Inverse Planning Simulated Annealing Plans Research Articles

A Comparison of Two Plan Optimization Methods in Three-Dimensional Brachytherapy for Cervical Cancer

To compare dose distributions created by using two Inverse Planning Simulated Annealing (IPSA) and Hybrid Inverse Planning Optimization (HIPO) in three-dimensional (with CT image guidance) brachytherapy planning for cervical cancer. Brachytherapy plans for thirty patients with cervical cancer were created using the IPSA and HIPO algorithms (The IPSA algorithm is calculated based on the anatomical structure, and the simulated annealing algorithm is used to optimize the residence time, and the HIPO algorithm is the optimization and replacement for the IPSA). To obtain a HIPO plan, a manually optimized post-loading treatment plan was applied to these 30 patients, and then the treatment plan was reoptimized using the HIPO algorithm based on the original image information. Individual patients will consider interpolation therapy according to the needs of their condition. The types of plans were compared based on a variety of dose volume parameters, including the mean dose covering 90% of high-risk clinical target volume (D90 for HR-CTV), the mean dose to 2 cm3 volume (D2cc) for bladder, rectum, intestine and sigmoid, and average treatment time were compared and analyzed. Compared with the two groups of plans, mean value of HR-CTV D90 for the HIPO plans was (585 cGy), which was significantly higher than that for the IPSA plans (567 cGy. This difference is statistically significant (P<0.05). The HIPO plans had mean D2cc 422±47 cGy for bladder, 403±38 cGy for rectum, which were lower than those from the SA plans, i.e., 446±42 cGy for bladder and 427±31 cGy for rectum; These differences were statistically significant (t = 5.125, 4.729, P <0.05). There was no statistically significant difference in the sigmoid D2cc doses between the two algorithms. The treatment times for delivering the two types of plans were not significant different. Depending on patient's condition, whether conventional brachytherapy therapy or interpolation therapy is used, the use of the HIPO algorithm to design the treatment regimen without additional treatment time can provide a higher target dose than the manually optimized brachytherapy regimen. Meanwhile, the bladder and rectum doses can be reduced to a certain extent under the premise of ensuring that the target dose met the treatment requirements. There is some increasement for the intestine dose with HIPO planning group, but the dose limits required by the guidelines are still met clinical requirement.

Dosimetric Evaluation of Different Optimization Algorithms Used in Interstitial Brachytherapy of Cervical Carcinoma.

Background: Conventional optimization techniques are based on the planning approach in which positions and weights are varied to generate the desired dose distribution. Inverse planning simulated annealing (IPSA) is an advanced optimization method developed to automatically determine a suitable combination of positions to design an acceptable plan.Objective: In this study, three optimization techniques namely IPSA, graphical optimization (GROPT), and geometrical optimization (GOPT) methods are compared in high-dose-rate interstitial brachytherapy of cervical carcinoma.Material and Methods: In this retrospective study, twenty computed tomography (CT) data sets of 10 cervical cancer patients treated with Martinez Universal Perineal Interstitial Template-based interstitial brachytherapy were studied. The treatment plans generated were optimized using the IPSA, and GOPT methods. The prescribed dose was 24 Gy in 4 fractions. Plans produced using IPSA, GrOPT, and GOPT techniques were analyzed for comparison of dosimetric parameters, including target coverage, homogeneity, conformity, and organs at risk (OAR) doses.Results: V100 values for IPSA, GrOPT and GOPT plans were 95.81±2.33%, 93.12±2.76% and 88.90±4.95%, respectively. The mean D90 values for the IPSA, GrOPT, and GOPT plans were 6.45±0.15 Gy, 6.12±0.21 Gy, and 5.85±0.57 Gy, respectively. Significantly lower doses of OAR were in the IPSA plans that were more homogeneous (HI=0.66). Conformity was comparatively higher in IPSA-based plans (CI=0.75).Conclusion: IPSA plans were superior and resulted in better target coverage, homogeneity, conformity, and minimal OAR doses.

