Irradiation position confirmation support device, irradiation position confirmation support method, and irradiation position confirmation support program

Abstract

To improve accuracy of irradiation position checking.SOLUTION: An irradiation position checking support device includes: an acquisition unit for acquiring a first medical image capturing the inside of the body of a subject, a second medical image capturing the inside of the body of the subject after capturing the first medical image, and a third medical image capturing the inside of the body of the subject after capturing the second medical image; a region analysis unit for analyzing a region included in the first medical image acquired by the acquisition unit; a relation analysis unit for calculating first change information showing a change on a same tissue in the first medical image and in the second medical image by aligning the first medical image to the second medical image acquired by the acquisition unit, deforming a region analysis result by the region analysis unit on the basis of the first change information, and outputting a deformed region analysis result; and a generation unit for superimposing the deformed region analysis result by the relation analysis unit on the third medical image acquired by the acquisition unit, and generating a superimposition image.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an irradiation position confirmation support device, an irradiation position confirmation support method, and an irradiation position confirmation support program for assisting in the confirmation of an irradiation position.

Background Art

[0002] Stereotactic Irradiation (SRT), which has recently become mainstream in radiotherapy, is a technique for concentrating and irradiating radiation from a plurality of angles onto a treatment target site, thereby reducing the impact on normal tissues and cells and enabling precise irradiation of the treatment target site with radiation.

[0003] In addition to this, Intensity Modulated Radiation Therapy (IMRT), which can change the intensity of the irradiated radiation, has also been developed, and according to this, it has become possible to irradiate radiation pinpointedly even to tumors that are in complex contact with normal cells.

[0004] These functions have come to be standardly equipped in recent radiotherapy devices, and development of Image-Guided Radiotherapy (IGRT), which is an essential technology for SRT and IMRT, is also progressing. IGRT is a technique for accurately treating while correcting the position error during radiotherapy by referring to the image information (such as X-ray images) of the subject obtained immediately before and during irradiation.

[0005] With SRT, IMRT, and IGRT, it has become possible to concentrate radiation on tumors and reduce exposure to healthy cells, but there are still problems in applying them particularly to trunk tumors such as lung cancer. Lung cancer has a variable position even during treatment beam irradiation due to breathing, and it is said that the movement distance at this time can reach up to several tens of millimeters even within about one second. In order to surely administer radiation to the treatment target site accompanied by this respiratory movement, irradiation assuming that the tumor moves is required.

[0006] Traditionally, the irradiation area has been defined as the area to be treated plus a margin representing the expected range of movement, thereby ensuring that the actual area to be treated is irradiated. However, this method has the drawback of increasing the amount of radiation exposure to healthy tissue.

[0007] In contrast, there are methods such as breath-holding, where subjects temporarily hold their breath, but this places a significant burden on the subjects. As a method that simultaneously reduces exposure to normal tissue and the burden on the subjects as much as possible, motion tracking irradiation is used. Various methods using motion tracking irradiation have been developed. For example, there are methods that measure the movement of the body surface with infrared light and estimate the tumor location based on that, methods that measure and track metal markers inserted near the tumor using X-ray fluoroscopy, and even methods that perform real-time tracking based on accurate measurement of tumor dynamics (position changes, deformation, etc.) without markers.

[0008] Regardless of the method used above with motion tracking irradiation, when irradiating with the treatment beam, the angle and dose set in the treatment plan are used, and irradiation is performed semi-automatically to the identified tumor location. However, the identified treatment area is not always accurate. To avoid irradiation outside the treatment area, it is necessary to confirm that the tumor is being correctly tracked using X-ray fluoroscopic motion images during actual treatment irradiation.

[0009] Here, X-ray fluoroscopy images have the characteristic that, for objects on the same irradiation line, the area with the highest radiation absorption rate is depicted. Therefore, even in such confirmation screens, depending on the location and movement of the tumor, it may be hidden by other tissues and the tumor itself may not be depicted on the X-ray fluoroscopy image. This could lead to variability in judgment among physicians and hesitation in decision-making during treatments that require immediate decisions, and this aspect is considered a very significant challenge for motion tracking functionality.

[0010] Existing technologies for solving this problem include the following Patent Documents 1 and 2. The radiotherapy system of Patent Document 1 comprises a bed on which the patient is placed, a bed positioning device for positioning the bed during radiotherapy, and an X-ray imaging device having an X-ray generator for generating X-rays and an X-ray receiver for receiving X-rays from the X-ray generator. The bed positioning device generates bed positioning data based on first X-ray fluoroscopy image data taken by the X-ray imaging device and soft tissue projection image data generated from X-ray CT image data acquired during treatment planning.

