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Background Volumetric modulated arc therapy (VMAT) has been shown feasible for radiosurgical treatment of multiple cranial lesions with a single isocenter. Objective To investigate whether equivalent radiosurgical plan quality and reduced delivery time could be achieved in VMAT for patients with multiple intracranial targets previously treated with Gamma Knife (GK) radiosurgery. Methods We identified 28 Gamma Knife treatments of multiple metastases. These were replanned for multi-arc (MA) and single-arc (SA), single-isocenter VMAT (RapidArc) in Eclipse. The prescription for all targets was standardized to 18 Gy. Each plan was normalized for 100% prescription dose to 99–100% of target volume. Plan quality was analyzed by target conformity (RTOG, Paddick CI), dose fall-off (area under DVH curve), as well as the V4.5, V9, V12, and V18 isodose volumes. Other endpoints included beam-on and treatment time. Results Compared to Gamma Knife, multi-arc VMAT improved median plan conformity (CIVMAT = 1.14, CIGK = 1.65; p<0.001) with no significant difference in median dose fall-off (p=0.269), 12Gy isodose volume (p=0.500), or low isodose spill (p=0.49). Multi-arc VMAT plans were associated with markedly reduced treatment time. A predictive model of the 12Gy isodose volume as a function of tumor number and volume was also developed. Conclusion For multiple target SRS, 4-arc VMAT produced clinically equivalent conformity, dose fall-off, 12 Gy isodose volume, and low isodose spill, and reduced treatment time compared to GK. Due to its similar plan quality and increased delivery efficiency, single-isocenter VMAT radiosurgery may constitute an attractive alternative to multi-isocenter radiosurgery for some patients.

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This report describes the current state of flattening filter‐free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF technology was reviewed, along with technical specifications provided by vendors. Based on this information, supplemented by the clinical experience of the group members, consensus guidelines and recommendations for implementation of FFF technology were developed. Areas in need of further investigation were identified. Removing the flattening filter increases beam intensity, especially near the central axis. Increased intensity reduces treatment time, especially for high‐dose stereotactic radiotherapy/radiosurgery (SRT/SRS). Furthermore, removing the flattening filter reduces out‐of‐field dose and improves beam modeling accuracy. FFF beams are advantageous for small field (e.g., SRS) treatments and are appropriate for intensity‐modulated radiotherapy (IMRT). For conventional 3D radiotherapy of large targets, FFF beams may be disadvantageous compared to flattened beams because of the heterogeneity of FFF beam across the target (unless modulation is employed). For any application, the nonflat beam characteristics and substantially higher dose rates require consideration during the commissioning and quality assurance processes relative to flattened beams, and the appropriate clinical use of the technology needs to be identified. Consideration also needs to be given to these unique characteristics when undertaking facility planning. Several areas still warrant further research and development. Recommendations pertinent to FFF technology, including acceptance testing, commissioning, quality assurance, radiation safety, and facility planning, are presented. Examples of clinical applications are provided. Several of the areas in which future research and development are needed are also indicated.PACS number: 87.53.‐j, 87.53.Bn, 87.53.Ly, 87.55.‐x, 87.55.N‐, 87.56.bc

A substantial barrier to the single- and multi-institutional aggregation of data to supporting clinical trials, practice quality improvement efforts, and development of big data analytics resource systems is the lack of standardized nomenclatures for expressing dosimetric data. To address this issue, the American Association of Physicists in Medicine (AAPM) Task Group 263 was charged with providing nomenclature guidelines and values in radiation oncology for use in clinical trials, data-pooling initiatives, population-based studies, and routine clinical care by standardizing: (1) structure names across image processing and treatment planning system platforms; (2) nomenclature for dosimetric data (eg, dose-volume histogram [DVH]-based metrics); (3) templates for clinical trial groups and users of an initial subset of software platforms to facilitate adoption of the standards; (4) formalism for nomenclature schema, which can accommodate the addition of other structures defined in the future. A multisociety, multidisciplinary, multinational group of 57 members representing stake holders ranging from large academic centers to community clinics and vendors was assembled, including physicists, physicians, dosimetrists, and vendors. The stakeholder groups represented in the membership included the AAPM, American Society for Radiation Oncology (ASTRO), NRG Oncology, European Society for Radiation Oncology (ESTRO), Radiation Therapy Oncology Group (RTOG), Children's Oncology Group (COG), Integrating Healthcare Enterprise in Radiation Oncology (IHE-RO), and Digital Imaging and Communications in Medicine working group (DICOM WG); A nomenclature system for target and organ at risk volumes and DVH nomenclature was developed and piloted to demonstrate viability across a range of clinics and within the framework of clinical trials. The final report was approved by AAPM in October 2017. The approval process included review by 8 AAPM committees, with additional review by ASTRO, European Society for Radiation Oncology (ESTRO), and American Association of Medical Dosimetrists (AAMD). This Executive Summary of the report highlights the key recommendations for clinical practice, research, and trials.