Dosimetric impact of dwell time deviation constraint on inverse brachytherapy treatment planning and comparison with conventional optimization method for interstitial brachytherapy implants.

High-dose rate remote afterloading brachytherapy machine and advanced treatment planning system help in getting optimum dose to tumor and low dose to normal structures. Inverse planning simulated annealing (IPSA) optimization technique has a unique feature of dwell time deviation constraint (DTDC). In this study, six IPSA-based plans having different DTDC values with routinely practiced geometric plus graphical optimization (GO + GrO) have been compared using various dosimetric parameters. For this retrospective study, we have generated IPSA-optimized interstitial brachytherapy plans for ten cancer cervix patients. Routinely practiced GO + GrO-based plans were compared with six different IPSA plans having varying DTDC values from 0.0 to 1.0 using different dosimetric indices. Conformity index and homogeneity index (HI) were higher in GO + GrO plans, compared to IPSA-optimized plans. However, HI of IPSA plans was increasing with increasing DTDC values. High-dose volumes were well controllable using DTDC parameter in IPSA-optimized plans. Dose to the rectum and bladder was smaller for IPSA-optimized plans than GO + GrO plans. One of the benefits of applying DTDC in IPSA-optimized plan is that it reduces high-dose volumes. Another advantage is the reduction in rectum and bladder dose.

An Inverse Dose Optimization Algorithm for Three-Dimensional Brachytherapy

To report an implementation method and results of an inverse dose optimization algorithm (Gradient Based Planning Optimization, GBPO) in three-dimensional brachytherapy. The GBPO used a standard quadratic objective function, and a dwell time modulation item was added to the objective function to restrict the dwell time variance. We retrospectively selected 6 cervical cancer patients using different applicators and 15 cervical cancer patients using the Fletcher applicator. The plan quality of GBPO was assessed by isodose lines for the patients using different applicators. For the 15 patients used the same applicator, dose-volume histogram (DVH) parameters of CTV (D100%,V150%) and organs at risk (D0.1cc,D1cc , D2cc) were used to evaluate the difference between the GBPO plans and the IPSA (Inverse Planning Simulated Annealing) plans, the GBPO plans and the Graphic plans. For the patients using different applicators, the dose distributions are conformable. For the 15 patients using the Fletcher applicator, when the dwell time modulation factor (DTMF) is less than 20, the dwell time deviation reduces quickly, but the dwell time deviation has no remarkable change after the DTMF increased to 110. The difference of dosimetric parameters between the GBPO plans and the IPSA plans are not statistically significant (P<0.05). The GBPO plans has a higher D100% (3.57±0.36, 3.38±0.34; P = 0.00) and a lower V150% (55.73±4.06, 57.75±3.79; P = 0.00) than that of the Graphic plans. The differences of other DVH parameters are negligible between the GBPO plans and the Graphic plans. The GBPO plans have a comparable quality as the IPSA plans and the Graphic plans for cervical cancer cases. The GBPO algorithm could be integrated into a three-dimensional brachytherapy treatment planning system.Tabled 1Abstract 2689; Table; Comparison of DVH parameters between target and organs at risk for patients using the same type of applicator. The dose unit is Gy and the volume is relative volume (%).OrganParameterGBPOIPSAP valueGraphicP valueCTVD100%3.57±0.363.54±0.340.503.38±0.340.00V150%55.73±4.0656.43±4.210.0657.75±3.790.00BladderD0.1cc6.08±0.646.05±0.750.606.15±0.700.17D1cc5.12±0.535.11±0.570.915.14±0.560.18D2cc4.74±0.494.73±0.530.294.76±0.520.07RectumD0.1cc5.69±0.905.76±0.860.225.74±0.870.33D1cc4.63±0.604.68±0.600.214.70±0.640.15D2cc4.17±0.574.20±0.540.524.22±0.610.16IntestineD0.1cc2.77±1.412.80±1.340.512.69±1.320.20D1cc2.22±1.212.25±1.140.342.18±1.100.50D2cc2.00±1.122.02±1.040.511.96±1.000.39 Open table in a new tab

An Inverse Dose Optimization Algorithm for Three-Dimensional Brachytherapy.

