CN111437521A - Non-uniform volume arc intensity modulation method - Google Patents

Non-uniform volume arc intensity modulation method Download PDF

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CN111437521A
CN111437521A CN202010328005.2A CN202010328005A CN111437521A CN 111437521 A CN111437521 A CN 111437521A CN 202010328005 A CN202010328005 A CN 202010328005A CN 111437521 A CN111437521 A CN 111437521A
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邱健健
郑向鹏
张书郡
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Huadong Hospital
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Abstract

The invention discloses a non-uniform volume arc-shaped intensity modulation method, which comprises the following steps: step S1, creating a VMAT treatment plan for the patient in the Eclipse treatment planning system; step S2, inquiring patient ID from Eclipse system, inputting the produced VMAT treatment plan and DICOMRT data information of the radiation field into MI calculation module; step S3, obtaining an MI coefficient curve of the VMAT plan by using an MI calculation module, and analyzing and determining peak and trough areas in the MI coefficient curve; step S4, optimizing and removing the angle range corresponding to the MI trough area, enhancing the angle optimization corresponding to the MI curve peak area, and modifying the arc field data in the plan according to the optimization result to obtain an NU-VMAT plan; and step S5, judging whether the MI curve of the NU-VMAT plan is converged or not, and circularly optimizing. The treatment method provided by the invention can ensure that the optimization quality of the treatment plan is improved, meanwhile, the radiation treatment efficiency is improved, and the original re-optimization module can automatically obtain the NU-VMAT optimization plan, so that the treatment method is scientific and innovative.

Description

Non-uniform volume arc intensity modulation method
Technical Field
The invention relates to the technical field of non-uniform volume arc intensity modulation, in particular to a non-uniform volume arc intensity modulation method.
Background
The radiotherapy technology is important for guaranteeing the quality of tumor radiotherapy and improving the treatment efficiency. At present, the commonly used technical method for international up-regulation treatment mainly comprises the following steps: beam Intensity Modulation (IMRT), and volume-modulated Arc modulation (VMAT).
IMRT technology can produce dose distribution which is highly suitable for the shape of a tumor target area, and the irradiated dose of normal tissues needing to be protected inside and outside the target area is reduced, so that the damage of the normal tissues is reduced. The IMRT technique divides an irradiation field into a plurality of small sub-fields, and gives different weights to different sub-fields to generate optimized and uneven radiation intensity distribution, so that the beam flux passing through the organs at risk is reduced, the beam flux of a target area is increased, and different intensity distributions of a plurality of sub-fields in each field direction are formed. A model diagram of this technique is shown in fig. 1.
① conventional IMRT radiotherapy scheme is time-consuming, needs to depend on experience of radiotherapy physicist to perform manual field distribution and manual debugging, after ② reverse optimization, the number of sub-fields in each radiation field direction is large, the execution time of an accelerator is long (total number of sub-fields is 50-100 in conventional IMRT plan, and single execution time is about 10 minutes or more), the currently widely used simplified intensity-adjusting S-IMRT technology needs about 7 minutes at least to complete irradiation of a relatively complex radiotherapy plan, ③ irradiation sub-field area is too small, the number of MU (monitor unit, MU) is too small, the uncertainty of dose is increased, ④ treatment scheme is complex, the number of MU is more and the body irradiation dose is increased.
In the treatment process, the VMAT technology simultaneously moves the angle of an accelerator frame, the position of a leaf of a multi-leaf collimator M L C (Multiple L eafCollimator, M L C), the dose rate, a backup diaphragm, the angle of the collimator and the like, allows a highly conformal treatment plan to be applied, can greatly improve the machine efficiency and reduce the treatment time of a patient, and simultaneously potentially reduces the occurrence of adverse radiotherapy reactions caused by irradiation of surrounding normal tissues and organs due to the body position movement of the patient during the treatment.
