JP2020185337A - Positioning device - Google Patents

Abstract

To provide a positioning device capable of facilitating rough positioning of a DR image and a DRR image.SOLUTION: A positioning device includes: a DR image generation section 31 for generating a DR image of a subject; a DRR image generation section 32 for generating a DRR image by performing virtual perspective projection with respect to CT data of a subject; a superimposition display section 33 for displaying a DR image and a DRR image by superimposition; a rough positioning section 34 for relatively moving a DRR image with respect to a DR image by an operation of an operation section 38 so as to perform rough positioning of a DR image and a DRR image; a positioning section 35 for performing calculation by using a DR image and a DRR image after rough positioning so as to perform positioning of a DR image and a DRR image; and a movement amount calculation section 36 for calculating a movement amount of a subject placement section based on a relative movement amount of a DRR image with respect to a DR image. The DRR image generation section 32 generates a DRR image of an area larger than an area of a DR image generated by the DR image generation section 31.SELECTED DRAWING: Figure 2

Description

The present invention relates to a positioning device.

In radiotherapy that irradiates an affected area such as cancer with radiation such as X-rays, electron beams, and particle beams, it is necessary to accurately irradiate the affected area with radiation. When performing radiation therapy using a radiation therapy device, a treatment plan is formulated prior to the treatment. Then, when performing radiotherapy, it is necessary to position the subject so that the position of the subject coincides with that at the time of treatment planning. Conventionally, the positioning of the subject in the radiotherapy device is performed by the engineer operating the position of the clinic table on which the subject is placed while visually checking the position indicated by the laser marking device. It was. On the other hand, in recent years, it has been proposed to position a subject using an X-ray image (see Patent Document 1).

At this time, in the positioning of the subject using the X-ray image, the geometrical arrangement of the X-ray imaging system was reproduced on the computer, and the three-dimensional image data collected by the X-ray CT device at the time of treatment planning was used. Using a DRR (Digital Reconstruted Radiography) image, which is a virtual fluoroscopic projection, the similarity between a DR (Digital Radiography) image taken by an X-ray imaging system and a DRR image is evaluated (image registration). The amount of misalignment between the person's current position and the position at the time of treatment planning is calculated. Since the calculation cost of DRR is enormous, Patent Document 1 reduces the calculation cost required for executing DRR and speeds up the positioning of the subject. Then, after the misalignment amount is calculated, the subject is placed in the correct position by moving the subject mounting portion on the examination table according to the misalignment amount.

Japanese Unexamined Patent Publication No. 2013-99431

When calculating the amount of misalignment between the current position of the subject and the position at the time of treatment planning by comparing the DR image and the DRR image, if the DR image and the DRR image are significantly misaligned, the position Not only does it take a long time to calculate the amount of deviation, but there are cases where a predetermined part of the subject is recognized as another part and the calculation is performed. Therefore, when calculating the amount of misalignment between the DR image and the DRR image by image registration, rough positioning is performed by the operator's operation to position the DRR image at a position that substantially matches the DR image.

When performing rough positioning, the DR image and the DRR image are displayed on the display unit in a superposed state, and the operator operates the operation unit to move the DRR image with respect to the DR image, and the DR image and the DRR image are displayed. A rough positioning operation is performed to place the image at a position that roughly matches it.

At this time, the DRR image is created so as to have a size representing a region of the DR image, that is, a region corresponding to the shooting size of the DR image. In other words, the DR image and the DRR image have the same size. Therefore, when the DR image and the DRR image are roughly positioned, the information for the operator to determine whether or not the rough positioning is completed depends on the region where the DR image and the DRR image are superimposed. Therefore, it is not easy to determine whether the position of the DR image and the position of the DRR image match or do not match, and it is extremely difficult to determine whether or not the rough positioning is completed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a positioning device capable of easily performing rough positioning of a DR image and a DRR image.

The first aspect of the present invention is to use an X-ray imaging apparatus including a plurality of X-ray imaging systems including an X-ray irradiation unit and an X-ray detection unit and capable of photographing a subject from two different directions. Perform virtual fluoroscopic projection simulating the geometric imaging conditions of the X-ray imaging system on the CT data of the subject created at the time of treatment planning and the DR image creation unit that creates the DR image of the person. A DRR image creating unit that creates a DRR image, a superimposed display unit that displays the DR image and the DRR image in a superimposed state, and an operation unit that displays a DRR image displayed by the superimposed display unit. The DR image is calculated by using the coarse positioning unit that roughly positions the DR image and the DRR image by moving the DR image relative to the DR image, and the DR image and the DRR image after the rough positioning. A movement amount calculation unit that calculates the movement amount of the subject mounting unit on which the subject is placed from the positioning unit that positions the DRR image and the movement amount of the DRR image relative to the DR image. And, the DRR image creation unit creates a DRR image in a region larger than the region of the DR image created by the DR image creation unit.

