3DCRT Plans Research Articles

Immobilization-assisted abdominal deep inspiration breath-hold in post-mastectomy radiotherapy of left-sided breast cancer with internal mammary chain coverage

Whether to prophylactically irradiate the ipsilateral internal mammary chain (IMC) in post-mastectomy radiotherapy (PMRT) remains controversial because of equivocal clinical benefits against the added toxicities. Our previous study revealed that the cardiac dose was decreased during left-sided breast radiotherapy with abdominal deep inspiration breath-hold (aDIBH) as compared with free-breathing (FB) and thoracic deep inspiration breath-hold (tDIBH). Here we present the dosimetric advantage of aDIBH for patients undergoing PMRT with IMC coverage. We prospectively analyzed 19 patients with left-sided breast cancer who underwent PMRT. Patients underwent computed tomography (CT) simulation under both free-breathing (FB) and aDIBH. The heart, left anterior descending coronary artery (LAD), lungs, and the contralateral breast was defined as organs at risk (OARs). Three-dimensional conformal radiation therapy (3D-CRT), inverse planning intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) were used to calculate the doses received by both the planning target volume (PTV) and OARs, which were compared using the Wilcoxon signed-rank test. Compared with FB, the Dmean of the heart and LAD were respectively reduced by 3.5 Gy (P<0.003) and 8.9 Gy (P<0.001) in 3D-CRT, 2.6 Gy (P<0.001), and 7.8 Gy (P=0.001) in IMRT, 1.5 Gy (P<0.001) and 4.5 Gy (P=0.001) in VMAT plans under aDIBH. Among all these plans, the Dmean of the heart was lowest in aDIBH IMRT and 1.3 Gy lower than in aDIBH VMAT (P=0.002). aDIBH IMRT also resulted in a significantly reduced dose to the ipsilateral lung than plans under FB (P<0.05). Dmean and V5 to the contralateral lung and breast were higher in VMAT plans (P<0.05). Using an immobilization-assisted aDIBH technique, radiation doses to the heart can be kept at reasonably low levels even if IMC is included in the clinical target volume (CTV). Among 3D-CRT, IMRT, and VMAT plans, IMRT plus aDIBH results in the best heart-sparing effect. We recommend that the aDIBH technique be routinely applied in suitable patients if the IMC is irradiated.

Predictors of heart and lung dose in left-sided breast cancer treated with VMAT relative to 3D-CRT: A retrospective study.

BackgroundBefore generating radiotherapy plans for breast cancer patients, the choice of plan techniques (three-dimensional conformal radiation therapy (3D-CRT) and volumetric modulated arc therapy (VMAT)) should be made. This study investigated the performance of two geometric indices in aiding the choice of 3D-CRT and VMAT plans in women undergoing left-sided whole breast radiotherapy.Materials and methods119 patients, previously treated with left-sided breast radiotherapy (61 3D-CRT treatments and 58 VMAT treatments) from a single institution, were retrospectively studied. Two geometric indices, which were cardiac junction (CJ) index and pulmonary junction (PJ) index, were defined and the relationship between these indices and dose of organs at risk (OARs) were evaluated. Two-tailed Student’s t-test was performed to compare patient characteristics between 3D-CRT and VMAT. Linear regressions were calculated to investigate the association between geometric indices and absorbed dose of heart and left lung, including mean dose of heart (MHD), V5, V30 of heart, and mean dose of left lung (MLLD), V5, V10, V20, V30, V40 of left lung.ResultsThe CJ index was strongly correlated with the MHD in 3D-CRT group and VMAT group. The linear regression formulas were MHD = 4826.59 ×CJ Index+310.48 (R = 0.857, F = 163.77, P = 0.000) in 3D-CRT plans and MHD = 1789.29×CJ Index+437.50 (R = 0.45, F = 14.23, P = 0.000) in VMAT plans. The intersection of the two formulas was CJ index = 4.2% and MHD = 512.33 cGy. The PJ index demonstrated a strongly positive correlation with MLLD in 3D-CRT group and VMAT group as well. The linear regression formulas were MLLD = 2879.54×PJ Index+999.79 (R = 0.697, F = 55.86, P = 0.000) in 3D-CRT plans and MLLD = 1411.79×PJ Index+1091.88 (R = 0.676, F = 47.11, P = 0.000) in VMAT plans, the intersection of the two formulas was PJ index = 6.3% and MLLD = 1180.46 cGy.ConclusionsCJ index and PJ index could be used as a practical tool to select 3D-CRT or VMAT before generating plans. We recommend that VMAT plan is preferable when CJ index is greater than 4.2% and/or PJ index is greater than 14.6%, while 3D-CRT plan is the first choice in the opposite.

