The effects of intrafraction motion on dose homogeneity in a breast phantom with physical wedges, enhanced dynamic wedges, and ssIMRT
- Department of Medical Physics, Saskatoon Cancer Centre, Saskatoon, Saskatchewan (Canada) and Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan (Canada) and School of Physics, Monash University, Clayton, Victoria (Australia)
- Department of Medical Physics, Saskatoon Cancer Centre, Saskatoon, Saskatchewan (Canada)
Purpose: This study attempts to compare how breathing motion affects intact-breast cancer patients between three different treatment techniques and to determine the degree of improvement on dose homogeneity when implementing gating therapy. Methods and Materials: A breast phantom and respiratory simulator were designed to simulate respiratory motion to a first-order approximation. Film was used as a dosimeter, and static dosimetry data were used as a control for comparison. Three velocities of the breast phantom were studied, and gating therapy was introduced for each data set. Dose area histograms (DAHs) were calculated for a breast and a 'lung' planning target area (PTA), and Normalized Agreement Test (NAT) indices were calculated in reference to the static case. Results: Deviations from the static case were highest if the collimator speed was of the same magnitude as the speed of the target. In general, gating therapy improved dose uniformity to the breast PTA by up to 14% and reduced dose to the 'lung' PTA by up to 24%. With step-and-shoot intensity-modulated radiation therapy (ssIMRT), gating the beam may compromise dose coverage of the breast PTA if the timing interval of the gate is too large. Gating the beam decreased NAT indices by 9 for physical wedges, by 16 for enhanced dynamic wedges, and by 6 for ssIMRT. Conclusions: Both the phantom and respiratory simulator are adequate for showing differences in dose distributions for all three treatment modalities. Gating therapy improves dose homogeneity to the PTAs and decreases the dose delivered to areas below the posterior border of the beams.
- OSTI ID:
- 20850054
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 66, Issue 1; Other Information: DOI: 10.1016/j.ijrobp.2006.03.045; PII: S0360-3016(06)00585-2; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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