According to the first aspect of the present invention, the rough positioning can be performed by using the entire region of the DR image, and the DRR image in the region outside the DR image can also be used for the rough positioning. .. Therefore, more information can be used for rough positioning, and rough positioning between the DR image and the DRR image can be easily performed.

It is a perspective view which shows the X-ray imaging apparatus provided with the positioning apparatus which concerns on embodiment of this invention together with the therapeutic beam irradiation apparatus 90. It is a block diagram which shows the main control system of the X-ray imaging apparatus provided with the positioning apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows typically the state which creates the DRR image by virtual fluoroscopy. It is a schematic diagram of the DR image X1 created by the DR image creation unit 31. It is a schematic diagram of the DRR image D2 having a region larger than the DR image X1 created by the DRR image creation unit 32. It is a schematic diagram of the DRR image D1 which has the same region as the DR image X1. It is a schematic diagram which shows the state of performing the rough positioning using the DR image X1 and the DRR image D2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an X-ray imaging apparatus including the positioning apparatus according to the embodiment of the present invention together with the treatment beam irradiation apparatus 90. The radiotherapy apparatus is composed of these X-ray imaging apparatus and the treatment beam irradiation apparatus 90.

The treatment beam irradiation device 90 performs radiotherapy on the subject on the examination table 27, and is a gantry that rotates about the isocenter with respect to the base 91 installed on the floor surface of the treatment room. A treatment beam irradiation unit 93 arranged in the gantry 92 for emitting the treatment beam is provided with the 92. The gantry 92, together with the treatment beam irradiation unit 93, has a structure that can rotate within a range of 360 degrees with respect to the base 91.

Therefore, according to the treatment beam irradiation device 90, the irradiation direction of the treatment beam emitted from the treatment beam irradiation unit 93 is changed by rotating the gantry 92 to an arbitrary angle position with respect to the base 91. Can be done. Therefore, it is possible to perform so-called multi-field irradiation in which the treatment beam is irradiated from various directions to the affected part such as a tumor in the subject.

The isocenter is a position where the treatment beam irradiated from the treatment beam irradiation unit 93 is most concentrated and irradiated in the radiotherapy treatment, and is the irradiation center of the treatment beam.

The X-ray imaging apparatus used together with the therapeutic beam irradiating apparatus 90 performs X-ray fluoroscopy for tracking a moving object to identify the position of the affected portion of the subject. That is, at the time of radiotherapy using the above-mentioned treatment beam irradiation device 90, it is necessary to accurately irradiate the affected portion that moves with the body movement of the subject. Therefore, in this X-ray imaging apparatus, the subject is seen through from two different directions, and image recognition is performed on the fluoroscopic image, so that the marker placed in the vicinity of the specific part of the subject is placed. By detecting the position and calculating the three-dimensional position information of the marker, the marker is detected with high accuracy, so-called moving object tracking is performed.

Instead of placing a marker near the affected area in the subject, a method of using an image of a specific site such as a tumor in the subject as a marker is also adopted. Such a moving object tracking method is called markerless tracking. In this specification, a specific site such as a tumor in a subject and a marker placed in the vicinity of the specific site of the subject are collectively referred to as "marker or the like".

As one embodiment of this image recognition, an image of a marker or the like placed near a specific part of the subject is registered as a template in advance, and the position of the marker or the like is detected and tracked using this template. Template matching is used. Further, as another embodiment of this image recognition, a classifier is created by learning from a large number of correct and incorrect image images registered in advance for a marker or the like, and the marker or the like is used by using the classifier. Machine learning is used to detect and track location.

This X-ray imaging apparatus includes a first X-ray tube 11a, a second X-ray tube 11b, a third X-ray tube 11c, a fourth X-ray tube 11d (collectively referred to as "X-ray tube 11"), and a first X-ray tube. It includes a flat panel detector 21a, a second flat panel detector 21b, a third flat panel detector 21c, and a fourth flat panel detector 21d (collectively referred to as "flat panel detector 21"). The X-rays emitted from the first X-ray tube 11a pass through the subject on the examination table 27 and then are detected by the first flat panel detector 21a. The first X-ray tube 11a and the first flat panel detector 21a form a first X-ray imaging system. The X-rays emitted from the second X-ray tube 11b pass through the subject on the examination table 27 and then are detected by the second flat panel detector 21b. The second X-ray tube 11b and the second flat panel detector 21b form a second X-ray imaging system. The X-rays emitted from the third X-ray tube 11c pass through the subject on the examination table 27 and then are detected by the third flat panel detector 21c. The third X-ray tube 11c and the third flat panel detector 21c form a third X-ray imaging system. The X-rays emitted from the 4th X-ray tube 11d pass through the subject on the examination table 27 and then are detected by the 4th flat panel detector 21d. The 4th X-ray tube 11d and the 4th flat panel detector 21d form a 4th X-ray imaging system.