Managing radiotherapy patients with implanted cardiac devices (implantable cardiac pacemakers and implantable cardioverter‐defibrillators) has been a great practical and procedural challenge in radiation oncology practice. Since the publication of the AAPM TG‐34 in 1994, large bodies of literature and case reports have been published about different kinds of radiation effects on modern technology implantable cardiac devices and patient management before, during, and after radiotherapy. This task group report provides the framework that analyzes the potential failure modes of these devices and lays out the methodology for patient management in a comprehensive and concise way, in every step of the entire radiotherapy process.

BACKGROUND.Retroperitoneal sarcomas (RPSs) are rare tumors with poor survival rates due to difficult resectability and high local and distant recurrence rates.Preoperative radiation therapy appears to have dosimetric advantages to utilize the tumor as a tissue expander to limit exposure of small bowel to higher radiation doses. METHODS.Between June 1999 and December 2003, 16 consecutive patients with biopsy-proven RPS were treated with preoperative radiation with selective dose escalation. This included 45 grays (Gy) in 25 fractions to the entire tumor plus margin and a boost dose of 57.5 Gy to the volume predicted as high risk for positive surgical margins. Treatment toxicity and local control were evaluated prospectively as primary endpoints. The secondary goal was the theoretical calculation of future dose escalation and feasibility. Each patient underwent laparotomy. Tumor response was judged using computed tomography (CT) scan and by necrosis on final pathology. Theoretical treatment plans evaluated the potential for additional radiation dose escalation. RESULTS.All patients completed the radiation protocol. The most common acute side effects were nausea/vomiting, which affected 4 patients (25%), with only 1 patient requiring inpatient intravenous hydration. There was no severe late postoperative morbidity or mortality. Twelve tumors (75%) decreased in maximum dimension, with a median decrease of 9.4%. Fourteen of 16 patients (88%) underwent complete macroscopic resection. With a median follow-up of 28 months (range, 7-52 months), there were only 2 local recurrences. The actuarial 2-year local control rate was 80%. Theoretical treatment plans suggest that significant dose escalation (up to 80 Gy) may be possible. CONCLUSIONS.Preoperative radiation therapy with selective dose escalation to the margin at risk is tolerable and allows higher radiation dose to the volume judged to be at greatest risk for local tumor recurrence. Cancer 2006;107:371-9.

A commercial electron dose calculation software implementation based on the macro Monte Carlo algorithm has recently been introduced. We have evaluated the performance of the system using a standard verification data set comprised of two-dimensional (2D) dose distributions in the transverse plane of a 15 X 15 cm2 field. The standard data set was comprised of measurements performed for combinations of 9-MeV and 20-MeV beam energies and five phantom geometries. The phantom geometries included bone and air heterogeneities, and irregular surface contours. The standard verification data included a subset of the data needed to commission the dose calculation. Additional required data were obtained from a dosimetrically equivalent machine. In addition, we performed 2D dose measurements in a water phantom for the standard field sizes, a 4 cm X 4 cm field, a 3 cm diameter circle, and a 5 cm X 13 cm triangle for the 6-, 9-, 12-, 15-, and 18-MeV energies of a Clinac 21EX. Output factors were also measured. Synthetic CT images and structure contours duplicating the measurement configurations were generated and transferred to the treatment planning system. Calculations for the standard verification data set were performed over the range of each of the algorithm parameters: statistical precision, grid-spacing, and smoothing. Dose difference and distance-to-agreement were computed for the calculation points. We found that the best results were obtained for the highest statistical precision, for the smallest grid spacing, and for smoothed dose distributions. Calculations for the 21EX data were performed using parameters that the evaluation of the standard verification data suggested would produce clinically acceptable results. The dose difference and distance-to-agreement were similar to that observed for the standard verification data set except for the portion of the triangle field narrower than 3 cm for the 6- and 9-MeV electron beams. The output agreed with measurements to within 2%, with the exception of the 3-cm diameter circle and the triangle for 6 MeV, which were within 5%. We conclude that clinically acceptable results may be obtained using a grid spacing that is no larger than approximately one-tenth of the distal falloff distance of the electron depth dose curve (depth from 80% to 20% of the maximum dose) and small relative to the size of heterogeneities. For judicious choices of parameters, dose calculations agree with measurements to better than 3% dose difference and 3-mm distance-to-agreement for fields with dimensions no less than about 3 cm.