[0011] Patent Document 2 discloses a medical image diagnostic device that superimposes information obtained by analyzing medical image data generated by a modality different from that of the device onto a medical image generated by the device itself. This medical image diagnostic device includes an acquisition unit that acquires at least one piece of analysis information obtained by analyzing medical image data of a subject generated by another medical image diagnostic device, which is a modality different from that of the device itself, and a generation unit that generates a superimposed image by superimposing an image showing the at least one piece of analysis information and a first medical image of the subject generated by the device itself, and displays it on a display. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2011-072457 [Patent Document 2] Japanese Patent Publication No. 2017-113312 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] With the existing technologies described above, it can be difficult to accurately display tumor and tissue area information on a two-dimensional irradiation position confirmation screen, even when dealing with variations between subjects at different points in time, such as during treatment planning and during treatment, which can occur over several days. The present invention aims to improve the accuracy of confirming the irradiation position. [Means for solving the problem]

[0014] An irradiation position confirmation support device, which is one aspect of the invention disclosed in this application, is characterized by comprising: an acquisition unit that acquires a first medical image taken inside the body of a subject, a second medical image taken inside the body of the subject after the acquisition of the first medical image, and a third medical image taken inside the body of the subject after the acquisition of the second medical image; a region analysis unit that analyzes a region included in the first medical image acquired by the acquisition unit; a related analysis unit that calculates first change information indicating changes in the same tissue in the first medical image and the second medical image by aligning the first medical image with the second medical image acquired by the acquisition unit, and outputs a deformed region analysis result by deforming the region analysis result by the region analysis unit based on the first change information; and a generation unit that generates a superimposed image by superimposing the deformed region analysis result by the related analysis unit onto the third medical image acquired by the acquisition unit. [Effects of the Invention]

[0015] According to a typical embodiment of the present invention, it is possible to improve the accuracy of confirming the irradiation position. Problems, configurations, and effects other than those mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a block diagram showing an example of the functional configuration of the irradiation position confirmation support system. [Figure 2] Figure 2 is a flowchart showing an example of the irradiation position confirmation support procedure using an irradiation position confirmation support device. [Figure 3] Figure 3 is an explanatory diagram showing an example of how superimposed images are displayed. [Figure 4] Figure 4 is an explanatory diagram showing an example of a contour line setting table. [Figure 5] Figure 5 is an explanatory diagram showing the inside of the human body. [Figure 6] Figure 6 is an explanatory diagram showing alignment example 1. [Figure 7] FIG. 7 is an explanatory diagram showing alignment example 2. [Figure 8] FIG. 8 is an explanatory diagram showing alignment example 3. [Figure 9] FIG. 9 is an explanatory diagram showing alignment example 4. [Figure 10] FIG. 10 is an explanatory diagram showing a display example of the monitor. [Figure 11] FIG. 11 is a block diagram showing an example of the hardware configuration of the irradiation position confirmation support system.

Mode for Carrying Out the Invention

[0017] In this embodiment, an example of an irradiation position confirmation support system capable of supporting the confirmation of estimation validity when presenting the estimated position of a lesion that is invisible or difficult to see depending on the angle or situation on the irradiation position confirmation screen during moving body tracking irradiation will be described.

[0018] <Functional Configuration Example of Irradiation Position Confirmation Support System> FIG. 1 is a block diagram showing a functional configuration example of the irradiation position confirmation support system. The irradiation position confirmation support system 100 includes an input device 101, an irradiation position confirmation support device 102, a medical information storage device 103, and a monitor 104.

[0019] The input device 101 receives data from an operator or a higher-level system and transmits it to the irradiation position confirmation support device 102. The medical information storage device 103 stores various data such as medical images and other medical information. The monitor 104 displays the medical images and other medical information output from the irradiation position confirmation support device 102.

[0020] The irradiation position confirmation support device 102 is connected to the input device 101, the medical information storage device 103, and the monitor 104. The irradiation position confirmation support device 102 accesses the medical information storage device 103 to read data from the medical information storage device 103 or write data to the medical information storage device 103.

[0021] The irradiation position confirmation support device 102 includes an acquisition unit 120, a region analysis unit 121, a related analysis unit 122, an image projection unit 123, and a generation unit 124.

[0022] The acquisition unit 120 acquires data output from the input device 101 and stores it in the medical information storage device 103. The data output from the input device 101 includes medical images such as planning CT (Computed Tomography) images, pre-treatment CBCT (Cone Beam Computed Tomography) images, and images for confirmation during treatment.

[0023] Planning CT images are CT images of a subject taken during the planning stage, several days before treatment, in the context of radiation therapy. Pre-treatment CBCT images are, for example, CBCT images taken to position the subject before the start of treatment. Intra-treatment confirmation images are images of the subject taken during treatment, and may be moving images or X-ray fluoroscopy moving images taken from two or more directions.

[0024] The region analysis unit 121 performs region analysis of the planning CT image. Region analysis is the process of identifying the regions of tissue, such as tumors and surrounding organs (for example, lungs, heart, spine, esophagus, etc., if the planning CT image is a chest image), from three-dimensional CT volume data, such as a planning CT image. The planning CT image after region analysis by the region analysis unit 121 is called the planning region analysis result. The region analysis unit 121 assigns a string indicating the name of the tissue (hereinafter referred to as the region name) to the region of the tissue identified in the planning region analysis result, for example.

