CN111603689B - DR image guiding and positioning method and device - Google Patents

DR image guiding and positioning method and device Download PDF

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CN111603689B
CN111603689B CN202010439868.7A CN202010439868A CN111603689B CN 111603689 B CN111603689 B CN 111603689B CN 202010439868 A CN202010439868 A CN 202010439868A CN 111603689 B CN111603689 B CN 111603689B
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CN111603689A (en
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谢嘉杰
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Konica Minolta Medical & Graphic Equipment Shanghai Co ltd
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    • A61N5/1049—Monitoring, verifying, controlling systems and methods for verifying the position of the patient with respect to the radiation beam
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    • A61N5/1049—Monitoring, verifying, controlling systems and methods for verifying the position of the patient with respect to the radiation beam
    • A61N2005/1061—Monitoring, verifying, controlling systems and methods for verifying the position of the patient with respect to the radiation beam using an x-ray imaging system having a separate imaging source

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Abstract

The embodiment of the invention belongs to the technical field of radiotherapy, and particularly relates to a DR image guiding and positioning method and a device, wherein the method comprises the following steps: extracting feature points and feature areas from CT images of a patient acquired on a first treatment couch; acquiring a plurality of digital radiography DR images of the patient on a second treatment couch; setting three-dimensional space transformation T, transforming the CT image to obtain a transformed CT image, and carrying out perspective projection on the transformed CT image by using the geometric parameters of each DR imaging to generate a plurality of corresponding digital reconstructed image DRR images; comparing the similarity of each DRR image with the only corresponding DR image, adjusting the transformation T, and outputting the transformation T with the maximum comprehensive similarity; and guiding the patient to correctly position according to the transformation T with the maximum comprehensive similarity. Compared with the prior art, the use requirement that the orthogonal two-way DR equipment or coplanar two-way DR equipment cannot be installed due to limited space in a treatment room can be met.

Description

DR image guiding and positioning method and device
Technical Field
The embodiment of the invention belongs to the technical field of radiotherapy, and particularly relates to a DR image guiding and positioning method and device.
Background
Proton heavy ion radiotherapy is the most advanced radiotherapy technology at present, and is very important for positioning a treatment target area, and an image guidance technology becomes a standard for radiotherapy equipment. In a general radiotherapy process, a three-dimensional CBCT image and an orthogonal DR positioning system are mainly used in a conventional image-guided positioning technology, and in the general radiotherapy process, a patient to be treated with radiotherapy is firstly subjected to CT scanning, the CT image is used as a treatment plan, and then radiotherapy is carried out in a treatment room according to the treatment plan. When the radiotherapy is carried out, the patient needs to be accurately positioned, so that the tumor treatment center of the patient in the treatment plan is positioned at the isocenter of the treatment equipment, and the image-guided tumor positioning technology becomes the standard matching of the radiotherapy equipment. Most of the 2D image guided positioning technologies on the market are designed for orthogonal DR, and some of the technologies are designed in such a way that the centerlines of the dual DR beams intersect at one point in space in a coplanar manner. In the case where the orthogonal two-way DR imaging apparatus or the coplanar two-way DR imaging apparatus cannot be installed due to the spatial limitation of the treatment room, the non-coplanar two-way DR imaging at an appropriate angle becomes an option.
Disclosure of Invention
The invention aims to provide a DR image guiding and positioning method and a DR image guiding and positioning device, which can meet the use requirement that an orthogonal two-way DR image device or a coplanar two-way DR image device cannot be installed in a treatment room due to limited space.
In order to achieve the above object, an embodiment of the present invention provides a DR image guiding and positioning method, including:
extracting feature points and feature areas from CT images of a patient acquired on a first treatment couch;
acquiring a plurality of digital radiography DR images of the patient on a second treatment couch; wherein the irradiation angle of each DR image is different;
setting coordinate values of the feature points and the feature areas from the first treatment couch to the second treatment couch in three-dimensional space transformation T, and transforming the CT image according to the coordinate values of the T to obtain a transformed CT image;
carrying out perspective projection on the transformed CT image by using the imaging geometric parameters of each DR image to generate a plurality of corresponding digital reconstruction image DRR images; wherein each DRR image uniquely corresponds to each DR image;
comparing the similarity of each DRR image with the only corresponding DR image, and adjusting and transforming the coordinate value of the T to enable the comprehensive similarity of each DR image and the only corresponding DRR image to be maximum;
outputting the coordinate value of the T with the maximum comprehensive similarity between each DR image and the corresponding DRR image, and guiding the patient to correctly position according to the coordinate value of the T.
