JP2010069086A - Radiation therapy system and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance safety, reliability, and efficiency in a therapy by providing a high-definition image synchronized with the respiration of a patient, with respect to a radiation therapy. <P>SOLUTION: The monitor image generating part 64 of a CT console 6 re-constitutes DRR images in the same direction as that of a KV-XR image, based on four-dimensional CT image data. Then, the monitor image generating part 64 generates a monitor image, which is obtained by replacing a real-time KV-XR image with the DRR image having the closest landmark coordinate, i.e., being most coincident in a respiration time phase among the reconstituted DRR images, or a monitor image where both images are displayed in parallel. An RT console 2 displays the generated monitor image on a display. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a monitor image display for accurately irradiating an affected area with radiation in radiotherapy.

  In radiotherapy, radiotherapy planning and dose distribution calculations are performed using preoperative CT images, and the patient position at the time of planning and the position at the time of irradiation are displayed on a CT simulator or X-ray simulator, such as a DRR (Digital Reconstructed Radiography) image. After collating by comparison and positioning the patient, irradiation is performed.

  However, when irradiating the lung, liver or other thoracic / abdominal organs, there is a risk of irradiating normal parts other than the affected area because of the respiratory movement of the affected area. For this reason, in radiation therapy to organs with respiratory motion, respiratory synchronized irradiation is often performed. In respiratory synchronized irradiation, respiration is monitored by the movement of the abdominal wall, and for example, the movement of the organ is stopped for a relatively long time in one respiratory cycle, and radiation irradiation is performed in accordance with the end expiratory period with high position reproducibility. (For example, refer to Patent Document 1).

  Recently, image-assisted radiotherapy that enables radiotherapy to be performed while displaying an image immediately before radiotherapy such as MV-XR, KV-XR, MV-CT, KV-CT, and confirming the image. (IGRT: Image-Guided Radiation Therapy) has attracted attention.

  The MV-XR (Mega Voltage X-Ray) displays a MV (megavolt) X-ray image from the viewpoint of the treatment source by providing a detector at the opposite position of the high-energy X-ray from the treatment radiation source. To do. KV-XR (Kilo Voltage X-Ray) is a KV that includes a treatment isocenter by arranging a pair of KV (kilovolt) X-ray tube and flat panel detector (FPD) perpendicular to the irradiation axis of the therapeutic radiation source. -An XR image is displayed (for example, refer patent document 2).

  For MV-CT (Mega Voltage CT) and KV-CT (Kilo Voltage CT), a radiation source for treatment and a radiation source similar to KV-XR are rotated about 200 ° around the patient, and a cone beam CT is imaged. And display.

JP 2006-51199 A JP-A-8-206103

  However, since MV-XR and MV-CT have an X-ray tube voltage that is too high, they are not suitable for imaging of soft tumor tissue, and the bone and lung structures are barely understood. Therefore, it is possible to monitor when the irradiation field is extremely off, but it is difficult to image and feed back a fine positional shift of the soft tissue cancer tissue. Further, KV-XR and KV-CT have an unsolved problem that the image quality is better than MV-XR / MV-CT, but it is difficult to say that it is sufficient.

  The present invention has been made to solve the above-described problems caused by the prior art, and provides a high-definition monitor image and can improve the safety and certainty of treatment and a radiotherapy system and image display. It aims to provide a method.

  In order to solve the above-mentioned problems and achieve the object, the present invention according to claim 1 is a volume image data collecting means for collecting volume image data for one respiratory cycle of a patient undergoing radiation therapy, and the volume image data. Reconstructing means for reconstructing images of each respiratory phase from volume image data collected by the collecting means, X-ray photographing means for performing X-ray photographing of the patient from two or more different directions, and the reconstructing means A matching image selecting means for selecting an image whose respiratory time phase most closely matches an image photographed by the X-ray photographing means from among the images reconstructed by the method, and an image selected by the matching image selecting means And an image display means for displaying in synchronization with respiration.

  According to a sixth aspect of the present invention, there is provided a volume image data collecting step for collecting volume image data for one respiratory cycle of a patient undergoing radiation therapy, and each volume image data collected by the volume image data collecting step. A reconstruction step for reconstructing an image of a respiratory time phase, an X-ray imaging step for performing X-ray imaging of the patient from two or more different directions, and the X from the images reconstructed by the reconstruction step A matching image selection step for selecting an image whose respiratory time phase most closely matches an image captured in the line imaging step, and an image display step for displaying the image selected in the matching image selection step in synchronization with the patient's breathing , Including.

  According to the first or sixth aspect of the present invention, it is possible to improve the safety and certainty of treatment by providing a high-definition monitor image.

