The aim of this study was to compare open asymmetric field-in-field (FIF) to physical wedge for compensation of dose inhomogeneity in tangential whole breast irradiation.
Patients and Methods:
Ten consecutive patients had undergone breast conserving surgery followed by whole breast irradiation were considered. Two 3D treatment plans were generated for each patient using: physical wedge and FIF techniques. For both plans, the doses to 2% (D 2 ) and 98% (D 98 ) of the planning target volume (PTV), as well as PTV<95%, PTV 97-103% , and PTV>107% of the prescribed dose were used to evaluate the effect on dose homogeneity. The evaluation of organ at risk (OAR) carried out by comparing volumes received over 40% of dose (17Gy) in the ipsilateral lung, 80% of dose (34Gy) in the heart, and mean dose of contralateral lung. Also, the average total monitor units (MU) for both were compared.
The FIF technique was better than physical wedged technique in terms of D 2 , D 98 , PTV>107%. FIF technique achieved 8.1% dose improvement index compared to physical wedges technique and 34% reduction in the mean monitor units as it reported 470 MU and 310 MU for physical wedges and FIF technique respectively. The differences between the two techniques were insignificant regarding the OAR. FIF can save up to 219 seconds compared to tangential wedged field.
Asymmetric FIF technique improves PTV conformity without compromising OAR. It also reduces treatment time and hence can replace physical wedge, especially in busy departments.
Keywords: FIF; wedge; breast cancer; whole breast irradiation.
This article is 6 pages long, and includes 4 table and 2 figures.
(Citation: Gastric & Breast Cancer 2011; 10(4) 250-255).