In addition, the embodiment of the present invention also provides a DR image guiding and positioning apparatus, including:
the CT imaging equipment is used for acquiring a CT image of a patient on a first treatment bed and extracting feature points and feature areas in the CT image;
a number of X-ray devices; for respectively irradiating X-rays to the patient on the second treatment couch and for respectively acquiring DR images of the patient; the angles of the X-ray equipment irradiating the X-ray to the patient are different;
the main control system is in communication connection with the X-ray equipment and the CT image equipment and is used for acquiring the CT image, the characteristic points, the characteristic areas and the DR images;
the main control system is used for setting a coordinate value of a three-dimensional space transformation T of the feature point and the feature area from the first treatment bed to the second treatment bed, and transforming the CT image according to the coordinate value of the T;
the main control system is further configured to perform perspective projection on the transformed CT image according to the imaging geometric parameters of each DR image to generate a plurality of corresponding DRR images, perform similarity comparison between each DRR image and the uniquely corresponding DR image, and output a coordinate value of the T at which the comprehensive similarity between each DR image and the uniquely corresponding DR image reaches a maximum;
the main control system is also used for controlling the treatment equipment to guide the patient to correctly position according to the output coordinate value of the T.
Compared with the prior art, the implementation mode of the invention can generate a plurality of digital reconstructed image DRR images in real time by carrying out perspective projection on the transformed CT image according to the imaging geometric parameters of the plurality of DR images, simultaneously carry out similarity comparison on each DRR image and the uniquely corresponding DR image, output the coordinate value of the T with the maximum comprehensive similarity of each DR image and the uniquely corresponding DRR image, and guide the patient to correctly position according to the coordinate value of the T, thereby ensuring that the X-ray equipment does not need to adopt an orthogonal DR design when carrying out X-ray irradiation on the patient, ensuring that the X-ray equipment can be randomly placed, and meeting the use requirement that an orthogonal bidirectional DR image equipment or a coplanar bidirectional DR image equipment cannot be installed due to space limitation in a treatment room.
Furthermore, the irradiation angle of each DR image is different, and the central beams of each X beam are not coplanar.
Further, the imaging geometry required to generate one of the DRR images includes:
the DR image Fi(x2D) The coordinate value of the X-ray source point in the imaging coordinate system;
the DR image Fi(x2D) Coordinate values of an intersection point of the FPD imaging plane and the beam center line;
the DR image Fi(x2D) The offset vector in the FPD two-dimensional plane of the center of the FPD imaging area and the intersection point of the FPD imaging plane and the beam center line;
the DR image Fi(x2D) The included angle between the edge of the FPD imaging area and the horizontal plane;
the DR image Fi(x2D) Must be perpendicular to the FPD imaging plane, allowing errors less than the set point.
Further, in the step of setting coordinate values of three-dimensional spatial transformation T of the feature points and the feature regions from the first treatment couch to the second treatment couch, a hierarchical registration method is adopted, which specifically includes:
t obtained from the n-1 th leveln-1A transformation initial coordinate value of the T as an nth level for transforming the CT image;
obtaining the T of the nth level by adopting a gradient descent method according to the registration of the nth levelnThe coordinate values of (a);
and when the n is the registration, the DRR image and the DR image are down-sampled to the layer levels with different resolutions.
Further, the step of comparing each DRR image with the DR image uniquely corresponding thereto and adjusting and transforming the coordinate value of T specifically includes:
calculating the similarity S between each DRR image and the only corresponding DR image;
summing the similarity S obtained through calculation to obtain a sum value L;
judging whether the summation value L is an approximate limit value or not;
and after the L is judged not to be approximate limit value, optimally updating the coordinate value of the T.
If the summation value L is judged to be approximate limit value, continuously judging whether the nth level is the original image level of the DRR image and the DR image;
if the nth level is determined to be the original image level of the DRR image and the DR image, taking the current coordinate value of the T as the coordinate value of the T when the comprehensive similarity between each DR image and the uniquely corresponding DRR image reaches the maximum.