  Exemplary embodiments of a radiation therapy system and an image display method according to the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the description will focus on the case of performing respiratory synchronization irradiation.

  First, the configuration of the radiation therapy system according to the present embodiment will be described. FIG. 1 is a diagram illustrating a configuration of a radiation therapy system according to the present embodiment. As shown in the figure, the radiotherapy system 100 includes a radiotherapy device 1, an RT console 2, a treatment planning device 3, a respiratory synchronization device 4, a CT scanner 5, and a CT console 6.

  The radiation therapy apparatus 1 includes a radiation therapy bed and a linac. The patient is laid on a radiation treatment bed, and irradiation is performed after the patient is positioned by moving the bed from 3 to 5 axes. A linac (linear accelerator: a linear accelerator) can generally generate MV class X-rays or electron beams, but a collimator is installed at the generating port to realize an irradiation shape and dose distribution based on a treatment plan. . In recent years, a multi-leaf collimator (MLC) that can form a dose distribution corresponding to a complicated tumor shape by a plurality of movable leaves is often used as a collimator.

  This radiotherapy apparatus 1 has two pairs of KV-X-ray source 11 and FPD 12. The pair of the KV-X-ray source 11 and the FPD 12 is arranged perpendicular to the irradiation axis of the therapeutic radiation source. The KV-X-ray source 11 is an X-ray source that emits X-rays for obtaining a KV-XR image, and the FPD 12 is a detector that detects X-rays transmitted through the patient. By aligning the center points of the two pairs of images with the isocenter of the radiation therapy, it is possible to calculate how much any landmark (LANDMARK) on the image is deviated from the isocenter in which direction.

  The RT console 2 is a console that controls the radiotherapy apparatus 1 based on the treatment plan created by the treatment planning apparatus 3. The RT console 2 includes a monitor display device and displays a monitor image. However, the RT console 2 does not simply display the KV-XR image as the monitor image, but displays the CT image corresponding to the KV-XR image by replacing it with the KV-XR image. Alternatively, the RT console 2 displays a CT image corresponding to the KV-XR image side by side with the KV-XR image. Details of the monitor image displayed on the RT console 2 will be described later.

  The treatment planning device 3 is a device for creating a radiation treatment plan. Specifically, the treatment planning apparatus 3 performs segmentation of the tumor using the image data transferred from the CT console 6, and sets the center of the tumor, that is, the treatment isocenter, and the optimal radiation dose distribution for the entire segmented tumor. Dose distribution calculation and treatment plan to realize The radiation treatment plan planned by the treatment planning device 3 is transferred to the RT console 2 in accordance with the DICOM-RT standard, and radiation irradiation is performed based on the treatment plan.

  The respiratory synchronization device 4 is a device that monitors a patient's respiratory state and generates a trigger in a specific respiratory state in order to perform radiation therapy in respiratory synchronization. Here, the respiratory synchronization device 4 generates a trigger at the end-expiratory period when the organ stops for a relatively long time in the respiratory cycle.

  The CT scanner 5 is a device that collects data for generating a volume CT image by scanning a patient with X-rays. At the time of treatment planning, the patient is laid on the bed of the CT scanner 5 in the same position as at the time of treatment, and one breath is imaged on the basis of a trigger signal at the end of expiration by the respiratory synchronization device 4.

  The CT console 6 is a device that controls the CT scanner 5 and performs image reconstruction. The volume CT image reconstructed by the CT console 6 is transferred to the treatment planning device 3 as DICOM standard image data, and irradiation is performed based on the treatment plan created by the treatment planning device 3.

  Specifically, the breathing of the patient laid on the radiation therapy bed is monitored by the same respiratory synchronization device 4 that performed the synchronous CT imaging, and the end-expiratory trigger similar to the synchronous CT imaging is generated. Here, the patient is fixed to the radiation treatment bed so that the center of the patient's affected area in the treatment plan coincides with the isocenter position of the radiation treatment apparatus. The patient's end-expiratory trigger signal is sent to the RT console 2, and the RT console 2 performs irradiation so that X-rays or electron beams are generated from the linac of the radiotherapy apparatus 1 when the end-expiratory trigger signal comes. By controlling, respiratory synchronized radiation irradiation is realized.

  Further, the CT console 6 receives the KV-XR image from the RT console 2 and generates a monitor image to be displayed on the display device of the RT console 2.

  Next, the functional configuration of the CT console 6 will be described. FIG. 2 is a block diagram showing a functional configuration of the CT console 6. As shown in the figure, the CT console 6 includes an imaging control unit 61, an image reconstruction unit 62, an image data storage unit 63, a monitor image generation unit 64, a communication unit 65, and a control unit 66. Have.