PurposeTo investigate an implementation method and the results of an inverse dose optimization algorithm, Gradient Based Planning Optimization (GBPO), for three-dimensional brachytherapy.MethodsThe GBPO used a quadratic objective function, and a dwell time modulation item was added to the objective function to restrict the dwell time variance. We retrospectively studied 4 cervical cancer patients using different applicators and 15 cervical cancer patients using the Fletcher applicator. We assessed the plan quality of GBPO by isodose lines for the patients using different applicators. For the 15 patients using the Fletcher applicator, we utilized dose-volume histogram (DVH) parameters of HR-CTV (D100%, V150%) and organs at risk (OARs) (D0.1cc, D1cc, D2cc) to evaluate the difference between the GBPO plans and the IPSA (Inverse Planning Simulated Annealing) plans, as well as the GBPO plans and the Graphic plans.ResultsFor the 4 patients using different applicators, the dose distributions are conformable. For the 15 patients using the Fletcher applicator, when the dwell time modulation factor (DTMF) is less than 20, the dwell time deviation reduces quickly; however, after the DTMF increased to 100, the dwell time deviation has no remarkable change. The difference in dosimetric parameters between the GBPO plans and the IPSA plans is not statistically significant (P>0.05). The GBPO plans have a higher D100% (3.57 ± 0.36, 3.38 ± 0.34; P<0.01) and a lower V150% (55.73 ± 4.06, 57.75 ± 3.79; P<0.01) than those of the Graphic plans. The differences in other DVH parameters are negligible between the GBPO plans and the Graphic plans.ConclusionsThe GBPO plans have a comparable quality as the IPSA plans and the Graphic plans for the studied cervical cancer cases. The GBPO algorithm could be integrated into a three-dimensional brachytherapy treatment planning system after studying more sites.

Dosimetric comparison of inverse optimisation methods versus forward optimisation in HDR brachytherapy of breast, cervical and prostate cancer

ObjectiveDosimetric comparison of HIPO (hybrid inverse planning optimisation) and IPSA (inverse planning simulated annealing) inverse and forward optimisation (FO) methods in brachytherapy (BT) of breast, cervical and prostate cancer.MethodsAt our institute 38 breast, 47 cervical and 50 prostate cancer patients treated with image-guided interstitial high-dose-rate BT were selected. Treatment plans were created using HIPO and IPSA inverse optimisation methods as well as FO. The dose–volume parameters of different treatment plans were compared with Friedman ANOVA and the LSD post-hoc test.ResultsIPSA creates less dose coverage to the target volume than HIPO or FO: V100 was 91.7%, 91% and 91.9% for HIPO, IPSA and FO plans (p = 0.1784) in breast BT; 90.4%, 89.2% and 91% (p = 0.0045) in cervical BT; and 97.1%, 96.2% and 97.7% (p = 0.0005) in prostate BT, respectively. HIPO results in more conformal plans: COIN was 0.72, 0.71 and 0.69 (p = 0.0306) in breast BT; 0.6, 0.47 and 0.58 (p < 0.001) in cervical BT; and 0.8, 0.7 and 0.7 (p < 0.001) in prostate BT, respectively. In breast BT, dose to the skin and lung was smaller with HIPO and FO than with IPSA. In cervical BT, dose to the rectum, sigmoid and bowel was larger using IPSA than with HIPO or FO. In prostate BT, dose to the urethra was higher and the rectal dose was smaller using FO than with inverse methods.ConclusionIn interstitial breast and prostate BT, HIPO results in comparable dose–volume parameters to FO, but HIPO plans are more conformal. In cervical BT, HIPO produces dosimetrically acceptable plans only when more needles are used. The dosimetric quality of IPSA plans is suboptimal and results in unnecessary larger active lengths.