Further, after the step of determining whether the nth layer is an original image level of the DRR image and the DR image, the method further includes the following sub-steps:
if the nth level layer is not the original image level of the DRR image and the DR image, optimally updating the coordinate value of the T at the (n + 1) th level.
Further, in the step of calculating the similarity S between each DRR image and the uniquely corresponding DR image, the similarity is calculated by using the following formula;
Figure GDA0003459726170000031
wherein A and B are both constants; IDR represents DR picture, IDRR represents DRR picture;
the lambda is a weight factor;
and u and v are all orthogonal coordinate axes in the plane of the DR image.
Further, in the step of summing each of the calculated similarities S to obtain a summation value L, the summation value L may be calculated by using the following formula;
Figure GDA0003459726170000041
wherein Si is each similarity S; n is the Nth;
further, in the step of determining whether the summation value L is an approximate limit value, the method specifically includes:
the sum L obtained from the k iterationkThe sum value L with the k-1 th timek-1Carrying out comparison;
as said sum value LkAnd the sum value Lk-1Is less than 10-4Determining the sum value LkIs an approximate limit value; as said sum value LkAnd the sum value Lk-1Is greater than 10-4Then, the sum value L is determinedkNot an approximate limit value; wherein k is the number of iterative cycles.
Furthermore, the irradiation directions of the DR images are different, and the central beams of the X beams are not coplanar.
Further, the characteristic point is a treatment central point of a tumor position of the patient, and the characteristic region is a treatment target area.
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FIG. 1 is a block flow diagram of a DR image guided positioning method according to a first embodiment of the present invention;
FIG. 2 is a block diagram of a specific process for setting three-dimensional transformation T of feature points and feature regions from a first treatment couch to a second treatment couch, and calculating positioning error values of the feature points and the feature regions in the three-dimensional space when acquiring a plurality of DR images of a patient according to the first embodiment of the present invention;
FIG. 3 is a schematic diagram of the position relationship between the isocenter of the treatment apparatus and the center lines of two cone beams of two X-ray apparatuses according to the first embodiment of the present invention;
fig. 4 is a block diagram of system modules of a DR image guiding and positioning apparatus according to a first embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in order to provide a better understanding of the present application in various embodiments of the present invention. However, the technical solutions claimed in the claims of the present application can be implemented without these technical details and with various changes and modifications based on the following embodiments.
The first embodiment of the present invention relates to a DR image guiding and positioning method, as shown in fig. 1, including the steps of:
step 110, acquiring a CT image of the patient on the first treatment couch, and extracting feature points and feature areas from the CT image.
In step 120, a plurality of digital radiography DR images of the patient are acquired on the second treatment couch. Wherein, the irradiation angle of each DR image is different.
And step 130, setting coordinate values of three-dimensional space transformation T of the feature points and the feature areas from the first treatment couch to the second treatment couch.
And 140, transforming the CT image according to the coordinate value of the T to obtain the transformed CT image.
And 150, carrying out perspective projection on the transformed CT image by using the imaging geometric parameters of each DR image to generate a plurality of digital reconstruction image DRR images, wherein each DRR image is uniquely corresponding to each DR image.
And 160, comparing the similarity of each DRR image with the uniquely corresponding DR image, and adjusting the coordinate value of the transformation T to maximize the comprehensive similarity of each DR image and the uniquely corresponding DRR image.
And 170, outputting a coordinate value of T with the maximum comprehensive similarity between each DR image and the corresponding DRR image, and guiding the patient to correctly position according to the coordinate value of T.
Through the content, the method can be found out that a plurality of digital reconstructed image DRR images can be generated in real time by carrying out rapid perspective projection on the transformed CT image according to the imaging parameters of a plurality of DR images, simultaneously, each DRR image is compared with the unique corresponding DR image in similarity, the coordinate value of T with the maximum comprehensive similarity of each DR image and the unique corresponding DRR image is output, and the patient is guided to be correctly positioned according to the coordinate value of T, so that the X-ray equipment is ensured to be free from adopting an orthogonal DR design when the X-ray equipment irradiates the X-ray to the patient, the X-ray equipment can be randomly placed, and the use requirement that an orthogonal bidirectional DR image equipment or a coplanar bidirectional DR image equipment cannot be installed due to space limitation in a treatment room can be met.
