Inverse Planning Simulated Annealing Research Articles

Dosimetric Comparison of Inverse Planning Simulated Annealing and Manual Optimization for Intracavitary Cervix Brachytherapy

Background/Aims: Different optimization methods in brachytherapy treatment planning is used. The aim of this study is to evaluate dosimetric differences between manual optimization (MO) and inverse planning simulated annealing (IPSA) planning techniques commonly used in brachytherapy of cervical cancer. Methods: Fifteen cervical cancer patients were included in this study. Nucletron standard tandem-ovoid (TO) applicators were used for treatment. High-risk clinical tumor volume (HR-CTV), bladder, rectum, and sigmoid contouring were performed according to GEC-ESTRO recommendations. Two plans were created for each patient using IPSA and MO techniques. While a dose of 700 cGy was prescribed to the target volume during the planning phase, an effort was made to protect the organs at risk in the best way possible. IPSA and MO planning techniques were compared via dose volume histogram (DVH). Results: There was no significant difference between HR-CTV and CI values for MO and IPSA techniques. There was a significant difference between IPSA and MO techniques for the 2cm3 volume of the rectum (p= 0.002). It was observed that the bladder was better protected by the IPSA technique. There was a 6.26% dose difference between IPSA and MO for the bladder. A significant difference was found between IPSA and MO techniques for the 2cm3 volume of the sigmoid (p= 0.002). The IPSA technique was superior to the MO technique in terms of time. Conclusions: The IPSA technique was superior to the MO technique in terms of protecting organs at risk (OARs). IPSA provides a faster and higher quality plan in cervical brachytherapy.

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.

Image-Guided High-Dose-Rate Brachytherapy for Definitive Management of Primary Vaginal Cancer: A Single Institutional Experience

To assess the safety and efficacy of image-guided high-dose-rate brachytherapy (IGBT) alone or in combination with external beam radiation therapy (EBRT) for the treatment of vaginal cancers. The study analyzed patients diagnosed with primary vaginal cancers from 2004 to 2021 who received definitive radiotherapy at a single institution. Interstitial implants were performed using a freehand technique and transvaginal or transrectal-ultrasound for imaging guidance. IGBT was planned using inverse planning simulated annealing (IPSA) software. Data collected and analyzed included patient and tumor characteristics, dose and fractionation, and treatment outcomes. Complications were assessed using CTCAEv4 scores, and descriptive and survival analyses were performed using R-studio. Sixty-six patients met inclusion criteria. Patients were staged as I (14), II (23), III (19), and IV (10) based on revised FIGO 2018 staging. 47 (72%) had squamous cell carcinoma histology, and median age was 65 years. The most common regimen was 45 Gy in 25 fractions of EBRT followed by IGBT boost of 18 Gy in 3 fractions with 1 implant (n = 40). For melanoma, an IGBT boost of 19 Gy in 2 fractions with a single implant was used (n = 7). For IGBT monotherapy, the most common regimen was 36 Gy in 6 fractions delivered over 2 implants (n = 3). 41 (66%) of the patients received systemic therapy. Local failures occurred in 8 (12%) patients, while 8 (12%) developed distant metastases. Median overall survival was 64.7 months. Overall survival was 64.3% (95% CI 51.9-79.7%) at 3 years, and 50.9% (95% CI 35.7-72.5%) at 5 years. Grade 3 or 4 toxicities were reported in 4 (6%) patients including vaginal fistula (n = 3) and urethral stricture (n = 1). The results suggest that utilizing IGBT for freehand interstitial implants in combination with EBRT is a safe and effective primary treatment for vaginal cancer, with durable local control and low toxicity. Further research is needed to establish multi-institutional practice patterns and recommendations.

Comparative analysis of dosimetric and radiobiological models of IPSA and HIPO algorithms in combined intra-cavitary/interstitial brachytherapy for cervical cancer.