The VMAT technology enables an accelerator handpiece to continuously move in a preset arc area, M L C also cooperates with the change of the angle of a frame to generate a field shape suitable for each angle, and simultaneously the dosage rate of the accelerator is also variable in the process of handpiece rotation, a VMAT technology model is shown in figure 2 and has the limitation that most of sub-fields of ① do not greatly contribute to the dosage of a target area, ② VMAT can ensure that the irradiation dosage of normal tissues and organs is controlled within a clinically acceptable range, but inevitably expands the low-dosage irradiation range of the whole body of a patient.
Conventional VMAT model analysis, for example a single arc of gantry rotation of 360 °, has subfields (denoted x 0.., xt + n) equally spaced (for example 2 °) for each gantry position that form a volumetric illumination. The VMAT is characterized in that only one sub-field exists in each direction, uneven intensity distribution of dose is formed by overlapping of adjacent sub-fields, the retention time of a machine frame is short during irradiation, and the efficiency is high.
The IMRT technology can make the dose of the treatment plan highly conformal, but the optimization process is complex, the accelerator execution time is long during treatment, and the efficiency is low; the accelerator of the VMAT technology has high execution speed and high efficiency and is humanized, but the optimization model thereof compromises the quality of a radiotherapy plan to a certain extent. Therefore, a new technology which combines the advantages of IMRT and VMAT and avoids the disadvantages thereof is urgently needed clinically. The requirements are that the IMRT and VMAT can be integrated and the respective bottlenecks can be overcome. The radiotherapy efficiency is improved while the quality of the optimized scheme is ensured to be improved, and the machine can be executed and accepted in the row, so that the clinical popularization is realized.
Disclosure of Invention
The invention aims to provide an arc-shaped intensity modulation method with non-uniform volume, so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme: a non-uniform volume arc intensity modulation method comprises the following steps:
step S1, creating a VMAT treatment plan for the patient in the Eclipse treatment planning system;
step S2, inquiring patient ID from Eclipse system, inputting the produced VMAT treatment plan and DICOMRT data information of the radiation field into MI calculation module;
step S3, obtaining an MI coefficient curve of the VMAT plan by using an MI calculation module, and analyzing and determining peak and trough areas in the MI coefficient curve;
step S4, optimizing and removing the angle range corresponding to the MI trough area, enhancing the angle optimization corresponding to the MI curve peak area, and modifying the arc field data in the plan according to the optimization result to obtain an NU-VMAT plan;
step S5, judging whether the MI curve of the NU-VMAT plan is converged, and circularly optimizing;
and step S6, importing the treatment planning system through the self-contained ESAPI software interface in the Eclipse system.
Preferably, the MI coefficient curve is in an arc form, and the intensity modulation degree of the VMAT is quantitatively analyzed by combining the correspondence of the frame angle and the movement speed of the collimator M L C, so that optimization is realized.
Preferably, the peak region of the MI curve corresponds to an angle with a large modulation intensity, and the valley region corresponds to an angle with a small modulation intensity.
Preferably, the formula for calculating the MI coefficient curve of the VMAT plan is:
Figure BDA0002463920290000031
wherein, A'kThe M L C blade motion conditions of two adjacent Control Points (CP) are shown, so that the modulation degree, A ', of M L C can be reflected'kIs formulated as:
Figure BDA0002463920290000032
where ρ isiIs the thickness of the blade of the i-th sheet, g: (α|μ，σ2) A is expressed by the above formula as a Gaussian distribution function with μ ═ 0kCan better reflect the more different movement angles of the frameThe larger and smaller the dose weight.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, the obtained treatment scheme can ensure that the optimization quality of the treatment plan is improved, meanwhile, the radiation treatment efficiency is improved, and the original re-optimization module can automatically obtain the NU-VMAT optimization plan, so that the method has scientific innovation.
Drawings
Fig. 1 is a technical model diagram of IMRT in the prior art.
FIG. 2 is a diagram of a prior art model of VMAT.
