Intensity Modulated Radiation Therapy Fields Research Articles

Using Scorecards to Tune Ethos Directive Templates: An Adaptive Radiation Therapy Individualized Approach-Cervix Dosimetric Planning Study

The Adaptive Radiation Therapy Individualized Approach-Cervix clinical trial uses predefined clinical directive templates (CDTs) combined with RapidPlan dose-volume histogram estimations (DVHe) to guide plan optimization in the Ethos treatment planning system. The dosimetric scorecard is a scoring tool that quantifies improvements in plan quality after physicians have precisely expressed their complete clinical intent. To our knowledge, this is the first study to use the dosimetric scorecard tool to tune an Ethos CDT to improve resulting plan quality. Iterative replanning was used to modify the draft CDT (CDT-1) in Ethos 1.1 to generate a new CDT (CDT-2) that maximized the clinical consensus scorecard's total score compared with CDT-1. CDT-2 was established, and resulting plans were compared with and without a DVHe. Additional fixed field intensity modulated radiation therapy beam geometries were compared between CDT-1 and CDT-2, both with DVHe. After obtaining favorable results when comparing CDT-1 versus CDT-2 for 2 test cases, 10 additional cases were retrospectively identified and tested. CDT-2 reduced organ at risk doses without compromising planning target volume coverage in the initial test cases. When combined with DVHe, CDT-2 marginally outperformed CDT-1. Plan quality further improved with a 19-field geometry. In the expanded analysis, CDT-2 achieved higher scores than CDT-1 in most cases, with the 19-field approach showing superiority. Optimization and calculation time increased by 1.9 minutes, monitor unit (MU)/field decreased by 44.4, whereas beam-on time increased by 2.8 minutes when increasing fields to 19 from 9. Reoptimization with Ethos 1.1 Maintenance Release 1 resulted in decreased MU and minimal score changes. The scorecard is an effective tool to adjust an Ethos CDT to improve the average calculated plan quality. It also allowed for easy evaluation of the dosimetric impact of other planning parameters (beam arrangements and use of DVHe) to identify the best approach. Using a finely tuned CDT is expected to improve planning efficiency and decrease intrainstitutional plan quality variability, benefiting cone beam computed tomography-guided adaptive radiation therapy.

Automated treatment planning for whole breast irradiation with individualized tangential IMRT fields.

This study aimed to develop and validate algorithms for automating intensity modulated radiation therapy (IMRT) planning in breast cancer patients, with a focus on patient anatomical characteristics. We retrospectively selected 400 breast cancer patients without lymph node involvement for automated treatment planning. Automation was achieved using the Eclipse Scripting Application Programming Interface (ESAPI) integrated into the Eclipse Treatment Planning System. We employed three beam insertion geometries and three optimization strategies, resulting in 3600 plans, each delivering a 40.05Gy dose in 15 fractions. Gantry angles in the tangent fields were selected based on a criterion involving the minimum intersection area between the Planning Target Volume (PTV) and the ipsilateral lung in the Beam's Eye View projection. ESAPI was also used to gather patient anatomical data, serving as input for Random Forest models to select the optimal plan. The Random Forest classification considered both beam insertion geometry and optimization strategy. Dosimetric data were evaluated in accordance with the Radiation Therapy Oncology Group (RTOG) 1005 protocol. Overall, all approaches generated high-quality plans, with approximately 94% meeting the acceptable dose criteria for organs at risk and/or target coverage as defined by RTOG guidelines. Average automated plan generation time ranged from 6 min and 37 s to 9 min and 22 s, with the mean time increasing with additional fields. The Random Forest approach did not successfully enable automatic planning strategy selection. Instead, our automated planning system allows users to choose from the tested geometry and strategy options. Although our attempt to correlate patient anatomical features with planning strategy using machine learning tools was unsuccessful, the resulting dosimetric outcomes proved satisfactory. Our algorithm consistently produced high-quality plans, offering significant time and efficiency advantages.

Dosimetric Impact of Voluntary Deep Inspiration Breath Hold (DIBH) in Mediastinal Hodgkin Lymphomas: A Comparative Evaluation of Three Different Intensity Modulated Radiation Therapy (IMRT) Delivery Methods Using Voluntary DIBH and Free Breathing Techniques.