[0025] The correlation analysis unit 122 performs alignment of medical images. Specifically, for example, the correlation analysis unit 122 compares the planning CT image and the pre-treatment CBCT image and aligns the positions of objects contained in each image. For example, the correlation analysis unit 122 moves the planning CT image to match the pre-treatment CBCT image and calculates first change information as a result of the alignment.

[0026] The related analysis unit 122 transforms the planning-time region analysis results using the first change information to obtain the pre-treatment CBCT image analysis results. The pre-treatment CBCT image analysis results should be equivalent to the region analysis results obtained by the region analysis unit 121 performing region analysis on the pre-treatment CBCT images.

[0027] Furthermore, the related analysis unit 122 aligns the projection medical image with the treatment confirmation image and calculates second change information to move the projection medical image in accordance with the treatment confirmation image.

[0028] Furthermore, the related analysis unit 122 uses the second change information to deform the projection analysis result generated by the image projection unit 123 and outputs the deformed projection analysis result.

[0029] The image projection unit 123 projects three-dimensional images and three-dimensional region information onto a two-dimensional plane. Specifically, for example, the image projection unit 123 generates a two-dimensional projected medical image by projecting a pre-treatment CBCT image, which is a three-dimensional image, onto a two-dimensional plane using pre-set projection conditions.

[0030] Projection conditions include the X-ray irradiation angle (treatment confirmation angle) used when creating the X-ray fluoroscopic measurement image (treatment confirmation image) displayed on the treatment confirmation screen. The projected medical image is a two-dimensional image that simulates the X-ray fluoroscopic measurement image when X-rays are irradiated from the same angle as the treatment confirmation image.

[0031] Furthermore, the image projection unit 123 generates a two-dimensional projection analysis result by projecting the pre-treatment CBCT image analysis result obtained from the related analysis unit 122 onto a two-dimensional plane based on the two-dimensional conversion information. The two-dimensional conversion information is information (for example, volume rendering) for converting the pre-treatment CBCT image analysis result, which includes the projection conditions described above and is three-dimensional region information, into two two-dimensional region information.

[0032] The generation unit 124 generates a superimposed image by superimposing two medical images and outputs it to the monitor 104. Specifically, for example, the generation unit 124 generates a superimposed image of the deformation projection analysis result and the image used for confirmation during treatment.

[0033] <Procedure for confirming irradiation position> Figure 2 is a flowchart showing an example of the irradiation position confirmation support procedure using the irradiation position confirmation support device 102. In Figure 2, the execution timing of each step is clearly indicated by a time axis that identifies various shooting timings.

[0034] After acquiring the planning CT image and before acquiring the pre-treatment CBCT image, the region analysis unit 121 performs region analysis on the planning CT image and generates the planning region analysis results (step S201) based on instructions from a higher-level system or operator. The region analysis unit 121 stores the planning region analysis results in the medical information storage device 103.

[0035] After acquiring pre-treatment CBCT images and before acquiring images for confirmation during treatment, the related analysis unit 122 aligns the planning CT image with the pre-treatment CBCT image and calculates first change information as a result of the alignment (step S202). The related analysis unit 122 stores the first change information in the medical information storage device 103.

[0036] After acquiring pre-treatment CBCT images and before acquiring images for confirmation during treatment, the related analysis unit 122 transforms the planning-time region analysis results generated in step S201 using the first change information calculated in step S202 to generate pre-treatment CBCT image analysis results (step S203). These pre-treatment CBCT image analysis results should be equivalent to the region analysis results obtained by region analysis of the pre-treatment CBCT images by the region analysis unit 121. The related analysis unit 122 stores the pre-treatment CBCT image analysis results in the medical information storage device 103.

[0037] After acquiring pre-treatment CBCT images and before acquiring intra-treatment confirmation images, the image projection unit 123 generates a two-dimensional projected medical image by projecting the pre-treatment CBCT images onto a two-dimensional plane using pre-set projection conditions (step S204). The image projection unit 123 stores the projected medical image in the medical information storage device 103.

[0038] After acquiring pre-treatment CBCT images and before acquiring images for confirmation during treatment, the image projection unit 123 generates a two-dimensional projected medical image as a projection analysis result by projecting the pre-treatment CBCT image analysis results onto a two-dimensional plane based on the two-dimensional conversion information (step S205). The image projection unit 123 stores the projected medical image in the medical information storage device 103.

[0039] After capturing the image for confirmation during treatment, the related analysis unit 122 aligns the projected medical image and the image for confirmation during treatment using the same method as in step S202, and calculates second change information for moving the projected medical image to match the image for confirmation during treatment (step S206). The second change information is also a vector for each coordinate value, similar to the first change information. The related analysis unit 122 stores the second change information in the medical information storage device 103.

[0040] After capturing images for confirmation during treatment, the related analysis unit 122 deforms the projection analysis results using the second change information and outputs the deformed projection analysis results (step S207). These deformed projection analysis results should be equivalent to the region analysis results obtained by the region analysis unit 121 from the images used for confirmation during treatment.

