Evaluation of various head flexion angles in hippocampal-avoidance whole-brain radiotherapy using volumetric modulated arc therapy

Contralateral tissue sparing in lymph node-positive breast cancer radiotherapy with VMAT technique

The purpose of this study is to investigate the potential for reducing dose to the scalp, parotid glands, and external auditory canals using intensity-modulated radiation therapy (IMRT) or volumetrically modulated arc therapy (VMAT) to deliver whole brain radiation therapy (WBRT). Nine patients with brain metastases previously treated with standard opposed lateral (OL) WBRT were studied. Four new plans were created for each patient: (1) four-beam IMRT, (2) seven-beam IMRT, (3) 13-beam IMRT, and (4) VMAT (single arc technique). All plans were optimized to achieve equivalent planning target volume (PTV) coverage while minimizing dose to the scalp, parotid gland, and external ear. Each of the plans was then dosimetrically compared via multiple dose–volume histogram (DVH) parameters. All IMRT and VMAT plans significantly reduced dose to the scalp, ears, and parotid glands without increasing dose to other critical structures. Improved scalp sparing for low, intermediate, and high doses (V5, V10, V20, and V30), was achieved with the 4- and 13-beam IMRT plans. The 7-field plan reduced intermediate and high scalp doses (V10, V20, and V30) while only high doses (V20 and V30) were reduced with the VMAT plan. Depending on the DVH parameter, IMRT/VMAT reduced scalp dose between 10 % and 70 %, parotid gland dose by 3 % and 31 %, and external auditory canal dose by 2 % and 96 %. IMRT or VMAT is able to reduce dose to the scalp, parotid glands, and external auditory canal without sacrificing PTV coverage when compared to a standard OL treatment plan. Such improvement is promising and may decrease non-cognitive WBRT toxicities (e.g., alopecia, xerostomia, otitis), which could improve quality of life for patients receiving WBRT. Future planning will attempt to reduce cochlear dose to avoid hearing loss but will likely require PTV modification.

Improving Lung Stereotactic Body Radiation Therapy Dose Conformity Using a Simple Noncoplanar Volumetric Modulated Arc Therapy Technique.

Multiple brain metastases patients are typically treated by stereotactic radiosurgery (SRS) or whole brain radiation therapy (WBRT). In addition, there are advanced techniques for treating multiple brain metastases such as 3-dimensional Conformal Radiation Therapy (3D-CRT), Intensity Modulated Radiation Therapy (IMRT), and Volumetric Modulated Arc Therapy (VMAT). A new isocentric VMAT technique called HyperArc was developed for non-coplanar, it is an automated setting for couch angle and collimator angle. This study aims to compare the dosimetric effect for a single isocenter among Intensity Modulated Radiation Therapy, Volumetric Modulated Arc Therapy, and HyperArc for multiple brain metastases stereotactic radiosurgery. For 25 patients with multiple brain metastases (2-4 targets). IMRT, Coplanar VMAT (co-VMAT), Non-coplanar VMAT (non-co VMAT), and HyperArc plans with a prescription dose of 18 Gy in single-fraction were generated. All plans used 6 MV flattening filter-free energy. IMRT plans consisted of 9 coplanar fields. The co-VMAT plan used 2 full coplanar arcs, while non-co VMAT and HyperArc plans consisted of 1 full coplanar arc and 3 half arcs with non-coplanar planes at 45, 90, and 135 couch angles. The organs at risk (OARs) dose constraints at Dmax of the brainstem was 8 Gy, while Dmax of the eye lens, optic nerve, and optic chiasm should be less than 5 Gy. Paddick gradient index (GI), Paddick conformity index (CI), homogeneity index (HI), total number of monitor units, delivery time and normal brain tissue volume (V2-V16) were used to evaluate the plan quality. Showed that OAR doses were lower than the dose limits for all plans. HyperArc presented good results with the lowest GI (5.18± 1.15), and the highest CI (0.63±0.14) values compared with other techniques. For HI all techniques are hardly different (0.19±0.02). For the HyperArc the beam on time was significantly reduced from other techniques around 4 minutes. Also, MUs and the normal brain's moderate to low dose spreads (V2-V16) were reduced considerably in the HyperArc plan (5226.50±650.88, 10.08±3.84, respectively). Eventually, HyperArc plans led to a significant reduction in both the total number of monitor units and delivery time. We can conclude that the HyperArc plans provided a significantly better rapid dose falloff and higher conform the dose distribution to the targets with respect to the other plans. This is consistent with the computed reduction in V12 to the normal brain. Ultimately, HyperArc treatments were accomplished within around 4 minutes, signifying a noteworthy reduction in time compared to the other plans.