Dosimetric study on middle ear with three whole-brain radiotherapy techniques

Objective This study aims to compare the advantages and disadvantages of the three techniques in improving the target volume dose and protecting the auris media cavity and eustachian tube isthmus region by investigating the dosimetric differences of three whole-brain radiotherapy techniques. Methods Thirty patients with whole brain metastases were randomly selected to design fixed field intensity modulated radiotherapy (ff-IMRT) plan, volumetric arc modulated therapy (VMAT) and three-dimensional conformai radiotherapy (3DCRT) plan, and to meet a 95% PTV prescription dose (40 Gy). The dosimetric parameters and monitor units of the target volume and organ at risk (OAR) in the three groups of treatment plans were compared and analyzed. Results The Conformity Index ( CI) of the ff-IMRT plan (0.93 ± 0.02) was better than the VMAT plan (0.89 ± 0.01) and the 3DCRT plan (0.73 ± 0.03), respectively, and the difference was statistically significant ( P < 0.05). The Homogeneity Index ( HI) of the three plans were ff-IMRT (0.05 ± 0,01)、VMAT (0.08 ± 0.1) and 3DCRT (0.08 ± 0.01), respectively, and the difference was not statistically significant ( P > 0.05). The Gradient Index ( GT) were ff-IMRT (1.77 ± 0.1), VMAT (1.61 ± 0.07), 3DCRT (1.39 ± 0.08), respectively. The difference was statistically significant ( P< 0.05). The monitor units (MU) were ff-IMRT (1 551.97 ± 85.02), VMAT (303.7 ± 24.28) and 3DCRT (226.2 ± 2.5), respectively, the difference was statistically significant ( P < 0.05). The D max of the middle ear of the three plans were ff-IMRT (2 557.54 ± 477.39) cGy, VMAT (3 107.9 ± 362.28) cGy, 3DCRT (4 055.37 ± 71.45) cGy, respectively. The D max of the eustachian tube isthmus were ff-IMRT (2 425 ± 380.4) cGy, VMAT (2 902.4 ± 526.3) cGy and 3DCRT (3 862.7 ± 135.9) cGy, the difference were statistically significant ( P < 0.05). Conclusion In whole-brain radiotherapy, ff-IMRT and VMAT significantly reduced fhe dose of fhe bilateral middle ear cavities and eustachian tube isthmus compared with 3DCRT. VMAT is recommended for WBRT for reducing the number of monitor units significantly. 摘要： 目的 比较脑转移瘤全脑放射治疗 (WBRT)3 种放疗技术对中耳的剂量学差异, 对比 3 种放疗技术在改善靶区 剂量和保护中耳腔和咽鼓管峡部的优劣势。 方法 选取 2018 年 7 月 1 日一2019 年 8 月 1 日我院收治的 30 例脑转移 瘤患者, 分别设计固定野调强放疗 (ff-IMRT) 计划、容积旋转调强放疗 (VMAT) 和三维适形放疗 (3DCRT) 计划, 要求处 方剂量 (40 Gy) 覆盖 95% 的计划靶区 (PTV)。对比分析 3 组计划的靶区和危及器官剂量学参数、机器跳数等差异。 结果 ff-IMRT 计划的适形指数 (0.93 ± 0.02) 优于VMAT计划 (0.89 ± 0.01) 和 3DCRT 计划 (0.73 ± 0.03), 差异有统计 学意义 ( P < 0.05); ff-IMRT、VMAT 和 3DCRT 3 种计划的均匀指数分别为 (0.05 ± 0.01)、(0.08 ± 0.1)、(0.08 ± 0.01), 差异无统计学意义 ( P > 0.05); 梯度指数分别为 (1.77 ± 0.1)、(1.61 ± 0.07)、(1.39 ± 0.08), 差异有统计学意义 ( P < 0.05); 机器跳数分别为 (1 551.97 ± 85.05)、(303.7 ± 24.28)、(226.2 ± 2.5), 差异有统计学意义 ( P < 0.05)。ff-IMRT、VMAT 和 3DCRT 3 种计划中耳腔最大剂量点 ( D max) 分别为 ff-IMRT (2 557.54 ± 477.39) cGy、VMAT (3 107.9 ± 362.28) cGy、3DCRT (4 055.37 ± 71.45) cGy; 咽鼓管峡部 D max 分别为 ff-IMRT (2 425 ± 380.4) cGy、VMAT (2 902.4 ± 526.3) cGy、3DCRT (3 862.7 ± 135.9) cGy, 差异均有统计学意义 ( P < 0.05)。 结论 在全脑放射治疗中, ff-IMRT 和 VMAT 与 3DCRT 相比明显减少了双侧中耳腔和咽鼓管峡部的照射剂量; 而 VMAT 与 ff-IMRT 相比, 明显减少机器跳数、降低 了机器损耗, WBRT 时推荐使用 VMAT 技术。