[0041] After capturing an image for confirmation during treatment, the generation unit 124 superimposes the deformation projection analysis results onto the image for confirmation during treatment to generate a superimposed image, which is then output to the monitor 104 (step S208). As a result, the superimposed image is displayed on the monitor 104.

[0042] <Example of superimposed image display> Figure 3 is an explanatory diagram showing an example of superimposed image display. (a) is the treatment confirmation image 301 used in step S206. (b) is the deformation projection analysis result 302 obtained in step S207 when the region is deformed by the related analysis unit 122 to match the treatment confirmation image 301. (c) shows the superimposed image 303 superimposed in step S208.

[0043] The intra-treatment confirmation image 301 and the deformation projection analysis result 302 are images of the chest of the same subject. In the case of the intra-treatment confirmation image 301 (a), region analysis has not been performed by the region analysis unit 121, so the contour lines and region names of the regions have not been identified.

[0044] On the other hand, in (b), the deformation projection analysis result 302 is obtained by the region analysis (step S201) in the region analysis unit 121, and in the region analysis result at the time of planning, region names (right lung 311, left lung 312, tumor 313, heart 314, spine 315) have already been assigned to the region along with the contour lines.

[0045] In (b), for convenience, there is no overlap of regions, but in reality, there may be overlap. The generation unit 124 superimposes the contour lines (indicated by white dotted lines, dashed lines, chain lines, and double lines) and region names of each region (right lung 311, left lung 312, tumor 313, heart 314, spine 315) of the deformation projection analysis result 302 onto the intra-treatment confirmation image 301, as in (c). Note that the contour line settings can also be defined in advance according to the region.

[0046] Figure 4 is an explanatory diagram showing an example of a contour line setting table. The contour line setting table 400 is stored in the medical information storage device 103. The contour line setting table 400 has as fields a region 401, a line type 402, a line color 403, and a line thickness 404.

[0047] Region 401 includes the right lung 311, left lung 312, tumor 313, heart 314, spine 315, and the irradiation target area in motion tracking irradiation. Line type 402 distinguishes the drawing format of the contour line for each region 401, such as dotted line, dashed line, chain line, double line, etc. Line color 403 distinguishes the color of the contour line for each region 401, such as red, blue, purple, etc. Line thickness 404 distinguishes the thickness of the contour line for each region 401, such as 1 mm, 0.75 mm, etc.

[0048] Figures 3 and 4 show examples of overlaying the contour lines of region 401. However, the information overlaid here is not limited to contour lines. For example, each region 401 can be represented as a semi-transparent fill and then overlaid. In this case as well, by utilizing color representation in addition to black and white, it is possible to display region 401 in an easily understandable way. However, since using a fill representation would overwrite the original treatment confirmation image 301 with color information, the representation of region 401 in this way should be designed according to the user's preference and in a way that does not make the treatment confirmation image 301 itself difficult to see.

[0049] <Projection method> Next, we will explain how the image projection unit 123 uses two-dimensional conversion information to project the three-dimensional pre-treatment CBCT image analysis results as two-dimensional projection analysis results.

[0050] Figure 5 is an explanatory diagram showing the inside of the human body. (a) is a partial lateral cross-sectional view of the subject's body 500. In (a), assuming that another person's eye 501 is in front of the body 500 and the body 500 is in the line of sight of the eye 501, the position of the eye 501 becomes the X-ray irradiation position where the X-rays are irradiated. (b) is a partial orthogonal cross-sectional view of the subject's body 500. In (b), the three-dimensional positional relationship is correctly represented in two dimensions (excluding the skin).

[0051] In other words, if we consider the line of sight direction 502 from the position of the eye 501 in (a) as the projection direction, then inside the human body 500, the organ tissues are located in the order of ribs 511, lungs 512 (right lung 311, left lung 312), and spine 315. Therefore, a part of the lungs 512 and most of the spine 315 are located in front of them (towards the starting point of the arrow indicating the line of sight direction 502) and are therefore not depicted.

[0052] Incidentally, in the case of X-ray fluoroscopic images, regardless of their three-dimensional positional relationship, objects with high radiation absorption rates are preferentially depicted from the line of sight 502. Therefore, objects with low radiation absorption rates that are on the same irradiation line as objects with high radiation absorption rates are not depicted. Since bones such as ribs 511 and vertebrae 315 are objects with high radiation absorption rates, according to the principle of radiation absorption rates, if a tumor 313 is on the same irradiation line as objects with high radiation absorption rates such as bone regions, not only the ribs 511 in front of the tumor 313 but also the vertebrae 315 behind the tumor 313 will be measured by X-ray fluoroscopy, resulting in the tumor 313 not being depicted.

[0053] Here, regarding the 2D transformation information in the image projection unit 123, the image projection unit 123 may project faithfully to the 3D positional relationship, as shown in (b). In this case, the projection method can be implemented by applying a technique called volume rendering. Volume rendering methods include a method that displays the highest value in the line of sight direction 502 (MIP: Maximum Identification Projection), a method that displays a value obtained by adding voxel values ​​from the side furthest from the viewpoint (Ray Sum: Sum Projection), a method that changes the color (pseudocolor) and transparency according to the voxel value, and a method that prioritizes displaying areas where the voxel value changes abruptly. In addition, a surface rendering method can also be used to represent the surface by depicting only the isosurfaces of the voxel values.