When performing X-ray fluoroscopy for tracking a moving object, two of the first X-ray imaging system, the second X-ray imaging system, the third X-ray imaging system, and the fourth X-ray imaging system will be described later. An X-ray imaging system is selected and used.

The examination table 27 includes a base 28 and a subject placement unit 29, which is also called a couch. The subject mounting portion 29 is movable in the four-axis or six-axis direction with respect to the base portion 28. The subject mounting unit 29 moves based on the movement signal from the movement signal transmission unit 37, which will be described later. Further, it is also possible to move the subject mounting portion 29 by the operation of the operator.

FIG. 2 is a block diagram showing a main control system of an X-ray imaging apparatus including the positioning apparatus according to the embodiment of the present invention.

This X-ray imaging apparatus includes a control unit 30 that controls the entire apparatus. The control unit 30 is composed of a computer on which software is installed. The functions of each unit included in the control unit 30 are realized by executing the software installed in the computer.

The control unit 30 is connected to the above-mentioned X-ray tube 11, flat panel detector 21, examination table 27, and treatment beam irradiation device 90. Further, the control unit 30 is connected to an operation unit 38 provided with an input mechanism such as a keyboard and a mouse to execute various operations, and a display unit 39 provided with a liquid crystal display panel and the like. Further, the control unit 30 is connected online or offline to a treatment planning device 99 that formulates a treatment plan prior to radiotherapy. The treatment planning device 99 has acquired CT image data of the subject photographed by a CT imaging device (not shown). The control unit 30 acquires the CT image data from the treatment planning device 99.

As a functional configuration, the control unit 30 uses two X-ray imaging systems of the first X-ray imaging system, the second X-ray imaging system, the third X-ray imaging system, and the fourth X-ray imaging system for X-rays. A virtual perspective projection that simulates the geometric imaging conditions of the X-ray imaging system for the CT data of the subject acquired from the treatment planning device 99 and the DR image creation unit 31 that creates a DR image by performing imaging. The DRR image creation unit 32 that creates a DRR image by performing the above, the superimposition display unit 33 that displays the DR image and the DRR image on the display unit 39 in a superposed state, and the operator operating the operation unit 38. The rough positioning unit 34 that roughly positions the DR image and the DRR image by moving the DRR image displayed by the superimposed display unit 33 relative to the DR image, and after the DR image and the rough positioning From the positioning unit 35 that positions the DR image and the DRR image and the relative movement amount of the DRR image with respect to the DR image by performing the calculation using the DRR image of, the subject on which the subject is placed. By transmitting the movement signal of the subject mounting unit 29 to the moving amount calculation unit 36 that calculates the moving amount of the mounting unit 29 and the examination table 27, the subject is examined on the subject mounting unit 29. A movement signal transmission unit 37 for moving a person to a correct position is provided.

Next, operations such as positioning of the subject by the X-ray imaging apparatus having the above configuration will be described. The following positioning operation is executed in the direction corresponding to two X-ray imaging systems of the first X-ray imaging system, the second X-ray imaging system, the third X-ray imaging system, and the fourth X-ray imaging system. To. In the following description, one X-ray imaging system will be described, but the same operation is executed for the other X-ray imaging system.

When starting treatment for a subject, first, the DR image creation unit 31 uses two X-rays of the first X-ray imaging system, the second X-ray imaging system, the third X-ray imaging system, and the fourth X-ray imaging system. A DR image is created by performing X-ray photography using a line photography system. This DR image is, for example, an image of 512 × 512 pixels. At this time, an X-ray imaging system in which the gantry 92 does not use for X-ray imaging is selected based on the arrangement of the treatment beam irradiation unit 93 in the treatment beam irradiation device 90.

Next, a DRR image used for positioning the subject is created together with the DR image.

FIG. 3 is an explanatory diagram schematically showing a state in which a DRR image is created by virtual fluoroscopy.