Hodgkin lymphomas are radiosensitive and curable tumors that often involve the mediastinum. However, the application of radiation therapy to the mediastinum is associated with late effects including cardiac and pulmonary toxicities and secondary cancers. The adoption of conformal IMRT and deep inspiration breath- hold (DIBH) can reduce the dose to healthy normal tissues (lungs, heart and breast). We compared the dosimetry of organs at risk (OARs) using different IMRT techniques for two breathing conditions, i.e., deep inspiration breath hold (DIBH) and free breathing. Twenty-three patients with early-stage mediastinal Hodgkin lymphomas were accrued in the prospective study. The patients were given treatment plans which utilized full arc volumetric modulated arc therapy (F-VMAT), Butterfly VMAT (B-VMAT), and fixed field IMRT (FF-IMRT) techniques for both DIBH and free breathing methods, respectively. All the plans were optimized to deliver 95% of the prescription dose which was 25.2 Gy to 95% of the PTV volume. The mean dose and standard error of the mean for each OAR, conformity index (CI), and homogeneity index (HI) for the target using the three planning techniques were calculated and compared using Student's t-test for parametric data and Wilcoxon signed-rank test for non-parametric data. The HI and CI of the target was not compromised using the DIBH technique for mediastinal lymphomas. The mean values of CI and HI for both DIBH and FB were comparable. The mean heart doses were reduced by 2.1 Gy, 2.54 Gy, and 2.38 Gy in DIBH compared to FB for the F-VMAT, B-VMAT, and IMRT techniques, respectively. There was a significant reduction in V5Gy, V10Gy, and V15Gy to the heart (p < 0.005) with DIBH. DIBH reduced the mean dose to the total lung by 1.19 Gy, 1.47 Gy, and 1.3 Gy, respectively. Among the 14 female patients, there was a reduction in the mean right breast dose with DIBH compared to FB (4.47 Gy vs. 3.63 Gy, p = 0.004). DIBH results in lower heart, lung, and breast doses than free breathing in mediastinal Hodgkin Lymphoma. Among the different IMRT techniques, FF-IMRT, B-VMAT, and F-VMAT showed similar PTV coverage, with similar conformity and homogeneity indices. However, the time taken for FF-IMRT was much longer than for the F-VMAT and B-VMAT techniques for both breathing methods. B-VMAT and F-VMAT emerged as the optimal planning techniques able to achieve the best target coverage and lower doses to the OARs, with less time required to deliver the prescribed dose.

The potential overdose of heart and left anterior descending coronary artery region during intensity-modulated radiation therapy in patients with esophageal cancer.

This study aimed to investigate the changes in dose distribution in the heart and left anterior descending coronary artery region (LADR) during intensity-modulated radiation therapy (IMRT) in patients with esophageal cancer (EC) treated at our institution. The heart and LADR were delineated on the initial and off-cord boost planning computed tomography (CT) images. Cardiac volume reduction (CVR) was defined as the reduction in cardiac volume between the initial CT and off-cord boost CT at the dose of 36Gy irradiated. The involved field IMRT plan was created based on each initial and off-cord boost CT image and was analyzed based on the relationship between CVR and heart and LADR dose-volume parameters (Heart-Dmax, Heart-Dmean, Heart-V20, Heart-V30, Heart-V40, LADR-Dmax, LADR-Dmean, LADR-V15 and LADR-V30). Forty patients with EC were investigated between January 2016 and January 2022. The median CVR ratio during radiation therapy (RT) was 5.57% (range, -7.79 to 18.26%). Simple linear regression analysis revealed significant correlations between CVR during RT and changes in the heart and LADR dose-volume parameters. Some patients (>10%) experienced severe changes in the heart and LADR dose distribution. In three cases with reduced heart volume and primary tumor mass, the changes in LADR-V15 and LADR-V30 showed outliers. In conclusion, CVR during RT correlated with an increase in the heart and LADR dose. When both CVR and tumor volume reduction are large, a potential overdose of LADR during RT should be noted in the IMRT era.

