JP7172850B2 - positioning device - Google Patents

Description

The present invention relates to positioning devices.

2. Description of the Related Art In radiation therapy in which radiation such as X-rays, electron beams, and particle beams is applied to an affected area such as cancer, it is necessary to accurately irradiate the affected area with radiation. When performing radiotherapy using a radiotherapy apparatus, a treatment plan is formulated prior to treatment. Then, when radiotherapy is performed, it is necessary to perform positioning so that the subject's position matches that at the time of treatment planning. Positioning of a subject in a radiotherapy apparatus has conventionally been performed by a technician by manipulating the position of the examination table on which the subject is placed while visually confirming the position indicated by the laser marking device. rice field. 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 geometric 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 was used during treatment planning. DRR (Digital Reconstructed Radiography) image, which is a virtual perspective projection, is used to evaluate the similarity between the DR (Digital Radiography) image and the DRR image taken by an X-ray imaging system (image registration). The amount of positional deviation between the current position of the patient and the position at the time of treatment planning is calculated. Since the calculation cost of DRR is enormous, in Patent Document 1, the calculation cost required for executing DRR is reduced to speed up the positioning of the subject. After the positional deviation amount is calculated, the subject is placed in the correct position by moving the subject placement section on the medical examination table according to the positional deviation amount.

JP 2013-99431 A

When calculating the amount of positional deviation 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 greatly deviated, the position Not only does it take a long time to calculate the amount of deviation, but there are cases where the calculation is performed while recognizing a predetermined part of the subject as another part. Therefore, when the amount of positional deviation between the DR image and the DRR image is calculated by image registration, coarse positioning is performed by the operator's operation to position the DRR image at a position that roughly matches the DR image.

When performing rough positioning, the DR image and the DRR image are displayed in a superimposed state on the display unit, and the operator operates the operation unit to move the DRR image with respect to the DR image. A coarse positioning operation is performed to place the images in roughly matching positions.

At this time, the DRR image is created to have a size that represents the area of the DR image, that is, the area that matches 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 the rough positioning is completed depends on the area where the DR image and the DRR image are superimposed. Therefore, it is not easy to determine whether the positions of the DR image and the positions of the DRR image match or disagree, and it becomes extremely difficult to determine whether the rough positioning has been completed.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a positioning device capable of easily performing rough positioning between a DR image and a DRR image.

A first aspect of the present invention provides a plurality of X-ray imaging systems comprising an X-ray irradiation unit and an X-ray detection unit, and uses an X-ray imaging apparatus capable of imaging the subject from two different directions. and 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 DRR image creating unit that creates a DRR image having an area larger than the area of the DR image created by the DR image creating unit; and a superimposed display unit that displays the DR image and the DRR image in a superimposed state. a rough positioning unit that performs rough positioning of the DR image and the DRR image by relatively moving the DRR image displayed by the superimposed display unit with respect to the DR image in accordance with the user's operation of the operation unit; The DR image and the DRR image are positioned by extracting the DRR image of the region corresponding to the DR image from among the DRR images after rough positioning and performing calculations using the extracted DRR image and the DR image. movement for calculating the amount of movement of the subject placement section on which the subject is placed from the relative movement amount of the DRR image with respect to the DR image by the positioning section and the rough positioning section and the positioning section and a quantity calculator, wherein the DRR image generator includes areas of the DR image generated by the DR image generator that can be used by a user to determine whether the coarse positioning is complete. , to create a DRR image with an area larger than that of the DR image .

According to the first aspect of the invention, the entire area of the DR image can be used for coarse registration, and the DRR image in areas outside the DR image can also be used for coarse registration. . For this reason, more information can be used to perform rough positioning, and rough positioning of the DR image and the DRR image can be easily performed.

1 is a perspective view showing an X-ray imaging apparatus equipped with a positioning device according to an embodiment of the present invention together with a therapeutic beam irradiation device 90; FIG. 1 is a block diagram showing main control systems of an X-ray imaging apparatus equipped with a positioning device according to an embodiment of the present invention; FIG. FIG. 4 is an explanatory diagram schematically showing a state in which a DRR image is created by virtual fluoroscopic imaging; 3 is a schematic diagram of a DR image X1 created by a DR image creation unit 31; FIG. FIG. 3 is a schematic diagram of a DRR image D2 having an area larger than that of a DR image X1, created by a DRR image creating unit 32; FIG. 4 is a schematic diagram of a DRR image D1 having the same region as the DR image X1; FIG. 4 is a schematic diagram showing how rough positioning is performed using a DR image X1 and a DRR image D2;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an X-ray imaging apparatus equipped with a positioning device according to an embodiment of the present invention together with a treatment beam irradiation device 90. FIG. The X-ray imaging apparatus and the treatment beam irradiation apparatus 90 constitute a radiotherapy apparatus.