ObjectiveThis retrospective, exploratory study evaluated the dosimetric comparison and feasibility of simultaneous integrated boost (SIB) delivered with volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) in patients with locally advanced cervical cancer ineligible for brachytherapy (BRT).MethodsThis exploratory study involved dosimetric treatment planning based on data from 10 patients diagnosed with locally advanced cervical cancer. SIB plans delivering 77.5 Gy to the primary tumor and 45 Gy to elective regions in 25 fractions were generated using VMAT and HT techniques. SIB plans were created using the VMAT technique in the Monaco 5.51 treatment planning system (TPS) (Elekta, Stockholm, Sweden) and the HT technique in the Precision 3.3.1 TPS (Accuray, Madison, Wisconsin, USA). Planning target volume (PTV) coverage, organ‐at‐risk (OAR) doses, and dose–volume metrics of SIB plans were compared between the VMAT and HT techniques using appropriate statistical tests.ResultsThe median PTV77.5 volume was 83.4 cc (range: 14.9–218.2 cc). For PTV77.5, HT yielded a higher mean dose (79.52 Gy vs. 77.54 Gy, p = 0.001) and a superior conformity index (0.81 vs. 0.71, p < 0.001). Bladder dose metrics were significantly lower with HT, including V53.28 Gy (5.66% vs. 10.31%; p = 0.006) and D2cc (66.47 Gy vs. 70.60 Gy; p < 0.05), while bowel V36.89 Gy volume was also reduced (94.03 cc vs. 115.13 cc; p = 0.038). No statistically significant differences were observed in rectal, sigmoid, or femoral head dose parameters. Beam‐on time was significantly longer for HT than for VMAT (11.0 min vs. 3.4 min, p = 0.005).ConclusionsBRT remains the standard of care for cervical cancer. For patients ineligible for BRT, SIB is dosimetrically feasible; in this exploratory planning study, HT‐SIB provided better target coverage and OAR sparing than VMAT‐SIB. Prospective multicenter validation is necessary before wider clinical adoption.

Volumetric Modulated Arc Therapy vs. IMRT for the Treatment of Distal Esophageal Cancer

The purpose of this study was to compare dosimetric and radiobiological parameters of treatment plans using coplanar and noncoplanar beam arrangements in patients with fronto‐temporal high‐grade glioma (HGG) generated for intensity‐modulated radiotherapy (IMRT) or volumetric‐modulated arc therapy (VMAT). Ten cases of HGG overlapping the optic apparatus were selected. Four separate plans were created for each case: coplanar IMRT, noncoplanar IMRT (ncIMRT), VMAT, and noncoplanar VMAT (ncVMAT). The prescription dose was 60 Gy in 30 fractions. Dose‐volume histograms and equivalent uniform doses (EUD) for planning target volumes (PTVs) and organs at risk (OARs) were generated. The four techniques resulted in comparable mean, minimum, maximum PTV doses, and PTV EUDs (p≥0.33). The mean PTV dose and EUD averaged for all techniques were 59.98 Gy (Standard Deviation (SD)±0.15) and 59.86 Gy (SD±0.27). Noncoplanar IMRT significantly reduced contralateral anterior globe EUDs (6.7 Gy versus 8.2 Gy, p=0.05), while both ncIMRT and ncVMAT reduced contralateral retina EUDs (16 Gy versus 18.8 Gy, p=0.03). Noncoplanar techniques resulted in lower contralateral temporal lobe dose (22.2 Gy versus 24.7 Gy). Compared to IMRT, VMAT techniques required fewer monitor units (755 vs. 478, p≤0.001) but longer optimization times. Treatment delivery times were 6.1 and 10.5 minutes for coplanar and ncIMRT versus 2.9 and 5.0 minutes for coplanar and ncVMAT. In this study, all techniques achieved comparable target coverage. Superior sparing of contralateral optic structures was seen with ncIMRT. The VMAT techniques reduced treatment delivery duration but prolonged plan optimization times, compared to IMRT techniques. Technique selection should be individualized, based on patient‐specific clinical and dosimetric parameters.PACS number: 87

