CN106682409B - Sampling method, radiotherapy plan optimization method and dose calculation method - Google Patents

Sampling method, radiotherapy plan optimization method and dose calculation method Download PDF

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Publication number
CN106682409B
CN106682409B CN201611185113.9A CN201611185113A CN106682409B CN 106682409 B CN106682409 B CN 106682409B CN 201611185113 A CN201611185113 A CN 201611185113A CN 106682409 B CN106682409 B CN 106682409B
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region
sub
sampling
sampling points
interest
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CN201611185113.9A
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CN106682409A (en
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赵轲俊
王伟远
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上海联影医疗科技有限公司
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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00Radiation therapy
    • A61N5/10X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N5/103Treatment planning systems
    • A61N5/1031Treatment planning systems using a specific method of dose optimization
    • GPHYSICS
    • G16INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16HHEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
    • G16H50/00ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics
    • G16H50/20ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

The invention relates to the field of radiotherapy, and provides a method for sampling images in radiotherapy plan optimization, which comprises the following steps: the method comprises the steps of obtaining an image to be sampled, wherein the image to be sampled comprises at least one region of interest, obtaining the upper limit of the total number of sampling points and the number of the sampling points contained in each sub-region in the region of interest, dividing the region of interest into a plurality of sub-regions according to the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-region in the region of interest, and performing down-sampling on each sub-region by using a cluster analysis algorithm to obtain the sampling points of the region. The sampling method provided by the invention can keep the shape characteristics of each organ or target area while reducing the number of sampling points, and is beneficial to improving the effectiveness of a radiotherapy plan and the accuracy of dose distribution calculation.

Description

Sampling method, radiotherapy plan optimization method and dose calculation method

Technical Field

The invention relates to the field of radiotherapy, in particular to a clustering-based sampling method in a radiotherapy plan.

Background

Radiotherapy is a method of treating malignant tumors using radiation, such as α, β, gamma rays generated by radioisotopes, and x-rays, electron beams, proton beams, and other particle beams generated by various types of x-ray treatment machines or accelerators.

Due to the high beam energy, normal cells are affected while tumor cells are killed. In order to minimize damage to normal tissues, radiation treatment plans need to be developed. In the radiation treatment plan, a doctor needs to give a prescription and a treatment plan, and a physicist draws the organ and the tumor position, and Target areas such as total tumor Volume (GTV), Clinical Target Volume (CTV) and Planned Treatment Volume (PTV) according to the doctor prescription, and makes and optimizes the radiation treatment plan.

In order to determine the quality of the radiation treatment plan, a dose calculation algorithm (e.g., monte carlo algorithm, volume calculation method, pencil beam algorithm, etc.) is generally used to simulate the distribution of the dose received by various parts of the human body according to the radiation treatment plan.

Both optimization of the radiation treatment plan and dose calculation need to be based on the image, e.g. optimization of the radiation treatment plan and dose calculation based on CT images. The CT images generally have higher resolution and a larger number of pixels, which results in too long computation time and too large memory space if all the pixels participate in the optimization of the radiation treatment plan and the dose calculation.

In order to solve the problems, the CT image can be subjected to down-sampling, and sampling points represent all pixel points to participate in optimization of a radiation treatment plan and calculation of dose distribution, so that the selection of the sampling points directly influences a calculation result.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method for sampling images in radiation treatment plan optimization, which comprises the following steps: the method comprises the steps of obtaining an image to be sampled, wherein the image to be sampled comprises at least one region of interest, obtaining the upper limit of the total number of sampling points and the number of the sampling points contained in each sub-region in the region of interest, dividing the region of interest into a plurality of sub-regions according to the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-region in the region of interest, and performing down-sampling on each sub-region by using a cluster analysis algorithm to obtain the sampling points of the region.