Specifically, in the present embodiment, as shown in fig. 3, the feature point will be described by taking, as an example, a treatment center point of a tumor position of a patient and a feature region as a treatment target region. In fig. 1, the ISO point is the isocenter of the treatment device, i.e., the position where the tumor treatment center of the patient should be placed. S1 and S2 are X-ray source points of two X-ray devices, FPDs 1 and 2 are flat panel detectors of the two X-ray devices, a thick broken line is a cone beam center line of DR imaging, and the cone beam center line of each imaging group needs to be perpendicular to the FPD flat panel detectors. In a non-coplanar DR imaging mode, the cone beam center line does not need to pass through an ISO point, and the two cone beam center lines do not need to intersect at one point in a three-dimensional space. In addition, as shown in fig. 3, the treatment apparatus has two treatment heads: a vertical treatment head 3 and a horizontal treatment head 4. The non-coplanar imaging design easily avoids the interference of multiple treatment heads and other devices in the treatment room, the imaging device has a large degree of freedom in installation, and the treatment couch 5 is used to support the patient.
The DR image guiding and positioning method of the embodiment is based on hardware, and realizes calculation of a patient positioning error value with 6 degrees of freedom by software. The 6 degrees of freedom refer to translation and rotation on three coordinate axes in three-dimensional space, respectively. I.e., X-axis translation and rotation, Y-axis translation and rotation, and Z-axis translation and rotation. And hardware installation and imaging geometric design during DR image acquisition, for example, DR image guiding and positioning hardware as shown in fig. 3, two X-ray imaging devices 1 are adopted, two DR images are acquired on site before or during treatment, the two acquired DR images are used as reference images to be registered with a planned CT image, and an error value of current patient positioning is calculated. Also, the two cone beam centerlines X1 and X2 do not need to pass through ISO points, and the two cone beam centerlines X1 and X2 do not need to intersect at a point in three-dimensional space. So that the present embodiment may adopt a non-coplanar bi-directional or multi-directional DR image-guided positioning method.
In this embodiment, first, let M (x)3D) Representing planning CT data, namely scanning a patient on a first treatment bed through a CT imaging device; let x3DRepresenting a coordinate vector in three-dimensional space; let Fi(x2D) Representing the ith two-dimensional DR image (reference image); let x2DRepresenting a coordinate vector in a two-dimensional image plane; let T denote the three-dimensional spatial transformation. And, for each reference image FiThere should be a corresponding two-dimensional DRR image Pi。
Then, for three-dimensional M (x)3D) Applying T transformation to obtain three-dimensional M (T (x) after transformation3D) M (T (x)) (3D) According to DR image Fi(x2D) The imaging geometric parameters are calculated by adopting a ray projection method to obtain a projected DRR image Pi. Wherein a DRR image P is generatediThe imaging geometry parameters that need to be used include:
A) corresponding DR image Fi(x2D) Coordinate values of the X-ray source point in the imaging coordinate system;
B) corresponding DR image Fi(x2D) Coordinate values of an intersection point of the FPD imaging plane and the beam center line;
C) corresponding DR image Fi(x2D) The offset vector in the FPD two-dimensional plane of the center of the FPD imaging area and the intersection point of the FPD imaging plane and the beam center line;
D) corresponding DR image Fi(x2D) The included angle between the edge of the FPD imaging area and the horizontal plane;
E) corresponding DR image Fi(x2D) Must be perpendicular to the FPD imaging plane with an allowed error of less than 0.1 degrees.
Specifically, in the present embodiment, as shown in fig. 2, the step 130 of setting the T coordinate values of the feature points and the feature regions from the first treatment couch to the second treatment couch at a time includes:
step 1301, obtaining T from the (n-1) th leveln-1The initial coordinate value is a transformation initial coordinate value of T for transforming the CT image in the nth level. Wherein, when the transformation T is set for the first time, the default initial coordinate value T0Is (0,0,0,0,0, 0).
Step 1302, obtaining the T of the nth level by a gradient descent method according to the registration of the nth levelnThe coordinate values of (2). And when n is the registration, the DRR image and the DR image are down-sampled into the layer levels with different resolutions.