Independent verification of treatment planning system calculations

Abstract Purpose According to the available international recommendations, at least one independent verification of the calculations of number of monitor unit (MU) is required for every patient treated by teleradiotherapy. The aim of this study was to estimate the differences of dose distributions calculated with two treatment planning systems: Eclipse (Varian) and Oncentra MasterPlan (Elekta). Materials and methods The analysis was performed for 280 three-dimensional conformal radiotherapy treatment (3D-CRT) plans with photon beams from Varian accelerators: CL 600C/D X6 MV (109 plans), CL 2300C/D X6 MV (43 plans), and CL 2300C/D X15 MV (128 plans). The mean doses in the planning target volume (PTV) and doses at the isocenter point obtained with Eclipse and Oncentra MasterPlan (OMP) were compared with Wilcoxon matched-pairs signed rank test. Additionally, the treatment planning system (TPS) calculations were compared with dosimetric measurements performed in the inhomogeneous phantom. Results Data were analysed for 6 MV plans and for 15 MV plans separately, independently of the treatment machine. The dose values calculated in Eclipse were significantly (p &lt;0.001) higher compared to calculations of OMP system. The average difference of the mean dose to PTV was (1.4 ± 1.0)% for X6 MV and (2.5 ± 0.6)% for X15 MV. Average dose disparities at the isocenter point were (1.3 ± 1.9)% and (2.1 ± 1.0)% for X6 MV and X15 MV beams, respectively. The largest differences were observed in lungs, air cavities, and bone structures. Moreover the variation in dosimetric measurements was less as compared to Eclipse calculations. Conclusions OMP calculations were introduced as the independent MU verification tool with the first action level range equal to 3.5%.

Risk for second bladder and rectal malignancies from cervical cancer irradiation.

The objective of this study was to estimate the risk of developing second malignancies to partially in‐field organs from volumetric modulated arc therapy (VMAT) of cervical cancer and to compare the above risks with those from the conventional three‐dimensional conformal radiotherapy (3D‐CRT). Seventeen consecutive patients with uterine cervix carcinoma were selected. VMAT and 3D‐CRT plans were generated with 6 and 10 MV photons, respectively. The prescribed tumor dose was 45 Gy given in 25 fractions. Differential dose‐volume histogram data from the treatment plans were obtained for the partially in‐field organs such as bladder and rectum. These data were used to estimate the patient‐specific lifetime attributable risk (LAR) for bladder and rectal cancer induction with a non‐linear model based on a mixture of plateau and bell‐shaped dose–response relationships. The estimated risks per 10000 people were compared with the baseline risks for unexposed population. The patient‐specific rectal cancer risk estimates from VMAT were significantly lower than those from 3D‐CRT (P = 0.0144). The LARs for developing bladder malignancies from VMAT were significantly high compared to those from conventional irradiation (P = 0.0003). The mean difference between the patient‐specific LARs for radiation‐induced bladder and rectal malignancies as derived from 3D‐CRT and VMAT plans was 6.6% and 2.0%, respectively. The average LAR for developing bladder and rectal malignant diseases due to VMAT was 9.2 × 10‐4 and 43.7 × 10‐4, respectively. The corresponding risks following 3D‐CRT were 8.6 × 10‐4 and 44.6 × 10‐4. These average risks showed that pelvic irradiation increases the baseline probability for cancer induction by 12.6‐19.1%. The differences in the second cancer risks associated with the VMAT and 3D‐CRT for cervical cancer were found to be small. Both treatment techniques resulted in considerable increased probabilities for developing bladder and rectal malignancies relative to those of unirradiated population.