Optionally, dividing the region of interest into a plurality of sub-regions according to the upper limit of the total number of the sampling points and the number of the sampling points included in each sub-region in the region of interest includes: dividing the region of interest into a plurality of sub-regions according to a preset rule, calculating the sum of the number of sampling points contained in each sub-region, comparing the sum of the number of sampling points contained in each sub-region with the upper limit of the total number of the sampling points, if the sum of the number of sampling points contained in each sub-region is greater than the upper limit of the total number of the sampling points, expanding the plurality of sub-regions, calculating the sum of the number of sampling points contained in each expanded sub-region, comparing the sum of the number of sampling points contained in each expanded sub-region with the upper limit of the total number of the sampling points until the sum of the number of sampling points contained in each expanded sub-region is less than the upper limit of the total number of the sampling points, wherein the sub-region in the last cycle is the final sub-region, if, and reducing the plurality of sub-areas and calculating the sum of the number of sampling points contained in each reduced sub-area, comparing the sum of the number of sampling points contained in each reduced sub-area with the upper limit of the total number of the sampling points until the sum of the number of sampling points contained in each reduced sub-area is greater than or equal to the upper limit of the total number of the sampling points, wherein each sub-area in the current cycle is the final sub-area, and if the sum of the number of sampling points contained in each sub-area is equal to the upper limit of the total number of the sampling points, each sub-area is the final sub-area.

Optionally, the number of sampling points included in the sub-region is related to at least one of the type of the region of interest, the weight, and the distance between the region of interest and the target region.

Optionally, the down-sampling each sub-region by using the cluster analysis algorithm includes: sampling each sub-region according to the number of sampling points contained in each sub-region in the region of interest to obtain initial sampling points, calculating Euler distances from each pixel point to the initial sampling points in each sub-region, classifying each pixel point into a cluster corresponding to the initial sampling point with the minimum Euler distance, and iteratively executing the following steps in each sub-region until the down-sampling of each sub-region is completed: and calculating the center of each cluster as a new sampling point, calculating the Euler distance between the new sampling point and the last sampling point, comparing the Euler distance with a threshold value, taking the new sampling point as the sampling point of the sub-region if the Euler distance does not exceed the threshold value, calculating the Euler distance from each pixel point to the new sampling point if the Euler distance exceeds the threshold value, and classifying each pixel point into the cluster corresponding to the new sampling point with the minimum Euler distance.

Optionally, before downsampling each sub-region by using a cluster analysis algorithm, it is determined whether the number of pixel points belonging to the corresponding region of interest in the sub-region exceeds the number of corresponding sampling points, if not, all the pixel points belonging to the corresponding region of interest in the sub-region are taken as the sampling points, and if so, downsampling the pixel points belonging to the corresponding region of interest in the sub-region by using the cluster analysis algorithm.

Optionally, before performing down-sampling on each sub-region by using a cluster analysis algorithm, it is determined whether pixel points not belonging to the corresponding region of interest are included in the sub-region, if so, the pixel points belonging to the corresponding region of interest in the sub-region are down-sampled by using the cluster analysis algorithm, if not, the sub-region is uniformly divided into grids according to the number of sampling points, and the central point of each grid is used as the sampling point.

According to another embodiment, the present invention further provides a method for sampling images in radiation treatment plan optimization, comprising: the method comprises the steps of obtaining an image to be sampled, wherein the image to be sampled comprises an interested region, obtaining the upper limit of the total number of sampling points, determining the number of the sampling points of each interested region, and performing down-sampling on the interested region by utilizing a cluster analysis algorithm to obtain the sampling points of the interested region.

According to another embodiment, the present invention also provides a radiation therapy plan optimization method, including: the method comprises the steps of obtaining an image of a patient and sketching interested areas, obtaining a dosage target of each interested area, sampling each interested area by using any one of the sampling methods, establishing an optimization model and optimizing so that the dosage of sampling points meets the dosage target.

According to another embodiment, the present invention also provides a radiation therapy plan optimization system, comprising: the system comprises an acquisition unit, a delineation unit, an input unit, a sampling unit and an optimization unit, wherein the acquisition unit is used for acquiring a patient image, the delineation unit is used for delineating interested areas, the input unit is used for setting dosage targets of the interested areas, the sampling unit is used for sampling the interested areas by using the sampling method, and the optimization unit is used for establishing an optimization model and optimizing the optimization model so that the dosage of sampling points meets the dosage targets.

According to another embodiment, the present invention also provides a dose calculation method including: acquiring a patient image, delineating interested regions, sampling the interested regions by using the sampling method, and calculating the dose distribution of the interested regions based on the sampling points.

Compared with the prior art, the method for sampling the image in the optimization of the radiation treatment plan clusters the pixels based on the characteristics of the pixels, and selects one pixel point from various types as the sampling point, so that the shape characteristics of each organ or target area can be kept while the number of the sampling points is reduced, and the effectiveness of the radiation treatment plan and the accuracy of dose distribution calculation are improved;

by dividing the region of interest into a plurality of sub-regions, pixels are clustered in each sub-region based on the characteristics of the pixels, thereby reducing the amount of computation and improving the computation speed.

