Field Margins in Prostate Radiotherapy

by Bennie Smit (University of Aberdeen, UK)

Wednesday 3 Nov 2010, 15:00 → 16:00 Europe/Zurich

WBGB/019 (PSI)

Prostate cancer is the second most common cancer in males and is often treated with radiotherapy. To ensure that the tumour receives an adequate dose, a margin is added around the tumour to account for patient positioning, patient movement and organ motion. The aim of this project was to look at the normality of the prostate motion and make recommendations on optimal margin sizes.<o:p></o:p>

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In <st1:city w:st="on"><st1:place w:st="on">Aberdeen</st1:place></st1:city>, gold fiducial markers are implanted into the prostate in order to allow alignment of the target using treatment images. We used statistical techniques to analyze 11 patients to determine optimal inter-fraction margins. We also studied the movement of the prostate relative to surrounding bony anatomy for 6 of these 11 patients.<o:p></o:p>

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The prostate can shift in different directions: superior - inferior, left - right and anterior - posterior. Optimal margins depend both on the magnitude and distribution of the target movements. Goodness of fit tests showed that 19 out of 33 inter-fraction patient results were nonnormally distributed. Assessment of the collective motion distributions of all patients showed only the superior - inferior motions to be normally distributed, although visual approach indicated otherwise.<o:p></o:p>

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Contact: Thomas Schietinger (3274)<o:p></o:p>