Fig. 3 is a schematic diagram of a uniform VMAT being converted to a non-uniform VMAT, wherein (a) is the uniform VMAT and (b) is the non-uniform VMAT.
Fig. 4 is a flow diagram of a NU-VMAT technology implementation in accordance with the present invention.
Fig. 5 is a schematic diagram of NU-VAMT modulation based on MI values.
FIG. 6 is a mathematical model diagram of a non-uniform VMAT.
Figure 7 is a graph of mean DVH for three technical 5 patient head tumor test protocols.
Figure 8 is a plot of mean DVH for three technical 5 patient breast tumor test protocols.
Figure 9 is a graph of mean DVH for three technical 5 patient total pelvic irradiation test protocols.
Figure 10 is a graph of MI values for brain glioma VMAT and NU-VMAT optimization protocols.
FIG. 11 is a graph of MI values for breast tumor VMAT and NU-VMAT optimization protocols.
Figure 12 is a graph of MI values for pelvic tumor VMAT and NU-VMAT optimization protocols.
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.
Referring to fig. 1-12, the present invention provides a technical solution: a non-uniform volume arc intensity modulation method comprises the following steps:
step S1, creating a VMAT (treatment plan from Varian warrior medical systems) treatment plan of the patient in the Eclipse treatment planning system;
step S2, inquiring patient ID from Eclipse system, inputting the produced VMAT treatment plan and DICOMRT data information of the radiation field into MI calculation module;
step S3, obtaining an MI coefficient curve of the VMAT plan by using an MI calculation module, and analyzing and determining peak and trough areas in the MI coefficient curve;
step S4, optimizing and removing the angle range corresponding to the MI trough area, enhancing the angle optimization corresponding to the MI curve peak area, and modifying the arc field data in the plan according to the optimization result to obtain an NU-VMAT plan;
step S5, judging whether the MI (modulation index) curve of the NU-VMAT plan is converged, and circularly optimizing;
step S6, the treatment planning system is imported through the self-contained ESAPI (self-contained correctable application software interface of Eclipse system) software interface in Eclipse system.
Specifically, the MI coefficient curve is in an arc form, and the intensity modulation degree of the VMAT is quantitatively analyzed by combining the correspondence of the frame angle and the movement speed of the collimator M L C, so that optimization is realized.
Specifically, the peak region of the MI curve corresponds to an angle with a large modulation intensity, and the valley region corresponds to an angle with a small modulation intensity.
Specifically, the formula for calculating the MI coefficient curve of the VMAT plan is:
Figure BDA0002463920290000041
wherein, A'kThe M L C blade motion conditions of two adjacent Control Points (CP) are shown, so that the modulation degree of M L C, AkIs formulated as:
Figure BDA0002463920290000042
Figure BDA0002463920290000051
where ρ isiIs the thickness of the blade of the i-th sheet, g: (α|μ，σ2) A is expressed by the above formula as a Gaussian distribution function with μ ═ 0kThe actual situation that the larger the frame motion angle difference is, the smaller the dose weight is can be better reflected.
Fig. 5 is a plot of MI values for a VMAT plan, showing distinct peaks (peak) for critical angles requiring more intensity modulation, and distinct valleys (valley) for less aggressive angles of excessive modulation.
