Figure 7. Out‐of‐field peripheral dose for a helical tomotherapy system. Water tank measurements taken for a $2.5\times 40.0\hspace{0.17em}{\text{cm}}^2$ open field at $d_{max}$. Leakage and scatter measurements taken at $d_{max}$ with an A17 Exradin Chamber. Leakage plus scatter measurements taken for a clinical delivery sequence with a slice thickness of 2.5 cm. Leakage‐only measurements taken with primary jaws and all MLCs closed. All distances are from the field edge, and the peripheral dose is normalized to the prescribed dose.