  The imaging control unit 61 is a control unit that controls the CT scanner 5 and collects data for respiratory synchronization CT images, and stores the collected data in the image data storage unit 63. The image reconstruction unit 62 is a processing unit that reconstructs the data collected by the imaging control unit 61 and generates a CT image, and stores the reconstructed CT image in the image storage unit 63. The image data storage unit 63 is a storage unit that stores data collected by the imaging control unit 61, CT images reconstructed by the image reconstruction unit 62, and the like.

  The monitor image generation unit 64 receives a KV-XR image created by using a pair of the KV-X-ray source 11 and the FPD 12 from the RT console 2, and displays a monitor image to be displayed on the display device of the RT console 2 as CT image data. It is a processing part generated using it. The monitor image generation unit 64 generates a monitor image to be displayed on the display device of the RT console 2 using the CT image data, so that the radiation therapy system 100 can provide a high-definition monitor display.

  The communication unit 65 is a processing unit that communicates with the RT console 2, the treatment planning apparatus 3 and the like via a network, and performs reception of KV-XR images, transmission of CT images, monitor images, and the like. The control unit 66 is a processing unit that controls the CT console 6 as a whole. Specifically, the control unit 66 moves the control between the function units, transfers data between the function units and the storage unit, and the like. 6 is made to function as one apparatus.

  Next, details of the monitor image generation unit 64 will be described. FIG. 3 is a block diagram illustrating a functional configuration of the monitor image generation unit 64. As shown in the figure, the monitor image generation unit 64 includes a CT image mark extraction unit 641, a mark reference position determination unit 642, a DRR image generation unit 643, a KV-XR image reception unit 644, and a KV-XR. The image mark extracting unit 645, the corresponding image selecting unit 646, and the monitor image transmitting unit 647 are included.

  The CT image mark extraction unit 641 is a processing unit that extracts the center of the affected area and the mark designated by the user from the volume CT image set (volume CT image × time). Here, the mark may be any part as long as it moves with respiratory movement. For example, a branch of a blood vessel, a cyst, or an affected tumor can be used as the mark. However, it is desirable that the mark shows movement as close as possible to the affected part and is not extremely away from the affected part. Further, the mark can be set each time, but it is desirable that the mark can be monitored with the same mark whenever possible. Of course, it is also possible to embed a coil or the like from the outside in the tumor or the vicinity thereof and use it as a mark.

  The mark reference position determination unit 642 is a processing unit that determines the reference position of the mark. Specifically, the mark reference position determination unit 642 matches the center of the affected part of the volume CT image at the end-expiratory trigger time phase with the isocenter of the radiotherapy coordinate system, The mark coordinates at that time are set as the reference position.

  The DRR image generation unit 643 is a processing unit that generates a DRR image viewed from the same direction as the axis of the KV-X line from the volume CT image data of each respiratory phase for each of the two KV-X line axes. If these generated DRR images are displayed side by side on the time axis, it is possible to observe a high-definition image from the same viewpoint as the real-time KV-X-ray. Note that the axes of the two KV-X rays can be calculated from the direction of the therapeutic radiation source in the radiation treatment plan.

  The KV-XR image receiving unit 644 is a processing unit that receives a biaxial KV-XR image from the RT console 2 in real time. The RT console 2 images a patient fixed to the radiation treatment bed in the same position as that at the time of CT scan by biaxial KV-X-rays. The KV-XR image mark extraction unit 645 is a processing unit that extracts the same mark as the mark extracted from the CT image from the KV-XR image.

  The corresponding image selection unit 646 is a processing unit that selects a DRR image corresponding to the KV-XR image and generates a monitor image. Specifically, the corresponding image selection unit 646 displays the trajectory of the landmark between the biaxial KV-XR image and the DRR image reconstructed from the CT image by the DRR image generation unit 643 as an end-expiratory trigger time phase. Align with reference to. Then, the closest DRR image is selected from the real-time KV-XR image and the coordinates of the mark extracted by the KV-XR image mark extraction unit 645 are aligned, and the KV-XR image is replaced with the DRR image. A monitor image is generated. Alternatively, a monitor image that displays the KV-XR image and the DRR image side by side is generated. FIG. 4 shows an example of a monitor image that displays a KV-XR image and a DRR image side by side along two axes.

  The monitor image transmission unit 647 transmits the monitor image generated by the corresponding image selection unit 646 to the RT console 2. The RT console 2 displays the received monitor screen on the display device.