The sampling method is applied to optimization of the radiation treatment plan, which is beneficial to improving the optimization speed and effectiveness of the radiation treatment plan and enables the calculation result of the dose distribution to be more consistent with the actual dose distribution.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a flowchart of a first method for image sampling in radiation treatment plan optimization according to an embodiment of the present invention;

FIG. 2 is a flowchart of a second method for image sampling in radiation treatment plan optimization according to an embodiment of the present invention;

FIG. 3 is a flow chart of a radiation treatment plan optimization method provided by an embodiment of the present invention;

fig. 4 is a flowchart of a dose calculation method according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In radiation therapy, it is desirable to deliver as high a dose of radiation as possible to the target tumor volume, minimizing damage to the organs. It is therefore desirable to optimize the radiation treatment plan and calculate the dose distribution in the patient to which the radiation treatment plan corresponds. Both the optimization of the radiation treatment plan and the dose distribution are calculated based on the sampling points and are therefore influenced by the distribution of the sampling points. In order to better control the dose distribution within each organ or target volume, the embodiments of the present invention propose a new sampling method.

Fig. 1 is a flowchart of a method for sampling images in radiation treatment plan optimization according to an embodiment of the present invention. Referring to fig. 1, the sampling method 100 provided by the present invention includes:

and step S101, acquiring an image to be sampled.

Acquiring an image to be sampled, wherein the image to be sampled comprises at least one region of interest, and the region of interest comprises an organ in which a doctor is interested and a tumor target area.

The patient image may be a CT image, a PET image, an MR image, or a fusion image, etc., but is not limited thereto.

And step S102, acquiring the upper limit of the total number of the sampling points and determining the number of the sampling points of each region of interest.

The upper limit N of the total number of sampling points limits the total number of sampling points of the at least one region of interest, which can be set in advance.

The number of the sampling points of each interested area is related to the type, weight and size of the interested area, for example, the interested area can be a tumor target area and can also be an organ, the weight of the target area is not less than that of the organ, and the weight of the organ at risk is more than that of the common organ; under the condition that the weight is kept unchanged, the larger the interested region is, the more the number of the sampling points is, therefore, the number of the sampling points of each organ and the target region is determined according to the type, the weight and the size of each interested region, and the condition that the sum of the number of the sampling points of each interested region does not exceed the upper limit N of the total number of the sampling points is met.

And S103, performing down-sampling on the region of interest by using a cluster analysis algorithm to obtain sampling points of the region of interest.

And sampling each organ and the target area according to the number of the sampling points of each interested area determined in the step. The number of sampling points of the ith organ or target area is recorded as NiThe sampling algorithm is used for sampling each organ and the target area, and the sampling algorithm is not limited herein. For the sake of simplicity, the process of downsampling the region of interest by using the cluster analysis algorithm in this embodiment is described here by taking a random sampling algorithm as an example, but the scope of the invention is not limited thereto.

Suppose that N is randomly selected from all pixel points in the ith organiEach sampling point, calculating the Euler distance from each pixel point to each sampling point, and grouping each pixel point to the cluster corresponding to the sampling point with the minimum Euler distance, thereby forming NiAnd (4) recalculating the center of each cluster as a new sampling point, and comparing the new sampling point with the last sampling point to judge whether the convergence condition is met.

The center of the cluster can be calculated by using a k-means algorithm, for example, the coordinates of each pixel point in a certain cluster are respectively (x)1,y1),(x2,y2),…,(xn,yn) And n is the number of pixel points in the cluster, the center coordinate of the cluster isThe center of the cluster may also be calculated by using a k-center algorithm, for example, for a certain cluster, the sum of euler distances from each pixel point to other pixel points is calculated, and the point with the minimum sum of the euler distances is used as the center of the cluster.

And judging whether the Euler distance between the new sampling point and the last determined sampling point does not exceed a threshold value, if not, finishing the circulation, taking the new sampling point as the sampling point of the region of interest, and if not, continuing the circulation until the Euler distance between the new sampling point and the last sampling point does not exceed the threshold value. The threshold value can here be set empirically beforehand.