Comparison of Rapid Arc and Intensity Modulated Radiotherapy in a True Beam Linear Accelerator for 6 MV: Application of AAPM TG‐119 tests in treatment planning and quality assurance

AbstractObjectiveWe developed rapid arc (RA) and intensity‐modulated radiotherapy (IMRT) plans based on the American Association of Physicists in Medicine Task Group‐119 (AAPM TG‐119) proposals and compared the planning and quality assurance results.Materials and MethodsTwo treatment plans were used for each study patient: one using 7–9 IMRT fields and the other using the two full‐arc RA methods. Plan optimization and dose calculations were performed using 6 MV photons and EclipseTM with the anisotropic analytical algorithm (AAA). Task group (TG)‐119 described the planning objectives used to evaluate the treatment plans generated for this study. Point dose, planar fluence measurement, and trajectory log file analysis are used for quality assurance.ResultsThe conformity index (CI) for treatment plans varied between 0.76–0.91 when using IMRT and 0.75–0.93 when using RA. The homogeneity index (HI) was approximately 0.10–0.24 (IMRT) and 0.07–0.23 (RA). The ratio of the total number of monitor units required for IMRT to that required for RA was between 0.87 and 2.14. The treatment log files exhibited higher gamma passing with RA than with IMRT.ConclusionRA plans were more effective than IMRT plans in achieving the test goals. Point dose measurements and electronic portal imaging device (EPID)‐based planar fluence measurements showed statistically insignificant differences between the IMRT and RA plan quality assurance (QA) results. However, the trajectory log file analysis exhibited better gamma‐passing results for RA than for IMRT.

Performance assessment of variant UNet-based deep-learning dose engines for MR-Linac-based prostate IMRT plans

Objective. UNet-based deep-learning (DL) architectures are promising dose engines for traditional linear accelerator (Linac) models. Current UNet-based engines, however, were designed differently with various strategies, making it challenging to fairly compare the results from different studies. The objective of this study is to thoroughly evaluate the performance of UNet-based models on magnetic-resonance (MR)-Linac-based intensity-modulated radiation therapy (IMRT) dose calculations. Approach. The UNet-based models, including the standard-UNet, cascaded-UNet, dense-dilated-UNet, residual-UNet, HD-UNet, and attention-aware-UNet, were implemented. The model input is patient CT and IMRT field dose in water, and the output is patient dose calculated by DL model. The reference dose was calculated by the Monaco Monte Carlo module. Twenty training and ten test cases of prostate patients were included. The accuracy of the DL-calculated doses was measured using gamma analysis, and the calculation efficiency was evaluated by inference time. Results. All the studied models effectively corrected low-accuracy doses in water to high-accuracy patient doses in a magnetic field. The gamma passing rates between reference and DL-calculated doses were over 86% (1%/1 mm), 98% (2%/2 mm), and 99% (3%/3 mm) for all the models. The inference times ranged from 0.03 (graphics processing unit) to 7.5 (central processing unit) seconds. Each model demonstrated different strengths in calculation accuracy and efficiency; Res-UNet achieved the highest accuracy, HD-UNet offered high accuracy with the fewest parameters but the longest inference, dense-dilated-UNet was consistently accurate regardless of model levels, standard-UNet had the shortest inference but relatively lower accuracy, and the others showed average performance. Therefore, the best-performing model would depend on the specific clinical needs and available computational resources. Significance. The feasibility of using common UNet-based models for MR-Linac-based dose calculations has been explored in this study. By using the same model input type, patient training data, and computing environment, a fair assessment of the models’ performance was present.

A dosimetric comparative study following RTOG and ESTRO contouring guidelines for breast radiation therapy

