JP4159227B2 - Patient position deviation measuring device, patient positioning device using the same, and radiotherapy device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention, patient position displacement meter HakaSo location and patient Positioning equipment using the same, and relates to a radiotherapy apparatus, in particular, suitable for use in patient positioning of radiotherapy by external irradiation, the patient patients positional displacement meter HakaSo location for measuring the amount of deviation from the target position of the position, and the patient positioning equipment using the same, and to a radiation therapy device.
[0002]
[Prior art]
In general, when performing radiotherapy by external irradiation, particularly radiotherapy with excellent dose localization, it is necessary to accurately position a patient in order to accurately irradiate a lesion that is an irradiation target.
[0003]
FIG. 1 shows a state of patient positioning generally performed in radiation therapy.
[0004]
When positioning a patient, as shown in FIG. 2, first, in step 100, in order to determine an irradiation plan (referred to as a treatment plan) such as the number, direction, and intensity of radiation irradiation, Ten X-ray CT images are taken.
[0005]
Next, in step 110, the treatment planning apparatus 30 uses the X-ray CT image to grasp the position and size of the affected area to be irradiated, and determines conditions (so-called irradiation parameters) such as the irradiation direction and thickness. Make a plan. Specifically, using the acquired X-ray CT image, the setting of the patient's body contour and tumor region, and the input setting of important organs that should not be irradiated with radiation are performed, and these three-dimensional models are created. A treatment plan is performed using this three-dimensional model and image, and the irradiation direction and irradiation dose are determined by computer simulation. When X-ray CT used for planning and the position and posture of the patient on the treatment table are misaligned, accurate irradiation cannot be performed. Therefore, patient positioning during irradiation treatment determines the success or failure of treatment. This is an important task.
[0006]
After the treatment plan is completed, in step 120, a pseudo X-ray image for patient positioning is created by computer simulation. The pseudo X-ray image is created, for example, in two directions from above and from the side of the patient, and is recorded and stored in a recording device.
[0007]
The steps up to here are preparations for irradiation treatment.
[0008]
Next, an operation for patient positioning is performed. This includes two operations, a pre-positioning stage 130 and an on-irradiation positioning stage 140. The pre-positioning 130 is performed only once before irradiation treatment. In the case of external irradiation treatment of radiation, 20 to 30 divided irradiations are usually performed, but the irradiation positioning 140 is performed every time irradiation is performed. Therefore, if this positioning operation can be simplified, the burden on both the technician and the patient can be reduced.
[0009]
In the pre-positioning step 130, for example, marking on the patient's body surface (or the surface of the patient fixture) and X-ray imaging for positioning during irradiation are performed.
[0010]
Specifically, as shown in FIG. 1, in step 132, the position of the patient 10 on the treatment table 16 in the rotating gantry 14 for treatment is roughly estimated, and the treatment table 16 is manually visually adjusted accordingly. Move by operation (referred to as rough positioning).
[0011]
Next, the routine proceeds to step 134 where X-ray transmission imaging apparatuses 20A and 20B including X-ray generation apparatuses 22A and 22B and X-ray imaging apparatuses 24A and 24B, respectively, are used from two directions of the patient 10, for example, from above and from the side. Radiographic imaging is performed, and the treatment table 16 is moved so as to coincide with the pseudo X-ray image created in step 120. After moving the treatment table 16, an X-ray image is taken again and the result is confirmed. This operation is repeated as necessary (referred to as detailed positioning).
[0012]
If they match, the process proceeds to step 136, and two X-ray transmission images are recorded and stored in the recording apparatus.
[0013]
Next, in step 138, the marker projected onto the patient's body surface is transferred to the body surface or fixture using, for example, ink, by a projector fixed to the irradiation apparatus system, for example.
[0014]
Finally, positioning 140 at the time of irradiation is performed for each actual irradiation treatment. Specifically, in step 142, the treatment table 16 is moved by visual manual operation so as to match the marker on the body surface with the projection marker by the projector fixed to the irradiation apparatus system (referred to as rough positioning).
[0015]
Next, in step 144, X-ray transmission imaging is performed, and the treatment table 16 is moved so as to coincide with the positioning X-ray transmission image stored in step 136. When the treatment table 16 is moved, an X-ray transmission image is taken again and the result is confirmed. This operation is repeated as necessary (referred to as detailed positioning).
[0016]
[Problems to be solved by the invention]
Although radiation is irradiated based on the irradiation parameters determined in the treatment plan, since the X-ray CT imaging apparatus 12 and the treatment apparatus (rotating gantry 14) are different apparatuses, the coordinates of the patient 10 on the treatment table 16 are used. There will be a slight shift between the system and the coordinate system of the X-ray CT image used during treatment planning. Therefore, in order to irradiate the affected area accurately according to the treatment plan, it is necessary to correct the deviation of the coordinate system. If the amount of deviation can be measured accurately, the patient position can be corrected by the treatment table 16 having six degrees of freedom, for example.
