) Project 3 will analyze how to include patient related geometric uncertainties (due primarily to patient setup variability and organ motion) in the calculation, compilation and treatment of conformal radiotherapy dose distributions. These very important and fundamental realities associated with the therapeutic treatment of cancer patients with external beam ionizing radiation are not reflected in the standard computation of dose distributions for patient treatment plans. While knowledge of the magnitude of these uncertainties, when available, can be exploited to design geometric safety margins for the treatment of tumors, these same margins often compromise the dose that can be safely delivered to the patient's target volume(s) due to the irradiation of large volumes of normal tissue. Further, even given adequate treatment of clinical target volumes, the dose distribution actually received by the patient (especially normal tissue) is not accurately represented in the single dose calculation performed prior to treatment, using a static imaging study as the underlying anatomical model. This is of importance in the continuing studies of conformal therapy techniques, as many dose escalation and optimization schemes are based on (or constrained by) the perceived probability of expressing a treatment-related complication. This project has specific aims associated with the inclusion of patient-related setup uncertainties and organ motion in the calculation of realizable dose distributions, the compilation of delivered dose distributions that reflect individual patient and organ positions over the course of treatment, and ultimately the combination of these realizable dose calculations with patient specific, realized dose compilations in the development of dynamic refinement strategies for the optimization of individual patient treatments. Stylized, realizable dose treatment plans for individual patients should result in achieving required clinical target volume coverage, with more confident descriptions of normal tissue doses. Optimal safe treatments at a given prescription dose, or further tumor dose escalation at specified levels of normal tissue risk can then be attained. It is anticipated that the investigations will permit further optimization of treatments for individual patients.
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