Study of the effects of dwell time deviation constraints on inverse planning simulated annealing optimized plans of intracavitary brachytherapy of cancer cervix.

High Dose Rate (HDR) remote afterloading brachytherapy machine and advanced treatment planning system have made it possible to make variations in individual dwell times across a catheter according to tumour density and for sparing normal structures. New inverse planning technique such as Inverse Planning Simulated Annealing (IPSA) has also been introduced. But very few institutions are venturing towards volume based IPSA optimised intracavitary brachytherapy. This study focuses on dwell time deviation constraint (DTDC) feature of IPSA based optimization which restricts the large variation of dwell time across the catheter. For this retrospective study we have generated IPSA optimised intracavitary brachytherapy plans for 20 cancer cervix applications. The initial DTDC value of each IPSA plan was kept 0.0. Later on gradual increment was made in DTDC values in step of 0.2. Plan modulation index (M) defined by Ryan L. Smith et al was used for characterising the variation of dwell time modulation with respect to gradual increase in DTDC parameter. Plan modulation index gradually decreases with increasing value of DTDC from 0.0 to 1.0. There was the 83% decrease in M value from IPSA of DTDC 0.0 to fully constrained IPSA of DTDC1.0. There is reduction of 8.26% and 6.95% for D2cc values of rectum and bladder respectively for DTDC 1.0 compared to DTDC 0.0. One of the benefits of applying DTDC constrained in IPSA plan is that, it removes local hot spots. It's another advantage is the reduction in rectum and bladder dose.

Comparison of the IPSA and HIPO algorithms for interstitial tongue high-dose-rate brachytherapy.

PurposeThis study aimed to compare the inverse planning simulated annealing (IPSA) stochastic algorithm with the hybrid inverse planning and optimization (HIPO) algorithm for interstitial tongue high-dose-rate (HDR) brachytherapy.MethodsTwenty patients who received radiotherapy for tongue cancer using interstitial HDR brachytherapy were retrospectively selected for this study. Oncentra Brachy v. 4.3 was used for IPSA and HIPO planning. Four to eight fixed catheter configurations were determined according to the target shape. During the optimization process, predetermined constrain values were used for each IPSA and HIPO plan. The dosimetric parameters and dwell time were analyzed to evaluate the performances of the plans.ResultsThe total dwell time using IPSA was 4 seconds longer than that of HIPO. The number of active positions per catheter for the IPSA plans were approximately 2.5 fewer than those of the HIPO plans. The dose-volumetric parameters related to the clinical target volume with IPSA were lower than those with HIPO. In terms of the dose-volumetric parameters related to normal tissue, HIPO tended to associate with slightly higher values than IPSA, without statistical significance. After GrO, the target coverages were satisfied to clinical goal for all patients. The total dwell times was approximately increased by 10%.ConclusionsThe IPSA and HIPO dose optimization algorithms generate similar dosimetric results. In terms of the dwell time, HIPO appears to be more beneficial.

Dosimetric evaluation of manually and inversely optimized treatment planning for high dose rate brachytherapy of cervical cancer