[0017]
In the detailed positioning in steps 134 and 144, the patient position is measured using an X-ray transmission image. In an X-ray transmission image, a substance with high density such as bone is relatively easy to visually recognize, but it is difficult to distinguish muscles and other soft tissues. Accordingly, positioning is usually performed using landmarks such as bones nearby as landmarks, but the trunk, such as the chest and abdomen, has a problem that contrast is low and accurate positioning is difficult. It was.
[0018]
The present invention has been made to solve the above-mentioned conventional problems, and a first problem is to improve positioning accuracy by directly measuring the position of an irradiation target in a soft tissue that is difficult to discriminate.
[0019]
The second object of the present invention is to improve the radiation accuracy and reduce the burden on the hospital staff and patient.
[0020]
[Means for Solving the Problems]
The present invention relates to a patient position deviation measuring apparatus for measuring a deviation amount of a patient position from a target position , and an optical representation of the motion of pixels on an image within a predicted range of a patient position deviation amount calculated in advance as a vector. The storage means for storing all the flows, the measuring means for measuring the actual optical flow, the stored optical flow stored in the storing means and the actually measured optical flow are compared, and the amount of positional deviation of the patient is calculated. The first problem is solved by providing a matching means to be obtained.
[0023]
The irradiation target is also provided with means for calculating a norm of a composite vector with each optical flow calculated in advance, and obtaining a reference norm that maximizes the norm, and measuring the actual optical flow in the vicinity of the reference norm. Is easy to detect.
[0025]
In the patient positioning apparatus, the present invention further includes the above-described patient misalignment measuring apparatus and a patient positioning control apparatus that positions the patient according to the misalignment amount obtained by the patient misalignment measuring apparatus. Thus, the first problem is solved.
[0026]
The present invention also solves the second problem by providing the patient positioning device and a radiation irradiation device for irradiating the patient positioned by the patient positioning device in a radiation therapy apparatus. It is.
[0027]
The optical flow is a vector representing the flow (motion) of pixels on an image. Usually, the movement direction is detected by obtaining the motion of each pixel between frames of a moving image as a vector. It is used for. The feature is that a minute change at the moment is handled, and if the change is continuous, it is determined that the movement of each pixel changes. If the movement vector can be detected, it is possible to grasp and track the moving object, and it has been studied to use it for traffic volume surveys and human gesture recognition.
[0028]
In the present invention, the irradiation target is three-dimensionally positioned using this optical flow.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0030]
As shown in FIG. 3, an embodiment of the radiotherapy apparatus according to the present invention is an image database (DB) for storing X-ray CT images necessary for radiotherapy, which are imaged by the X-ray CT imaging apparatus 12 shown in FIG. ) 32, and an X-ray CT image is taken out from the image DB 32, the irradiation target for radiation treatment is determined by inputting a three-dimensional position / shape of the irradiation target and performing a dose distribution simulation, and the same treatment planning apparatus 30 as in the prior art. And optical flow information in the vicinity of the irradiation target set by the treatment planning apparatus 30 and rotation information of the rotating gantry 14 for performing treatment by irradiating radiation from an irradiation nozzle 18 that can rotate around the patient 10. Is calculated and transmitted to the later-described three-dimensional (3D) positioning control device 36. First, the three-dimensional (3D) positioning planning device 34 according to the present invention, and the 3D position X-ray transmission imaging is performed based on the gantry rotation information calculated by the planner 34, and the image is collected. Next, the optical flow is calculated from this image, and the deviation from the optical flow information in the vicinity of the irradiation target And a three-dimensional (3D) positioning control device 36 according to the present invention, which converts this into rotation / movement information of the treatment table 16, and these are connected to the network of the treatment system. ing.
[0031]
In the 3D positioning planning apparatus 34, as shown in FIG. 4, first, in step 200, an X-ray transmission image performed at the patient positioning immediately before treatment is set for one rotation (gantry angle 0 to 360 °). The simulation is performed at each rotation angle step (for example, 2 °), and X-ray transmission simulation images XI (n), XI (n + 1),... Although the step angle can be set arbitrarily, for example, when it is set to 2 °, 180 X-ray transmission simulation images are created.
[0032]
Next, in step 210, an optical flow near the irradiation target set by the treatment planning apparatus 30 is calculated between the simulation images. Specifically, as shown in FIG. 6, in the two adjacent X-ray transmission simulation images X (n) and X (n + 1), the same luminance pixels in a certain small area set at the same place are the same. The optical flow is calculated by calculating a movement vector between two pixels on the assumption that the movement has occurred, and an optical flow image O as shown on the right side of FIG. 6 is obtained. Arrows in the image indicate the amount and direction of movement between X (n) and X (n + 1). It is possible to discriminate movement even in muscles and other soft tissues with low contrast.