In this embodiment, a clustering analysis algorithm is applied to sampling of an image, pixels are clustered based on distances, the closer the distance, the more similar the pixels are in representing the shape of an area of interest, and a pixel point can be selected from each class as a sampling point, so that the shape characteristics of the area of interest can be retained while the number of the sampling points is reduced.

Fig. 2 is a flowchart of a method for sampling images in radiation treatment plan optimization according to an embodiment of the present invention. Referring to fig. 2, the sampling method 200 provided by the present invention includes:

s201, acquiring an image to be sampled.

Acquiring an image to be sampled, wherein the image to be sampled comprises at least one region of interest, and the region of interest comprises an organ in which a doctor is interested and a tumor target area.

The patient image may be a CT image, a PET image, an MR image, or a fusion image, etc., but is not limited thereto.

In this embodiment, only the pixel points belonging to the region of interest are sampled, so that the region of interest can be represented by a matrix. The pixel points in the region of interest are represented by "1" and the pixels outside the region of interest are represented by "0", so that each region of interest can be represented by a matrix. Subsequent processing may only process areas covered by "1".

Step S202, acquiring the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-area in the region of interest.

The upper limit N of the total number of sampling points limits the total number of sampling points in the region of interest, which can be set by the physician.

The number of sampling points in each sub-region in the region of interest determines the number of sampling points in the region of interest, and can be set by a doctor. The number of sampling points in the sub-regions may be different in different organs or target regions, depending on at least one of the type and weight of the region of interest, and the distance between the region of interest and the target region, for example, if the type of the region of interest includes an organ and a target region, the number of sampling points in the sub-regions in the target region is not less than the number of sampling points in the sub-regions in the organ; the weight of the target area is not less than the weight of the organ, the weight of the organ at risk is higher than the weight of the common organ, the number of sampling points of the sub-area in the target area is not less than the number of sampling points of the sub-area in the organ at risk, and the number of sampling points of the sub-area in the organ at risk is greater than the number of sampling points of the sub-area in the common organ; the closer to the target area, the greater the number of sample points for sub-areas within the region of interest. Considering at least one factor, the number of sampling points of each sub-region in the target area can be set to be 2-4, for example 4, the number of sampling points of the sub-region in the organ at risk is 2-3, for example 2, and the number of sampling points of the sub-regions in other organs is 1.

And step S203, dividing the region of interest into a plurality of sub-regions according to the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-region in the region of interest.

And dividing each organ of interest and the target area into a plurality of sub-areas according to a preset rule. For the convenience of calculation, all organs and target regions may be divided into a plurality of sub-regions by using the same rule, for example, each organ and target region may be divided by using an equidistant grid, and the side length of the grid is a multiple of the pixel pitch. Each organ and target area are divided into equidistant grids, for example with 10 times the pixel pitch. The preset rule may be set in advance, and the content of the rule is not limited herein.

And calculating the sum of the number of the sampling points contained in each sub-region according to the number of the sampling points contained in each sub-region acquired in the step S202. For example, each sub-region of the target region includes 4 sampling points, each sub-region of the organ at risk includes 2 sampling points, each sub-region of the other organs includes 1 sampling point, and the number of sampling points included in all sub-regions is added to obtain the sum of the number of sampling points.

And comparing the sum of the number of the sampling points obtained by calculation with the upper limit of the total number of the sampling points, and judging whether the size of the sub-region needs to be adjusted according to the comparison result.

If the sum of the number of the sampling points contained in each sub-region is greater than the upper limit of the total number of the sampling points, the plurality of sub-regions are expanded, the sum of the number of the sampling points contained in each expanded sub-region is calculated, the sum of the number of the sampling points contained in each expanded sub-region is compared with the upper limit of the total number of the sampling points until the sum of the number of the sampling points contained in each expanded sub-region is less than the upper limit of the total number of the sampling points, and the sub-region in the last cycle is the final sub-region. The sub-regions may be enlarged in predetermined steps, for example by increasing the length of the grid side by one pixel pitch at a time.

If the sum of the number of the sampling points contained in each sub-area is smaller than the upper limit of the total number of the sampling points, reducing the sub-areas and calculating the sum of the number of the sampling points contained in each reduced sub-area, comparing the sum of the number of the sampling points contained in each reduced sub-area with the upper limit of the total number of the sampling points until the sum of the number of the sampling points contained in each reduced sub-area is larger than or equal to the upper limit of the total number of the sampling points, and each sub-area in the current cycle is the final sub-area. The sub-regions may be reduced in predetermined steps, for example by reducing the grid edge length by the length of one pixel pitch at a time.