[0054] Furthermore, it is possible to superimpose only organs that are physically in contact with the tumor 313, or organs whose surface (boundary) is closer than a certain point. In any case, as mentioned earlier, the design ensures that the treatment confirmation image 301 itself does not become difficult to see.

[0055] <Example of image change> Next, we will describe a method for indicating the extent of changes in the subject's body from the time of treatment planning to the time of treatment implementation. The series of processes described here are achieved by aligning the analysis results of the 3D image at the time of treatment planning with the image at the time of treatment implementation. Therefore, changes that occurred between the time of treatment planning and the time of treatment can be quantified using the change information obtained during this alignment process.

[0056] Figure 6 is an explanatory diagram showing alignment example 1. It includes tissue images 610 and 620 that simulate a certain tissue depicted in the planning CT image 601 and the pre-treatment CBCT image 602. Each intersection point (grid point) of the grid in the planning CT image 601 and the pre-treatment CBCT image 602 represents a coordinate point. Compared to the tissue image 610 in the planning CT image 601, the tissue image 620 in the pre-treatment CBCT image 602 is located to the upper left.

[0057] When the related analysis unit 122 aligns the planning CT image 601 and the pre-treatment CBCT image 602 at the same coordinate points, a alignment image 603 is obtained. In the alignment image 603, each coordinate point of the planning CT image 601 is fixed. On the other hand, each coordinate point of the pre-treatment CBCT image 602 is shifted from the position of each coordinate point of the planning CT image 601 according to the movement component from the tissue image 610 to the tissue image 620, and the grid of the pre-treatment CBCT image 602 becomes distorted according to this shift.

[0058] The related analysis unit 122 calculates first change information 604 from the alignment image 603. The first change information 604 is represented by a vector between each coordinate point of the planning CT image 601 and each coordinate point of the pre-treatment CBCT image 602, where the grid has shifted according to the positional misalignment. In other words, the vector is information indicating where each coordinate point of the planning CT image 601 moves after alignment.

[0059] To quantitatively estimate the degree of movement within the subject's body, the related analysis unit 122 first performs rigid body alignment without deformation on the planning CT image 601 and the pre-treatment CBCT image 602. Subsequently, the related analysis unit 122 calculates the first change information 604 as shown here from the results of the non-rigid body alignment.

[0060] The correlation analysis unit 122 calculates, for example, the sum or average displacement of the vectors of each coordinate point as the first change information 604. The correlation analysis unit 122 may then determine whether the first change information 604 is greater than or equal to a preset threshold, or normalize the first change information 604 to a value between 0 and 1. Such determination results and normalization results are called estimated likelihoods because they indicate the likelihood of alignment. Furthermore, if it is desired to determine the first change information 604 for each tissue individually, the correlation analysis unit 122 may calculate the first change information 604 for each tissue.

[0061] The generation unit 124 may also superimpose the estimated likelihood onto the region in the treatment confirmation image, along with the contour lines of the region analyzed by the region analysis unit 121.

[0062] Figure 7 is an explanatory diagram showing Alignment Example 2. In Alignment Example 2, the pre-treatment CBCT image 702 is an image taken when the tissue contracted, and the size of the tissue image 620 is smaller compared to Figure 6. For example, if the tissue depicted as tissue images 610 and 620 is a tumor, the size of the tumor will decrease during the course of treatment due to the effect of the treatment. The related analysis unit 122, similar to Alignment Example 1, aligns the planning CT image 601 and the pre-treatment CBCT image 702 to generate an alignment image 703, and calculates the first change information 704 from the alignment image 703.

[0063] Figure 8 is an explanatory diagram showing registration example 3. In registration example 3, the pre-treatment CBCT image 802 is an image acquired when the tissue was magnified, and the size of the tissue image 620 is larger compared to Figure 6. For example, if the tissue depicted as tissue images 610 and 620 is a tumor, and it has worsened between the planning stage and the treatment stage, the size of the tumor will decrease. Similar to registration examples 1 and 2, the related analysis unit 122 aligns the planning stage CT image 601 with the pre-treatment CBCT image 802 to generate a registration image 803, and calculates the first change information 804 from the registration image 803.

[0064] As shown in Figures 7 and 8, the vector directions of each coordinate point after alignment can be radial. In such cases, as in alignment example 1 in Figure 6, the sum or average of the vectors cancels each other out, making it impossible to show the change in tumor size. Therefore, in alignment examples 2 and 3 shown in Figures 7 and 8, the correlation analysis unit 122 can quantify the change in size by using the sum or average of the magnitudes of each vector as a quantitative value. It is also possible that both the size and movement occur, but by using both the sum or average of the vectors and the sum or average of their magnitudes, both the size change and movement can be quantified.