When creating the DRR image, the control unit 30 acquires the CT image data 100 from the treatment planning device 99. The CT image data 100 is three-dimensional voxel data which is a set of a plurality of two-dimensional image data. The CT image data 100 has a structure in which about 200 two-dimensional images are stacked in a direction crossing the subject (direction along the line segment L1 or L2 shown in FIG. 3). The CT image data 100 is created by the treatment planning device 99 based on the data obtained from the CT device (not shown) at the time of creating the treatment plan.

Then, the DRR image creation unit 32 performs a virtual perspective projection on the CT image data 100 by simulating the geometrical imaging conditions for the subject of each X-ray imaging system used at the time of creating the DR image. , Create a DRR image of the subject. This DRR image is, for example, an image of 1024 × 1024 pixels.

The DR image created by the DR image creation unit 31 is, for example, an image of 512 × 512 pixels. On the other hand, the DR image created by the DRR image creation unit 32 is, for example, an image of 1024 × 1024 pixels. In this way, the DRR image creation unit 32 creates a DRR image having a region larger than the region of the DR image created by the DR image creation unit 31. As described above, the DRR image is created by performing a virtual perspective projection on the CT image data 100, which is three-dimensional voxel data. Therefore, the area of the DRR image created by the DRR creation unit 32 can be arbitrarily set within the range of the CT image data.

Then, the superimposed display unit 33 displays the DR image and the DRR image on the display unit 39 in a superimposed state. After that, based on the operation of the operation unit 38 by the operator, the coarse positioning unit 34 moves the DRR image displayed on the display unit 39 relative to the DR image to coarsen the DR image and the DRR image. Perform positioning. At this time, for example, the operator drags the DRR image displayed on the display unit 39 by using the mouse on the operation unit 38 to move the DRR image so that the DR image and the DRR image roughly match. Let me.

Hereinafter, this rough positioning operation will be described in comparison with the case where a DRR image having the same size as the DR image is used and the case where a DRR image larger than the DR image is used. FIG. 4 is a schematic view of the DR image X1 created by the DR image creation unit 31. FIG. 5 is a schematic view of the DRR image D2 having a region larger than the DR image X1 created by the DRR image creation unit 32. FIG. 6 is a schematic view of a DRR image D1 having a size corresponding to the same region as the DR image X1 as a comparative example. FIG. 7 is a schematic view showing a state in which rough positioning is performed using the DR image X1 and the DRR image D2. Note that FIGS. 4 to 6 show a case where the rough positioning operation is executed based on the image near the chest of the subject.

In the DR image X1 shown in FIG. 4 and the DRR image D2 having a large region shown in FIG. 5, the spine 51, the clavicle 52, and the ribs 53 of the subject can be confirmed. On the other hand, in the DRR image D1 having a small region similar to the DR image X1 shown in FIG. 6, the spine 51 and the ribs 53 of the subject can be confirmed.

Of the DR image X1 and the DRR image superimposed and displayed on the display unit 39 in order to perform coarse positioning, when the DRR image is moved and superimposed on the DR image, the DRR image representing a small area as the DRR image. When D1 is used, the information for the operator to determine whether or not the rough positioning is completed depends on the region where the DR image X1 and the DRR image D1 are superimposed. Therefore, the amount of information for rough positioning is small, and it is difficult to identify which of the plurality of ribs 53 corresponds to each other. Therefore, it is not easy to determine whether the position of the DR image X1 and the position of the DRR image D1 match or do not match, and it is extremely difficult to determine whether or not the rough positioning is completed.

On the other hand, when the DR image X1 and the DRR image D2 representing a large area are superimposed and displayed on the display unit 39, as shown in FIG. 7, not only the internal area of the DR image X1 but also the DRR image is displayed. Rough positioning can also be performed by using the region outside the DR image X1 in D2. Therefore, the amount of information for rough positioning becomes large, and in the case of the embodiment shown in FIG. 7, all the information of the subject's spine 51, clavicle 52, and rib 53 is used. Rough positioning can be performed. As a result, more information can be used for rough positioning, and rough positioning of the DR image X1 and the DRR image D2 can be easily performed.

When the coarse positioning of the DR image and the DRR image is completed, the positioning unit 35 accurately positions the DR image and the DRR image by performing an calculation using the data of the DR image and the DRR image after the rough positioning. .. That is, the amount of misalignment between the DR image and the DRR image is calculated by image registration. At this time, if the operation is performed by image registration using the DR image X1 and the DRR image D2 representing a large area, the data at the time of calculation becomes large and it takes time for positioning. Therefore, the positioning unit 35 performs the calculation using only the data of the DRR image in the region corresponding to the DR image X1 among the data of the DRR image D2 after positioning. This makes it possible to perform positioning without requiring a long time for the calculation for positioning.