And if the sum of the number of the sampling points contained in each sub-region is equal to the upper limit of the total number of the sampling points, each current sub-region is the final sub-region.

The at least one region of interest may be partitioned by an iterative loop process as described above. However, the present invention is not limited thereto, and it is within the protection scope of the present invention to divide the region of interest by using other manners according to the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-region in the region of interest.

In this embodiment, the image to be sampled may be uniformly divided, or each organ and the target area may be individually divided, which is not limited herein.

And S204, performing down-sampling on each sub-region by using a cluster analysis algorithm to obtain sampling points of the region of interest.

Taking a certain sub-region as an example, sampling the sub-region according to the number of corresponding sampling points to obtain initial sampling points. The sampling algorithm is not limited herein. For the sake of simplicity, the process of downsampling the region of interest by using the cluster analysis algorithm in this embodiment is described here by taking a random sampling algorithm as an example, but the scope of the invention is not limited thereto.

Calculating the Euler distance from each pixel point in the sub-region to the initial sampling point, classifying each pixel point to a cluster corresponding to the initial sampling point with the minimum Euler distance, recalculating the center of each cluster as a new sampling point, calculating the Euler distance between the new sampling point and the last sampling point, and comparing the Euler distance with a threshold value to judge whether the convergence condition is met.

The center of the cluster can be calculated by using a k-means algorithm, for example, the coordinates of each pixel point in a certain cluster are respectively (x)1,y1),(x2,y2),…,(xn,yn) And n is the number of pixel points in the cluster, the center coordinate of the cluster isThe center of the cluster may also be calculated by using a k-center algorithm, for example, for a certain cluster, the sum of euler distances from each pixel point to other pixel points is calculated, and the point with the minimum sum of the euler distances is used as the center of the cluster.

Judging whether the Euler distance between a new sampling point and the last determined sampling point does not exceed a threshold value, if not, taking the new sampling point as the sampling point of the sub-region, if so, calculating the Euler distance between a pixel point in the sub-region and the new sampling point, classifying each pixel point into a cluster corresponding to the new sampling point with the minimum Euler distance, calculating the central point of each cluster again, taking the central point as the new sampling point, comparing the central point with the original sampling point until the Euler distance between the new sampling point and the sampling point in the last cycle is smaller than the threshold value, and taking the new sampling point as the sampling point of the sub-region. The threshold value in this embodiment may be set empirically in advance.

The above steps are performed iteratively within each sub-region, thereby completing the sampling of each organ and target region.

In the embodiment, each organ or target area is divided into a plurality of sub-areas, and down-sampling is performed in the sub-areas by using a cluster analysis algorithm, so that not only can sampling points for reserving the shape characteristics of the region of interest be obtained, but also the calculation amount can be reduced, and the calculation speed can be improved.

After the region of interest is divided into a plurality of sub-regions, the number of pixel points contained in the sub-regions is limited. In the above embodiment, before the cluster analysis algorithm is used to perform downsampling on the sub-region, it may be determined whether the number of the pixel points belonging to the region of interest in the sub-region exceeds the number of the corresponding sampling points, if not, all the pixel points belonging to the region of interest in the sub-region are taken as the sampling points, and if so, the cluster analysis algorithm is used to perform downsampling on the pixel points belonging to the region of interest in the sub-region.

After dividing the region of interest into a plurality of sub-regions, the sub-regions may contain pixel points that do not belong to the organ (pixel points represented by "0") near the edge of the region of interest. In the above embodiment, before the sub-region is down-sampled by using the cluster analysis algorithm, it may be determined whether a pixel point not belonging to the region of interest is included in the sub-region, if so, the pixel point not belonging to the region of interest in the sub-region is down-sampled by using the cluster analysis algorithm, if not, the sub-region may be uniformly divided into a corresponding number of grids according to the number of sampling points, and the central point of the grid is used as the sampling point, so as to further reduce the amount of computation, improve the computation speed, and save time.