That is, in the present embodiment, when calculating the coordinate values of the transformation T, the images under three scales are respectively registered step by using the automatic registration algorithm, that is, firstly, the registration is performed by descending the samplingProcessing an original image to obtain DR and DRR images with a third-level scale (minimum size), automatically registering under the image with the third-level scale, searching for a global optimal solution, registering to the image with the second-level scale step by step, and finally registering under the resolution of the original image. Finally obtaining the optimal solution
Figure GDA0003459726170000061
Therefore, it is easy to see that, the automatic registration algorithm flow is adopted to perform once under the image of each level of scale, the T obtained by the automatic registration of the previous level is used as the initial value of the image registration of the second level of scale, and the registration is performed step by step until the final original image is obtained at the first level
Figure GDA0003459726170000062
This can improve the efficiency and robustness of the registration algorithm.
In addition, it should be noted that, in the step of comparing the similarity between each DRR image and the uniquely corresponding DR image and adjusting the coordinate value of the transformation T, that is, step 160, as shown in fig. 2, specifically includes:
step 1601, calculate the similarity S of each DRR image to the uniquely corresponding DR image. And the similarity S can be calculated using the following formula:
Figure GDA0003459726170000071
wherein A, B are all constants; λ is a weighting factor; u and v are all orthogonal coordinate axes in the plane of the DR image.
Step 1602, summing the calculated similarities S to obtain a sum L. The summation value L can be calculated using the following formula:
Figure GDA0003459726170000072
in step 1603, it is determined whether the sum L is an approximate limit.
If the summation value L is not determined to be approximate to the limit value, the coordinate values of the three-dimensional space transformation T of the characteristic points and the characteristic areas from the first treatment couch to the second treatment couch are optimized and updated, and the step 130 is returned.
If the summation value L is determined to be an approximate limit value, the step 1604 determines whether the nth level is the original image level of the DRR image and the DR image.
Step 1605, if the nth level is determined to be the original image level of the DRR image and the DR image, then using the current coordinate value of the transformation T, i.e. the 6 corresponding degree of freedom values of T in the three-dimensional space, as the coordinate value of T when the comprehensive similarity between each DR image and the uniquely corresponding DRR image reaches the maximum. That is, the coordinate value of T at this time can be used as a placement error of the feature point and the feature region in the three-dimensional space.
If it is determined that the nth level layer is not the original image level of the DRR image and the DR image, the coordinate values of the three-dimensional spatial transformation T of the feature points and the feature regions from the first couch to the second couch are optimally updated at the (n + 1) th level, i.e., the process returns to step 130 at the (n + 1) th level.
In the present embodiment, in the step of determining whether L is an approximate limit value, the sum L obtained in the k-th iteration may be determined as followskSum with k-1 th order Lk-1And (6) carrying out comparison. Such as the sum LkAnd the sum value Lk-1Is less than 10-4I.e. determining the sum LkIs an approximate limit value; such as the sum LkAnd the sum value Lk-1Is greater than 10-4When it is determined that the sum L iskNot an approximate limit. Wherein k is the number of iterative cycles.
In the image guidance positioning method according to the present embodiment, parameters such as an SAD value (the distance from the X-ray source point to the origin of the imaging coordinate system), an SI D value (the distance from the X-ray source point to the FPD plane), and an angle between the beam center lines are not calculated. But the DRR image is matched with the DR actually shot, so that the registration algorithm can automatically search more accurate coordinate values of T. Therefore, when the X-ray equipment irradiates X-rays to a patient, the X-ray equipment does not need to adopt an orthogonal DR design, so that the X-ray equipment can be placed at will, and the use requirement that the orthogonal two-way DR image equipment or coplanar two-way DR image equipment cannot be installed in a treatment room due to limited space can be met.
A second embodiment of the present invention relates to a DR image guiding and positioning apparatus, as shown in fig. 4, including: the X-ray CT imaging system comprises a CT imaging device, a plurality of X-ray devices and a main control system which is in communication connection with the X-ray devices and the CT imaging device respectively.