Since the MI (modulation Index) value is a dimensionless Index value indicating that "modulation intensity Index" is a result of quantitative analysis of a variable between the gantry angle and the VMAT, and a region of high or low modulation intensity cannot be determined by an absolute threshold value, the present invention uses a relative percentage of the MI value for determination. If the average MI value is greater than 150% (adjustable) of the overall average MI value in the 30 DEG adjacent range of the peak of the MI value, then this is considered as a region with large modulation intensity; in the adjacent range of 30 ° to the trough of MI values, the average MI value is less than 50% of the overall average MI value, and this is considered as a region where the modulation intensity is small. Theoretically, the NU-VMAT has higher execution efficiency under the condition of obtaining equivalent dose conformality, different treatment parameters can be given to different target areas while treatment is carried out due to the nonuniformity of the NU-VMAT, the treatment machine frame can rotate more quickly in the empty window area, the machine dwell time can be enhanced to give proper irradiation under the condition that a machine motion threshold value allows at the target area, the problem that the contribution degree of the VMAT to the empty window area is not high is solved, and the low-dose irradiation range of a patient is prevented from being expanded. Therefore, we build the following model for the planned execution time as follows: the time function is used for calculating the optimal planning time, machine hop count, accelerator time and the like, and is matched with the implemented hardware conditions to generate the optimal NU-VMAT plan.
Figure BDA0002463920290000052
Where T is the execution time of the treatment plan, i.e., the time from the linear accelerator from the exit line to the stop of the exit line; MU is the total number of hops per fraction planned; DR is the dose rate of the accelerator; t isGThe time taken for the accelerator to rotate 360 degrees; n is a radical ofBThe number of planned shots; the second term in the formula gives the rotation time of the accelerator from the initial position to the end position; delta TGExtra acceleration and deceleration time during the accelerator rotation to a certain designated position; the last term is the time of the grating motion,
Figure BDA0002463920290000053
for the mean time of movement of each subfield grating, NSThe number of all the planned subdomains.
The above formula is only used for estimation, and in the actual implementation process, the grating motion time also depends on the projection area size of the target area and the planning complexity. But for the same complexity of planning and the same target volume size
Figure BDA0002463920290000061
Different plans are more or less.
And (4) judging an objective function of the NU-VMAT algorithm, wherein the physical objective function obtains an optimal treatment plan by setting physical dose or limiting dose to be reached in a target area, normal tissues and critical organs. The physical objective functions that are commonly used clinically are dose distribution based objective functions and Dose Volume Histogram (DVH) based objective constraints.
Let N denote the maximum number of subfields allowed for a plan. The goal of the NU-VMAT is to find a series of subfields (angle θ)bShape of field XbIntensity of the subdomain ηb(b 1.., n)) to minimize the defined objective function F.
Figure BDA0002463920290000062
Figure BDA0002463920290000063
So phik(Xb，θb) Represents an angle thetabThe unit dose contribution of the subfield of (a) to voxel k; phik(Xb，θb)ηbI.e. the angle thetabThe total dose contribution of the subfield of (a) to voxel k; zkThe dose contribution to voxel k for all fields, i.e. the final dose of voxel k.
In the present invention, f (z) is selected as a commonly used piecewise quadratic objective function:
Figure BDA0002463920290000064
wherein:
Figure BDA0002463920290000065
and
Figure BDA0002463920290000066
representing the lowest and highest dose constraints for voxel j respectively,
Figure BDA0002463920290000067
and
Figure BDA0002463920290000068
representing the weights of these two constraints, respectively.
NU-VMAT is a very parameter-scale optimization problem, with optimization parameters varying from tens of thousands to hundreds of thousands or even millions. This problem can be handled well here using the column generation method (column generation) in the sequence optimization method. The idea is to select a set of parameters that contribute most to the objective function to be added to the parameter pool by solving a pricing problem at each iteration.
For determining the shape X of the sub-fieldsbAnd angle thetabSet of (X)1，θ1)，(X2，θ2)，...，(Xk，θk) The pricing problem is from all X' sbAnd thetabFind one (X) in spacek+1，θk+1) The cost function reduction is maximized. The stopping condition of the iteration of the algorithm is that the number of the found sub-fields reaches a preset maximum value, or the reduction amplitude of the cost function is lower than a preset value (for example, the iteration value of the cost function is reduced by less than 1%).