  Next, a processing procedure of monitor image display processing by the radiation therapy system 100 according to the present embodiment will be described. FIG. 5 is a flowchart illustrating a processing procedure of monitor image display processing by the radiation therapy system 100 according to the present embodiment. As shown in the figure, the radiation therapy system 100 captures a volume image of all breathing phases by a 4DCT (real-time volume CT) scan before treatment (step S1).

  At this time, it is desirable that the interval between CT images for one breath is not equal time intervals, but is data at equal distance intervals in which markers are arranged on the respiratory trajectory at almost equal intervals. This is effective when extracting a mark from the CT image at a coordinate position closest to the mark coordinates from the KV-XR image. For example, if the irradiation position accuracy in radiation irradiation requires 2 mm, it is desirable to prepare in advance data for one breath as a volume CT image set at intervals of 2 mm.

  Then, the affected part center and the mark are extracted from the volume CT image of each respiratory time phase (step S2). Then, among the volume CT images, the setting of the radiation therapy patient and the coordinates of the CT image with the affected area center of the CT image coincident with the trigger time phase of the respiratory synchronizer, that is, the end-expiratory time phase, as the isocenter of the radiation therapy coordinate system The systems are matched (step S3).

  Then, the axis of each KV-X-ray is calculated from the radiation treatment plan, and a DRR image viewed from the calculated direction is generated from the volume CT image data of each respiratory time phase (step S4). Then, the same mark as the mark extracted on the CT image is extracted on the biaxial KV-XR image of the patient on the radiotherapy bed (step S5).

  Then, the trajectories of the landmarks of both the real-time biaxial KV-XR image and the DRR image from the same direction reconstructed from the CT image data are aligned on the basis of the position in the end-expiratory trigger time phase (step) S6).

  Then, a DRR image reconstructed from the volume CT image data of the time phase closest to the mark coordinates on the KV-XR image is selected, replaced with each KV-XR image, and displayed on the display device of the RT console 2. indicate. Alternatively, it is displayed side by side with the KV-XR image (step S7).

  Thus, each KV-XR image can be replaced with the corresponding DRR image and displayed, or both images can be displayed side by side to provide a better monitor image.

  As described above, in this embodiment, the monitor image generation unit 64 of the CT console 6 reconstructs a DRR image in the same direction as the KV-XR image from the four-dimensional CT image data. Then, the monitor image generation unit 64 replaces the real-time KV-XR image with the DRR image with the closest landmark coordinates among the reconstructed DRR images, that is, the DRR image with the best respiratory time phase, or both images. A monitor image to be displayed in parallel is generated. Then, the RT console 2 displays the generated monitor image on the display device. Therefore, a high-definition monitor image can be provided. Therefore, it is possible to perform treatment while confirming the affected tumor, and it is possible to improve the safety, certainty, efficiency, etc. of the radiotherapy.

  In the above embodiment, the monitor image generation unit 64 operates on the CT console 6. However, the monitor image generation unit 64 may be operated on another device such as the RT console 2. In the above embodiment, the monitor image generated by the monitor image generation unit 64 is displayed on the display device of the RT console 2. However, the monitor image is displayed on another display device such as the display device of the CT console 6. You can also.

  In the above embodiment, the monitor image is generated and displayed from the KV-XR image in real time. However, the monitor image is generated collectively for the KV-XR image for one breath, and a certain time delay is generated. It is also possible to display a monitor image under.

  Naturally, the state of breathing is different each time, and even if the mark trajectory is first aligned, the position of the actual mark may deviate from the range of the volume CT image set for one breath taken first. Naturally, a deviation of the trajectory itself due to body movement is also expected. On the other hand, the positional accuracy of radiation irradiation is required to be about 2 to 3 mm.

  Therefore, for example, as shown in FIG. 6, the display allowable range is designated in advance as a deviation d (mm) from the mark locus. For example, when the coordinates of the mark on the KV-XR image that is actually monitored in real time is less than d = 2 mm, the reconstructed image from the volume CT image data with the close mark coordinates has an error. It can also be displayed and not displayed.

  Further, assuming that the mark locus first positioned is a standard locus, if the mark is significantly shifted on the real-time KV-XR image from there, there is a possibility that the patient setting is greatly deviated for some reason. For this reason, it is possible to perform processing such as displaying a warning that the deviation from the standard trajectory has occurred or stopping radiation irradiation.

  Moreover, even if it deviates from the standard trajectory, the end-expiration end mark coordinates from the CT image set and the end-expiration end mark coordinates from the KV-XR image are d (mm) with reference to the mark position at the end-expiration trigger If it returns to within the initial setting range, the subsequent display and irradiation can be continued as a temporary positional deviation. Furthermore, when each mark coordinate at the time of the end-expiratory trigger is greatly deviated, a display for prompting repositioning can be performed.