PurposeTo compare the dosimetric parameters considering the Radiation Therapy Oncology Group (RTOG) and European Society for Radiotherapy and Oncology (ESTRO) guidelines for breast cancer radiotherapy. Two radiotherapy techniques, intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT), were considered. Patients and methodsTwenty-eight patients with left-sided medially-located TanyN2M0 tumors were contoured based on RTOG and ESTRO guidelines. 9-field IMRT, 10-field IMRT, 11-field IMRT, and VMAT treatment plans were applied as radiotherapy (RT) techniques for both contouring sets. The dosimetric parameters of the RT plans were extracted and compared. ResultsComparing dose-volume histogram (DVH) parameters, equivalent uniform dose (EUD), and normal tissue complication probability (NTCP) of OARs across the contouring guidelines and considering each RT technique showed that the only significant differences were higher Dmax, Dmean, V30, and V45, EUD, and NTCP of the thyroid in all treatment modalities when the RTOG guideline had been adopted. Using the VMAT technique, PTV's EUD and the tumor control probability (TCP) were considerably higher when the ESTRO guideline was adopted. Moreover, the conformity index (CI) of VMAT plans was significantly higher when the ESTRO guideline was used. ConclusionUnless having higher doses to thyroid when the RTOG guideline was adopted, the doses to other organs-at-risk (OAR) were similar between the two considering guidelines. Moreover, except for higher EUD, TCP, and CI for VMAT when the ESTRO guideline was used, no other significant differences were obtained between dosimetric parameters of target volumes considering the RT techniques and contouring guidelines.

Dosimetric comparison of volumetric-modulated arc therapy (VMAT) and fixed field intensity-modulated radiotherapy (IMRT) in patients with nasal tumor: a meta-analysis

Dosimetric comparison of volumetric-modulated arc therapy (VMAT) and fixed field intensity-modulated radiotherapy (IMRT) in patients with nasal tumor: a meta-analysis

Optimal plan target in cases with locally advanced nasopharyngeal cancer: Comparison of VMAT, IMRT, hybrid, and tomotherapy results.

In locally advanced nasopharyngeal cancer (NC), the spread of the disease, proximity to critical structures, and high dose requirement for tumor control may complicate the treatment plan. In this study, VMAT/IMRT/hybrid/tomotherapy plans were made to reach the safest and most effective dose distribution for each of the patients and the results were compared. Double volumetric-modulated arc therapy (VMAT) and 7- and 9-field intensity-modulated radiation therapy (IMRT) plans were made to 21 locally advanced NCs with Varian Trilogy System. It was observed that appropriate dose distributions could not be achieved with IMRT or VMAT, and hybrid IMRT-VMAT plans were made. All cases were also planned with Tomotherapy Precision System, and the data of four different techniques were compared retrospectively. For normal tissue tolerances in 73 structures could not be obtained with VMAT and 38 structures with IMRT whereas the desired tolerance was provided with the hybrid plan. Hybrid plans were made with an average of 14 VMATs and 20 IMRTs. The maximum brainstem and spinal cord doses were found significantly lower in hybrid and tomotherapy techniques. Homogeneity index (HI) and conformity index (CI) values were the best in hybrid plans. No statistically significant difference between the hybrid plan and tomotherapy in terms of normal tissue tolerance doses and HI whereas a significant difference was found in the hybrid plan for CI. It was observed that the most ideal plans for the locally advanced NC could be obtained with tomotherapy and hybrid plan techniques that the better protection in critical structures and desired dose distribution at target volumes.

Patient-specific quality assurance prediction models based on machine learning for novel dual-layered MLC linac.

Patient-specific quality assurance (PSQA) is an indispensable and essential procedure in radiotherapy workflow, and several studies have been done to develop prediction models based on the conventional C-arm linac of single-layered multileaf collimator (MLC) with machine learning (ML) and deep learning techniques to predict PSQA results and improve efficiency. Recently, a newly designed O-ring gantry linac "Halcyon" equipped with unique jawless stacked-and-staggered dual-layered MLC was released. However, few studies have focused on developing PSQA prediction models for this novel dual-layered MLC system. To evaluate the performance of ML to predict PSQA results of fixed field intensity-modulated radiation therapy (FF-IMRT) plans for linac equipped with dual-layered MLC. A total of 213 FF-IMRT treatment plans, including 1383 beams from various treatment sites, were selected and delivered with portal dosimetry verification on Halcyon linac. Gamma analysis was performed using 1%/1, 2%/2, and 3%/2mm criteria with a 10% threshold. The training set (TS) of ML models consisted of 1106 beams, and an independent evaluation set (ES) consisted of 277 beams. For each beam, 33 complexity metrics were extracted as input data for training models. Three ML algorithms (gradient boosting decision tree/GBDT, random forest/RF, and Poisson Lasso/PL) were utilized to build the models and predict gamma passing rates (GPRs). To improve the prediction accuracy in the rare region, a method of reweighting for TS has been performed and compared to the unweighted results. The importance of complexity metrics was studied by permuted interesting features. The GBDT model had the best performance in this study. In ES, the minimal mean prediction error for unweighted results was 1.93%, 1.16%, 0.78% under 1%/1, 2%/2, and 3%/2mm criteria, respectively, from GBDT model. Comparing to the unweighted results, the models after reweighting gained up to 30% improvement in the rare region, whereas the overall prediction error was slightly worse depending on the kind of models. For feature importance, 2 tree-based models (GBDT and RF) had in common the top 10 most important metrics as well as the same metric with the largest impact. For linac equipped with novel dual-layered MLC, the ML model based on GBDT algorithm shows a certain degree of accuracy for GPRs prediction. The specific ML model for dual-layered MLC configuration could be a useful tool for physicists detecting PSQA measurement failures.

