Development of a new SBRT dose planning strategy for thoracic tumours in RayStation

Sammanfattning: Umeå University Hospital has acquired a new treatment planning system, RayStation, for radiotherapy. It has a different set of dose calculation algorithms that require new planning strategies for stereotactic lung cancer treatments. This \paper{} has two parts and the first investigates the Monte Carlo algorithm, recalculating doses for 21 historical treatments, and finds that it is slow but fast enough to be used and that it reports dose coverage that is usually lower than that of simpler algorithms, particularly for small tumours in low density lungs. The second part investigates the performance of four alternative planning methods: a straight forward PTV/ITV based method, a method using density override of the PTV, an ITV based semi-robust method and a fully robust method treating both setup margins and breathing motion robustly. The new methods are tested on 12 historical cases and are compared, using robust evaluation, to each other and the original plans. The first three are found to all be viable alternatives, while the fully robust method, while impressive, is found not to be a practical alternative at this time.