[0033]
Next, the process proceeds to step 220, and as shown in FIG. 7, the optical flow vector of (i) and its norm (absolute value) near the center of the image are calculated in each optical flow image, and the maximum norm value is searched from among them. The reference norm XN (n) is used. Further, the optical flow at this time is set as a reference optical flow, and a total of three pieces of information are stored together with the calculated rotation angle information. In the vicinity of the reference norm, the optical flow vector is large, and it is thought that there is a large change in the appearance of the image near the irradiation target. Therefore, if the X-ray transmission imaging is performed using this rotation angle information, the irradiation target is detected. It becomes easy to do.
[0034]
Next, the 3D positioning planner 34 proceeds to step 230 in FIG. 8, and rotates and moves the X-ray CT image within the range of the patient setup error (for example, ± 30%) in the vicinity of this rotation angle. 9, the X-ray transmission simulation image of the micro area around the reference angle is recreated with the bed angle and tilt angle included, and the rotation / movement amount (n) and the optical flow (n) at that time (step) 250), the norm (n) (step 260) of the composite vector is calculated and stored in the table. This stored information is transferred to the 3D positioning control device 36.
[0035]
As shown in FIG. 10, the 3D positioning control device 36 controls the rotating gantry and the X-ray transmission imaging device using the rotation angle information and the rotation angle step information output from the 3D positioning planning device 34 in step 310. X-ray transmission imaging is performed, and in step 320, the measured optical flow is calculated and stored as a measured optical flow. Further, in step 330, the norm of the composite vector is also calculated and stored as a measurement norm.
[0036]
Next, the process proceeds to step 340 in FIG. 11, and pattern matching between this measured optical flow Ofm (i) and the optical flow Ofm (i) stored as a table is performed, for example, as shown in FIG. The rotation / movement amount at which the matching value is minimized (PM is the maximum) is output as the rotation / movement displacement amount.
[0037]
In this embodiment, X-ray transmission imaging is performed using rotation angle information in the vicinity of the reference norm, which is considered to have a large change in the appearance of the image in the vicinity of the irradiation target. It can be detected with high accuracy. When sufficient accuracy is obtained even if it is not in the vicinity of the reference norm, it is also possible to detect misalignment at other rotation angles.
[0038]
Furthermore, if high-speed calculation becomes possible, real-time simulation is also possible.
[0039]
【The invention's effect】
According to the present invention, since the irradiation target itself is measured instead of using a high-density substance such as bone, the positioning accuracy is improved. Therefore, the radiation irradiation accuracy is improved, and the burden on both the hospital staff and the patient can be reduced.
[0040]
In addition, the actual X-ray transmission imaging may be performed only once, and the amount of exposure of the patient is reduced.
[0041]
In particular, when positioning is performed fully automatically, variations among operators can be prevented.
[Brief description of the drawings]
FIG. 1 is a diagram showing a state of patient positioning generally performed in radiotherapy. FIG. 2 is a flowchart showing a procedure of the patient positioning operation. FIG. 3 is an overall view of a radiotherapy apparatus adopting the present invention. FIG. 4 is a flowchart showing the first half of the operation of the three-dimensional positioning planner used in the embodiment. FIG. 5 is a schematic diagram of creating a simulation image from multiple gantry angle directions in the three-dimensional positioning planner. FIG. 6 is a diagram showing a state in which an optical flow is being calculated. FIG. 7 is a diagram showing a state in which a feature quantity of the optical flow is being calculated. FIG. 9 is a flowchart showing the second half of the operation of the 3D positioning planning apparatus. FIG. 10 is a flowchart showing the first half of the operation of the 3D positioning control device used in the embodiment. FIG. 11 is a flowchart showing the second half. FIG. 12 is an optical flow pattern in the 3D positioning control device. Diagram showing how matching is performed [Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Patient 12 ... X-ray CT imaging device 14 ... Rotating gantry 16 ... Treatment table (patient bed)
20A, 20B ... X-ray transmission imaging devices 22A, 22B ... X-ray generators 24A, 24B ... X-ray imaging device 30 ... Treatment planning device 32 ... Image database (DB)
34 ... 3D (3D) positioning planning device 36 ... 3D (3D) positioning control device O ... Optical flow image

Claims (4)

In the patient position deviation measuring device for measuring the amount of deviation of the patient position from the target position,
Storage means for storing all optical flows in which the motion of the pixels on the image is represented by a vector within the expected range of the amount of patient position deviation calculated in advance;
A measuring means for measuring the actual optical flow;
A matching means for comparing a stored optical flow stored in the storage means and a measured optical flow actually measured to determine the amount of positional deviation of the patient;
A patient positional deviation measuring apparatus comprising: Means for calculating a norm of a composite vector in each optical flow calculated in advance, and obtaining a reference norm that maximizes the norm;
Patients positional deviation measuring device according to claim 1, characterized in that measuring the actual optical flow in the reference norm vicinity. The patient positional deviation measuring device according to claim 1 or 2,
A patient positioning control device for positioning a patient in accordance with the amount of positional deviation obtained by the patient positional deviation measuring device;
A patient positioning device comprising: A patient positioning device according to claim 3 ;
A radiation irradiation device for irradiating the patient positioned by the patient positioning device with radiation;
A radiotherapy apparatus comprising:

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