Feasibility of the photon spectrum generalisation model for rapid Monte Carlo dose calculation with a deep learning-based framework

PurposeWe propose a deep learning-based strategy for the training of the radiotherapy dose calculation using limited data based on two known energy spectra within the general range of radiotherapy linear accelerators. MethodsWe constructed a dose map using complete photon and electron Monte Carlo (MC) simulations with random rectangular field sizes, iso-centres, and gantry angles for pelvic computed tomography images with Mohan 4 and 24 MV spectrum photon beams. Two trained models, the virtual dose map-MC (VDM-MC) and improved VDM-MC (IVDM-MC) were tested under Mohan 4, 6, 10, 15, and 24 MV energy conditions in rectangular and intensity-modulated radiation therapy (IMRT) fields. A 3D gamma evaluation assessed the model's performance. ResultsFor VD-MC, the 3%/3 mm and 2%/2 mm criteria gamma pass rates were 92.58 ± 0.87% and 85.31 ± 1.56%, respectively, using the rectangular field test, whereas they were 97.03 ± 0.63% and 90.97 ± 1.46%, respectively, using the IMRT field test. For IVD-MC, the 3%/3 mm and 2%/2 mm criteria gamma pass rates were 97.86 ± 0.35% and 92.98 ± 0.77%, respectively, using the rectangular field test, and 98.57 ± 0.14% and 95.11 ± 0.33%, respectively, using the IMRT field test. ConclusionFeasibility of a single model to achieve accurate and rapid MC dose calculations for photons with different energy spectra was preliminarily verified. This data augmentation strategy effectively generalised the scope of the model.

Effect of field number on intensity modulated radiation therapy plan quality in head and neck cancer

Background: Radiotherapy of head and neck cancer is a difficult process because of the complex anatomy and close proximity of various organs at risk (OARs). This study aimed to assess the impact of field number of intensity modulated radiation therapy (IMRT) technique on the quality of the treatment of the head and neck cancer patient.. Methods and materials: The CT scans of thirteen head and neck cancer patients were selected at the Zhianawa Cancer Center (ZCC). The Monaco treatment planning system (TPS) V5.51.10 with the Monte Carlo (XVMC) algorithm V1.6 were utilized to generate nine and eleven field IMRT plans, all plans were carried out on an ELEKTAMLCi2 linear accelerator. The effect of field number was assessed by planning target volume (PTV) coverage, homogeneity index (HI), conformity index (CI), OARs dose, the monitor units (MUs), and delivery time. Results: The 11F-IMRT had improved tumor coverage and better spared ipsilateral and contralateral optic nerves, on the contrary the doses to the were above acceptance limit value. The CI of 11F-IMRT was better than 9F-IMRT, while the HI was similar. The 9F-IMRT had a reduced treatment time by 37.7 %, although increased MUs by 12.8%.