[0065] Figure 9 is an explanatory diagram showing alignment example 4. Figure 9 shows an example of quantifying the positional relationship between the tumor and each organ after alignment. That is, it is an example of quantifying the relative change (distance) between organs and tumors, rather than the absolute change (movement) of each organ or tumor as in Figure 6. The region analysis unit 121 does not perform region analysis on the pre-treatment CBCT image, but information equivalent to the region analysis results of the region analysis unit 121 can be obtained through alignment by the association analysis unit 122. In alignment example 4, the association analysis unit 122 can also determine the centroid of the tumor and the centroid of each tissue region in both the planning region analysis result 901 and the pre-treatment image analysis result 902, and use the distance between the centroids as an indicator to quantify the positional relationship between the tumor and each tissue.

[0066] Specifically, for example, in the planning CT image 901, the distance between the center of gravity w11 of the tumor 911 and the center of gravity w12 of the right lung 912 is D1, and in the pre-treatment image analysis result 902, the distance between the center of gravity w21 of the tumor 911 and the center of gravity w22 of the right lung 912 is D2. The related analysis unit 122 can calculate the displacement, which is a change in positional relationship, as first change information by calculating the absolute value |D1-D2| of the difference between the distances between the centers of gravity D1 and the distance between the centers of gravity D2.

[0067] Even in this case, the correlation analysis unit 122 may determine whether the absolute value of the difference |D1-D2| is greater than or equal to a pre-set threshold, or it may normalize the absolute value of the difference |D1-D2| to a value between 0 and 1. Such determination results and normalization results also become the estimated likelihood described above.

[0068] Therefore, the generation unit 124 may superimpose the estimated likelihood onto the region in the treatment confirmation image, along with the contour lines of the region analyzed by the region analysis unit 121. This makes it possible to quantitatively show the positional relationship between the tumor and the tissue, rather than the amount of change in each tissue.

[0069] <Visualization of the estimated likelihood of tumor location> Next, we will describe an example of visualizing the estimated likelihood of tumor location. For example, for the tumor location estimated by the process shown in Figure 2, the irradiation position confirmation support device 102 can determine how much it has changed from the planning stage, as explained in the indices in Figures 6 to 9, calculate the estimated likelihood, and superimpose it.

[0070] Furthermore, the irradiation position confirmation support device 102 can also use methods other than the processing shown in Figure 2 to estimate the tumor's location. For example, it may be possible to perform region analysis on pre-treatment CBCT images. The irradiation position confirmation support device 102 can also determine the difference in results when the location is estimated using multiple methods (including the processing shown in Figure 2), and if the difference is large, it can determine that the estimated likelihood is low, and if it is small, it can determine that the estimated likelihood is high. The generation unit 124 can change the type of contour line according to the magnitude of the estimated likelihood, or it can superimpose the estimated likelihood value as text.

[0071] While it is difficult to guarantee the accuracy of the estimated tumor location since the tumor is not depicted on the pre-treatment CBCT image, visualizing it as a likelihood, as shown here, can help assist operators in judging its validity.

[0072] <Video> This section describes the case where the planning CT image and pre-treatment CBCT image are four-dimensional images, i.e., moving images (multiple images in a time series). For example, it is known that the chest is greatly affected by respiration, and tumors in the lung region can move significantly. In this case, the related analysis unit 122 aligns images that are aligned with the periodically fluctuating respiratory cycle within the body, such as the planning CT image during exhalation and the pre-treatment CBCT image during exhalation, and the planning CT image during inspiration and the pre-treatment CBCT image during inspiration.

[0073] One method for acquiring respiratory cycle data involves simultaneously attaching markers to the subject's body surface when acquiring planning CT images (video), pre-treatment CBCT images (video), and intra-treatment confirmation images (video), capturing their movement with a camera, and the acquisition unit 120 acquiring respiratory cycle waveform data for each image. The data is then analyzed by synchronizing the timing. Alternatively, the acquisition unit 120 may pre-determine the movement of bone and other regions at each point in the respiratory cycle and estimate the respiratory cycle point for each acquired image.

[0074] The related analysis unit 122 synchronizes (matches) the waveform data of two respiratory cycles and performs alignment between images taken at the same time. Specifically, for example, in step S202, the related analysis unit 122 synchronizes the waveform data of the respiratory cycle at the time of acquisition of the planning CT image (moving image) with the waveform data of the respiratory cycle at the time of acquisition of the pre-treatment CBCT image (moving image), and performs alignment between the planning CT image and the pre-treatment CBCT image taken at the same time.

[0075] Similarly, in step S206, the waveform data of the respiratory cycle at the time of acquisition of the intra-treatment confirmation image (moving image) and the waveform data of the respiratory cycle at the time of acquisition of the pre-treatment CBCT image (moving image) are synchronized, and alignment is performed using the intra-treatment confirmation image and pre-treatment CBCT image at the same time. This makes it possible to perform alignment while reducing the effect of tumor movement due to respiration.

