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An investigation of tomotherapy beam delivery
Author(s) -
Yang James N.,
Mackie T. Rock,
Reckwerdt Paul,
Deasy Joseph O.,
Thomadsen Bruce R.
Publication year - 1997
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 - 10.1118/1.597909
Subject(s) - tomotherapy , medical physics , dosimetry , beam (structure) , medical imaging , nuclear medicine , optics , medicine , physics , radiation therapy , radiology
Experimental simulations for tomotherapy beam delivery were performed using a computer‐controlled phantom positioner, a cylindrical phantom, and a 6 MV x‐ray slit beam. Both continuous helical beam and sequential segmented tomotherapy (SST) beam deliveries were evaluated. Beam junctioning problem due to couch indexing error or field width errors presented severe dose uniformity perturbations for SST, while the problem was minimized for helical beam delivery. Longitudinal breathing motions were experimentally simulated for helical and SST beam delivery. While motions reduced the dose uniformity perturbations for SST, small artifacts in dose uniformity can be introduced for helical beam delivery. With typical breath frequency and magnitude, for a slit beam of 2.0 cm width at 4 rpm, the dose uniformity perturbation was not significant. A running start/stop technique was implemented with helical beam delivery to sharpen the 20%–80% longitudinal dose fall‐off from 1.5 to 0.5 cm. The latter was comparable to the corresponding dose penumbra of a conventional 6 MV 10×10 cm 2field. All together, helical beam delivery showed advantages over SST for tomotherapy beam delivery under similar delivery conditions.