  In the above embodiment, the biaxial KV-XR image is displayed. Further, the DRR image viewed from the therapeutic radiation source from the volume CT image data in the same phase, and the tumor isocenter viewed from the same direction. It is also possible to reconstruct and display an MPR image including In addition, a dose distribution map in the treatment plan can be superimposed on these displays so that the positional relationship with the tumor can be confirmed in real time. Furthermore, not only the display method viewed from the therapeutic radiation source, but also the three-dimensional display of the organ and the affected area target by volume rendering can be performed by utilizing the strength of the three-dimensional information of CT. In addition, a three-dimensional radiation dose distribution can be superimposed on the three-dimensional image.

  In addition, since breathing is continuous, it may occur in a gap between CT image sets prepared in advance. In the above-described embodiment, the image complementation is not performed for the replacement with the high-definition CT image. However, the luminance linear complementation image is generated from the two closest volume CT image data and displayed. You can also.

  In this embodiment, two pairs of KV-XR image X-ray tubes and FPDs are provided so that the spatial coordinates of the mark of the affected area can be measured. It is also possible to perform 3D tomography by moving the lens in an arc shape or rotating around the isocenter of radiotherapy.

  In this embodiment, CT is used as a real-time volume scanner. However, MRI having better contrast resolution of soft tissue may be used. In this embodiment, an image observed from the same direction as the real-time KV-XR image is reconstructed from the CT image and replaced or displayed side by side. However, the present invention is not limited to this. For example, both images are superimposed and displayed, or a marker extracted from a real-time KV-XR image is superimposed and displayed on a high-definition CT reconstructed DRR image in real time. You can also.

  As described above, the present invention is suitable for a medical system that performs radiation therapy.

It is a figure which shows the structure of the radiotherapy system which concerns on a present Example. It is a block diagram which shows the function structure of CT console. It is a block diagram which shows the function structure of a monitor image generation part. It is a figure which shows an example of the monitor image which arranges and displays a KV-XR image and a DRR image about 2 axes. It is a flowchart which shows the process sequence of the monitor image display process by the radiotherapy system concerning a present Example. It is a figure which shows a display allowable range.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiotherapy apparatus 2 RT console 3 Treatment planning apparatus 4 Respiration synchronization apparatus 5 CT scanner 6 CT console 11 KV-X-ray source 12 FPD
61 imaging control unit 62 image reconstruction unit 63 image data storage unit 64 monitor image generation unit 65 communication unit 66 control unit 641 CT image landmark extraction unit 642 landmark reference position determination unit 643 DRR image generation unit 644 KV-XR image reception unit 645 KV-XR image landmark extraction unit 646 Corresponding image selection unit 647 Monitor image transmission unit

Claims (6)

Volume image data collection means for collecting volume image data for one respiratory cycle of a patient undergoing radiotherapy;
Reconstructing means for reconstructing images of each respiratory phase from the volume image data collected by the volume image data collecting means;
X-ray imaging means for performing X-ray imaging of the patient from two or more different directions;
A coincidence image selection means for selecting an image having the best respiratory time phase with an image photographed by the X-ray photographing means from among the images reconstructed by the reconstruction means;
Image display means for displaying the image selected by the coincidence image selection means in synchronization with the breathing of the patient;
A radiation therapy system comprising:   The coincidence image selecting means selects an image in which the position of the mark most coincides with the image photographed by the X-ray photographing means from the images reconstructed by the reconstruction means. .   The reconstructing unit reconstructs a DRR image from the axial direction captured by the X-ray imaging unit from volume image data collected by the volume image data collecting unit. Radiation therapy system.   The radiotherapy system according to claim 1, 2 or 3, wherein the image display means replaces and displays the image captured by the X-ray imaging means with the image selected by the coincidence image selection means. .   The radiotherapy system according to claim 1, 2 or 3, wherein the image display means displays the image photographed by the X-ray photographing means and the image selected by the coincidence image selecting means side by side. A volume image data collection step for collecting volume image data for one respiratory cycle of a patient undergoing radiation therapy;
A reconstruction step of reconstructing an image of each respiratory time phase from the volume image data collected by the volume image data collection step;
An X-ray imaging step of performing X-ray imaging of the patient from two or more different directions;
A coincidence image selection step of selecting an image having the best respiratory time phase with an image captured by the X-ray imaging step from among the images reconstructed by the reconstruction step;
An image display step for displaying the image selected in the matching image selection step in synchronization with the patient's breathing;
An image display method comprising:

Images