The therapeutic beam irradiation device 90 performs radiation therapy on the subject on the medical examination table 27, and has a gantry that rotates around the isocenter with respect to a base 91 installed on the floor of the treatment room. 92 and a therapeutic beam irradiation unit 93 arranged on the gantry 92 for emitting a therapeutic beam. The gantry 92 is structured to be rotatable within a range of 360 degrees with respect to the base 91 together with the therapeutic beam irradiation unit 93 .

Therefore, according to this therapeutic beam irradiation apparatus 90, by rotating the gantry 92 to an arbitrary angular position with respect to the base 91, the irradiation direction of the therapeutic beam emitted from the therapeutic beam irradiation unit 93 can be changed. can be done. Therefore, it is possible to perform so-called multifield irradiation, in which treatment beams are applied from various directions to an affected area such as a tumor in a subject.

It should be noted that the isocenter is a position where the treatment beam emitted from the treatment beam irradiation unit 93 is most concentrated in radiotherapy treatment, and is the irradiation center of the treatment beam.

The X-ray imaging apparatus used together with this treatment beam irradiation apparatus 90 performs X-ray fluoroscopy for performing moving body tracking for specifying the position of the affected part of the subject. That is, during radiotherapy using the above-described therapeutic beam irradiation apparatus 90, it is necessary to accurately irradiate radiation to the affected area that moves along with body movement of the subject. For this reason, in this X-ray imaging apparatus, the subject is viewed from two different directions, and image recognition is performed on the fluoroscopic images, thereby recognizing the marker placed near the specific site of the subject. By detecting the position and calculating the three-dimensional positional information of the marker, the marker is detected with high accuracy, which is a so-called moving object tracking.

Note that a method of using an image of a specific site such as a tumor on the subject as a marker instead of placing the marker near the affected area of the subject has also been adopted. Such a moving object tracking method is called markerless tracking. In this specification, a specific site such as a tumor on a subject and a marker indwelled near 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 site of the subject is registered in advance as a template, and the template is used to detect and track the position of the marker or the like. template matching is used. Further, as another embodiment of this image recognition, a classifier is created by learning from a large number of pre-registered correct images and incorrect images for markers and the like, and this classifier is used to recognize markers and the like. It uses machine learning to detect and track your 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. 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") are provided. The X-rays emitted from the first X-ray tube 11a are detected by the first flat panel detector 21a after passing through the subject on the examination table 27. FIG. The first X-ray tube 11a and the first flat panel detector 21a constitute a first X-ray imaging system. The X-rays emitted from the second X-ray tube 11b are detected by the second flat panel detector 21b after passing through the subject on the examination table 27. FIG. The second X-ray tube 11b and the second flat panel detector 21b constitute a second X-ray imaging system. The X-rays emitted from the third X-ray tube 11c are detected by the third flat panel detector 21c after passing through the subject on the examination table 27. FIG. The third X-ray tube 11c and the third flat panel detector 21c constitute a third X-ray imaging system. The X-rays emitted from the fourth X-ray tube 11d are detected by the fourth flat panel detector 21d after passing through the subject on the examination table 27. FIG. The fourth X-ray tube 11d and the fourth flat panel detector 21d constitute a fourth X-ray imaging system.

When performing X-ray fluoroscopy for tracking a moving body, two of the first X-ray imaging system, second X-ray imaging system, third X-ray imaging system, and fourth X-ray imaging system are used as described later. A radiographic system is selected and used.

The examination table 27 comprises a base 28 and a subject placement part 29, also called a couch. The subject placement section 29 is movable in four-axis or six-axis directions with respect to the base section 28 . The subject placement section 29 moves based on a movement signal from a movement signal transmission section 37, which will be described later. In addition, it is also possible to move the subject placement section 29 by an operator's operation.

FIG. 2 is a block diagram showing main control systems of an X-ray imaging apparatus equipped with a positioning device according to an embodiment of the invention.

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

This control unit 30 is connected to the X-ray tube 11, flat panel detector 21, examination table 27 and treatment beam irradiation device 90 described above. The control unit 30 is also connected to an operation unit 38 having an input mechanism such as a keyboard and a mouse and executing various operations, and a display unit 39 having a liquid crystal display panel or the like. Furthermore, this 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 acquires CT image data of the subject photographed by a CT imaging device (not shown). The control unit 30 acquires this CT image data from the treatment planning device 99 .