When the positioning of the DR image X1 and the DRR image D2 is completed, the movement amount calculation unit 36 arranges the subject at the position according to the treatment plan based on the movement amount of the DRR image D2 with respect to the DR image X1. The amount of movement of the subject mounting unit 29 required for the above is calculated. Then, the movement signal transmission unit 37 transmits the movement signal of the subject mounting unit 29 to the examination table 27. This makes it possible to move the subject on the subject placing portion 29 to the correct position according to the treatment plan.

When the positioning of the subject is completed, X-ray photography is performed again, the captured DR image is compared with the DRR image based on the data at the time of treatment planning, and the amount of their misalignment is within the preset threshold value. Check if it is. If the amount of misalignment is less than the preset threshold, radiation therapy is continued. On the other hand, when the amount of misalignment is larger than the preset threshold value, the positioning operation is executed again.

In the above-described embodiment, the DR image is created by using an X-ray imaging apparatus that performs X-ray fluoroscopy for tracking the moving object to identify the position of the affected part of the subject. Ordinary radiographing equipment that does not perform this may be used.

It will be understood by those skilled in the art that the plurality of exemplary embodiments described above are specific examples of the following embodiments.

(Section 1)
A DR image that is provided with a plurality of X-ray imaging systems including an X-ray irradiation unit and an X-ray detection unit, and creates a DR image of the subject using an X-ray imaging device capable of photographing the subject from two different directions. With the creator
A DRR image creation unit that creates a DRR image by performing a virtual perspective projection that simulates the geometric imaging conditions of the X-ray imaging system on the CT data of the subject created at the time of treatment planning.
A superposed display unit that displays the DR image and the DRR image in a superposed state,
A coarse positioning unit that roughly positions the DR image and the DRR image by moving the DRR image displayed by the superimposed display unit relative to the DR image by operating the operation unit.
A positioning unit that positions the DR image and the DRR image by performing an operation using the DR image and the DRR image after rough positioning.
A movement amount calculation unit that calculates the movement amount of the subject mounting unit on which the subject is placed from the movement amount of the DRR image relative to the DR image.
With
The DRR image creation unit creates a DRR image in a region larger than the region of the DR image created by the DR image creation unit.

According to the positioning device according to the first item, rough positioning can be performed by using the entire region of the DR image, and the DRR image in the region outside the DR image can also be used for rough positioning. it can. Therefore, more information can be used for rough positioning, and rough positioning between the DR image and the DRR image can be easily performed.

(Section 2)
In the positioning device according to paragraph 1,
The positioning unit positions the DR image and the DRR image by performing a calculation using the DR image and the DRR image in the region corresponding to the DR image among the positioned DRR images.

According to the positioning device according to the second item, positioning can be performed without requiring a long time for the calculation for positioning.

The above description is for the purpose of explaining the embodiment of the present invention, and does not limit the present invention.

11 X-ray tube 21 Flat panel detector 27 Examination table 29 Subject mounting unit 30 Control unit 31 DR image creation unit 32 DRR image creation unit 33 Superimposition display unit 34 Coarse positioning unit 35 Positioning unit 36 Movement amount calculation unit 37 Movement signal Transmission unit 38 Operation unit 39 Display unit 90 Treatment beam irradiation device 92 Gantry 93 Treatment beam irradiation unit 99 Treatment planning device

Claims (2)

A DR image that is provided with a plurality of X-ray imaging systems including an X-ray irradiation unit and an X-ray detection unit, and creates a DR image of the subject using an X-ray imaging device capable of photographing the subject from two different directions. With the creator
A DRR image creation unit that creates a DRR image by performing a virtual perspective projection that simulates the geometric imaging conditions of the X-ray imaging system on the CT data of the subject created at the time of treatment planning.
A superposed display unit that displays the DR image and the DRR image in a superposed state,
A coarse positioning unit that roughly positions the DR image and the DRR image by moving the DRR image displayed by the superimposed display unit relative to the DR image by operating the operation unit.
A positioning unit that positions the DR image and the DRR image by performing an operation using the DR image and the DRR image after rough positioning.
A movement amount calculation unit that calculates the movement amount of the subject mounting unit on which the subject is placed from the movement amount of the DRR image relative to the DR image.
With
The DRR image creation unit is a positioning device that creates a DRR image in a region larger than the region of the DR image created by the DR image creation unit. In the positioning device according to claim 1,
The positioning unit is a positioning device that positions a DR image and a DRR image by performing a calculation using the DR image and a DRR image in a region corresponding to the DR image among the DRR images after positioning.

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