Dosimetric evaluation of the tangential and supraclavicular breast radiotherapy fields junction in mono and dual isocentric techniques with practical measurement and comparison versus TomoDirect technique.

PURPOSE: Accurate dose distribution at the junction of tangential and supraclavicular fields in breast radiotherapy is affected by various dosimetric uncertainties. This study evaluates the accuracy of the Monaco treatment planning system (TPS) and compares the dose distributions of monoisocentric (MI), dual-isocentric (DIHS, DIFS), and TomoDirect techniques to determine the most effective approach for dose accuracy and homogeneity.

MATERIALS AND METHODS: An anthropomorphic phantom was used for experimental dose verification. Dose distributions of 3DCRT techniques (MI, dual-isocentric half-field (DIHS), and dual-isocentric full-field (DIFS) techniques) were calculated in Monaco TPS. Gamma index analysis was performed on dose profiles obtained at depths of 0.5, 1, 2, and 3 cm to evaluate the agreement between calculated and measured doses using EBT3 films. Additionally, TomoDirect 3DCRT (TD-3DCRT) and IMRT (TD-IMRT) techniques were compared with 3DCRT techniques.

RESULTS: The Monaco TPS with the XVMC algorithm demonstrated superior accuracy in the buildup region compared to the CCC algorithm, achieving gamma agreement above 90% at deeper depths. Among techniques, TD-IMRT provided the most homogeneous dose distribution at the junction of breast and supraclavicular PTVs. The MI technique resulted in lower dose variations than DIHS, DIFS, and TD-3DCRT and minimized dose escalation in the superficial layers of the supraclavicular region.

CONCLUSION: The Monaco TPS with the XVMC algorithm ensures greater accuracy than the CCC algorithm. TD-IMRT offers optimal dose homogeneity at the field junction, while the MI technique achieves superior tumor dose coverage with reduced surface dose in the supraclavicular region, making it a preferable choice.