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Po‐Poster ‐ 05: An evaluation of treatment dose error due to beam attenuation from a carbon fiber table top
Author(s) -
Myint K,
Niedbala M,
Wilkins D,
Gerig L
Publication year - 2005
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 - 10.1118/1.2030984
Subject(s) - imaging phantom , attenuation , radiation treatment planning , table (database) , absorption (acoustics) , materials science , medical physics , computer science , optics , nuclear medicine , radiation therapy , medicine , physics , radiology , data mining
The emergence of carbon fiber materials for use in radiation therapy was largely due to its high mechanical strength, low specific density, and its perceived radio‐translucence. These characteristics made it an ideal material for the patient support assembly utilized during treatments. Modern radiation therapy commonly employs beams delivered at oblique angles. With the introduction of carbon fiber table tops the attenuation of the couch is often ignored during treatment planning and there is little effort to avoid intersection of the beam with the table during patient setup. The perception that carbon fiber is relatively radio‐translucent has permitted it to be used while neglecting to consider the effects it may have on the dose to the patient. In this study we have measured the attenuation of the couch under various conditions for 6 and 18 MV photons. We have found dose reductions in phantom of greater than 7%. We further investigate the ability of a commercial treatment planning system (Theraplan Plus) to properly model this effect during the planning stage. Our results show that incorporating the carbon fiber couch in the patient model reduces the dose error to less than 2%. These results reveal that it is worthwhile addressing this real clinical problem in such a manner that it can be routinely considered for all patient treatments. Thus, practical suggestions are proposed for the incorporation of the treatment tabletop into patient treatment planning dose calculations.