Abstract
Purpose:
To investigate the dose calculation accuracy of the Eclipse TPS in the presence of temporary breast tissue expanders with high-density metallic ports.
Materials and Methods:
Four anthropomorphic phantoms were prepared, with integrated Nagor (FIN) and Mentor metallic ports (FIM), remote Mentor port (FRM) and reference one without high-density materials (FR). For each phantom, 16-bit CTs were performed, and several treatment plans (3D, VMAT) were prepared in the Eclipse TPS. X6FF, X15FF and X6FFF and two dose calculation algorithms (AAA, AXB) were used. Two calibration curves (CalC) were used to calculate the dose: standard and extended (with higher material densities added). The calculation and film measurements were compared. Differences in the dose distributions obtained for both CalC were analyzed.
Results:
For FR, differences below 5% were obtained for 95% of all measurement points (mean −0.1 ± 2.5%), whereas for phantoms with ports, the differences were 90% (FIN), 91% (FIM) and 93% (FRM). For FIN and FIM only at one point close to the port (no. 3), a significantly greater difference was observed (9.2%). The beam energy and calculation algorithm do not seem to impact the results. When comparing calculations for standard and extended CalC, dose differences were more pronounced for the 3D technique than for the VMAT technique.
Conclusions:
The calculation algorithm and beam energy do not seem to impact the results when appropriate CT parameters and the extended CalC are implemented. A slightly higher dose is measured at the surface of the phantom, although this appears to also apply to points away from the ports. VMAT appears to be less sensitive to errors.