The CT imaging equipment is used for acquiring a CT image of a patient on a first treatment bed and extracting feature points and feature areas from the CT image. The X-ray devices are used for respectively irradiating X-rays to the patient on the second treatment bed and respectively acquiring DR images of the patient, and the X-ray devices are different in X-ray irradiation angle to the patient.
In the practical application process, firstly, the main control system obtains a CT image, feature points and feature areas in the CT image and DR images, then the main control system sets coordinate values of three-dimensional space transformation T of the feature points and the feature areas from a first treatment bed to a second treatment bed, the CT image is transformed according to the coordinate values of the T, then the main control system carries out perspective projection on the transformed CT image according to imaging geometric parameters of the DR images to generate a plurality of corresponding digital reconstruction image DRR images, each DRR image is compared with the unique corresponding DR image in similarity, the coordinate value of the T with the maximum comprehensive similarity between each DR image and the unique corresponding DRR image is output, and finally, the main control system is further used for controlling a treatment device to guide a patient to correctly position according to the output coordinate values of the T.
Specifically, in the present embodiment, as shown in fig. 4, each X-ray apparatus includes: the X-ray source, and the flat panel detector FPD arranged opposite to the X-ray source. The connecting lines of the source points of the X-ray sources of the respective ray devices to the pendants of the only oppositely arranged FPD may not intersect within the three-dimensional coordinate system.
Through the content, the method can be found out that a plurality of digital reconstructed image DRR images can be generated in real time by carrying out rapid perspective projection on the transformed CT image according to the imaging parameters of a plurality of DR images, simultaneously, each DRR image is compared with the unique corresponding DR image in similarity, the coordinate value of T with the maximum comprehensive similarity of each DR image and the unique corresponding DRR image is output, and the patient is guided to be correctly positioned according to the coordinate value of T, so that the X-ray equipment is ensured to be free from adopting an orthogonal DR design when the X-ray equipment irradiates the X-ray to the patient, the X-ray equipment can be randomly placed, and the use requirement that an orthogonal bidirectional DR image equipment or a coplanar bidirectional DR image equipment cannot be installed due to space limitation in a treatment room can be met.
As described above, the present embodiment is an example of the guide positioning device corresponding to the first embodiment, and can be implemented in cooperation with the first embodiment. The related technical details mentioned in the first embodiment are still valid in this embodiment, and are not described herein again in order to reduce repetition. Accordingly, the related-art details mentioned in the present embodiment can also be applied to the first embodiment.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.

Claims (11)

1. A DR image guiding and positioning method is characterized by comprising the following steps:
extracting feature points and feature areas from CT images of a patient acquired on a first treatment couch;
acquiring a plurality of digital radiography DR images of a patient on a second treatment bed; wherein the irradiation angle of each DR image is different;
setting coordinate values of three-dimensional space transformation T of the feature points and the feature areas from the first treatment bed to the second treatment bed;
transforming the CT image according to the coordinate value of the T to obtain a transformed CT image;
carrying out perspective projection on the transformed CT image by using the imaging geometric parameters of all the DR images to generate a plurality of DRR images of digital reconstruction images, wherein each DRR image is uniquely corresponding to each DR image;
comparing the similarity of each DRR image with the only corresponding DR image, and adjusting and transforming the coordinate value of the T to enable the comprehensive similarity of each DR image and the only corresponding DRR image to be maximum;
outputting the coordinate value of the T with the maximum comprehensive similarity between each DR image and the corresponding DRR image, and guiding the patient to correctly position according to the coordinate value of the T;
the central beam of the X-beam for each of the DR images acquired of the patient is non-coplanar.
2. The DR image guided location method of claim 1, wherein generating the DRR image includes:
the DR image Fi(x2D) The coordinate value of the X-ray source point in the imaging coordinate system;
the DR image Fi(x2D) Coordinate values of an intersection point of the FPD imaging plane and the beam center line;
the DR image Fi(x2D) The offset vector in the FPD two-dimensional plane of the center of the FPD imaging area and the intersection point of the FPD imaging plane and the beam center line;
the DR image Fi(x2D) The included angle between the edge of the FPD imaging area and the horizontal plane;
the DR image Fi(x2D) Must be perpendicular to the FPD imaging plane, allowing errors less than the set point.
