SU‐FF‐T‐152: Convolution/superposition Algorithm and High‐Z Dental Materials: Dosimetric Study in a Solid Water Slab Phantom

S. Spirydovich, L. Papiez, Mark Langer, V. Thai

Research output: Contribution to journalArticle

Abstract

Purpose To address the accuracy of the dose calculated with convolution/superposition algorithm in the presence of high‐Z dental materials. Methods and Materials Three methods were utilized to access the dose: convolution/superposition algorithm, Fluence Map Monte Carlo (FMMC) method, and radiochromic film. We considered a solid water® slab phantom which had an embedded high‐Z material. For dose calculations and measurements we used a 6MV photon beam from a clinically commissioned linear accelerator. Results We observed a close agreement for the dose measured with radiochromic film and the dose calculated with FMMC algorithm. On the other hand, a large discrepancy was discovered for the dose calculated with the convolution/superposition algorithm compared to the dose obtained with measurement or FMMC algorithm. The greatest discrepancy was observed downstream from the high‐Z cerrobend inhomogeneity where the convolution/superposition algorithm calculated a dose which was higher than the dose measured with radiochromic film by 10–20% depending on the size of and the distance from the inhomogeneity. Clinically this finding shows that the delivered dose would be 10– 20% less than the prescribed dose which was calculated with convolution/superposition algorithm. In the region upstream from all the studied high‐Z inhomogeneities the convolution/superposition algorithm was underestimating the delivered dose. The convolution/superposition algorithm was unable to properly estimate the dose enhancement due to the increased backscatter near the inhomogeneity. Conclusions The convolution/superposition algorithm may significantly overestimate the actual dose in the site of the tumor located downstream from the high‐Z dental restorations or prostheses.

Original languageEnglish (US)
Pages (from-to)2083-2084
Number of pages2
JournalMedical Physics
Volume33
Issue number6
DOIs
StatePublished - Jan 1 2006

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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