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SU‐GG‐T‐488: Dosimetric Parameter Comparison of the Electronic Tissue Compensator Technique with the Conventional Physical Wedge Technique for the Whole Breast Treatment
Author(s) -
Su M,
Ayzenberg V,
Li W
Publication year - 2008
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 - 10.1118/1.2962237
Subject(s) - nuclear medicine , dosimetry , breast tissue , radiation treatment planning , medicine , linear particle accelerator , dose profile , field size , physics , radiation therapy , beam (structure) , breast cancer , optics , radiology , cancer
Purpose: To compare a dosimetric benefit between electronic tissue compensator (ETC) technique and the conventional physical wedge (PW) technique for a whole breast (WB) tangential field irradiation treatment. Method and Materials: 17 breast cases, with chest wall separation 16 to 26 cm at normalization point slice, were included in this study. Eclipse Planning System (V7.3) was used to generate a plan. The plan remained with a same beam setup, beam weighting, normalization point, and energy (6MV or 6MV mixed with 18MV) in both technique for each case. The breast tissue was outlined as a planning target volume (PTV). For a PTV dose coverage information, PTV encompassed by 95% isodose line (V 95 ) and PTV received the minimum dose (D min ) were studied. To examine a high dose region, a PTV received at least 105% prescription dose (V 105 ) was computed. To study dose inhomogeneity (DI) in the PTV, a ratio of the difference of D max and D min to the prescription dose was estimated. In additional, a total MU from each plan was recorded to not only measure the linac beam on time, but also as a factor for the machine scatter and leakage evaluation. Results: By comparing with the PW plan, (1) The PTV coverage, V 95 , showed quite similar (difference within 0.5%) in both techniques and D min was lower on a percentage of 1.2±9.1 from ETC plan; (2) The hotspot, V 105 , was reduced by a percentage of 2.9±2.2 in ETC plan. (3) DI was decreasing by a percentage of 1.3±12.3 in ETC plan. The total MU reduced by about 8.9±17.1 percent in ETC plan. Conclusion: ETC technique presented a dosimetric benefit for the WB tangential field treatment. And these benefits were subjected to case‐by‐case study. A careful comparison is needed for the treatment plan selection.