3. The DR image guiding and positioning method according to claim 1, wherein a hierarchical registration method is adopted in the step of setting coordinate values of the three-dimensional spatial transformation T of the feature points and the feature regions from the first treatment couch to the second treatment couch, and specifically comprises:
t obtained from the n-1 th leveln-1A transformation initial coordinate value of the T as an nth level for transforming the CT image;
obtaining the T of the nth level by adopting a gradient descent method according to the registration of the nth levelnThe coordinate values of (a);
and when the n is the registration, the DRR image and the DR image are down-sampled to the layer levels with different resolutions.
4. The method as claimed in claim 3, wherein the step of comparing the similarity between each DRR image and the corresponding DR image uniquely and adjusting and transforming the coordinate value of T comprises:
calculating the similarity S between each DRR image and the only corresponding DR image;
summing the similarity S obtained by calculation to obtain a summation value L;
judging whether the summation value L is an approximate limit value or not;
if the L is not determined to be approximate limit value, optimizing and updating the coordinate value of the T;
if the summation value L is judged to be approximate limit value, continuously judging whether the nth level is the original image level of the DRR image and the DR image;
if the nth level is determined to be the original image level of the DRR image and the DR image, taking the current coordinate value of the T as the coordinate value of the T when the comprehensive similarity between each DR image and the uniquely corresponding DRR image reaches the maximum.
5. The method of claim 4, further comprising the following sub-steps after the step of determining whether the nth layer is an original image level of the DRR image and the DR image:
and if the nth level layer is judged to be not the original image level of the DRR image and the DR image, optimizing and updating the coordinate value of the T at the (n + 1) th level.
6. The method of claim 4, wherein in the step of calculating the similarity S between each DRR image and the corresponding DR image, the similarity is calculated by the following formula;
Figure FDA0003459726160000021
wherein A and B are both constants; i isDRRepresenting a DR image, IDRRRepresenting a DRR image;
the lambda is a weight factor;
and u and v are all orthogonal coordinate axes in the plane of the DR image.
7. The DR image guided positioning method of claim 4,
in the step of summing each of the calculated similarities S to obtain a sum L, the sum L may be calculated by using the following formula;
Figure FDA0003459726160000022
si is each similarity S; n is the Nth.
8. The method of claim 7, wherein the step of determining whether the summation value L is an approximate limit value specifically comprises:
the sum L obtained by the k iterationkSum with k-1 th order Lk-1Carrying out comparison;
as said sum value LkAnd the sum value Lk-1Is less than 10-4Determining the sum value LkIs an approximate limit value; as said sum value LkAnd the sum value Lk-1Is greater than 10-4Then, the sum value L is determinedkNot an approximate limit value; wherein k isThe number of iterative cycles.
9. A DR image guided positioning method according to any one of claims 1 to 8, wherein the feature point is a treatment center point of a tumor position of a patient, and the feature region is a treatment target region.
10. A DR image guided positioning apparatus, comprising:
the CT imaging equipment is used for acquiring a CT image of a patient on a first treatment bed and extracting feature points and feature areas in the CT image;
a number of X-ray devices; for respectively irradiating X-rays to the patient on the second treatment couch and for respectively acquiring DR images of the patient; the angles of the X-ray equipment irradiating the X-ray to the patient are different; acquiring central beams of X beams of each DR image of a patient, wherein the central beams are not coplanar;
the main control system is in communication connection with each X-ray device and the CT image device and is used for acquiring the CT image, the characteristic points, the characteristic areas and each DR image;
the main control system is used for setting a coordinate value of a three-dimensional space transformation T of the feature point and the feature area from the first treatment bed to the second treatment bed, and transforming the CT image according to the coordinate value of the T;
the main control system is further configured to perform perspective projection on the transformed CT image according to the imaging geometric parameters of each DR image to generate a plurality of corresponding DRR images, perform similarity comparison between each DRR image and the uniquely corresponding DR image, and output a coordinate value of the T at which the comprehensive similarity between each DR image and the uniquely corresponding DR image reaches a maximum;
the main control system is also used for controlling the treatment equipment to guide the patient to correctly position according to the output coordinate value of the T.
11. A DR image-guided positioning apparatus as recited in claim 10 wherein each of said X-ray devices comprises: the X-ray detector comprises an X-ray source and a Flat Panel Detector (FPD) which is only arranged opposite to the X-ray source.
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