Deep-inspirational breath-hold (DIBH) technique in left-sided breast cancer: various aspects of clinical utility

BackgroundStudying the clinical utility of deep-inspirational breath-hold (DIBH) in left breast cancer radiotherapy (RT) was aimed at focusing on dosimetry and feasibility aspects.MethodsIn this prospective trial all enrolled patients went through planning CT in supine position under both DIBH and free breathing (FB); in whole breast irradiation (WBI) cases prone CT was also taken. In 3-dimensional conformal radiotherapy (3DCRT) plans heart, left anterior descending coronary artery (LAD), ipsilateral lung and contralateral breast doses were analyzed. The acceptance of DIBH technique as reported by the patients and the staff was analyzed; post-RT side-effects including radiation lung changes (visual scores and lung density measurements) were collected.ResultsAmong 130 enrolled patients 26 were not suitable for the technique while in 16, heart or LAD dose constraints were not met in the DIBH plans. Among 54 and 34 patients receiving WBI and postmastectomy/nodal RT, respectively with DIBH, mean heart dose (MHD) was reduced to < 50%, the heart V25 Gy to < 20%, the LAD mean dose to < 40% and the LAD maximum dose to about 50% as compared to that under FB; the magnitude of benefit was related to the relative increase of the ipsilateral lung volume at DIBH. Nevertheless, heart and LAD dose differences (DIBH vs. FB) individually varied. Among the WBI cases at least one heart/LAD dose parameter was more favorable in the prone or in the supine FB plan in 15 and 4 cases, respectively; differences were numerically small. All DIBH patients completed the RT, inter-fraction repositioning accuracy and radiation side-effects were similar to that of other breast RT techniques. Both the patients and radiographers were satisfied with the technique.ConclusionsDIBH is an excellent heart sparing technique in breast RT, but about one-third of the patients do not benefit from that otherwise laborious procedure or benefit less than from an alternative method.Trial registration: retrospectively registered under ISRCTN14360721 (February 12, 2021)

Potential gains: Comparison of a mono-isocentric three-dimensional conformal radiotherapy (3D-CRT) planning technique to hybrid intensity-modulated radiotherapy (hIMRT) to the whole breast and supraclavicular fossa (SCF) region.

IntroductionUntil late 2018, standard of practice at the Northern Sydney Cancer Centre (NSCC) for breast and nodal treatment was a conformal mono‐isocentric technique. A planning study comparing an existing mono‐isocentric three‐dimensional conformal radiotherapy (3D‐CRT) planning technique to a hybrid intensity‐modulated radiotherapy (hIMRT) approach for the whole breast and supraclavicular fossa (SCF) region was undertaken with the aim to improve plan quality by improving dose conformity/homogeneity across target volumes and reducing hotspots outside the target.MethodsA cohort of 17 patients was retrospectively planned using the proposed hIMRT technique, keeping the same planning constraints as the original treated breast and SCF 3D‐CRT plan and normalising the 3D‐CRT plans to achieve minimum breast/SCF target coverage to compare organs at risk (OARs). Normal tissue index (NTI) and homogeneity index (HI) were compared for plan quality as well as for evaluating OARs.ResultsThe hIMRT technique showed statistically significant improvements in NTI and HI, as well as improvement in maximum brachial plexus and thyroid doses. There was a negligible increase in maximum oesophagus dose which could be improved if used in optimisation. Other OAR doses in the irradiated region were comparable to the 3D‐CRT plans, however maximum doses were reduced overall.ConclusionThe hIMRT planning technique maintained clinically acceptable doses to OARs and reduced normal tissue dose while maintaining equivalent dose coverage to breast and SCF planning target volumes with improved conformity and homogeneity. The reduction in maximum doses promotes a favourable toxicity profile, with potential benefit of improved long‐term cosmesis.