Dosimetric comparison between intensity modulated radiotherapy and three-dimensional conformal radiotherapy in adjuvant setting after radical cystectomy in high-risk urothelial bladder cancer

Objective: To compare the 4-field 3D conformal radiotherapy technique (3DCRT) to the intensity-modulated radiotherapy (IMRT) 9-field technique for adjuvant radiotherapy post radical cystectomy in high-risk urothelial bladder cancer cases. Patients and Methods: A dosimetric analysis of 11 urothelial bladder cancer patients who underwent radical cystectomy was performed. These patients were presented to the radiotherapy department, National Cancer Institute, Cairo, between 2018 and 2020 with adjuvant radiotherapy using the IMRT technique. Two plans were designed for each patient, one using 9-field IMRT and the second using 4-field 3DCRT. The two techniques were compared, including the PTV, bowel bag, rectum, neobladder, and pelvic bone marrow. Results: Comparing different DVHs, the planning target volume (PTV) was adequately covered in both plans, while the 9-field IMRT technique delivered significantly lower doses to OARs (bowel, rectum, and pelvic bone marrow). Conclusion: The IMRT technique incredibly spared the OARs more than that obtained by the 3DCRT technique, while both techniques covered the PTV adequately. The IMRT technique, through sparing OARs, was expected to decrease early and late radiation side effects.

Association between the cardiac contact distance and the maximum dose at the left anterior descending coronary artery in post mastectomized patients.

The clinical information on the relationship between the cardiac contact distance (CCD), the maximum dose (Dmax) delivered to the left anterior descending (LAD) coronary artery and the mean heart dose has mostly focused on patients with breast-conserving surgery (BCS), being scarce in postmastectomy patients. The aim of this study is to determine the association between the CCD and the Dmax delivered to the LAD. The secondary objective was to evaluate the dosimetric results of comparing three-dimensional conformal radiotherapy (3D-CRT) to intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques for post mastectomized breast cancer patients with irradiation to the left chest wall. 53 cases of women who received adjuvant standard fractionated postmastectomy radiotherapy (PMRT) were used. Three types of plans were created for each patient: 3D-CRT, seven equidistant IMRT fields, and four partial VMAT arcs. Correlations were evaluated using Pearson's correlation coefficient. Plans made with IMRT and VMAT showed improved homogeneity and conformity. Associations between CCD and Dmax to LAD were positive for all three plan types. Compared to 3D-CRT, the modulated intensity plans obtained better dose homogeneity and conformity to the target volume. The LAD and heart doses were significantly lower for IMRT and VMAT plans. The CCD can be used as a predictor of the maximum and mean doses of the LAD. Modulated intensity techniques allow for better dose distribution and dose reduction to the heart and LAD.

Investigating the number of radiation fields in intensity-modulated radiotherapy plans of optic nerve sheath meningioma patients using dose gradient index

Purpose: In optic nerve radiotherapy, vital organs are very close to the target volume, they are highly sensitive to radiation and have low dose tolerance. In this regard, evaluating dose fall-off steepness around the target volume is required to assess various intensity-modulated radiation therapy (IMRT) plans in the treatment of the optic nerve sheath meningioma (ONSM) patients. Materials and Methods: Thirteen ONSM patients were analyzed with three IMRT techniques, including three (IMRT-3F), five (IMRT-5F), and seven fields (IMRT-7F). These plans were studied using Dmean, Dmax, D2%, D98%, V100%, uniformity index (UI), homogeneity index (HI), conformity index (CI), and specifically the dose gradient indices (DGIs). Results: The values of Dmax and Dmean for IMRT-3F, IMRT-5F and IMRT-7F were (5637.42 ± 57.08, 5322.84 ± 83.86), (5670.51 ± 67.87, 5383.00 ± 58.45), and (5692.99 ± 31.65, 5405.72 ± 51.73), respectively, which were increased with increment in the number of IMRT fields from 3 to 7. The UI and HI indices were significantly different between IMRT-3F and IMRT-7F (p = 0.010 and p = 0.005, respectively), and CI was close to the ideal value (0.99 ± 0.01) in IMRT-7F. The significant findings of the dose gradient indices represented smaller values in IMRT-7F, which led to a faster dose fall-off, particularly at the 70%-85% isodose levels around the target. Conclusion: Increasing the number of radiation fields in IMRT treatment plans of ONSM patients had a considerable difference in both the dosimetric parameters of the target volume and at-risk organs, as well as the dose gradient indices. Overall, IMRT-7F could be considered as a preferred technique in the treatment of this meningioma.

Comparison of intensity-modulated radiotherapy with the 5-field technique, helical tomotherapy and volumetric modulated arc therapy for localized prostate cancer.