[0076] Then, the related analysis unit 122 deforms the projection analysis results obtained with reduced influence of tumor movement due to respiration (step S205) using the second change information obtained with reduced influence of tumor movement due to respiration (step S206) (step S207), thereby obtaining a more accurate deformed projection analysis result.

[0077] <Example of display on monitor 104> Figure 10 is an explanatory diagram showing an example of the display of monitor 104. Monitor 104 displays a frontal superimposed image 1001, a side superimposed image 1002, and a graph 1003. The frontal superimposed image 1001 is a superimposed image 303 viewed from the front of the subject, and the side superimposed image 1002 is a superimposed image 303 viewed from the side of the subject.

[0078] Graph 1003 shows the waveform data 1004 of the subject's respiratory cycle. The horizontal axis represents time, and the vertical axis represents the amplitude of respiration (inspiratory volume). The waveform data 1004 is synchronized waveform data of the respiratory cycle at the time of acquisition of the planning CT image (moving image) and the respiratory cycle at the time of acquisition of the pre-treatment CBCT image (moving image). The frontal superimposed image 1001 and the lateral superimposed image 1002 are superimposed images 303 at respiratory timing 1005. When an analysis that takes the respiratory cycle into account as described above is performed, it becomes possible to determine whether the current time is during exhalation or inhalation in the respiratory cycle.

[0079] Although the above-described embodiment did not include a medical image acquisition device (not shown) in the irradiation position confirmation support device 102, the irradiation position confirmation support device 102 may include a medical image acquisition device, and the irradiation position confirmation support device 102 may function as part of the medical image acquisition device.

[0080] <Example of hardware configuration for the irradiation position confirmation support system 100> Figure 11 is a block diagram showing an example of the hardware configuration of the irradiation position confirmation support system 100. The irradiation position confirmation support system 100 includes a processor 1101, a storage device 1102, an input device 1103, an output device 1104, and a communication interface (communication IF) 1105. The processor 1101, storage device 1102, input device 1103, output device 1104, and communication IF 1105 are connected by a bus 1106. The processor 1101 controls the irradiation position confirmation support system 100. The storage device 1102 serves as the work area for the processor 1101. The storage device 1102 is also a non-temporary or temporary recording medium that stores various programs and data. Examples of storage devices 1102 include ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), and flash memory. The input device 1103 receives data. Input devices 1103 include, for example, a keyboard, mouse, touch panel, numeric keypad, scanner, microphone, and sensor. Output devices 1104 output data. Output devices 1104 include, for example, a display, printer, and speaker. Communication IF 1105 connects to the network and sends and receives data.

[0081] The input device 1103 may include the input device 101 shown in Figure 1. The storage device 1102 may include the medical information storage device 103 shown in Figure 1. The output device 1104 may include the monitor 104 shown in Figure 1.

[0082] As explained above, the irradiation position confirmation support device 102 can assist in confirming the validity of the estimation when presenting the estimated position of a lesion that is not visible or difficult to see depending on the angle or situation on the irradiation position confirmation screen during motion tracking irradiation.

[0083] In the above-described embodiment, the image projection unit 123 performs projection in steps S204 and S205, but the 3D planning CT image and the 3D pre-treatment CBCT image may be projected onto a 2D plane before the region analysis by the region analysis unit 121.

[0084] It should be noted that the present invention is not limited to the embodiments described above, but includes various modifications and equivalent configurations within the spirit of the attached claims. For example, the embodiments described above are described in detail to make the present invention easier to understand, and the present invention is not necessarily limited to having all of the described configurations. Furthermore, some of the configurations of one embodiment may be replaced with those of another embodiment. Furthermore, some of the configurations of one embodiment may be added to those of another embodiment. Furthermore, some of the configurations of each embodiment may be added, deleted, or replaced with other configurations.

[0085] Furthermore, each of the aforementioned configurations, functions, processing units, and processing means may be implemented in hardware, for example, by designing them as integrated circuits, or they may be implemented in software by having a processor interpret and execute programs that realize each function.

[0086] Information such as programs, tables, and files that implement each function can be stored in memory, hard disks, SSDs (Solid State Drives), or on recording media such as IC (Integrated Circuit) cards, SD cards, and DVDs (Digital Versatile Discs).

[0087] Furthermore, the control lines and information lines shown are those deemed necessary for explanation purposes and do not necessarily represent all control lines and information lines required for implementation. In reality, it can be assumed that almost all components are interconnected. [Explanation of symbols]

[0088] 100 Irradiation Position Confirmation Support System 101 Input Device 102 Irradiation position confirmation support device 103 Medical information storage device 104 Monitors 120 Acquisition Department 121 Area Analysis Department 122 Related Analysis Department 123 Image projection unit 124 Generation part

Claims

1. An acquisition unit that acquires a first medical image taken inside the body of a subject, a second medical image taken inside the body of the subject after the acquisition of the first medical image, and a third medical image taken inside the body of the subject after the acquisition of the second medical image. A region analysis unit analyzes the region included in the first medical image acquired by the acquisition unit, The related analysis unit aligns the first medical image with the second medical image acquired by the acquisition unit, calculates first change information indicating changes in the same tissue within the first medical image and the second medical image, and outputs a deformed region analysis result by deforming the region analysis result from the region analysis unit based on the first change information. A generation unit generates a superimposed image by superimposing the deformation region analysis results obtained by the related analysis unit onto the third medical image obtained by the acquisition unit. An irradiation position confirmation support device characterized by having the following features.

