Room: Exhibit Hall | Forum 7
Purpose: To evaluate the dosimetric effects of the AeroFormáµ€á´¹ (AirXanpdersÂ®, Palo Alto, CA) tissue expander in-situ for breast cancer patients receiving postmastectomy radiation therapy(PMRT).
Methods: A film phantom (S1) was constructed by placing the metallic cannister of the AeroForm on a solid water phantom with EBT3 films at five depths ranging from 2.6mm to 66.2mm. A breast phantom (S2), a 3-D printed tissue equivalent breast with fully expanded AeroForm in-situ, was placed on a thorax phantom. A total of 21 optical luminescent dosimeters(OLSD) were placed on the anterior gas-skin interface and the posterior metal-chestwall interface of the AeroForm. Both phantoms were scanned with a 16-bit CT scanner with OMAR. S1 was irradiated with 6MVX and 15MVX open fields at 0, 90, and 270 gantry angles. S2 was irradiated with a VMAT plan using 6MVX and a tangent plan with 15MVX. Doses were calculated with Eclipse (Varian, Palo Alto, CA) AAA and AcurosXB algorithms.
Results: The average dose differences in the region adjacent to the canister in S1 was 3.0% for 15MV and 4.0% for 6MV compared with calculations. Local dose differences over 10% was also observed. In chestwall region of S2, the OSLDs median doses in percentage of prescription dose were 108.4% (range 95.4% to 113.0%) for 15MV tangents plan and 110.4% (range 99.1% to 113.8%) for 6MV VMAT plan. In the gas-skin interface, the OSLDs median doses were 102.3% (range 92.7% to 107.7%) for 15X plan and 108.2% (range 97.8 to 113.5%) for 6X plan. Measured doses were in general higher than calculated doses. The AcurosXB slightly improved the agreement with measurements over the AAA.
Conclusion: The AeroForm creates significant dose uncertainties in the chestwall-metal interface. The AcurosXB dose calculation algorithm is recommended for more accurate calculations. If possible, PMRT should wait after the permanent implant is in place.
Funding Support, Disclosures, and Conflict of Interest: This work was partially supported by the Grant/Core Grant (P30 CA008748). AirXanpders, Palo Alto, CA supplied AeroForm devices for this research.