Which radiotherapy technique is better for neoadjuvant treatment of rectal cancer: A dosimetric comparison

Locoregional irradiation including internal mammary nodal region for left-sided breast cancer after breast conserving surgery: Dosimetric evaluation of 4 techniques

Purpose: To investigate the feasibility of volumetric modulated arc therapy (VMAT) for post-mastectomy radiotherapy (PMRT) and to compare dual-arc VMAT treatment plans to helical tomotherapy (HT) plans on the basis of dosimetric quality, radiobiological calculations and delivery efficiency. Methods: Dual-arc VMAT and HT treatment plans were created for fifteen patients previously treated at our clinic. Planning target volumes (PTV) included the chest wall and regional lymph nodes. The following metrics were used to compare treatment plans for each patient: dose homogeneity index (DHI) and conformity index (CI); coverage of the PTV; dose to organs at risk (OAR); tumor control probability (TCP), normal tissue complication probability (NTCP) and secondary cancer complication probability (SCCP); and treatment delivery time. Differences between treatment plans were tested for significance using the paired Student’s t-test. Results: Both modalities produced clinically acceptable PMRT plans. VMAT plans showed better CI (p < 0.01) and better OAR sparing at low doses than HT plans. For example, VMAT plans showed a 26% (p < 0.01) and 9% (p < 0.01) decrease in V5Gy in the lungs and heart respectively. On the other hand, HT plans showed better DHI (p < 0.01) and PTV coverage (p < 0.01). HT plans also showed better sparing at higher doses for some OARs, including 8% (p < 0.01) and 9% (p < 0.01) lower maximum doses to the lungs and heart, respectively. Both modalities achieved nearly 100% tumor control and approximately 1% NTCP in the lungs and heart, with VMAT showing lower SCCP (p < 0.01). VMAT plans also required 66.2% less time to deliver. Conclusion: Both VMAT and HT provide acceptable treatment plans for PMRT. Our study showed that VMAT — in addition to being significantly faster — achieved better CI and low-dose OAR sparing while HT achieved better DHI.

To compare dosimetric data for the planning target volume (PTV) and organs at risk (OARs) between 3-dimensional conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy [1]. The dosimetric data for 15 gastric cancer patients treated with 3DCRT, VMAT, or HT techniques were used. Cumulative dosimetric parameters, homogeneity index (HI), and conformal index (CI) were compared for the PTV and OARs. The average maximum doses of PTV were significantly higher in VMAT plans than in 3DCRT (p=0.04) and HT (p=0.02) plans, whereas minimum dose values were significantly lower in 3DCRT plans compared with VMAT (p<0.001) and HT (p=0.02) plans. Liver mean dose (D mean) and D mean values for both kidneys were significantly lower in HT plans than in 3DCRT and VMAT plans. The doses in high dose regions (V30-V45) using 3DCRT plans were significantly higher compared to both VMAT and HT plans. The bowel V5-V30 and V45 was significantly less in HT plans compared to VMAT plans. There were no significant differences in dose sparing of the spinal cord. The HT plans reduced the maximum dose applied to the target and improved the conformality and homogeneity of radiation, while providing sufficient PTV coverage.

PurposeTo compare the dosimetry and biological risk of volumetric modulated arc therapy (VMAT), helical tomotherapy (HT) and cyberKnife (CK) in the treatment of lung oligometastases.Methods and materialsThis retrospective study included a cohort of 21 lung oligometastasis patients, each with 2 or 3 lesions, who had previously undergone stereotactic body radiation therapy (SBRT). VMAT, HT and CK plans were made for each patient. The dose distribution of planning target volume (PTV) and organs at risk (OARs) were evaluated. Three biological risks were evaluated, namely radiation pneumonitis (RP), coronary artery disease (CAD) and congestive heart failure (CHF). Monitor Units (MUs) and beam-on-time were also recorded.ResultsAll techniques were able to produce clinically deliverable plans. The expected biological risks for VMAT plans, CK plans, and HT plans were 6.69%, 5.05%, 5.88% for RP, 1.20%, 1.15%, and 1.17% for CAD, 1.26%, 1.19%, and 1.22% for CHF. The expected risks of RP were slightly lower in CK plans compared to VMAT and HT plans (p < 0.001), with VMAT plans showing the highest expected risks. For central lung cancer, the expected CAD risks of CK and HT plans were lower than those of VMAT plans (p < 0.05). The delivery efficiency of VMAT plans was significantly higher than that of CK plans and HT plans.ConclusionsAll three techniques, VMAT, HT, and CK, meet the therapeutic requirements for target coverage and dose constraints for OARs. Although there are statistical differences, the difference between the expected risk values of RP and CAD is very small, so the clinical manifestations may not show differences.

