Open AccessPotential therapeutic misadministration due to inappropriate electron beam field shaping
Author(s) -
Olch Arthur J.,
Fallen Robert,
Conrad Jill,
Lavey Robert S.
Publication year - 2000
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1120/jacmp.v1i3.2641
Subject(s) - strips , linear particle accelerator , electron , field (mathematics) , cathode ray , beam (structure) , computer science , frame (networking) , field size , insert (composites) , optics , medical physics , materials science , physics , nuclear physics , telecommunications , mathematics , composite material , artificial intelligence , pure mathematics
Lead or cerrobend blocking strips are used to shape electron treatment fields when an appropriate custom insert is not available. For the Varian 2100C accelerator, the structural supports of the electron applicators impede the free placement of these field‐shaping strips on the open custom insert frame while placement at the top of the applicator is unimpeded. We have investigated the dosimetric ramifications of placing field shaping strips at the top level of the 15 × 15 applicator for 6, 9, and 16 MeV electrons. Our results demonstrate as much as a 30% dose decrease and 2 cm penumbral increase when this is done compared to field shaping at the insert level. The magnitude of this dosimetric error qualifies as a therapeutic misadministration in many states depending on how many treatments are delivered in this manner. Based on this finding, we recommend that routine use of lead strip blocking be discouraged in favor of custom inserts due to the potential for inappropriate placement on some linear accelerators. PACS number(s): 87.53.–j, 87.52.–g