The outcomes of three methods of intensity-modulated radiation therapy (IMRT) for localized prostate cancer were evaluated. Between 2010 and 2018, 308 D’Amico intermediate- or high-risk patients were treated with 2.2 Gy daily fractions to a total dose of 74.8 Gy in combination with hormonal therapy. Overall, 165 patients were treated with 5-field IMRT using a sliding window technique, 66 were then treated with helical tomotherapy and 77 were treated with volumetric modulated arc therapy (VMAT). The median age of patients was 71 years. The median follow-up period was 75 months. Five-year overall survival (OS) and biochemical or clinical failure-free survival (FFS) rates were 95.5 and 91.6% in the 5-field IMRT group, 95.1 and 90.3% in the tomotherapy group and 93.0 and 88.6% in the VMAT group, respectively, with no significant differences among the three groups. The 5-year cumulative incidence of late grade ≥2 genitourinary and gastrointestinal toxicities were 7.3 and 6.2%, respectively, for all patients. Late grade ≥2 gastrointestinal toxicities were less frequent in patients undergoing VMAT (0%) than in patients undergoing 5-field IMRT (7.3%) and those undergoing tomotherapy (11%) (P = 0.025), and this finding appeared to be correlated with the better rectal DVH parameters in patients undergoing VMAT. Other toxicities did not differ significantly among the three groups, although bladder dose-volume parameters were slightly worse in the tomotherapy group than in the other groups. Despite differences in the IMRT delivery methods, X-ray energies and daily registration methods, all modalities may be used as IMRT for localized prostate cancer.

Evaluation of Plan Robustness Using Hybrid Intensity-Modulated Radiotherapy (IMRT) and Volumetric Arc Modulation Radiotherapy (VMAT) for Left-Sided Breast Cancer.

Purpose: We aim to evaluate the robustness of multi-field IMRT and VMAT plans to target motion for left-sided BC radiotherapy. Methods: The 7-field hybrid IMRT (7F-H-IMRT) and 2-arc VMAT (2A-VMAT) plans were generated for ten left-sided BC patients. Shifts of 3 mm, 5 mm, and 10 mm in six directions were introduced and the perturbed dose distributions were recalculated. The dose differences (∆D) of the original plan and perturbed plan corresponded to the plan robustness for the structure. Results: Higher ∆D98%, ∆D95%, and ∆Dmean of CTV were observed in 2A-VMAT plans, which induced higher tumor control probability reductions. A higher ∆Dmean of CTV Boost was found in 7F-H-IMRT plans despite lower ∆D98% and ∆D95%. Shifts in the S-I direction exerted the largest effect on CTV and CTV Boost. Regarding OARs, shifts in R, P, and I directions contributed to increasing the received dose. The 2A-VMAT plans performed better dose sparing, but had a higher robustness in a high-dose volume of the left lung and heart. The 2A-VMAT plans decreased the max dose of LAD but exhibited lower robustness. Conclusion: The 2A-VMAT plans showed higher sensitivity to position deviation. Shifts in the S-I direction exerted the largest effect for CTV and CTV Boost.

Skin Dosimetric Comparison of 3DCRT and IMRT Planning for Post-Mastectomy Breast Radiotherapy

Breast cancer is the most common cancer for incidence and mortality among females globally and in Indonesia. Mastectomy is still the most common surgery for female breast cancer in Indonesia. After the mastectomy, several patients will receive a whole breast radiotherapy session. About 68.75 % of breast cancer patients in the radiotherapy department at Lavalette Hospital during 2019 had undergone the mastectomy. Radiotherapy treatment for breast cancer can be delivered using Intensity Modulated Radiotherapy (IMRT) or 3D-Conformal Radiotherapy (3DCRT) technique. This study is aimed to compare the skin dosimetric between IMRT and 3DCRT for post-mastectomy breast radiotherapy. Left-sided breast cancer patients who underwent radiotherapy at Lavalette Hospital during 2019 were included in this study, and 15 patients were selected. All patients received 50 Gy in 25 fractions over 5 weeks using 6 MV photons. The planning target volume (PTV) and organ at risk (OAR) were delineated. Skin with 3 mm thickness along PTV was also contoured for evaluating the dose delivered to the skin. The treatment planning was conducted using 3DCRT and 5 fields IMRT planning. The plans were optimized for at least 95 % of the prescribed dose to cover 95 % volume of the PTV. The mean dose and maximum dose were used for evaluating and comparing each plan. The skin’s mean dose from 3DCRT planning was 24.65 ± 4.12 Gy and 22.85 ± 3.68 Gy ( p = 0.002) for IMRT planning. Meanwhile, skin maximum doses were 54.15 ± 0.68 Gy and 53.89 ± 1.05 Gy ( p = 0.001) respectively for 3DCRT and IMRT planning. These results showed that IMRT offered a lower dose to the skin and a better skin-sparing effect than 3DCRT. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";}