Novel hybrid treatment planning approach for irradiation a pediatric craniospinal axis

To investigate the feasibility of volumetric modulated arc therapy (VMAT) for post-mastectomy radiotherapy (PMRT) and to compare dual- arc VMAT treatment plans to helical tomotherapy (HT) plans on the basis of dosimetric quality, radiobiological calculations and delivery efficiency. Dual-arc VMAT and HT treatment plans were created for fifteen patients previously treated at our clinic. Planning target volumes (PTV) included the chest wall (CW) and regional lymph nodes. The following metrics were used to compare treatment plans for each patient: dose homogeneity index (DHI) and conformity index (CI); coverage of the PTV; dose to organs at risk (OAR); tumor control probability (TCP), normal tissue complication probability (NTCP) and secondary cancer complication probability (SCCP); and treatment delivery time. Differences between treatment plans were tested for significance using the paired Student's t-test. Both modalities produced clinically acceptable PMRT plans. VMAT plans showed better CI (p < 0.01), and better OAR sparing at low doses than HT plans. For example, VMAT plans showed a 26% (p < 0.01) and 9% (p < 0.01) decrease in V5Gy in the lungs and heart respectively. On the other hand, HT plans showed better DHI (p < 0.01) and PTV coverage (p < 0.01). HT plans also showed slightly better OAR sparing at higher doses, including 8% (p < 0.01) and 9% (p < 0.01) lower maximum doses to the lungs and heart, respectively. Both modalities achieved nearly 100% tumor control and approximately 1% NTCP in the lungs and heart, with VMAT showing lower SCCP (p < 0.01). VMAT plans also required 66.2% less time to deliver. Both VMAT and HT are suitable treatment options for PMRT. Our study showed that VMAT"'in addition to being significantly faster'"achieved better CI and low dose OAR sparing while HT achieved better DHI. This work was supported in part by a research support from Elekta, Ltd. However, Elekta, Ltd., did not participate in the study design; in the collection, analysis, and interpretation of data; in the writing of the manuscript; or in the decision to submit.

Dosimetric comparison of helical tomotherapy, volumetric-modulated arc therapy, intensity-modulated radiotherapy, and field-in-field technique for synchronous bilateral breast cancer

This study aimed to discuss the dosimetric advantages of helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) technology in hippocampal avoidance whole-brain radiotherapy and provide references for clinical selection of ideal radiotherapy technology. A total of 20 patients with hippocampal avoidance whole-brain radiotherapy were chosen randomly. Computed tomography (CT) and MRI scanning images were input into the treatment planning system (TPS). After the CT and enhanced magnetic resonance T1 weighted images were fused and registered, the same radiation therapy physician was invited to outline the tumor target volume. PTV-HS refers to the whole brain subtracted by 5mm outward expansion of the hippocampus (HP). The prescribed dose was 30Gy/10 fractions. HT and VMAT plans were designed for each patient in accordance with PTV. Under the premise that the 95% isodose curve covers the PTV, dose-volume histogram was applied to evaluate the PTV, conformal index (CI), heterogeneity index (HI), maximum dose (Dmax), mean dose (Dmean), minimum dose (Dmin) and absorbed doses of organs at risk (OARs) in HT and VMAT plans. Paired t-test was performed to compare the differences between two radiation therapy plans, and p < 0.05 was considered statistically significant. These two plans had no significant difference in PTV-HS (max, min, and mean). However, the HI and CI of the HT plan were significantly better than those of the VMAT plan, showing statistically significant difference (p<0.05). The HT plan was significantly superior to the VMAT plan in terms of the Dmax, Dmin, and Dmean of HP, left and right eye lens, left and right eye, and spinal cord, showing statistically significant difference (p<0.05). The HT plan was also better than the VMAT plan in terms of the Dmax of the left optic nerve. However, the two plans showed no obvious differences in terms of the absorbed doses of the right optic nerve and brainstem, without statistical significance. Compared with the VMAT plan of hippocampal avoidance, HT technology has significant dosimetric advantages. HT plans significantly decreased the radiation dose and radiation volume of OARs surrounding the target area (e.g., surrounding eye lens and eye, especially hippocampal avoidance area) while increasing the CI and HI of PTV dose in whole brain radiotherapy (WBRT) greatly, thus enabling the decrease in the incidence rate of radioactive nerve function impairment.

From organ at risk to target organ: Dosimetric comparison of myocardial stereotactic ablative body radiotherapy between helical tomotherapy and volumetric arc therapy for refractory ventricular tachycardia.