In the above embodiment, before the sub-region is down-sampled by using the cluster analysis algorithm, it may be determined whether the sub-region includes a pixel that does not belong to the region of interest, if yes, judging whether the number of the pixel points belonging to the interested region in the sub-region exceeds the number of the corresponding sampling points, if not, all the pixel points belonging to the interested region in the region are taken as sampling points, if the number of the pixels in the sub-region exceeds the threshold value, the pixel points belonging to the interesting region in the sub-region are down-sampled by utilizing a cluster analysis algorithm, if not, the sub-region can be uniformly divided into a corresponding number of grids according to the number of the sampling points, the central point of the grid is taken as the sampling point, therefore, the calculation amount is further reduced, the calculation speed is improved, the time is saved, and other sampling algorithms can be adopted to directly sample the sub-region.

The method for sampling the region of interest based on the cluster analysis algorithm provided by the above embodiment can be applied to a radiation therapy plan optimization method. Fig. 3 is a flowchart of a radiation treatment plan optimization method according to an embodiment of the present invention. Referring to fig. 3, the radiation treatment plan optimization method 300 includes:

s301, acquiring a patient image and delineating the region of interest.

An image of the patient is loaded and a region of interest within the image is delineated. In this embodiment, the patient image may be loaded into a radiation therapy planning system, and a region of interest, including an organ of interest to the physician and a tumor target, is delineated on an interface of the radiation therapy planning system. The sketching can be manually sketched by a doctor or automatically sketched, or the manual sketching and the automatic sketching are combined.

The patient image may be a CT image, a PET image, an MR image, or a fusion image, etc., but is not limited thereto.

S302, obtaining the dose target of each interested area.

The dose targets for each region of interest may be set by the physician. Prior to radiation treatment planning, the physician sets the prescribed dose for each region of interest, such as the upper organ-at-risk dose limit and the lower and upper tumor target volume dose limits. In planning the radiation treatment, the radiation treatment planning system receives the prescribed dose as a dose target.

And S303, down-sampling each region of interest.

The method in fig. 1 or fig. 2 in the above embodiment may be adopted to perform down-sampling on each region of interest based on a cluster analysis algorithm.

S304, establishing an optimization model and optimizing so that the dose of the sampling points meets the dose target.

In an embodiment of the present invention, the objective function f (d) of the sampling point-based radiation therapy plan optimization can be expressed by the following formula:

wherein d isvCurrent dose, u, for sampling point vvUpper dose limit for sampling point v,/vLower dose limit for sampling point v.

And optimizing the objective function by using an optimization algorithm (such as a simulated annealing algorithm, a gradient algorithm, an ant colony algorithm and the like), so that the dose of each sampling point meets the dose constraint and an optimized radiation flux map is obtained.

Correspondingly, an embodiment of the present invention further provides a radiation therapy plan optimization system, including:

an acquisition unit for acquiring an image of a patient,

a delineation unit for delineating the region of interest,

an input unit for setting a dose target for each region of interest,

a sampling unit for sampling the regions of interest by using the method of the above embodiment in FIG. 1 or FIG. 2,

and the optimization unit is used for establishing an optimization model and optimizing the optimization model so that the dosage of the sampling point meets the dosage target.

The method and system for optimizing the radiation therapy plan in the embodiment retain the shape characteristics of each organ and the target region based on the sampling points, so that the obtained radiation therapy plan is high in effectiveness.

The method for sampling the region of interest based on the cluster analysis algorithm provided by the above embodiment can be applied to dose calculation. Fig. 4 is a flowchart of a dose calculation method according to an embodiment of the present invention. Referring to fig. 4, the dose calculation method 400 includes:

s401, acquiring a patient image and delineating the region of interest.

An image of the patient is loaded and a region of interest within the image is delineated, including the organ of interest of the physician and the tumor target area. The sketching can be manually sketched by a doctor or automatically sketched, or the manual sketching and the automatic sketching are combined.

The image may be a CT image, a PET image, an MR image, a fusion image, or the like, but is not limited thereto.

S402, down-sampling each region of interest.

The method in fig. 1 or fig. 2 in the above embodiment may be adopted to perform down-sampling on each region of interest based on a cluster analysis algorithm.

And S403, calculating the dose distribution of each region of interest based on the sampling points.

The dose distribution in each organ and target volume is calculated based on the sampling points to obtain the dose distribution in the patient's body corresponding to the radiation treatment plan, which can be provided to a physician for determining the quality of the radiation treatment plan. There are many algorithms for dose calculation, such as monte carlo algorithm, volume calculation method, pencil beam algorithm, etc., and there is no limitation here.

