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We report in-vivo dosimetry and phantom study results for determining complication rate of the eye lens for trigeminal neuralgia (TN) patients treated using gamma knife radiosurgery. This study is driven by the observation that a large dose such as 70-80 Gy was generally prescribed for trigeminal neuralgia, and, therefore, a small percentage (2-3%) of scattering dose to the lens of the eye could reach or even exceed its tolerance dose. In-vivo dosimetry measurements on six patients and a head phantom were performed to investigate these effects. The average lens dose was measured to be 0.077/spl plusmn/0.006 Gy. This value is significantly lower than the 1-2% as predicated from the gamma knife treatment planning system. Using an empirical biological model, the probability of the lens complication was determined to be 0.1%. This low rate confirms our clinical findings that few TN patients develop cataracts.

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.