A Comparative Dosimetric Study for the Treatment of Left-Sided Breast Cancer using Three-Dimensional Conformal Deep Inspiration Breath-Hold and Free-Breathing Intensity-Modulated Radiotherapy Techniques

Introduction: Most women with left-sided breast cancer are at an increased risk of heartmorbidity and mortality from the adjuvant radiotherapy due to an increase in heart absorbed dose during radiotherapy treatment. This study aimed to compare free-breathing intensity-modulated radiotherapy (FB-IMRT) and three-dimensional conformal deep inspiration breath-hold (3DCRT-DIBH) techniques in terms of the cardiac dose. Material and Methods: In total, 15 women with left-sided breast cancer underwent FB and DIBH computed tomography (CT) scans in the same supine position. For DIBH CT, 3D-CRT plans were created using two opposing wedged tangential fields and for FB-CT, 4-5 IMRT optimized tangential fields were created. All plans were evaluated using the dose-volume histogram. The data were analyzed in SPSS software version 20 (IBM, IL). Results: The FB-IMRT plans were more homogeneous and had more dose coverage and fewer hotspots, than the 3DCRT-DIBH plans; however, the planning target volume V95% was clinically acceptable for both techniques. Furthermore, the 3DCRT-DIBH plans were much faster and require fewer monitor units. A significantly lower mean dose of heart, left lung, left anterior descending coronary artery, right lung, and V10% left lung were observed in 3DCRT-DIBH plans, compared to FB-IMRT plans. Moreover, FB-IMRT plans showed a significant further dose reduction in heart V25% and V30%. Conclusion: The majority of the patients with left-sided breast cancer who treated with the DIBH technique were getting sufficient benefits of radiotherapy, and DIBH was a comprehensive strategy for reducing cardiac doses during radiotherapy treatment.

Optimization of CT slice thickness in 3D-CRT and IMRT planning of low grade glioma

Optimization of CT slice thickness in 3D-CRT and IMRT planning of low grade glioma

Optimization of CT slice thickness in 3D-CRT and IMRT planning of low grade glioma

Optimization of CT slice thickness in 3D-CRT and IMRT planning of low grade glioma

Dosimetric analysis of Deep Inspiratory Breath-hold technique (DIBH) in left-sided breast cancer radiotherapy and evaluation of pre-treatment predictors of cardiac doses for guiding patient selection for DIBH

The risk of radiotherapy-associated cardiovascular disease has been a concern for decades in breast cancer survivors. The objective of our study is to evaluate the dosimetric benefit of Deep Inspiratory Breath-hold technique (DIBH) on organs-at-risk (OAR) sparing in left-sided breast cancer radiotherapy and to find out pre-treatment predictors of cardiac doses for guiding patient selection for DIBH. Pre-radiotherapy planning CT scans were done in Free Breathing (FB) and in DIBH [using Active Breathing Coordinator system (ABC™)] in 31 left sided breast cancer patients. 3DCRT plans were generated for both scans. Comparison of anatomical and dosimetric variables were done using paired t test and correlation was evaluated using Pearson correlation. Linear regression was used to get independent predictors of cardiac sparing and Receiver Operating Characteristic (ROC) curve analysis was done to find out the specific threshold of the predictors. There was a 39.15% reduction in mean heart dose in DIBH compared to FB (2.4 Gy vs 4.01 Gy) (p < 0.001), 19% reduction in maximum Left Anterior Descending (LAD) dose and a 9.9% reduction in ipsilateral lung mean dose (p = 0.036) with DIBH. A significant correlation was observed between reduction in Heart Volume in Field (HVIF) and Maximum Heart Depth (MHD) with reduction in mean heart dose. Reduction in HVIF (ΔHVIF) independently predicted cardiac sparing. DIBH leads to significant reduction in OAR doses and is suggested for all patients of left-sided breast cancer undergoing radiotherapy. However, HVIF and MHD predicted for cardiac sparing and threshold criteria of ΔHVIF and ΔMHD may be used by centres with high workload to select patients for DIBH.

Free breathing VMAT versus deep inspiration breath-hold 3D conformal radiation therapy for early stage left-sided breast cancer.

The purpose of the in silico study was to compare free breathing volumetric modulated arc therapy (VMAT) to standard deep inspiration breath‐hold (DIBH) three‐dimensional conformal radiotherapy (3DCRT) and determine whether the former is a viable option for elderly patients with left‐sided early stage breast cancer. Data from 22 patients with early‐stage left breast carcinoma requiring breast‐only radiation therapy were used for this planning study. The robustness of VMAT plans when using the free breathing method was compared to that of standard 3DCRT plans using the DIBH method. The endpoints for evaluation were the target dose coverage as well as doses to the organs‐at‐risk. The free breathing VMAT plans produced a significantly higher mean dose to the heart and right breast than the DIBH‐3DCRT plans. Free breathing VMAT plans resulted in significantly better target coverage than did 3DCRT using DIBH. The external volume that received more than 40 Gy was significantly smaller in the VMAT plans. Free breathing VMAT is a viable alternative to DIBH 3DCRT in elderly patients with a limited life expectancy and in subjects who are unable to perform DIBH. The choice of treatment should be individualized, and all relevant risks ought to be considered.

