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A systematic study of imaging uncertainties and their impact on 125 I prostate brachytherapy dose evaluation
Author(s) -
Lindsay Patricia E.,
Van Dyk Jake,
Battista Jerry J.
Publication year - 2003
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1586451
Subject(s) - contouring , brachytherapy , dosimetry , prostate , prostate cancer , medicine , nuclear medicine , radiation treatment planning , prostate brachytherapy , medical imaging , radiation therapy , radiology , computer science , cancer , computer graphics (images)
In order to calculate the dose distribution delivered by a prostate brachytherapy implant, the seed positions and prostate volume are normally identified on post‐implant CT images. We have systematically considered the impact of uncertainties in contouring the prostate, seed localization, and visualization of all the seeds on the calculated dose distributions, dose–volume histograms, and predicted radiobiological outcome. This study was done for a collection of 27 clinical125 I prostate brachytherapy implants, performed at the London Regional Cancer Centre during our early adoption of this technique. For these clinical dose distributions, the median D90 was 76% of the prescription dose, or 110 Gy, and the median V90 was 80%. We calculated the changes in these dosimetric indices (D90 and V90) and radiobiological outcome ( SF 2TCP) as a function of contouring uncertainty, seed localization uncertainty, inability to localize all of the seeds, and binary combinations of these three. The results are presented for a range of uncertainties, which allows the possible application of these results to a variety of imaging modalities that have differing spatial resolutions. We found that both contouring uncertainties and seed localization uncertainties had a large impact on the predicted radiobiological outcome, but that seed localization uncertainties of 6 mm had the largest impact on the dosimetric indices. We also found that the variability in both the predicted radiobiological and dosimetric outcome was largest for contouring uncertainties of 4–8 mm. We conclude that accounting for contouring uncertainties is crucial in accurately deducing the DVHs for post‐implant prostate brachytherapy, and hence enabling valid correlation with ultimate clinical outcome.