Purpose:The 4π non‐coplanar radiotherapy delivery technique has demonstrated significantly better normal tissue sparing and dose conformality than the clinically used volumetric modulated arc therapy (VMAT). It is unclear whether this is a fundamental limitation of VMAT delivery or the coplanar nature of its typical clinical plans. The non‐coplanar basis of 4π is incorporated into VMAT treatment planning to compare its effect on plan quality.Methods:Clinical stereotactic body radiation therapy plans for 9 liver patients treated with 30–60 Gy using coplanar VMAT (cVMAT) were re‐planned using non‐coplanar VMAT (nVMAT) with 3 arcs and 4 π with 20 intensity‐modulated non‐coplanar fields. All plans were optimized to deliver 100% of the prescribed dose to 95% of the planning target volume (PTV), and nVMAT and 4π plans were tailored to match the maximum and mean PTV dose from the clinical plan. The conformality index (CI), 50% dose spillage volume (R50), normal liver volume receiving &gt;15 Gy (VL&gt;15), and doses to organs at risk (OARs) were compared for all three treatment plans.Results:Compared to cVMAT, the nVMAT and 4π plans reduced VL&gt;15 by an average of 30.6 cm3 and 96.3 cm3, respectively. The average CI was also reduced from 1.22 (cVMAT) to 1.17 (nVMAT) and 1.14 (4π), indicating higher conformality in the same order. Similarly, R50 was reduced from 3.87 (cVMAT) to 3.58 (nVMAT) and 2.74 (4π). With the exception of the mean right kidney dose, which increased by an average of only 0.6 Gy for nVMAT, the dose differences to OARs were not statistically significant between the two VMAT plans. 4π plans either significantly decreased or maintained OAR doses.Conclusion:While the manual selection of intuitive non‐coplanar arcs does show some improvement over coplanar VMAT, the automated beam selection for 4π still results in superior plan quality.This project is supported in part by Varian Medical Systems and NIH R43 CA183390.

Introduction Esophageal cancer is a significant global health concern, with high incidence and mortality rates, particularly in India, where it ranks among the top causes of cancer-related deaths. Radiotherapy plays a critical role in the treatment of advanced-stage esophageal cancer. This study aims to compare the dosimetric outcomes of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) to evaluate their efficacy and safety in managing mid-esophageal carcinoma. Materials and methods A retrospective study was carried out on thirty patients with middle-third esophageal cancer who received treatment at Rohilkhand Medical College and Hospital, Bareilly, India.The patients, aged between 50 and 70 years (mean age of 66.5 years), were in stages II to III of cancer according to the American Joint Committee on Cancer (AJCC) 2018 guidelines.All patients had histologically confirmed cases of moderately differentiated squamous cell carcinoma. The treatment procedure included immobilization using a thoracic mold, CT simulation with intravenous and oral contrast, and contouring of the gross tumor volume (GTV), clinical target volume (CTV), planning target volume (PTV), and organs at risk (OARs) following the Radiation Therapy Oncology Group (RTOG) 0436 protocol. VMAT planning was done using the Varian Eclipse™Treatment Planning System, while IMRT planning employed a seven-field non-coplanar beam setup. Comparative virtual IMRT plans were generated for these patients. Both VMAT and IMRT plans were evaluated based on dosimetric parameters for the PTV and OARs. Results Both VMAT and IMRT achieved sufficient PTV coverage, with no statistically significant differences in dosimetric parameters (dose to 99 % volume of PTV, dose to 95 %volume of PTV, maximum dose to PTV, minimum dose to PTV). VMAT demonstrated reduced lung and heart doses compared to IMRT; however, the observed differences were not statistically significant.There was a reduction in lung dose with VMAT when evaluating the dose-volume constraints: volume receiving 15 Gy dose (V15) by 11%, volume receiving 20 Gy dose (V20) by 20%, and volume receiving 25 Gy dose (V25) by 41%, though these differences were not statistically significant. Themeanmaximum spinal cord dose was significantly lower with VMAT (19.69 Gy) compared to IMRT (30.80 Gy, p=0.01). Heart dosimetry showed slight improvements with VMAT, particularly in volume receiving 30 Gy dose (V30), volume receiving 40 Gy dose (V40), and mean heart dose, though these differences were not statistically significant. Conclusion Both VMAT and IMRT provided similar PTV coverage. VMAT showed a reduction in spinal cord dose, which was statistically significant, and a trend toward lower lung and heart doses, though these differences were not statistically significant. VMAT appears to be an effective option for treating mid-esophageal carcinomawhile reducing exposure to critical organs.