Because the characteristics of organs and target areas are reserved by the sampling points obtained based on the clustering analysis algorithm, the dose distribution obtained based on the sampling point calculation is more consistent with the actual dose distribution, and the accuracy of the dose distribution calculation is improved.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Claims (6)

1. A method of sampling images in radiation treatment plan optimization, comprising:
acquiring an image to be sampled, wherein the image to be sampled comprises at least one region of interest,
acquiring the upper limit of the total number of sampling points and the number of the sampling points contained in each sub-area in the region of interest,
dividing the region of interest into a plurality of sub-regions according to the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-region in the region of interest,
performing down-sampling on each sub-region by using a cluster analysis algorithm to obtain sampling points of the region of interest;
dividing the region of interest into a plurality of sub-regions according to the upper limit of the total number of the sampling points and the number of the sampling points contained in each sub-region in the region of interest comprises:
dividing the region of interest into a plurality of sub-regions according to a preset rule, calculating the sum of the number of sampling points contained in each sub-region,
comparing the sum of the number of samples contained in each sub-region with an upper limit on the total number of samples,
if the sum of the number of the sampling points contained in each sub-region is greater than the upper limit of the total number of the sampling points, expanding the plurality of sub-regions, calculating the sum of the number of the sampling points contained in each expanded sub-region, comparing the sum of the number of the sampling points contained in each expanded sub-region with the upper limit of the total number of the sampling points until the sum of the number of the sampling points contained in each expanded sub-region is less than the upper limit of the total number of the sampling points, wherein the sub-region in the last cycle is the final sub-region,
if the sum of the number of the sampling points contained in each sub-area is less than the upper limit of the total number of the sampling points, reducing the sub-areas and calculating the sum of the number of the sampling points contained in each reduced sub-area, comparing the sum of the number of the sampling points contained in each reduced sub-area with the upper limit of the total number of the sampling points until the sum of the number of the sampling points contained in each reduced sub-area is greater than or equal to the upper limit of the total number of the sampling points, wherein each sub-area in the current cycle is the final sub-area,
and if the sum of the number of the sampling points contained in each sub-region is equal to the upper limit of the total number of the sampling points, each current sub-region is the final sub-region.
2. A method of sampling an image in radiation therapy plan optimization as set forth in claim 1, wherein the sub-regions contain a number of sample points related to at least one of a type of the region of interest, a weight, and a distance of the region of interest from the target volume.
3. A method of sampling images in radiation treatment plan optimization as set forth in claim 1, wherein down-sampling each sub-region using a cluster analysis algorithm comprises:
sampling each sub-region according to the number of sampling points contained in each sub-region in the region of interest to obtain initial sampling points,
calculating the Euler distance from each pixel point to the initial sampling point in each sub-region, and classifying each pixel point to the cluster corresponding to the initial sampling point with the minimum Euler distance,
iteratively performing the following steps within each sub-region until down-sampling of each sub-region is completed: and calculating the center of each cluster as a new sampling point, calculating the Euler distance between the new sampling point and the last sampling point, comparing the Euler distance with a threshold value, taking the new sampling point as the sampling point of the sub-region if the Euler distance does not exceed the threshold value, calculating the Euler distance from each pixel point to the new sampling point if the Euler distance exceeds the threshold value, and classifying each pixel point into the cluster corresponding to the new sampling point with the minimum Euler distance.
4. The method of claim 1, wherein the number of pixels belonging to the corresponding region of interest in the sub-region is determined before downsampling each sub-region using a cluster analysis algorithm, if not, all pixels belonging to the corresponding region of interest in the sub-region are used as sampling points, and if so, downsampling the pixels belonging to the corresponding region of interest in the sub-region using the cluster analysis algorithm.
5. The method of claim 1, wherein the image is sampled before downsampling each sub-region using a cluster analysis algorithm to determine whether pixels not belonging to the corresponding region of interest are included in the sub-region,
if yes, utilizing a cluster analysis algorithm to perform down-sampling on pixel points belonging to the corresponding interested region in the sub-region,
if not, the sub-area is evenly divided into grids according to the number of the sampling points, and the central points of the grids are used as the sampling points.
6. A radiation treatment plan optimization system, comprising:
an acquisition unit for acquiring an image of a patient,
a delineation unit for delineating the region of interest,
an input unit for setting a dose target for each region of interest,
a sampling unit for sampling regions of interest using the sampling method of any one of claims 1 to 5,
and the optimization unit is used for establishing an optimization model and optimizing the optimization model so that the dosage of the sampling point meets the dosage target.
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