Finding subdomains (X) by pricingk+1，θk+1) To maximize the reduction of the cost function. Field of view thetabFor a beamlet sub-field, the rate of change, i.e. derivative, of the objective function with respect to the intensity of the sub-field is:
Figure BDA0002463920290000071
from this, the sub-field θ can be obtainedbThe derivative of the cost function with respect to the intensity of the segments is:
Figure BDA0002463920290000072
where R is the row index set of the raster blade.
From the above analysis, the pricing problem can be defined as:
Figure BDA0002463920290000073
to solve the above equation, the algorithm is: and finding an optimal sub-field shape meeting the sub-field constraint conditions (such as minimum sub-field area, minimum number of communication areas in the sub-field and the like) of the clinical requirements at each moment of the frame angle, and then selecting the machine hop number and the sub-field shape which have the maximum contribution to the objective function to generate an optimal treatment plan.
For each angle, the above equation can be decomposed into subfield per row processing, i.e. the grating blades can be processed individually per pair. The method is to find the position of the left blade and the right blade of each row (pi)i，j(θb) ) is minimal. The simplest method is to traverse the entire row of subfields with a temporal complexity of O (n)2) N is oneThe number of the row and the child fields.
The non-uniform VMAT optimization scheme has the advantages that the automatic optimization and automatic debugging ESAPI interface is used for automatically acquiring the plan data, the MI value curve is automatically analyzed, the VMAT plan is subjected to non-homogenization and optimization calculation to obtain the optimization scheme, the artificial error is reduced, and the radiotherapy plan quality is improved. The method has the advantages that the irradiation volume of the normal tissue is reduced while the execution efficiency is broken through on the basis of ensuring the quality of the radiotherapy plan.
The treatment planning system supports the production of IMRT and VMAT treatment plans, and meanwhile, the TPS system of Eclipse can be used for scientific research personnel to call internal data structures and algorithm interfaces through an Enterprise Security Application Program Interface (ESAPI) provided by the TPS system, so that the radiation physical research is carried out. The data base of the invention is the VMAT treatment plan of the historical patients made in the Eclipse system, an ESAPI program interface is used, the function of automatically acquiring the plan data is compiled by utilizing Python language, the MI value curve is automatically analyzed, the VMAT plan is further subjected to non-homogenization and optimization calculation, and finally the optimization result is led back to the Eclipse system through the ESAPI for dose evaluation. The dose distribution and DVH curve were recalculated.
The accelerator has the requirements of rapid movement of M L C (the movement speed needs to be 2.5cm/s at least), large-range adjustable frame rotation speed (the lower limit is decimal number which is not zero and the upper limit needs to be 5.9 degrees/s at least), real-time beam response and continuous change of zero to the maximum value of dose rate.
The invention combines each parameter of the existing accelerator to improve two uniformity of the VMAT optimization model, on one hand, the high efficiency of the VMAT technology is kept, on the other hand, the number of irradiation fields which do not contribute much to the target area in the rotating process of the frame is reduced, thereby reducing the irradiation area of normal tissues. The realization of the non-uniform VMAT optimization scheme is based on artificial intelligence, and aims to obtain the optimization scheme by using a method of automatic optimization and automatic debugging, reduce human errors and improve the quality of radiotherapy plan. The method has the advantages that the irradiation volume of the normal tissue is reduced while the execution efficiency is broken through on the basis of ensuring the quality of the radiotherapy plan.
Based on the conventional VMAT technology, the construction of a model from a common VMAT to a non-uniform VMAT is realized by strengthening and weakening the optimization strength in certain frame angle directions. Experience proves that the optimization in the irradiation field direction can be enhanced by combining the IMRT characteristics while the high efficiency of the conventional VMAT is kept, the quality of the radiotherapy scheme is improved to a certain extent, the irradiation volume of normal tissues is effectively reduced, and normal organs are protected. By defining MI value, peak area finds 2 signal wave peak values (i.e. area with large and small modulation intensity) of MI value curve, time efficiency model is established for the execution time of planning, and the physical objective function obtains optimal treatment plan by setting the dose or limiting dose in target area, normal tissue and organs at risk.
