A study was undertaken to explore the use of volumetric modulated arc therapy (VMAT) for total body irradiation (TBI). Five patient plans were created in Pinnacle3 using nine 6 MV photon dynamic arcs. A dose of 12 Gy in six fractions was prescribed. The planning target volume (PTV) was split into four subsections for the head, chest, abdomen, and pelvis. The head and chest beams were optimized together, followed by the abdomen and pelvis beams. The last stage of the planning process involved turning all beams on and performing a final optimization to achieve a clinically acceptable plan. Beam isocenters were shifted by 3 or 5 mm in the left–right, anterior–posterior, and superior–inferior directions to simulate the effect of setup errors on the dose distribution. Treatment plan verification consisted of ArcCheck measurements compared to calculated doses using a global 3%/3 mm gamma analysis. All five patient plans achieved the planning aim of delivering 12 Gy to at least 90% of the target. The mean dose in the PTV was 12.7 Gy. Mean lung dose was restricted to 8 Gy, and a dose reduction of up to 40% for organs such as the liver and kidneys proved feasible. The VMAT technique was found to be sensitive to patient setup errors particularly in the superior–inferior direction. The dose predicted by the planning system agreed with measured doses and had an average pass rate of 99.2% for all arcs. VMAT was found to be a viable treatment technique for total body irradiation.

A volumetric modulated arc therapy (VMAT) approach to total body irradiation (TBI) has recently been introduced at our institution. The planning target volume (PTV) is divided into separate sub‐volumes, each being treated with 2 arcs with their own isocentre. Pre‐treatment quality assurance of beams is performed on a Sun Nuclear ArcCHECK diode array. Measurement of junction regions between VMAT arcs with separate isocentres has previously been performed with point dose ionization chamber measurements, or with films. Translations of the ArcCHECK with respect to a known distance between the adjacent isocentres of two arcs, which are repeated with the ArcCHECK in an inverted position, allows the recording of a junction dose map. A 3%/3 mm global gamma analysis (10% threshold) pass rate for arc junctions were comparable to their component arcs. Dose maps of junction regions between adjacent arcs with different isocentres can be readily measured on a Sun Nuclear ArcCHECK diode array.