Background:Since 2009, the use of IMRT for the treatment of breast cancer with lymph node involvement has been considerably growing at our institution. Helical Tomotherapy (HT) was chosen as main technique using field width of 2.5 cm (HT_FW_2.5). Alternatively HT using field width of 5 cm (HT_FW_5), Volumetric Modulated Arc Therapy (VMAT), or Proton Therapy with Pencil Beam Scanning (PT-PBS) were used to reduce treatment duration or optimize organs at risk (OAR) sparing. Purpose: the aim of this study is to compare the 4 modalities of treatment available at our site. Patients and methods: We studied 10 patients treated for breast cancer with lymph node involvement. The prescribed dose was 51.8 Gy to breast with simultaneous integrated boost till 63 Gy, 50.4 Gy to the lymph nodes in 28 fractions for all studied patients. The CTV (clinical target volume) were delineated using ESTRO Guidelines. Dosimetric plan used in routine clinical practice was done using HT_FW_2.5. Clinical plan approved was compared to the plan using the 3 others IMRT techniques. Dosimetric parameters were noted down. For Planning Target Volume (PTV) coverage, dosimetric goals were D95% ≥ 95% and D2% ≤ 107% of the prescribed dose. Regarding OAR, mean dose were noted for heart, contralateral/ipsilateral lung and contralateral breast. Maximum dose in the spinal cord was also recorded. Dosimetric score was made to evaluate plan quality. For both PTV score (PTVs) and OAR score (OARs), 1 was the best and 4 the worst achievable score. Results:HT_FW_5 and VMAT plans ensure an equivalent or even better PTV coverage than the initial clinically approved plan (PTVs = 2.3 and 2.0 VS 2.5) but at the cost of a deterioration of OAR sparing (OARs = 3.3 and 3.2 VS 2.3). PT_PBS plans show that an excellent PTV coverage can be maintained with significantly lower doses to OAR (PTVs = 2.0; OARs = 1.1) Conclusion:HT_FW_5 and VMAT plans allow significantly reducing treatment duration and can be good alternative to HT_FW_2.5 for specified population which has already a good OAR sparing and needs to reduce treatment duration. HT_FW_2.5 could be chosen for patient with higher risk of side effect. In addition PT_PBS treatment should be considered in the near future as it showed great potential benefit to lower the risk of side effects without deteriorating PTV coverage. Dosimetric Scores of different IMRT techniquesHT_FW_2,5HT_FW_5VMATPT_PBSD95% (Gy)PTV Breast49.449.950.149.7PTV Tumor Bed60.160.160.361.1PTV Lymph Nodes47.748.148.548.3PTV Score2.52.32.02.0Dmean (Gy)Heart7.28.47.31.0Contralateral Lung4.35.16.40.4Ipsilateral Lung13.513.714.59.3Contralateral Breast3.53.64.30.0OAR Score2.33.33.21.1 Citation Format: Wassim El Amine, Laurent Bartolucci, Camille Adrien, Marie Lejars, Alain Fourquet, Marion Vaillant, Magalie Robilliard, Emilie Costa, Alejandro Mazal, Farid Goudjil, Youlia Kirova. Intensity modulated radiotherapy (IMRT) for breast and lymph node irradiation [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-32.

Aims: Craniospinal irradiation (CSI) is a challenging task on halcyon due to its field size constraint (28 cm × 28 cm). CSI was planned by volumetric modulated arc therapy (VMAT) technique on Halcyon (6MV) linac with no junction shift with multiple arcs and numerous isocenter depending on the length of the patients. Methods and Materials: Planning CSI was achieved on Eclipse treatment planning system version 15.6 with anisotropic analytical algorithm and was optimized using autofeathering technique. Positioning accuracy was ensured by obtaining daily kvCBCT before radiation which ensured accurate field placement and avoidance of junctional errors. Pretreatment portal dosimetry was done to ensure the dose distribution calculated by the treatment planning system matches the dose delivered to the patient. Results: All VMAT CSI plans produced outstanding planning target volume (PTV) coverage with V95% &gt;98% and gave acceptable doses to organ at risk in all CSI cases. Furthermore, the dose distributions were highly uniform, with homogeneity index values ≤0.1 and target conformity was equally excellent with values more than 0.95. In portal dosimetry, all of the composite images of CSI plans were evaluated, yielding good passing criteria of &gt;98%. Conclusions: The remedy was straightforward to plan and deliver, thanks to autofeathering optimization. CSI plan was created with no junction shift which resulted in homogeneous and conformal doses to the PTV. The gamma analysis in the portal dosimetry composite image, which was utilized as a pretreatment verification, met all of the requirements and revealed a homogeneous and uniform junction dose.