Comparing treatment plans for stomach cancer: three-dimensional conformal radiotherapy (3D-CRT), physical wedge-based conformal RT (WB-CRT) and intensity-modulated radiotherapy (IMRT)

AbstractObjective:The aim of this study was to find the optimal radiotherapy (RT) method using three-dimensional (3D) conformal RT (CRT), physical wedge-based CRT (WB-CRT) and dynamic intensity-modulated RT (D-IMRT) techniques for stomach cancer.Methods:Ten patients with gastric cancer were selected for this study. For each patient, three different treatment plans were generated. 3D-CRT, WB-CRT and IMRT plans were evaluated in terms of dosimetry. Treatment plans were compared with respect to the planning target volume and organs at risk (OARs) volumes including right and left kidney doses (V13, V20 and V28), heart mean and maximum doses, spinal cord maximum doses, dose homogeneity index, conformity index (CI), delivery time and the monitor unit counts for the treatment. Statistical analysis was performed using the SPSS (Statistical Package for the Social Sciences) v25.1 software (IBM Inc., Chicago, IL, USA).Results:In stomach plans, IMRT showed a significantly lower dose for the left and right kidneys than that of WB-CRT or 3D-CRT (p &lt; 0·05). Compared with WB-CRT or 3D-CRT, IMRT reduced the V28, V20, V13 and mean dose to bilateral kidneys (p &lt; 0·05). IMRT plans indicated better dosimetry for at the Dmean of the liver and heart. Concerning the calculated CI, values for IMRT plans gave significant results than other plans (p &lt; 0·05).Conclusions:IMRT plans provided better protection for the kidneys, liver, heart and spinal cord. For the treatment of stomach cancer, considering the dose to the OARs, IMRT appears to be the most superior technique.

Provider-Level Variation in Treatment Planning of Radiation Oncology Procedures in the United States.

Variation in the use of radiation oncology procedures and technologies is poorly characterized. We sought to identify associations between the treatment planning codes used to bill for radiotherapy procedures and the demographic characteristics of the radiation oncologists submitting them. The Physician and Other Supplier Public Use File was linked to the Physician Compare database by using the physician National Provider Identifier for the year 2016. Analysis was stratified by practice setting, considering both the freestanding non-facility-based (NFB) setting and the facility-based (FB) setting. Multivariable logistic regression was used to determine provider characteristics (gender, practice rurality, and years since graduation) that predicted for the use of 3D-conformal RT (3DCRT) planning, intensity-modulated RT (IMRT) planning, and brachytherapy planning in the Medicare population. Three thousand twenty-nine physicians were linked for analysis. In both the FB and NFB settings together, male gender predicted for decreased likelihood of 3DCRT planning (OR, 0.70, 95% CI, 0.62 to 0.80, P < .001) and increased likelihood of IMRT planning (OR, 1.35, 95% CI, 1.19 to 1.54, P < .001). Brachytherapy planning was also more likely with increasing years since medical school graduation (OR, 1.03, 95% CI, 1.01 to 1.04, P < .001) in the combined FB and NFB settings. These significant associations persisted when examining the NFB and FB settings individually. In both settings overall, brachytherapy planning was more likely in male providers (OR, 1.75, 95% CI, 1.10 to 2.76, P = .02) and also more likely for providers practicing in metropolitan regions compared with those practicing in rural areas (OR, 3.01, 95% CI, 1.23 to 7.39, P = .02). Male gender predicts for utilization of IMRT planning, whereas female gender predicts for utilization of 3DCRT planning. Future research is warranted to better understand the role that provider gender and rurality play in the selection of radiation planning techniques for Medicare patients.

Evaluation of DIBH and VMAT in Hypofractionated Radiotherapy for Left-Sided Breast Cancers After Breast-Conserving Surgery: A Planning Study.

