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The aim of this study was to assess the potential for treating various common cancer sites with flattening filter free (FFF) rather than conventionally flattened (cFF) treatment plans considering both in-field and out-of-field dosimetry. This study seeks to extend previous work by others to the Elekta Agility VMAT treatments commonly used at our clinic. Nine matched pairs of conventional and FFF 6X treatment plans for prostate, head and neck, and brain cancer sites were generated using the Monaco treatment planning system (Elekta AB, Stockholm, Sweden). Absorbed dose distribution statistics for target and healthy tissue volumes reported by the Monaco treatment planning system were compared. One matched pair of plans for each cancer site was experimentally validated by film and ion chamber measurements in an anthropomorphic phantom. Head leakage was measured at various positions in a small water tank and corrections made to the out-of-field dose distributions calculated by the treatment planning system. Out-of-field organ doses and effective whole body doses were calculated according to ICRP103 (Charles in Radiat Prot Dosim 129:500-507, 2008). The in-field target and organ dose statistics for the cFF and FFF plans were comparable whereas the out-of-field organ and whole body effective doses for plans delivered using 6X FFF were generally lower than those delivered with 6X cFF. A modest increase in monitor unit (MU) delivery rates was also observed with the FFF beams. We conclude that treatment plan delivery using FFF rather than cFF beams is feasible and may provide benefits in terms of reduced out-of-field doses and secondary cancer risks for some patients.

Aim: We sought to improve error detection ability during volume modulated arc therapy (VMAT) by dividing and evaluating the treatment plan., Background: VMAT involves moving a beam source delivering radiation to tumor tissue through an arc, which significantly decreases treatment time. Treatment planning for VMAT involves many parameters. Quality assurance before treatment is a major focus of research., Materials and Methods: We used an established VMAT prostate treatment plan and divided it into 12° × 30° sections. In all the sections, only image data that generated errors in one segment and those that were integrally acquired were evaluated by a gamma analysis. This was done with five different patient plans., Results: The integrated image data resulting from errors in each section was 100% (tolerance 0.5 mm/0.5%) in the gamma analysis result in all image data. Division of the treatment plans produced a shift in the mean value of each gamma analysis in the cranial, left, and ventral directions of 94.59%, 98.83%, 96.58%, and the discrimination ability improved., Conclusion: The error discrimination ability was improved by dividing and verifying the portal imaging.

Purpose: Chest wall pain and discomfort has been recognized as a significant late effect of radiation therapy in historical and modern treatment models. Stereotactic Body Radiotherapy (SBRT) is becoming an important treatment tool in oncology care for patients with intrathoracic lesions. For lesions in close approximation to the chest wall with motion management, SBRT techniques can deliver high dose to the chest wall. As an unintended target of consequence, there is possibility of imposing significant chest wall pain and discomfort as a late effect of therapy. The purpose of this paper is to evaluate the potential role of Volume Modulated Arc Therapy (VMAT) technologies in decreasing chest wall dose in SBRT treatment of pulmonary lesions in close approximation to the chest wall., Materials and Methods: Ten patients with pulmonary lesions of various sizes and tomography in close approximation to the chest wall were selected for retrospective review. All volumes including tumor target, chest wall, ribs, and lung were contoured with maximal intensity projection maps and four-dimensional computer tomography planning. Radiation therapy planning consisted of static techniques including Intensity Modulated Radiation Therapy compared to VMAT therapy to a dose of 60 Gy in 12 Gy fraction dose. Dose volume histogram to rib, chest wall, and lung were compared between plans with statistical analysis., Results: In all patients, dose and volume were improved to ribs and chest wall using VMAT technologies compared to static field techniques. On average, volume receiving 30 Gy to the chest wall was improved by 74%; the ribs by 60%. In only one patient did the VMAT treatment technique increase pulmonary volume receiving 20 Gy (V20)., Conclusions: VMAT technology has potential of limiting radiation dose to sensitive chest wall regions in patients with lesions in close approximation to this structure. This would also have potential value to lesions treated with SBRT in other body regions where targets abut critical structures.