To compare inverse planning simulated annealing (IPSA) and hybrid inverse planning optimization (HIPO) using dosimetric and radiobiological models, and provide a basis for selecting the optimization method for cervical cancer. This was a retrospective study including 32 patients with radical cervical cancer. Brachytherapy treatment plans were re-optimized using IPSA, HIPO1 (with a locked uterine tube), and HIPO2 (with an unlocked uterine tube). Dosimetric data, including isodose lines, HR-CTV (D100, V150%, V200%, HI, and CI), and (bladder, rectum, and intestines) D1cc, D2cc for organs at risk (OARs) were also collected. Additionally, TCP, NTCP, BED, and EUBED were calculated, and differences were analyzed using matched samples t-test and Friedman test. Compared with IPSA and HIPO2, HIPO1 had better V150% and V200% (p < 0.05). Compared with IPSA and HIPO1, HIPO2 had better D100 and CI (p < 0.05). The doses to the bladder D1cc (4.72 ±0.33 Gy)/D2cc (4.47 ±0.29 Gy) and rectum D1cc (4.50 ±0.61 Gy)/D2cc (4.11 ±0.63 Gy) were lower in HIPO2 than in IPSA and HIPO1. EUBEDs for HR-CTV were higher in HIPO1 and HIPO2 than in IPSA by 1.39-1.63%. However, TCPs were not remarkably different among the three plans (p > 0.05). Also, the NTCP for the bladder was lower in HIPO2 than in IPSA and HIPO1 by 13.04% and 16.67%, respectively. Although the dosimetric parameters of IPSA, HIPO1, and HIPO2 are comparable, HIPO2 provides better dose conformability and lower NTCP. Therefore, HIPO2 is recommended as an optimization algorithm in IC/ISBT for cervical cancer.

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.

Feasibility of accelerated image-guided high-dose-rate interstitial brachytherapy with inverse planning simulated annealing (IPSA-HDRBT) for post-operative treatment of pathologically node-negative squamous cell carcinomas of the oral tongue

Inverse planning simulated annealing (IPSA) produces highly conformal dose distributions and quick optimizations for high-dose-rate interstitial brachytherapy (HDRBT). We report our dosimetry and overall outcomes using this approach for the accelerated post-operative treatment of pathologically node-negative squamous cell carcinomas of the oral tongue (OTSCC) with high risk of local recurrence. Patients with newly diagnosed pN0 OTSCC treated with partial glossectomy, neck dissection, and post-operative HDRBT alone from 2007 to 2021 were retrospectively reviewed. Patients received 30 Gy in 5 fractions over 2.5 days. Target volume and mandible dosimetry are reported. Actuarial rates of local control, regional control, disease-specific survival, and overall survival were estimated using the Kaplan-Meier method. Toxicity was categorized using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. 19 consecutive patients were reviewed. Median follow-up was 3.2 years (IQR 1.4-8.2 years) with a 3-year estimated local control rate of 81%. Target volumes were generally small, as the median volume was 12.66 cc. Median V150% and V200% were 52% and 24%, respectively. D1cc and D2cc to the mandible were 17.31 Gy and 14.42 Gy, respectively. IPSA-HDRBT is feasible and highly efficient for post-operative treatment of the primary tumor bed in patients with pathologically node-negative squamous cell carcinomas of the oral tongue. Further technical optimization and prospective clinical evaluation in a larger patient cohort are planned.

Optimizing the IPSA Conditions to Improve the Treatment Plan Quality in Brachytherapy for Cervical Cancer.