Background: Dosimetric parameters of the planning target volume (PTV) and organs at risk (OARs) were compared among 3 different radiotherapy (RT) modalities in left breast cancer patients after breast-conserving surgery (BCS). Methods: Eleven patients with left breast cancer after BCS were enrolled and underwent CT simulation in the free breathing (FB) and deep inspiration breath-hold (DIBH) position. Three-dimensional conformal RT (3DCRT) and volumetric modulated arc therapy (VMAT) plans were generated for each patient in the DIBH positions. A 3DCRT plan was also created in the FB position. A dose-volume histogram (DVH) was used to analyze each evaluation index of PTV and OARs. The principal outcomes were PTV dose, heart dose, right breast dose, left anterior descending coronary artery (LADCA) dose, and left lung dose. Results: For 3DCRT plans, significant dose reductions were demonstrated in all evaluation parameters of the heart, LADCA, and left lung doses in the DIBH position compared with those in the FB position (P < 0.05). In the DIBH position, significant dose reductions were found in the heart and LADCA in VMAT plans compared to those in 3DCRT plans (P < 0.05). For the right breast, VMAT reduced Dmean significantly (0.32 Gy vs 0.08 Gy, P < 0.01). There were no significant differences between 3DCRT and VMAT plans for the left lung dose in the DIBH position. The indicators of PTV had no significant difference between the 3 plans. Conclusion: DIBH and VMAT could reduce dosimetric parameters of the OARs in left breast cancer patients after BCS. RT plans for left breast cancer after BCS can be optimized by DIBH and VMAT techniques to minimize radiation-induced toxicity.

Adjuvant radiotherapy for endometrial cancer in a renal transplant patient - a case report

Background: Treatment of locally advanced endometrial cancer in patients with transplanted pelvic kidney requires precautions because of its anatomical position next to target volumes. Case Presentation: We report a case of 42-year-old woman with a right renal transplant for 3 years diagnosed with endometrial cancer for which she underwent total abdominal hysterectomy with bilateral salpingo-oophorectomy and pelvic lymphadenectomy. Adjuvant Radiotherapy (RT) was planned through intensity modulated RT (IMRT) with 45 Gy in 25 fractions followed by vaginal brachytherapy (5 Gy × 2 sessions) . Planning with IMRT quantified a mean dose of 2 Gy and maximum dose of 10 Gy over the transplanted kidney. This dose was further reduced with a comparative plan of three-dimensional conformal RT (3DCRT), recording a mean dose of 1 Gy and maximum dose of 5 Gy to the transplanted kidney. 3DCRT plan was accepted and delivered. At 2-year follow-up, patient is disease free with normal renal function. Conclusion: In the presence of advanced techniques, 3DCRT is still a valid radiation technique to keep the critical organ dose under acceptable dose-volume constraints without compromising the target volume.

Suggested Template Plan for Forward Intensity Modulated Radiotherapy in Head and Neck Cancer Patients

Background: We aimed to achieve full tumor control during every fraction with head and neck cancer patients using 3DCRT treatment technique. Method: We divided 16 head and neck cancer patients into two groups to deliver radiotherapy doses of 66Gy and intensity modulated radiotherapy (IMRT) 70Gy. We applied 3DCRT plan as a forward IMRT plan for each patient with coplanar beams arrangement technique designed with angles of (0o, 60o, 90o, 180o (or around 175o and 185o), 270o and 300o).We assessed the plans according to DVHs and satisfactory dose distributions. Results: Based on the overall evaluation of the two groups (16 cases), we achieved an accepted dose distribution for PTVs and OARs dose; simulating IMRT inverse plans dose distribution. Conclusion: Using such a mono-isocenteric plan, we were able to achieve a perfect uniform dose distribution for PTVs up to 70Gy, while sparing critical organs. This template could be used in countries with no access to forward IMRT planning.

Dosimetric analysis of normal tissue toxicity in 3D conformal radiotherapy planning with fused PET-CT imaging in non-small cell lung carcinoma

