration of the body size of the subject in the X-ray CT examination is calculated. An index representing the exposure dose may be calculated using the area of the maximum tomographic image or the contour length without using the major axis and the minor axis.

Therefore, it is possible to automatically extract the maximum tomographic image used for calculating the index representing the exposure dose in consideration of the physique of the subject from among the plurality of tomographic images of the abdominal circumference generated in the X-ray CT examination. , it is possible to efficiently and accurately calculate the index representing the exposure dose in consideration of the physique of the subject.

In addition, the control unit 41 selects two arbitrary points on the contour of the subject area in the maximum tomographic image, and selects an ellipse having the same center of gravity as the center of the subject area passing through the selected two points. The process of calculating the diameter is executed a plurality of times, and an elliptical shape that approximates the contour of the subject area is determined based on the obtained frequencies of the plurality of major and minor axes.
Therefore, since an elliptical shape close to the subject area can be determined more accurately in the tomographic image of the abdomen, it is possible to more accurately calculate the index representing the exposure dose in consideration of the subject's physique.

The description in the above embodiment is an example of the medical image processing apparatus according to the present invention, and the present invention is not limited to this.
For example, in the above embodiment, the calculation device 40 and the dose management device 50 are separate units, but the calculation device 40 and the dose management device 50 may be integrated. Further, the image storage device 30 and the arithmetic device 40 may be integrated, or the CT device 20 and the arithmetic device 40 may be integrated.

Also, for example, in the above-described embodiments, an example of using a semiconductor memory or an HDD as a computer-readable medium storing a program for executing each process has been disclosed, but the present invention is not limited to this example. As another computer-readable medium, it is also possible to apply a portable recording medium such as a CD-ROM. Also, a carrier wave may be applied as a medium for providing program data via a communication line.
In addition, the detailed configuration and detailed operation of each part constituting the arithmetic unit as a medical image processing apparatus can be changed as appropriate without departing from the spirit of the present invention.

10 RIS server 20 CT device 30 image storage device 40 computing device 41 control unit 42 communication unit 43 storage unit 100 medical imaging system 431 conversion coefficient table 50 dose management device N communication network

Claims (3)

Extracting the contour of the subject region from each of a plurality of tomographic images of the abdomen of the subject generated in the X-ray CT examination of the subject, and based on the extracted contour, the area of the subject region or extracting means for calculating a contour length and extracting a maximum tomographic image having the maximum calculated area or the longest contour length;
approximation means for approximating the contour of the subject region in the maximum tomographic image with an ellipse to acquire the major and minor axes of the ellipse;
Radiation exposure for calculating an index representing the exposure dose in consideration of the body size of the subject in the X-ray CT examination based on the acquired major axis and minor axis and the dose information acquired during the X-ray CT examination. dose calculation means;
A medical image processing apparatus comprising: The approximation means selects arbitrary two points on the contour of the subject area in the maximum tomographic image , and passes through the selected two points and has a major axis of an ellipse having the same center of gravity as the center of the subject area. 2. The medical device according to claim 1, wherein the process of calculating the minor axis and the minor axis is performed multiple times, and an elliptical shape that approximates the contour of the subject region is determined based on the frequency of the obtained plurality of major and minor axes. Image processing device. the computer,
Extracting the contour of the subject region from each of a plurality of tomographic images of the abdomen of the subject generated in the X-ray CT examination of the subject, and based on the extracted contour, the area of the subject region or Extraction means for calculating the contour length and extracting the maximum tomographic image in which the calculated area is the maximum or the contour length is the longest;
approximation means for approximating the contour of the subject region in the maximum tomographic image with an ellipse and acquiring the major and minor axes of the ellipse;
Radiation exposure for calculating an index representing the exposure dose in consideration of the body size of the subject in the X-ray CT examination based on the acquired major axis and minor axis and the dose information acquired during the X-ray CT examination. dose calculation means,
A program to function as

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