Recent prevalent use of three-dimensional image-guided brachytherapy (3D brachytherapy) has dramatically improved the treatment outcomes of cervical cancer. Inverse planning simulated annealing (IPSA) is one of the commonly used algorithms in 3D brachytherapy, but different conditions may affect the treatment plan quality. In this study, we compared HRCTV (high-risk clinical target volume) D90 (dose prescription) and HRCTV D95 D2cc (dose received by 2.0cc) of the rectum, bladder, and sigmoid in 30 patients with cervical cancer under four IPSA conditions. The HRCTV D90 (mean ± SD cGy) was 607.32 ± 37.86, 599.01 ± 23.62, 598.67 ± 13.07, and 596.45 ± 10.94 in four groups, respectively. The HRCTV D95 was 558.19 ± 38.51, 558.17 ± 25.72, 557.03 ± 16.12, and 555.26 ± 12.78, respectively. The sigmoid D2cc was 282.96 ± 44.84, 273.14 ± 60.69, 268.94 ± 62.32, and 292.69 ± 52.44. HRCTV D90, HRCTV D95, and sigmoid D2cc were not statistically different among the four groups (p > 0.05). However, the target fitness in group one, especially at the cervix, was poor. The rectum D2cc was 351.49 ± 32.90, 361.49 ± 28.09, 370.82 ± 24.44, and 375.33 ± 30.90. The rectum D2cc in group one was the lower than that in group three and group four (p < 0.05). The bladder D2cc was 423.59 ± 31.39, 380.75 ± 37.25, 383.27 ± 32.55, and 385.22 ± 25.79. The bladder D2cc in group one was higher than the other groups (p < 0.05). The maximum rectum limit dose (400cGy) is lower than the bladder (500cGy), and HRCTV is a whole in the IPSA algorithm; these result in the insufficiency or even absence of cervix dose that first need to meet in clinics. In conclusion, IPSA condition optimization can improve the quality of treatment plan in 3D brachytherapy and make it closer to clinical practice.

Deep reinforcement learning for treatment planning in high-dose-rate cervical brachytherapy.

High-dose-rate (HDR) brachytherapy (BT) is an effective cancer treatment method in which the radiation source is placed within the body. Treatment planning is a critical component for a successful outcome. Almost all currently proposed treatment planning methods are built on stochastic heuristic algorithms, which limits the generation of higher quality plans. This study proposed a novel treatment planning method to adjust dwell times in a human-like fashion to improve the quality of the plan. We built an intelligent treatment planner network (ITPN) based on deep reinforcement learning (DRL). The network architecture of ITPN is Dueling Double-Deep Q Network. The state is the dwell time of each dwell position and the action is which dwell time to adjust and how to adjust it. A hybrid equivalent uniform dose objective function was established and assigned corresponding rewards according to its changes. Experience replay was performed with the epsilon greedy algorithm and SumTree data structure. In the evaluation of ITPN using 20 patient cases, D90, D100 and V100 showed no significant difference compared with inverse planning simulated annealing (IPSA) optimization. However, D2cc of bladder, rectum and sigmoid, V150 and V200 were significant reduced, and homogeneity index and conformity index were significantly increased. The proposed ITPN was able to generate higher quality plans based on the learned dwell time adjustment policy than IPSA. This is the first artificial intelligence system that can directly determine the dwell times of HDR BT, which demonstrated the potential feasibility of solving optimization problems via DRL.

An inverse planning simulated annealing algorithm with adaptive weight adjustment for LDR pancreatic brachytherapy.

The inverse planning simulated annealing (IPSA) algorithm has shown good results in cancer surgical treatment planning. However, an adaptive approach has not well been proposed for different shapes and sizes of tumors. The purpose of this study was to propose an adaptive, efficient and safe algorithm to get high-quality treatment dose planning, which is presented for pancreatic cancer. An algorithm employs an optimized IPSA and an adaptive process for adjusting the weight of organs at risk (OAR) and tumor. The algorithm, which was combined with ant colony optimization, was further optimized to reduce the number of needles. It could meet the clinical dose objectives within the tumors, reduce the dose distribution within the OAR and minimize the number of needles. Ten clinical cases were chosen randomly from patients, previously successfully treated in clinic to test our method. The algorithm was validated against clinical cases, using clinically relevant dose parameters. The results were compared with clinical results in ten cases, indicating that the dose distribution within the tumor meets the clinical dose objectives. The dose received by OAR had been greatly reduced, and the number of needles could be reduced by about 50%. It was a significant improvement over the clinical treatment planning. In this paper, we have devised an algorithm to optimize the treatment planning in brachytherapy. The method in this paper could meet the clinical dose objectives and reduce the difficulty of operation. The results were clinically acceptable. This algorithm is also applicable to other cancers such as lung cancer.