Currently, radiotherapy treatment plan acceptance is based primarily on dosimetric performance measures. However, use of radiobiological analysis to assess benefit in terms of tumor control and harm in terms of injury to normal tissues can be advantageous. For pediatric craniospinal axis irradiation (CSI) patients, in particular, knowing the technique that will optimize the probabilities of benefit versus injury can lead to better long‐term outcomes. Twenty‐four CSI pediatric patients (median age 10) were retrospectively planned with three techniques: three‐dimensional conformal radiation therapy (3D CRT), volumetric‐modulated arc therapy (VMAT), and helical tomotherapy (HT). VMAT plans consisted of one superior and one inferior full arc, and tomotherapy plans were created using a 5.02 cm field width and helical pitch of 0.287. Each plan was normalized to 95% of target volume (whole brain and spinal cord) receiving prescription dose 23.4 Gy in 13 fractions. Using an in‐house MATLAB code and DVH data from each plan, the three techniques were evaluated based on biologically effective uniform dose (D¯¯), the complication‐free tumor control probability (P+), and the width of the therapeutically beneficial range. Overall, 3D CRT and VMAT plans had similar values of D¯¯ (24.1 and 24.2 Gy), while HT had a D¯¯ slightly lower (23.6 Gy). The average values of the P+ index were 64.6, 67.4, and 56.6% for 3D CRT, VMAT, and HT plans, respectively, with the VMAT plans having a statistically significant increase in P+. Optimal values of D¯¯ were 28.4, 33.0, and 31.9 Gy for 3D CRT, VMAT, and HT plans, respectively. Although P+ values that correspond to the initial dose prescription were lower for HT, after optimizing the D¯¯ prescription level, the optimal P+ became 94.1, 99.5, and 99.6% for 3D CRT, VMAT, and HT, respectively, with the VMAT and HT plans having statistically significant increases in P+. If the optimal dose level is prescribed using a radiobiological evaluation method, as opposed to a purely dosimetric one, the two IMRT techniques, VMAT and HT, will yield largest overall benefit to CSI patients by maximizing tumor control and limiting normal tissue injury. Using VMAT or HT may provide these pediatric patients with better long‐term outcomes after radiotherapy.PACS number: 87.55.dk

Background: Synchronous bilateral breast cancer (SBBC) is rare. The purpose of this study was to compare the dosimetric differences in intensity-modulated radiation therapy (IMRT), volumetric-modulated arc therapy (VMAT), helical tomotherapy (HT), and intensity-modulated proton therapy (IMPT) to find an optimal radiotherapy technique for bilateral breast cancer radiotherapy.Methods: For 11 patients who received synchronous bilateral whole-breast irradiation without local lymph nodal regions, six plans were designed for each patient: IMRT with a single isocenter (IMRT-ISO1), IMRT with two isocenters (IMRT-ISO2), VMAT with a single isocenter (VMAT-ISO1), VMAT with two isocenters (VMAT-ISO2), HT, and IMPT. The differences between the single- and dual-isocentric plans for IMRT and VMAT were compared, and the plan with the better quality was selected for further dosimetric comparisons with IMPT and HT. The plan aimed for a target coverage of at least 95% with the prescription dose of 50 Gy [relative biological effectiveness (RBE)] while minimizing the dose of organs at risk (OARs).Results: IMRT-ISO1 and VMAT-ISO2 plans were adopted for further dosimetric comparisons because of the reduced dose of the heart and/or lungs compared to IMRT-ISO2 and VMAT-ISO1 plans. The dose coverage of the planning target volume (PTV) was significantly higher in IMPT plans than that in all other plans. VMAT and IMPT plans showed the best conformity, whereas IMRT plans showed the worst conformity. Compared to IMRT and VMAT plans, IMPT and HT plans achieved significantly higher dose homogeneity. IMPT plans reduced the mean dose and low dose volume (V5, V10, and V20) of the heart, left anterior descending artery (LAD), and left ventricle (LV). In high-dose volumes of the heart and cardiac substructures, the IMPT, VMAT, and HT techniques showed similar advantages, and IMRT plans increased the values more than other techniques. IMPT plans had the maximal lung and normal tissue sparing but increased the skin dose compared to IMRT and VMAT plans.Conclusions: IMPT plans improve both the target coverage and the OARs sparing, especially for the heart, cardiac substructures (LAD and LV), lungs and normal tissue, in synchronous bilateral breast radiotherapy. VMAT and HT could be selected as suboptimal techniques for SBBC patients.

Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients

Comparative evaluation of treatment plan quality for a prototype biology-guided radiotherapy system in the treatment of nasopharyngeal carcinoma

Aim: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.

The aim of this study was to compare lateral photon–electron (LPE), helical tomotherapy (HT), and volumetric-modulated arc therapy (VMAT) plans for total scalp irradiation. We selected a single adult model case and compared the dosimetric results for the three plans. All plans mainly used 6-MV photon beams, and the prescription dose was 60 Gy in 30 fractions. First, we compared the LPE, HT and VMAT plans, with all plans including a 1-cm bolus. We also compared HT plans with and without the bolus. The conformity indices for LPE, HT and VMAT were 1.73, 1.35 and 1.49, respectively. The HT plan showed the best conformity and the LPE plan showed the worst. However, the plans had similar homogeneity indexes. The dose to the hippocampus was the highest in the VMAT plan, with a mean of 6.7 Gy, compared with 3.5 Gy in the LPE plan and 4.8 Gy in the HT plan. The doses to the optical structures were all within the clinically acceptable range. The beam-on time and monitor units were highest in the HT plan. The HT plans with and without a bolus showed similar target coverage and organ-at-risk (OAR) sparing. The HT plan showed the best target coverage and conformity, with low doses to the brain and hippocampus. This plan also had the advantage of not necessarily requiring a bolus. Although the VMAT plan showed better conformity than the LPE plan and acceptable OAR sparing, the dose to the hippocampus should be considered when high doses are prescribed.