Background. To compare five inverse treatment planning methods with the conventional manually optimized planning approach for brachytherapy of cervical cancer with respect to dosimetric parameters.Material and methods. Eighteen cervical cancer patients treated with magnetic resonance imaging (MRI)-guided high dose rate (HDR) brachytherapy were included in this study. Six plans were created for each of the 4 HDR brachytherapy fractions for each patient: 1 manually optimized and 5 inversely planned. Three of these were based on inverse planning simulated annealing (IPSA) with and without extra constraints on maximum doses of the target volume, and different constraints on doses to the organs at risk (OARs). In addition there were two plans based on dose to target surface points. The resulting dose-volume histograms were analyzed and compared from the dosimetric point of view by quantifying specific dosimetric parameters, such as clinical target volume (CTV) D90, CTV D100, conformal index (COIN), and D2cm3 for rectum, bladder and the sigmoid colon.Results. Manual optimization led to a mean target coverage of 78.3% compared to 87.5%, 91.7% and 82.5% with the three IPSA approaches (p < 0.001). Similar COIN values for manual and inverse optimization were found. The manual optimization led to better results with respect to the dose to the OARs expressed as D2cm3. Overall, the best results were obtained with manual optimization and IPSA plans with volumetric constraints including maximum doses to the target volume.Conclusions. Dosimetric evaluation of manual and inverse optimization approaches is indicating the potential of IPSA for brachytherapy of cervical cancer. IPSA with constraints of maximum doses to the target volume is closer related to manual optimization than plans with constraints only to minimum dose to the target volume and maximum doses to OARs. IPSA plans with proper constraints performed better than those based on dose to target surface points and manually optimized plans.

Optimization for high-dose-rate brachytherapy of cervical cancer with adaptive simulated annealing and gradient descent

To validate an in-house optimization program that uses adaptive simulated annealing (ASA) and gradient descent (GD) algorithms and investigate features of physical dose and generalized equivalent uniform dose (gEUD)-based objective functions in high-dose-rate (HDR) brachytherapy for cervical cancer. Eight Syed/Neblett template-based cervical cancer HDR interstitial brachytherapy cases were used for this study. Brachytherapy treatment plans were first generated using inverse planning simulated annealing (IPSA). Using the same dwell positions designated in IPSA, plans were then optimized with both physical dose and gEUD-based objective functions, using both ASA and GD algorithms. Comparisons were made between plans both qualitatively and based on dose-volume parameters, evaluating each optimization method and objective function. A hybrid objective function was also designed and implemented in the in-house program. The ASA plans are higher on bladder V75% and D2cc (p=0.034) and lower on rectum V75% and D2cc (p=0.034) than the IPSA plans. The ASA and GD plans are not significantly different. The gEUD-based plans have higher homogeneity index (p=0.034), lower overdose index (p=0.005), and lower rectum gEUD and normal tissue complication probability (p=0.005) than the physical dose-based plans. The hybrid function can produce a plan with dosimetric parameters between the physical dose-based and gEUD-based plans. The optimized plans with the same objective value and dose-volume histogram could have different dose distributions. Our optimization program based on ASA and GD algorithms is flexible on objective functions, optimization parameters, and can generate optimized plans comparable with IPSA.

SU-E-T-749: Effect of Different Optimization Techniques on Interstitial Breast Brachytherapy

Purpose: Purpose of this study is to compare the three doseoptimization techniques based on basal point, target dose point and inverse planning simulated annealing (IPSA) for flexible interstitial breast implant. Methods: Five carcinoma breast patients implanted with the flexible catheters (double plane, triangular geometry) were studied. After CT scan acquisition, clinical target volume (CTV), Organ at risks (OAR) such as lung and heart (in case of left breast) were delineated. Three plans were made for all the patients based on basal dose point, target dose point and IPSA using Nucletron Plato BPS (V3.5.1) planning system. All the plans were evaluated using following indices: Coverage Index (CI), External Volume Index (EI), Homogeneity Index (HI), Overdose Index (OI) and Conformity Index (COIN). For OAR lung and heart maximum dose(dose received by 1cc volume) was noted. Maximum dose to the skin was analyzed visually. Results: The CI (0.9049±0.024, 0.8920±0.015, and 0.96037±0.009), EI (0.1146±0.088, 0.1869±0.077, and 0.1985±0.064), HI (0.4128±0.079, 0.3482±0.080, and 0.3780±0.096), OI (0.2777±0.085, 0.3564±0.059, 0.2529±0.052) and COIN (0.8077±0.081, 0.7385±0.031, and 0.7969±0.041) were shown for basal dose point, target dose point and IPSA based plan respectively. The average of the maximum dose received by the ipsilateral lung is 892.8±378.8, 961.6±545.4 and 812.6±341.6 cGy for basal dose point, target dose point and IPSA based plan respectively. The average of the maximum dose received by heart 625.8±524.2, 687.2±712.8 and 580.0±391 cGy for basal dose point, target dose point and IPSA based plan respectively. Conclusions: IPSA plan showed better target coverage followed by basal dose point and target dose point based plans. Lesser doses of heart and lung volumes were observed for IPSA. For skindoses, no significant difference was found. Even though the classical basal dose point plan was slightly inferior to IPSA, it is easy to plan with the lesser resources.