Effect of the dwell time deviation constraint on brachytherapy treatment planning for cervical cancer.

ObjectiveThis study aimed to quantify the effect of the dwell time deviation constraint (DTDC) on brachytherapy treatment for cervical cancer.MethodsA retrospective study was carried out on 20 patients with radical cervical cancer. The DTDC values changed from 0.0 to 1.0 by a step size of 0.2. We adjusted the optimization objectives to ensure that all plans were optimized to a high-risk clinical target volume (HRCTV) D90 (the dose to 90% of the HRCTV) = 6 Gy, while keeping the dose to the organs at risk as low as possible. The dose–volume histogram parameters and the dwell time data were compared between plans with different DTDC values.ResultsThe HRCTV volume covered by 150% of the prescription dose gradually increased with increasing DTDC values. As the DTDC value increased from 0.0 to 1.0, the effective dwell point proportion increased from 61.78% to 90.30%. The mean dwell time initially decreased with an increase in the DTDC value, reached the minimum value at DTDC = 0.8, then slightly increased at DTDC = 1.0.ConclusionsWhen using inverse planning simulated annealing optimization for radical cervical cancer cases, the recommended DTDC value is approximately 0.6 if the organ dose needs to be limited.

Dose optimization comparison study of inverse planning simulated annealing [IPSA] and hybrid inverse planning optimization [HIPO] in interstitial brachytherapy of head and neck cancer

This study was a retrospective dose optimization comparison of two commercially available inverse planning algorithms, the inverse planning simulated annealing (IPSA) and hybrid inverse planning optimization (HIPO) for head and neck cancer interstitial brachytherapy. Seven patients with head and neck cancer were selected (4 with tongue cancer, 2 with buccal mucosa cancer and 1 with carcinoma lip) who were previously treated with interstitial brachytherapy using a flexible nylon tube catheter and graphical optimization/geometric optimization technique. All seven patients were retrospectively re-planned using both IPSA as well as HIPO algorithms available in the Oncentra Brachytherapy Treatment Planning System (TPS) version V4.5.3.30. The dosimetric parameters [PTV-V100, V150, V200, D90; mandible-D2cc, parotid-D2cc, conformity index (CI), dose homogeneity index (HI), overdose volume index (ODI)] were chosen for evaluation in compliance with the objective function and organ at risk dose constraints. Using the paired sample T test in chosen parameters (PTV-V100, V150, V200, D90; mandible-D2cc, CI, HI, ODI both the inverse planning algorithms), it was found that IPSA and HIPO were comparable. Even though both IPSA and HIPO are largely comparable in most of the dosimetric parameters for inverse planning in brachytherapy of head and neck cancers, differences in the algorithms can be exploited to improve certain parameters in specific situations such as D2cc parotid.

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.

Comparison of two inverse planning algorithms for cervical cancer brachytherapy.