As a functional configuration, the control unit 30 uses two X-ray imaging systems out of a first X-ray imaging system, a second X-ray imaging system, a third X-ray imaging system, and a fourth X-ray imaging system to detect X-rays. A DR image creation unit 31 that creates a DR image by performing imaging, and a virtual perspective projection that simulates the geometric imaging conditions of an X-ray imaging system for CT data of a subject acquired from a treatment planning device 99. , a superimposed display unit 33 for displaying the DR image and the DRR image in a superimposed state on the display unit 39, and the operator operating the operation unit 38 , a coarse positioning unit 34 for roughly positioning the DR image and the DRR image by relatively moving the DRR image displayed on the display unit 39 by the superimposed display unit 33 with respect to the DR image; By performing calculations using the DRR image, the positioning unit 35 that positions the DR image and the DRR image, and the amount of relative movement of the DRR image with respect to the DR image, the subject on which the subject is placed By transmitting a movement signal of the subject placement section 29 to the movement amount calculation section 36 that calculates the movement amount of the placement section 29 and the examination table 27, the subject on the subject placement section 29 is moved. and a movement signal transmitter 37 for moving the person to the correct position.

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 performed in directions corresponding to two X-ray imaging systems out 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. be. In the following description, one X-ray imaging system will be described, but the other X-ray imaging system also performs the same operation.

When starting treatment for a subject, first, the DR image generator 31 selects two X-rays from among 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 taking X-rays using a radiography system. This DR image is, for example, an image of 512×512 pixels. At this time, based on the arrangement of the therapeutic beam irradiation unit 93 in the therapeutic beam irradiation apparatus 90, an X-ray imaging system is selected in which the gantry 92 is not used for X-ray imaging.

Next, a DRR image to be 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 radiography.

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

Then, the DRR image creating unit 32 performs virtual perspective projection on the CT image data 100 simulating the geometric imaging conditions for the subject of each X-ray imaging system used when creating the DR image. , to 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 creating section 31 is, for example, an image of 512×512 pixels. On the other hand, the DR image created by the DRR image creating unit 32 is, for example, an image of 1024×1024 pixels. In this way, the DRR image creating section 32 creates a DRR image having an area larger than the area of the DR image created by the DR image creating section 31 . As described above, the DRR image is created by performing virtual perspective projection on the CT image data 100, which is three-dimensional voxel data. Therefore, the region of the DRR image created by the DRR creating 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 in a superimposed state on the display unit 39 . After that, based on the operation of the operation unit 38 by the operator, the rough positioning unit 34 relatively moves the DRR image displayed on the display unit 39 with respect to the DR image, thereby roughening the DR image and the DRR image. positioning. At this time, for example, the operator uses the mouse on the operation unit 38 to drag the DRR image displayed on the display unit 39, thereby moving the DRR image so that the DR image and the DRR image approximately match each other. Let

Hereinafter, this rough positioning operation will be described by comparing the case of using a DRR image having the same size as the DR image and the case of using a DRR image larger than the DR image. FIG. 4 is a schematic diagram of a DR image X1 created by the DR image creation unit 31. As shown in FIG. FIG. 5 is a schematic diagram of a DRR image D2 having an area larger than that of the DR image X1, created by the DRR image creation unit 32. As shown in FIG. FIG. 6 is a schematic diagram 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 diagram showing how rough positioning is performed using the DR image X1 and the DRR image D2. Note that FIGS. 4 to 6 show the case where the rough positioning operation is executed based on the image of the chest area of the subject.

In the DR image X1 shown in FIG. 4 and the DRR image D2 having a large area shown in FIG. 5, the subject's spine 51, collarbone 52, and rib 53 can be confirmed. On the other hand, in a DRR image D1 with a small area similar to the DR image X1 shown in FIG. 6, the subject's spine 51 and ribs 53 can be confirmed.

In order to perform rough positioning, when the operator moves the DRR image out of the DR image X1 and the DRR image superimposed and displayed on the display unit 39 and superimposes the DRR image 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 the rough positioning is completed depends on the area where the DR image X1 and the DRR image D1 are superimposed. Therefore, the amount of information for rough positioning is small, and it becomes difficult to identify which of the plurality of ribs 53 correspond 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 not, and it becomes extremely difficult to determine whether the rough positioning has been completed.

On the other hand, when the DR image X1 and the DRR image D2 representing a large area are superimposed on the display unit 39, as shown in FIG. Areas outside DR image X1 in D2 can also be used for coarse positioning. Therefore, the amount of information for rough positioning becomes large, and in the case of the embodiment shown in FIG. Coarse positioning can be performed. As a result, more information can be used to perform rough positioning, and rough positioning between the DR image X1 and the DRR image D2 can be easily performed.