2. The irradiation position confirmation support device according to claim 1, The region analysis results and the deformation region analysis results include information that identifies the shape of the region, The generation unit generates the superimposed image by superimposing information that identifies the shape of the region onto the third medical image. A device for confirming the irradiation position, characterized by the above features.

3. The irradiation position confirmation support device according to claim 2, The information that identifies the shape of the region is the contour line of the region. A device for confirming the irradiation position, characterized by the above features.

4. The irradiation position confirmation support device according to claim 2, The information that identifies the shape of the region is an image of the region made semi-transparent. A device for confirming the irradiation position, characterized by the above features.

5. The irradiation position confirmation support device according to claim 1, The first change information is information indicating the displacement of the tissue. A device for confirming the irradiation position, characterized by the above features.

6. The irradiation position confirmation support device according to claim 1, The first change information is information indicating a change in the size of the tissue. A device for confirming the irradiation position, characterized by the above features.

7. The irradiation position confirmation support device according to claim 1, The region analysis results and the deformation region analysis results include a string indicating the name of the region, The generation unit generates the superimposed image by superimposing the string onto the third medical image. A device for confirming the irradiation position, characterized by the above features.

8. The irradiation position confirmation support device according to claim 7, The generation unit generates the superimposed image by superimposing the string onto the location of the region indicated by the string on the third medical image. A device for confirming the irradiation position, characterized by the above features.

9. The irradiation position confirmation support device according to claim 1, The related analysis unit calculates an estimated likelihood indicating the plausibility of the change in the region due to the alignment of the first medical image and the second medical image, based on the first change information. The generation unit generates the superimposed image by superimposing the estimated likelihood onto the third medical image. A device for confirming the irradiation position, characterized by the above features.

10. The irradiation position confirmation support device according to claim 9, The generation unit generates the superimposed image by superimposing the estimated likelihood onto the location of the region on the third medical image that corresponds to the estimated likelihood. A device for confirming the irradiation position, characterized by the above features.

11. The irradiation position confirmation support device according to claim 1, The related analysis unit aligns the second medical image with the second medical image to calculate second change information indicating changes in the same tissue within the second medical image and the third medical image, and outputs the deformation region analysis result by deforming the deformation region analysis result based on the second change information. A device for confirming the irradiation position, characterized by the above features.

12. The irradiation position confirmation support device according to claim 1, The acquisition unit acquires a plurality of time-series first medical images, periodic first fluctuation information within the subject's body at the time the first medical images were taken, a plurality of time-series second medical images, periodic first fluctuation information within the subject's body at the time the first medical images were taken, and periodic second fluctuation information within the subject's body at the time the second medical images were taken. The related analysis unit performs alignment of the first medical image and the second medical image at the timing when the first variation information and the second variation information are synchronized. A device for confirming the irradiation position, characterized by the above features.

13. An irradiation position confirmation support method performed by an irradiation position confirmation support device having a processor for executing a program and a storage device for storing the program, The aforementioned irradiation position confirmation support method is: The aforementioned processor, An acquisition process that acquires a first medical image taken inside the subject's body, a second medical image taken inside the subject's body after the acquisition of the first medical image, and a third medical image taken inside the subject's body after the acquisition of the second medical image. A region analysis process that analyzes the region contained within the first medical image acquired by the acquisition process, The first medical image is aligned with the second medical image acquired by the acquisition process, thereby calculating first change information indicating changes in the same tissue within the first medical image and the second medical image, and based on the first change information, the region analysis results from the region analysis process are modified to output a modified region analysis result; and the related analysis process outputs a modified region analysis result. A generation process that generates a superimposed image by superimposing the deformation region analysis results obtained by the aforementioned related analysis process onto the third medical image obtained by the acquisition process, A method for supporting confirmation of irradiation position, characterized by performing the following:

14. In the processor, An acquisition process that acquires a first medical image taken inside the subject's body, a second medical image taken inside the subject's body after the acquisition of the first medical image, and a third medical image taken inside the subject's body after the acquisition of the second medical image. A region analysis process that analyzes the region contained within the first medical image acquired by the acquisition process, The first medical image is aligned with the second medical image acquired by the acquisition process, thereby calculating first change information indicating changes in the same tissue within the first medical image and the second medical image, and based on the first change information, the region analysis results from the region analysis process are modified to output a modified region analysis result; and the related analysis process outputs a modified region analysis result. A generation process that generates a superimposed image by superimposing the deformation region analysis results obtained by the aforementioned related analysis process onto the third medical image obtained by the acquisition process, A program to support confirmation of irradiation position, characterized by causing the program to execute.

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