SU‐FF‐T‐02: Plan Comparison On Magnetic Resonance Image Between Inverse Planning Simulated Annealing and Point A Normalization for High Dose Rate Brachytherapy On a Cervical Cancer Patient

Purpose: The availabilities of CT/MRI compatible tandem and ovoid (TNO) applicators in recent years have improved the visibility of the tumor and organs at risk (OAR) in the treatment of cervical cancer using HDR brachytherapy. The purpose of this study was to observe the dose differences between different optimization methods shown on MRI. Method and Materials: A stage IIIB cervical cancer patient was treated with HDR brachytherapy using CT/MRI compatible TNO applicator. CT and MRI images were taken for the first fraction. The patient was carefully transferred between the two image modalities to prevent applicator movements. Catheter reconstructions on the MRI were performed based on CT/MRI registration focusing mainly on the applicator and the soft tissue surrounding the applicator. Two plans using different optimization methods were generated on MRI images, inverse planning simulated annealing (IPSA) and point A normalization. Dose distribution on each image slices were reviewed and DVHs for two plan protocols were compared. Results: The IPSA method showed better dose coverage to the target area(s) when compared with point A method. For the organs at risk (OAR), lower bladder dose (−16.5% for D2cm3) and higher rectal dose (10.9% for D2cm3) were found in IPSA plan. The rectal dose was increased due to better conformity at the ovoid level. Both plans have similar dose homogeneity index. Conclusion: Better target coverage was achieved with an IPSA plan compared to point A prescription plan. In this study, MRI provided superior soft tissue resolution and CT offered better image quality for catheter and source dwell position definition. It is advantageous to use both CT and MRI for HDR TNO brachytherapy planning.

3D inverse treatment planning for the tandem and ovoid applicator in cervical cancer

Three-dimensional treatment planning systems and inverse planning optimization for brachytherapy are becoming commercially available. Guidelines for target delineation and dose constrictions have not been established using this new software. In this study we describe a method of target delineation for the tandem and ovoids applicator. We then compare inverse planning dose distributions with the traditional methods of prescribing dose. Target and organ-at-risk volumes were defined using systematic guidelines on 15 patients treated in our department with high-dose-rate brachytherapy for cervical cancer using tandem and ovoids. High-dose-rate distributions were created according to three different dose optimization protocols: inverse planning simulated annealing (IPSA), point A, and point A with a normalization of 2 cc of the bladder receiving 80% of the dose (bladder-sparing method). An uniform cost function for dose constraints was applied to all IPSA generated plans, and no manual optimization was allowed for any planning method. Guidelines for target and structure-at-risk volumes, as well as dose constraint cost functions, were established. Dose-volume histogram analysis showed that the IPSA algorithm indicated no difference in tumor coverage compared with point A optimization while decreasing dose to the bladder and rectum. The IPSA algorithm provided better target volume coverage compared with bladder-sparing method with equivalent doses to the bladder and rectum. This study uses a systematic approach for delineating target and organ-at-risk volumes and a uniform cost function for generating IPSA plans for cervical cancer using tandem and ovoids. Compared with conventional dose prescription methods, IPSA provides a consistent method of optimization that maintains or improves target coverage while decreasing dose to normal structures. Image-guided brachytherapy and inverse planning improve brachytherapy dosimetry.