The non-uniform VMAT mathematical model established by the invention has the characteristics that the rotation speed of a rack is non-uniformly variable, the M L C fast conversion can complete the execution of a plurality of small fields or increase the intensity regulation by a mode of supplementing partial arcs when the rack rotates at a low speed, the execution of a large field can be completed when the rack rotates at a high speed, and simultaneously a plurality of empty regions (no beams) can be generated, as shown in FIG. 6, the design concept of a single arc is the same, sub fields (X0, X1 and …) are divided at equal intervals in each irradiation arc to obtain a flux map, then adjacent sub fields are non-uniformly combined to reduce the total number of the sub fields (as shown by an arrow ②) so as to ensure that the optimization precision cannot be reduced, some regions are not distributed with intensity after combination to form 'empty window regions' (as shown by an arrow ①) so as to ensure that the unnecessary volume irradiation of an incidence region is reduced, and the improved planning scheme can ensure high efficiency, and can also enhance the intensity regulation capability of a single angle region.
The following clinical application of NU-VMAT to head, chest and pelvic radiotherapy, respectively, and in contrast to VMAT and IMRT techniques, further illustrates that NU-VMAT combines the advantages of VMAT and IMRT and overcomes the disadvantages thereof.
Firstly, case selection and target area delineation are carried out, secondly, treatment plan scheme is formulated, and finally, plan quality and dosimetry evaluation are carried out. Wherein the dosimetry evaluation parameters comprise:
① Dose Volume Histogram (DVH), whose horizontal axis generally represents the radiation Dose received (in Gy or cGy) and the vertical axis represents the Volume (in ml, cc or relative Volume%) that received the Dose indicated by the horizontal axis;
② comparison of MI values (curves) of VMAT and NU-VMATNU-VMATCompared with MIVMATObviously flat, the uniform sampling of angles by the VMAT is eliminated by reflecting the NU-VMAT optimization result, certain angle intensity modulation functions are added, the sharpness of the peak value of an MI curve is reduced, certain angle intensity modulation functions are reduced, the valley value of the MI curve is increased, and the MI curve is flatter;
③ target and organs at risk dose, including planned Tumor target maximum dose (PTV), average dose, minimum dose, and maximum dose average dose for relevant normal tissues, etc.;
④ average machine hop count and exposure time comparison for further quantitative comparison to assess treatment efficacy.
CT images of head, chest and pelvic cavity of more typical tumor patients are extracted from a radiotherapy patient image database of a radiotherapy department in east China Hospital affiliated to the university of Compound Dan, wherein the CT images comprise 5 cases. Relevant target areas and normal tissues are confirmed by a radiotherapy doctor, and then IMRT, VMAT and non-uniform VMAT optimization schemes are respectively made for relevant cases. For head tumors, 60Gy is uniformly administered according to the prescription dose; for breast tumors, the prescribed dose is also uniformly given as 60 Gy; for pelvic tumors, the prescription dose is uniformly given to 45 Gy. Selecting 7-9 fixed irradiation fields according to the relation between the target area and the anatomical position of normal tissues by the IMRT treatment plan and combining with the field distribution experience of a physicist; both VMAT and NU-VMAT treatment plans select a 360 degree full arc illumination field.
FIG. 7 shows the mean DVH plots for optimization of three techniques (IMRT, VMAT, NU-VMAT) for head tumors, showing that all three techniques can help achieve adequate volumetric dose distribution in the target region and meet clinical requirements; however, compared with IMRT and VMAT technologies, the NU-VMAT technology can obtain lower volume dose distribution on the brainstem, and is more beneficial to protecting the brainstem.
FIG. 8 shows the mean DVH plots for optimization of three techniques (IMRT, VMAT, NU-VMAT) for breast tumors, showing that all three techniques can help to achieve adequate volumetric dose distribution for PTV and meet clinical requirements.