Introduction: The prime modality for inoperable NSCLC is radiation therapy and or chemo-radiation and better results can be achieved by a higher dose of radiation. However dose escalation is difficult due to presence of critical and dose limiting sensitive structures in the vicinity of lung. Therefore success of radiotherapy in such tumors solely depends on the selective delivery of adequate dose to target with minimal irradiation of surrounding structures. The precision in target and normal tissue delineation needs to be achieved. So the aim of this study is to explore the possibility of using fused PET-CT images for accurate target and normal tissue delineation in 3D-conformal radiotherapy planning in patients of carcinoma lung (NSCLC) who are referred to us for radical radiotherapy. Materials and Methods: It’s a hospital based prospective study in which 14(n) cancer patients who had biopsy proven NSCLC and were referred to us for radical radiotherapy. After CT simulation and FDG-hybrid PET data sets were transferred to CMS planning system. The co-registration was done in Focal Pro using an auto fusion, 3D rotation and translation rigid body program, and the fiducial markers. The gross tumor volume (GTV), planning target volume (PTV) and normal tissue parameters were defined using the CT data and PET-CT data. 3D-CRT plans were generated for both CT data and PET-CT data sets and dosimetric analysis was done for same. Results: The mean age was 65 yrs, 78.5% (11) patients are male and 21.5 % (3) are female. The registration of fused images of PET with planning CT scan decreased the gross tumor volume (GTV) in 10 patients (71.42%), decreased volume in 4 patients (28.58%). The 3D-CRT planes were modified in 5patients (35%). CT-PET planning did not reduce the radiation fields in all patients. When all constraints of the lung, esophagus, and spinal cord were taken into account, normal tissue exposure was reduced with use of CT-PET. V20 decreased from 31.86% ± 4.17% to

Simple template-based optimization for pediatric total lymphoid irradiation (TLI) radiotherapy treatments

Total lymphoid irradiation (TLI) is used in the management of pediatric allogeneic hematopoietic stem cell transplantation (HSCT. This work aims to simplify the treatment planning process for TLI via a proposed template using the volumetric modulated arc therapy (VMAT) technique. Fifteen pediatric patients were planned, prescribed to 8 Gy in 4 fractions. Cost functions included in the template were the ones for the planning target volume (PTV), and conformality cost function (CCF) for the rest of the patient's volume. Conformity index (CI), homogeneity index (HI), conformation number (CN), gradient index (GI), integral dose, and doses to the organs at risk achieved with the template were reported. Cost function influence over various indexes was studied by Wilcoxon signed ranks test. Same 15 patients were planned with 3-dimensional conventional radiotherapy (3D-CRT) technique for comparison. Mean CI and HI were 1.33 and 0.13, respectively, which indicates good dose conformation and homogeneity. Mean CN and GI values were 0.69 and 4.51, respectively. Mean PTV coverage was reached (V100% > 95%). No correlation between the CCF and indexes values was found (p > 0.05). Doses to organs at risk (OARs) were as low as possible without losing PTV coverage. VMAT plan showed higher levels of conformation and similar homogeneity as 3D-CRT plans. Doses to OARs were inferior with VMAT except for the right kidney. The proposed template simplifies the planning of TLI treatments, and it is able to create acceptable plans with little modification in order to reduce doses to certain organs like the kidneys or the heart. VMAT technique showed higher conformation and lower doses to OAR compared to 3D-CRT.

Dosimetric comparison of different radiotherapy techniques for the treatment of Retinoblastoma

AbstractAim:This study aims to compare the dosimetric parameters among four different external beam radiotherapy techniques used for the treatment of retinoblastoma.Materials and methods:Computed tomography (CT) sets of five retinoblastoma patients who required radiotherapy to one globe were included. Four different plans were generated for each patient using three dimensional conformal radiotherapy (3DCRT), intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT) and VMAT using flattening filter free (VMAT-FFF) beam techniques. Plans were compared for target coverage and organs at risk (OARs) sparing.Results:The target coverage of planning target volume (PTV) for all the four modalities were clinically acceptable with a V95 of 95 ± 0%, 97·6 ± 1·87%, 99·3 ± 0·5% and 99·17 ± 0·45% for 3DCRT, IMRT, VMAT and VMAT-FFF respectively. The VMAT and IMRT plans had better target coverage than the 3DCRT plans (p = 0·001 and p = 0·07 respectively). IMRT and VMAT plans were also found superior to 3DCRT plans in terms of OAR sparing like brainstem, optic chiasm, brain (p &lt; 0·05). VMAT delivered significantly lower dose to the brainstem and contralateral optic nerve in comparison to IMRT. Use of VMAT-FFF beams did not show any benefit over VMAT in target coverage and OAR sparing.Conclusion:VMAT should be preferred over 3DCRT and IMRT for treatment of retinoblastoma owing to better target coverage and less dose to most of the OARs. However, IMRT and VMAT should be used with caution because of the increased low dose volumes to the OARs like contralateral lens and eyeball.