PurposeTo compare two inverse planning algorithms, the hybrid inverse planning optimization (HIPO) algorithm and the inverse planning simulated annealing (IPSA) algorithm, for cervical cancer brachytherapy and provide suggestions for their usage.Material and methodsThis study consisted of 24 cervical cancer patients treated with CT image‐based high‐dose‐rate brachytherapy using various combinations of tandem/ovoid applicator and interstitial needles. For fixed catheter configurations, plans were retrospectively optimized with two methods: IPSA and HIPO. The dosimetric parameters with respect to target coverage, localization of high dose volume (LHDV), conformal index (COIN), and sparing of organs at risk (OARs) were evaluated. A plan assessment method which combines a graphical analysis and a scoring index was used to compare the quality of two plans for each case. The characteristics of dwell time distributions of the two plans were also analyzed in detail.ResultsBoth IPSA and HIPO can produce clinically acceptable treatment plans. The rectum D2cc was slightly lower for HIPO as compared to IPSA (P = 0.002). All other dosimetric parameters for targets and OARs were not significantly different between the two algorithms. The generated radar plots and scores intuitively presented the plan properties and enabled to reflect the clinical priorities for the treatment plans. Significant different characteristics were observed between the dwell time distributions generated by IPSA and HIPO.ConclusionsBoth algorithms could generate high‐quality treatment plans, but their performances were slightly different in terms of each specific patient. The clinical decision on the optimal plan for each patient can be made quickly and consistently with the help of the plan assessment method. Besides, the characteristics of dwell time distribution were suggested to be taken into account during plan selection. Compared to IPSA, the dwell time distributions generated by HIPO may be closer to clinical preference.

Unresectable bulky chest wall recurrent breast cancer controlled with CT-guided interstitial high-dose-rate brachytherapy and external beam radiotherapy with adjuvant hormonal therapy – case report

PurposeBulky chest wall recurrence after mastectomy presents a therapeutic challenge because of high-dose of radiation required to control the disease, and its proximity to low-tolerance organs at risk. We report a case of successful computed tomography (CT)-guided high-dose-rate (HDR) salvage interstitial brachytherapy (ISBT) boost.Material and methodsA 70-year-old female initially presented with a tumor in right breast, and was treated with mastectomy and adjuvant chemotherapy, followed by hormonal therapy for 5 years without adjuvant radiotherapy. In 2018, 20 years after the initial treatment, she developed unresectable chest wall recurrence that measured 10.5 cm × 7.3 cm × 4.5 cm, with bone and parietal pleura invasion. Biopsy revealed invasive pleomorphic lobular carcinoma [estrogen receptor (ER)-positive, progesterone receptor (PR)-negative, HER2-negative]. There was no evidence of metastatic disease.ResultsThe patient underwent external beam radiotherapy (EBRT) plus ISBT. After EBRT of 50 Gy in 25 fractions was completed, CT-guided ISBT was performed as an outpatient treatment. HDR dose was 16 Gy delivered in 2 fractions with 2 implants. Dose was prescribed to gross tumor volume. ISBT plans were created using inverse planning simulated annealing (IPSA) algorithm. Gross tumor volume D90% plus EBRT dose was 82 Gy equivalent dose of 2 Gy (EQD2), assuming α/β of 4 for breast carcinoma. The patient continued on hormonal therapy. At the 30-month follow-up, the patient remains in remission. The tumor could not be detected by magnetic resonance imaging (MRI) or positron emission tomography (PET). There were no severe treatment-related complications.ConclusionsCT-guided HDR ISBT boost can be a useful modality in individualizing treatment strategies for breast cancer patients with unresectable bulky chest wall recurrence.

Paradigm Shift in Radiation Treatment Planning Over Multiple Treatment Modalities.

The inverse planning simulated annealing optimization engine was used to develop a new method of incorporating biological parameters into radiation treatment planning. This method integrates optimization of a radiation schedule over multiple types of delivery methods into a single algorithm. We demonstrate a general procedure of incorporating a functional biological dose model into the calculation of physical dose prescriptions. This paradigm differs from current practice in that it combines biology-informed dose constraints with a physical dose optimizer allowing for the comparison of treatment plans across multiple different radiation types and fractionation schemes.

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.

