Large-scale helical tomotherapy optimization: four clinical case studies

Helical tomotherapy is an integrated therapeutic technique that includes planning, delivery and verification capabilities. Helical tomotherapy allows for irradiation of a large number of targets and region at risk (RAR) over broad regions of the body; a large-scale optimization technique is necessary. Usually a tomotherapy treatment will have tens to hundreds of thousands of pencils beams for which intensity needs to be optimized. Moreover the number of voxels where the dose needs to be computed is on the order of 1,000,000. The complexity and size of the optimization is the price paid in tomotherapy in order to obtain coplanar deliveries that are neither limited by the number of beam directions nor the degree of modulation used during delivery. It is important to note, however, that because of the simplicity and capabilities of the tomotherapy concept, a complex optimization plan will not lead to a complex delivery. The complexity of delivery is almost independent of the complexity on the optimization. In this work 4 clinical conformal and conformal avoidance optimization cases are be shown. Breast, prostate, mesothelioma and nasopharyengeal cases are presented and compared with some of the standard techniques used currently distributions and DVH's are shown to illustrate examples of the deliveries that can be achieved. The flexibility obtained to optimize both conformal and conformal avoidance treatments is also discussed.