When the rough positioning of the DR image and the DRR image is completed, the positioning unit 35 performs calculations using the data of the DR image and the DRR image after rough positioning, thereby accurately positioning the DR image and the DRR image. . That is, the amount of positional deviation between the DR image and the DRR image is calculated by image registration. In this case, if calculation 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 will be large, and positioning will take time. Therefore, the positioning unit 35 performs calculation using only the data of the DRR image of the region corresponding to the DR image X1 among the data of the DRR image D2 after rough positioning. This makes it possible to perform positioning without requiring a long time for calculations for positioning.

When the positioning of the DR image X1 and the DRR image D2 is completed, the movement amount calculation unit 36 locates the subject at the position according to the treatment plan from the relative movement amount of the DRR image D2 with respect to the DR image X1. , the amount of movement of the subject placement section 29 required for . Then, the movement signal transmission section 37 transmits a movement signal of the subject placing section 29 to the medical examination table 27 . This makes it possible to move the subject on the subject placing section 29 to the correct position according to the treatment plan.

When the positioning of the subject is completed, X-ray imaging is performed again, the photographed DR image is compared with the DRR image based on the data at the time of treatment planning, and the amount of positional deviation between them is within a preset threshold value. Check whether it is If the positional deviation amount is smaller than the preset threshold value, radiotherapy is continued. On the other hand, if the amount of positional deviation is larger than the preset threshold value, the positioning operation is executed again.

In the above-described embodiment, a DR image is created using an X-ray imaging apparatus that executes X-ray fluoroscopy for performing moving body tracking for specifying the position of the affected area of the subject. Ordinary X-ray equipment may be used.

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

(Section 1)
A DR image for creating a DR image of a subject using an X-ray imaging apparatus having a plurality of X-ray imaging systems consisting of an X-ray irradiation unit and an X-ray detection unit and capable of imaging the subject from two different directions. creation department,
a DRR image creating unit that creates a DRR image by performing virtual perspective projection simulating the geometric imaging conditions of the X-ray imaging system on the CT data of the subject created during treatment planning;
a superimposed display unit that displays the DR image and the DRR image in a superimposed state;
a rough 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 calculations using the DR image and the DRR image after rough positioning;
a movement amount calculation unit that calculates a movement amount of a subject placement unit on which the subject is placed from the relative movement amount of the DRR image with respect to the DR image;
with
The DRR image creation unit creates a DRR image having an area larger than the area of the DR image created by the DR image creation unit.

According to the positioning device according to item 1, the entire area of the DR image can be used for rough positioning, and the DRR image in the area outside the DR image can also be used for rough positioning. can. For this reason, more information can be used to perform rough positioning, and rough positioning of 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 calculations using the DR image and a DRR image of a region corresponding to the DR image among the DRR images after positioning.

According to the positioning device described in the second aspect, positioning can be executed without requiring a long time for calculations for positioning.

It should be noted that the above description is for the description of the embodiments of the present invention, and does not limit the present invention.

REFERENCE SIGNS LIST 11 X-ray tube 21 flat panel detector 27 examination table 29 subject placing unit 30 control unit 31 DR image creating unit 32 DRR image creating unit 33 superimposed display unit 34 rough 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 (1)

A DR image for creating a DR image of a subject using an X-ray imaging apparatus having a plurality of X-ray imaging systems consisting of an X-ray irradiation unit and an X-ray detection unit and capable of imaging the subject from two different directions. creation department,
A DR image created by the DR image creation unit by performing virtual perspective projection simulating the geometric imaging conditions of the X-ray imaging system on the CT data of the subject created during treatment planning. a DRR image creation unit that creates a DRR image of an area larger than the area of
a superimposed display unit that displays the DR image and the DRR image in a superimposed state;
a rough positioning unit that roughly positions the DR image and the DRR image by relatively moving the DRR image displayed by the superimposed display unit with respect to the DR image in accordance with a user's operation of the operation unit;
The DR image and the DRR image are positioned by extracting the DRR image of the region corresponding to the DR image from among the DRR images after rough positioning and performing calculations using the extracted DRR image and the DR image. a positioning portion for
a movement amount calculation unit that calculates a movement amount of a subject placement section on which the subject is placed from the relative movement amount of the DRR image with respect to the DR image by the coarse positioning section and the positioning section ;
with
The DRR image creation unit includes an area of the DR image created by the DR image creation unit that can be used by the user to determine whether the rough positioning is completed. A positioning device that creates a DRR image of a large area.

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