Preclinical Assessment of Volumetric Modulated Arc Therapy for Total Marrow Irradiation

Energy‐dependent OAR sparing and dose conformity for total marrow irradiation of obese patients

“…As described in Ayodogan et al., contouring entire bones allows for a generous margin around the bone marrow 17. The PTV was not created from a uniform expansion of the CTV, but rather was drawn to encompass the CTV plus adjacent soft tissues (e.g., intercostal tissues, soft tissues between radius and ulna, soft tissues between scapulae and posterior chest wall) similar to other groups 26. Therapists reported difficulty in positioning the arms during patient treatments so a radial expansion of 5 mm was used for the arm bones from the surgical neck of humerus to the inferior aspect of radius and ulna to allow for a greater setup margin.…”

“…All treatment plans to date have used a beam energy of 6 MV, however, the retrospective planning study presented in this manuscript aims to investigate the effects of using a 10 MV beam for TMI VMAT fields in comparison to 6 MV. High energy beams (10–18 MV) have historically been a part of TBI treatments, particularly for patients of thickness greater than 35 cm;3, 22 however, published experience with modulated TMI fields has been limited to 6 MV IMRT and VMAT or helical tomotherapy 14, 15, 23, 24, 25, 26, 27, 28. Potential disadvantages of increasing beam energy include larger penumbra and the production of secondary neutrons originating in the head of the linac.…”

Verification of junction dose between VMAT arcs of total body irradiation using a Sun Nuclear ArcCHECK phantom

“…Helical tomotherapy (HT) based methods have been used for TMI/TMLI2, 3, 4, 5 as well as TBI 5, 6, 7. Using conventional linacs, intensity modulated radiotherapy (IMRT) TMI delivery proved feasible,8, 9 however, the predominant linac approach utilizes volumetric modulated arc therapy (VMAT) using Varian RapidArc (Varian Medical Systems, Palo Alto, CA, USA) 10, 11, 12, 13, 14, 15, 16, 17…”

“…A uniform dose of 12 Gy is prescribed to the PTV while limiting the mean lung dose to less than 8 Gy and mean kidney and liver doses to below 9 Gy. Based upon previously reported margins3, 5, 13, 14 the PTV was extended 3 mm into the lungs to account for setup, geometric, and intra‐fraction uncertainties. Patients are immobilized with a custom head and shoulder rest, thermoplastic mask, and full body vacuum bag.…”

“…Previous VMAT TBI and TMI/TMLI studies have utilized a variety of dose verification techniques. Portal imaging,13 Mapcheck,14 thermoluminescent dosimeters (TLDs) in an anthropomorphic phantom,15 ionization chamber array (Octavius)16 and diode array (ArcCHECK) 17. Junction measurements are seldom reported on.…”