Figure 9 shows the mean DVH plots for the optimization of three techniques (IMRT, VMAT, NU-VMAT) for pelvic tumors, which all help PTV to achieve adequate volumetric dose distribution and meet clinical requirements.
MI for 5 cases of gliomaNU-VMATBetween 2.8 and 6.6, MIVMATBetween 3.5 and 9.1, MINU-VMATCompared with MIVMATThe curves are clearly convergent, indicating that the re-optimization effect of the NU-VMAT plan versus the VMAT plan is significant, as shown in fig. 10.
MI for 5 breast tumorsNU-VMATBetween 7.4 and 14.1, and MIVMATMI is within the range of 6.8 to 20.1NU-VMATCompared with MIVMATThe curves are clearly converged, indicating that the re-optimization effect of the NU-VMAT plan relative to the VMAT plan is significant, as shown in fig. 11.
However, for 5 pelvic tumors, MI was shown in FIG. 12NU-VMATCompared with MIVMATThe curve difference is not significant, MINU-VMATBetween 5.5 and 11.8, and MIVMATIn the range of 9.6-16.9, the MI value of the NU-VMAT scheme is not obviously converged compared with the VMAT scheme. The difference was analyzed and may be correlated with the size of the tumor.
The average volumes of the target areas of the 5 cases of the head, the chest and the pelvic cavity of the invention are respectively 58.5 +/-22.3 cm3、45.6±14.7cm3And 489. + -. 45.7cm3The result shows that for the tumors with smaller target areas (such as brain glioma and the like), the re-optimization effect of the NU-VMAT on the VMAT is more obvious; while for tumors with large and irregular target volume, the re-optimization effect of NU-VMAT on VMAT is relatively existent but not significant.
Target and organ-at-risk doses, table 1 summarizes relevant dosimetry data for brain gliomas using IMRT, VMAT, and NU-VMAT techniques to develop a planned plan. As can be seen from Table 1, the irradiated dose of the tumor target area and the normal tissue both meet the clinical requirements; however, the proposal made by the NU-VMAT technology has the lowest dosage to the brain stem and the eye lens of normal tissues, which is reduced by about 10 percent compared with the IMRT technology and is lower than the proposal made by the VMAT technology, thereby showing that the proposal can better protect the organs.
Table 1 comparison of dosimetry data for different planned protocols for brain gliomas
Figure BDA0002463920290000101
Table 2 summarizes relevant dosimetry data for breast lung cancer planning using IMRT, VMAT and NU-VMAT techniques. As can be seen from Table 2, the irradiated doses of the tumor target area and the normal tissue both meet the clinical requirements; statistics show that the NU-VMAT, VMAT protocol yielded lower volumes on lung V20 than IMRT, but the IMRT data for V5 performed best (V20 and V5 refer to lung volume percentages contained in 20Gy and 5Gy doses, respectively), second for NU-VMAT, and worst for VMAT. This indicates that NU-VMAT has a significant optimization of VMAT regimens at lower dose distributions (e.g., 5Gy), with optimization results approaching IMRT.
TABLE 2 comparison of dosimetry data for different planning regimens for breast lung cancer
Figure BDA0002463920290000111
Table 3 summarizes relevant dosimetry data for pelvic tumors using IMRT, VMAT, and NU-VMAT techniques for planning. As can be seen from Table 3, the dose of the tumor target and the dose of the normal tissue both meet the clinical requirements. The results also show that NU-VMAT is superior to VMAT regimens for bladder and rectal protection, although inferior to IMRT, which is reflected by the average and maximum bladder and rectal doses. In the optimization scheme of the total pelvic cavity with irregular target area and large target area volume, NU-VMAT is slightly inferior to IMRT scheme although the optimization degree and the optimization result are better than those of VMAT.