Second cancer risk in childhood cancer survivors treated with intensity-modulated radiation therapy: An updated analysis of more than 10years of follow-up.

It is unclear how intensity-modulated radiation therapy (IMRT) impacts long-term risk of second malignant neoplasms (SMNs) in childhood cancer patients. Patients aged ≤21years treated with IMRT between 1998 and 2009 and who survived ≥5years after IMRT were included. SMN site in relation to isodose level (IDL) of IMRT was evaluated. Standardized incidence ratios (SIR) and excess absolute risks (EAR) were calculated. Cumulative incidences were estimated with death as a competing risk. Three-hundred twenty-five patients were included with median follow-up of 11.2years from IMRT (interquartile range: 9.4-14.0) among patients alive at the end of follow-up. Two hundred (62%) patients had ≥10years of follow-up and 284 (87%) patients were alive at the time of analysis. Fifteen patients developed SMNs (11 solid, four hematologic). Median time from IMRT to solid SMN was 11.0years (range: 6.8-19.2) with 10- and 15-year cumulative incidences 1.8% (95% CI: 0.7-3.9) and 3.5% (95% CI: 1.4-7.5), respectively; SIR was 13.7 (95% CI: 6.9-24.6) and EAR was 2.8 per 1000person-years (95% CI: 1.0-4.6). Eight solid SMNs developed within the IMRT field (100% IDL [n = 5], 80% IDL [n = 1], 50% IDL [n = 1], 40% IDL [n = 1]), one within the 70%-80% IDL of a conventional field, one was out-of-field, and one could not be determined. With median follow-up of >10years, many solid SMNs after IMRT in childhood cancer survivors develop in the high-dose region. These data serve as a foundation for comparison with other modalities of radiation treatment (e.g., proton therapy).

Investigation of 2D radiophotoluminescence films in radiotherapy: Multileaf collimator Quality Assurance and small field dosimetry

In radiotherapy, accurate dose determination and precise dose delivery to the tumor are directly associated with better treatment outcomes, such as better tumor control and lower post treatment complications. Challenges in Quality Assurance (QA) are a.o. (1) the varying amounts of primary and secondary scattered photons, the varying gantry angles and the energy heterogeneity and (2) the small field sizes used in Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT).As alternative to the commonly used GafChromic™ EBT films, radiophotoluminescence (RPL) films gained attention for high resolution 2D dosimetry in radiotherapy thanks to their insensitivity to ambient light, reusability, absence of fading and the few image corrections needed.In this work we characterize the response of improved Al2O3:C,Mg RPL films in a clinical 6 MV beam. Film response was evaluated in terms of uniformity, dose response, minimum detectable dose (MDD), small field dosimetry and its performance was evaluated for multileaf collimator (MLC) QA tests.The new films showed linear dose response up to 8 Gy, followed by supralinear response for higher doses up to 24 % at 20 Gy. QA checks for the MLC, including the chair and the alternating leaves, were compared with calculations from the treatment planning system (TPS) and showed an agreement within 5% for alternating leaves and a deviation in Full Width Half Maximum (FWHM) below 1.5 % for the chair test. The maximum FWHM discrepancy between RPL film results and reference data (diode) for small field sizes (30 × 30, 20 × 20, 10 × 10, 8 × 8, 6 × 6 mm2) was 1.9 %. Notwithstanding the variations in dose response, the studied films exhibit overall good agreement with reference data and demonstrate potential for QA in IMRT and small field radiotherapy