IMAGE-Guided Brachytherapy for Primary Vaginal Cancers

To evaluate disease control and toxicities of primary vaginal cancer treated with image-guided brachytherapy. A retrospective study was performed on 26 consecutive patients treated for vaginal cancer with brachytherapy (BT) between 2010 and 2018, all treated after the introduction of ultrasound-based catheter guidance and modified dose optimization to reduce vaginal toxicities. External beam radiation therapy (EBRT) was used in 25/26 patients, with a median dose of 45 Gy in 25 fractions. 16/25 patients had concomitant chemotherapy with EBRT. Endocavitary BT alone was used in 3/26 patients. Interstitial BT was used in 23/26 patients. Standard procedure involved the use of a cylinder and interstitial catheters. They were usually inserted under Transrectal Ultrasound (TRUS) and/or TransVaginal Ultrasound (TVUS) guidance. Inverse Planning Simulated Annealing (IPSA) was used for dose optimization and a class solution was developed to reduce high-dose points in the vaginal mucosa by keeping most of the high dose inside the cylinder. Acute (<6 months) and late genitourinary (GU), gastrointestinal (GI), and vaginal toxicities were reported using the Common Terminology Criteria for Adverse Events version 5 (CTCAE v5). Local control (LC), metastatic disease-free survival (mDFS) and overall survival (OS) were evaluated using Kaplan-Meier survival curves. Mean age was 69,7 years old. Median follow-up was 35,5 months (range 0-85months). 18/26 patients had Squamous Cell Carcinoma (SCC), 5/26 Adenocarcinoma, 1/26 Clear Cell Carcinoma, 1/26 Melanoma and 1/26 Squamous Transitional Carcinoma. 13%, 71%, 8%, and 8% of patients had FIGO stages I, II, III, and IV respectively. LC of 83% and 83%, mDFS of 91 % and 91%, and OS of 80% and 66 %, were respectively achieved at 3 and 5 years. When limited to SCC only, LC of 88% and 88%, mDFS of 94 % and 94%, and OS of 87% and 70 %, were respectively achieved at 3 and 5 years. There were only 4 local relapses, which all occurred within 8 months after treatment. One was a stage IV SCC at diagnosis, one had a squamous transitional carcinoma, one was a clear cell carcinoma, and the last one had concomitant multiple distant metastasis at time of local relapse. There were no late G3-4 GU/GI toxicity. Acute and late G3 vaginal toxicity (stenosis) occurred in 19% and 42% of patients, respectively. 3 cases of vaginal necrosis and 1 suspicion of fistula were reported, all associated with a local progression of the disease except for one case where necrosis was limited and healed spontaneously. No patient needed Hyperbaric Oxygen Therapy (HBOT). Excellent local control can be achieved with the use of TRUS/TVUS-guided vaginal brachytherapy in primary vaginal cancer, especially for Squamous Cell Carcinoma, with a favorable toxicity profile. GU and GI toxicities are mild, but there is a significant number of G3 vaginal stenosis in this cohort of older patients. This might be reduced with the regular use of a vaginal dilator.

Towards an Ultra-Fast GPU-Based Multi-Criteria Optimization Algorithm for HDR Brachytherapy

Most inverse planning optimization algorithms used in clinic such as Inverse Planning Simulated Annealing (IPSA) are designed to quickly optimize a single treatment plan based on a population-based template objective function called class solution. Since the weight values of each individual objective are patient specific, the user may have to manually change the weight values of the class solution and make several attempts to obtain a plan that encapsulates all the goals set forth by the physicians. This iterative process can be time consuming and can be dependent on the optimization skills of the user. This study intends to facilitate this process by proposing a graphics processing units (GPU)-based L-BFGS or gL-BFGS optimizer (Limited-memory Broyden Fletcher Goldfarb Shanno) which can calculate multiple plans in parallel for multi-criteria optimization (MCO) for high-dose-rate (HDR) brachytherapy. Thus a patient-specific plan pool of Pareto optimal plans can be generated in real-time for each patient from which the user can chose the most suitable option depending on the clinical situation.