TABLE 3 comparison of dosimetry data for different planning protocols for pelvic tumors
Figure BDA0002463920290000112
Figure BDA0002463920290000121
Average machine hop count and exposure time, table 4 summarizes the exposure field number, average machine hop count and average exposure time for all test protocols. As can be seen from table 4, MU used in the NU-VMAT test protocol for head tumors was reduced by 46.2% and 18.2% compared to IMRT and VMAT, respectively, for the average MU; NU-VMAT test protocol for breast tumors used 6.2% and 5.1% less MU than IMRT and VMAT, respectively; MU used in the NU-VMAT test protocol for pelvic tumors was reduced by 59.8% and 0.9% compared to IMRT and VMAT, respectively. The NU-VMAT test protocol for head tumors saved exposure times by 56.8% and 8.7% compared to IMRT and VMAT, respectively, in terms of mean exposure time; NU-VMAT test protocol for breast tumors saved exposure time by 32.7% compared to IMRT, but increased exposure time by 22.7% compared to VMAT; the NU-VMAT test protocol for total pelvic irradiation saved exposure time by 42.2% compared to IMRT, but increased exposure time by 51.1% compared to VMAT technology.
Table 4 irradiation field, average MU and irradiation time for different test protocols
Figure BDA0002463920290000122
In order to evaluate and verify the effectiveness and the performability of the NU-VMAT technology, 5 cases of common head, chest and pelvic tumors are selected, and IMRT, VMAT and NU-VMAT technologies are respectively used for making respective plan schemes on a treatment planning system.
The results show that the three technologies can help the PTV of the head, the chest and the pelvic tumors to obtain enough volume dose distribution and meet the clinical requirements. The NU-VMAT technology effectively solves the problem that the VMAT technology has underscience modulation intensity; compared with the VMAT technology, the NU-VMAT technology can obviously reduce the dosage of the brain stem and the eye crystal of the normal tissue when carrying out the treatment of the brain glioma, the dosage volume distribution of the lung high-dosage area (>10Gy) is better than that of the VMAT technology when carrying out the treatment of the lung tumor, and the dosage volume distribution of the bladder and the rectum is also better than that of the VMAT scheme when carrying out the treatment of the pelvic tumor. Compared with IMRT technology, the NU-VMAT technology can obviously save the machine jump number (MU) and reduce the treatment time when treating head, chest or pelvic tumors, and can effectively improve the treatment efficiency of the machine. The above-mentioned advantages of NU-VMAT are more pronounced for the treatment of small volume tumors relative to large, irregular tumors.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (4)

1. A non-uniform volume arc intensity modulation method is characterized by comprising the following steps:
step S1, creating a VMAT treatment plan for the patient in the Eclipse treatment planning system;
step S2, inquiring patient ID from Eclipse system, inputting the DICOM RT data information of the VMAT treatment plan and the radiation field which are made into MI calculation module;
step S3, obtaining an MI coefficient curve of the VMAT plan by using an MI calculation module, and analyzing and determining peak and trough areas in the MI coefficient curve;
step S4, optimizing and removing the angle range corresponding to the MI trough area, enhancing the angle optimization corresponding to the MI curve peak area, and modifying the arc field data in the plan according to the optimization result to obtain an NU-VMAT plan;
step S5, judging whether the MI curve of the NU-VMAT plan is converged, and circularly optimizing;
and step S6, importing the treatment planning system through the self-contained ESAPI software interface in the Eclipse system.
2. The method as claimed in claim 1, wherein the MI coefficient curve is in arc form, and intensity modulation degree of VMAT is quantitatively analyzed by combining the correspondence of gantry angle and collimator M L C movement speed.
3. The non-uniform volume arc intensity modulation method of claim 1, wherein: the peak region of the MI curve corresponds to an angle with a large modulation intensity, and the valley region corresponds to an angle with a small modulation intensity.
4. The non-uniform volume arc intensity modulation method of claim 1, wherein: the calculation formula of the MI coefficient curve of the VMAT plan is as follows:
Figure FDA0002463920280000011
Figure FDA0002463920280000012
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