The purpose of this study was to systematically examine the normal tissue objective (NTO) function by comparing its variations for planning solitary brain metastasis with intensity-modulated and volumetric-modulated arc radiosurgery techniques. Twenty-two cases were retrospectively planned with two NTO parameter sets named A and B using intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques. The Type A set used slope, k = 0.4 mm-1 plus end dose, De = 20%, whereas the Type B set used k = 1.0 mm-1 plus De = 10%. The resulting four plan types were assessed using mean dose to 5 mm exterior ring, normal brain receiving 12 Gy (V12), 5 Gy total brain dose volume (V5), gradient index (R50%), focal index (FI), Paddick conformity index (PCI), prescription isodose surface (PIDS), and MU/Gy. Brain doses were significantly lower for VMAT than for IMRT. R50% was more favorable for VMAT than for IMRT for each planning target volume (PTV). The mean FI was comparable between the corresponding IMRT and VMAT plan types. PCI was better for the IMRT_A plan type. PIDS was significantly lower for Type B plans than Type A for both techniques. For PTVs <3 cm3, IMRT plans showed poor dosimetry and required NTO settings stricter than Type B. The application of NTO variations demonstrated varied dosimetry for IMRT and VMAT techniques. The NTO parameter variations produced field size and/or beamlet size/shape variations. The strict NTO parameter set generated more conformal beam apertures to reduce the brain dose. VMAT plan types showed significantly lower brain doses and better dosimetry for all target sizes.

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

This study aimed to conduct a thorough dosimetric comparison between two advanced radiotherapy techniques, Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT), to ascertain the superior modality in terms of dose distribution and organ-at-risk sparing for rectal cancer patients. Thirty-three patients with ECOG performance status 1, aged between 18 to 60 years, diagnosed with Stage II to III rectal cancer, were included in this prospective study. Each patient underwent treatment planning with IMRT and VMAT techniques using Varian system simulation computed tomography scans. The dosimetric analysis encompassed the evaluation of target volume dose homogeneity, conformity, and doses to at-risk organs. The dosimetric comparison was conducted utilizing seven-field IMRT and dual arc VMAT plans. Statistical analysis was performed using paired t-tests and SPSS 20 software. Treatment plan constraints adhered to the RTOG 9406 guidelines, ensuring adequate planning target volume (PTV) coverage, homogeneity index, conformity index, and dose limits for organs at risk, including small bowel V20 (&lt;200cc), bladder V45 (&lt;21Gy), and femoral head V50 (≤30 Gy). Volumetric arc therapy plans demonstrated superior dose homogeneity to fixed-field intensity-modulated plans (p-value = 0.04), particularly in femoral head dose-limiting toxicity (p-value = 0.00). However, intensity-modulated therapy exhibited equivalent or superior performance in other evaluated parameters. Our findings suggest that while VMAT offers advantages in PTV coverage homogeneity and femoral head dose-limiting toxicity, IMRT remains competitive and potentially preferable in certain dosimetric aspects. The choice between IMRT and VMAT should be carefully considered based on individual patient characteristics and treatment goals. This comprehensive dosimetric comparison contributes valuable insights into optimizing radiotherapy planning for rectal cancer patients, potentially guiding clinical decision-making and improving treatment outcomes.

Complexity in MLC‐based radiosurgery treatment delivery can be characterized by the efficiency of monitor unit (MU) utilization and the average MLC leaf separation distance for a treatment plan. A reduction in plan complexity may be desirable if plan quality is not impacted. In this study, a number of strategies are explored to determine how plan quality is affected by efforts to reduce plan complexity. Ten radiosurgery cases of varying complexity are retrospectively planned using six optimization strategies: an unconstrained volumetric modulated arc therapy (VMAT) technique, a MU‐constrained VMAT technique, three techniques using various strengths of the aperture shape controller (ASC), and a hybrid technique consisting of a final‐stage VMAT optimization applied to a dynamic conformal arc leaf sequence (ODCA). The plans are compared in terms of MU efficiency, MLC leaf‐separation, conformity index (CI), gradient index (GI), and QA measurement results. The five VMAT techniques exhibited only minor differences in CI and GI values, though the ASC and MU‐constrained techniques did require 6–20% fewer MU and had mean field apertures 5–19% larger. On average, the ODCA technique had CI values 3.5% lower and GI values 1.0–2.5% higher than the VMAT techniques, but also had a mean field aperture 24–47% larger and required 16–32% fewer MU. The QA measurement results showed a 0.61% variation in mean per‐field 2%/1 mm gamma passing rates across all techniques (range 96.81%–97.42%), with no observed correlation between passing rate and technique. For simple targets, the ODCA technique achieved CI results that were equivalent to the unconstrained VMAT technique with an average 30% reduction in required MU, an average 50% increase in mean leaf separation distance, and brain V12Gy values within 0.38 cc of the VMAT technique for targets up to approximately 2 cm diameter. For MLC‐based single‐target radiosurgery, plan complexity can often be significantly reduced without an equivalent reduction in plan quality.