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Dosimetric Effect of Brass Mesh Bolus in Presence of Gas-Filled Tissue Expander for Post Mastectomy Patients Undergoing Radiation Therapy

T Li*, B Hasson , C Geraghty , Anne Arundel Medical Center, Annapolis, MD


(Tuesday, 7/31/2018) 1:15 PM - 1:45 PM

Room: Exhibit Hall | Forum 9

Purpose: Evaluating the dosimetric effect of a brass mesh bolus used to provide dose buildup on the tissue that overlies a gas-filled post mastectomy tissue expander. The dose distributions at the brass-tissue interface, in the tissue, and at the tissue-gas interface were measured with film and OSLD dosimeters.

Methods: The AeroForm Tissue Expander was covered with two layers of 3mm regular bolus and one layer of brass mesh bolus. Gafchromic EBT3 film strips and OSLDs were placed at three positions along the axis of the tissue expander and at three depths, below the brass mesh bolus, at depths of 3mm and 6mm. The whole setup was then irradiated with two opposed 6MV photon beams, delivering 400cGy to the device. The experiment was repeated after removal of the brass mesh bolus, and placements of new dosimeters. Films were then scanned, and analyzed with RIT software. The OSLDs were compared with film results.

Results: The dose at depth of 6mm with the brass mesh bolus in place was enhanced by 10%, and at depth of 3mm, the dose enhanced by 15%. Additionally, the dose was homogenized at the chest wall surface to within 10% of the prescribed dose compared with no brass bolus in place. OSLDs results agreed with film dosimetry results within 5% with one layer of brass mess bolus in place.

Conclusion: The Brass mesh bolus provided adequate dose buildup for the complex geometry of a thin rind of tissue between a gas cavity in the expander and the outer surface of the chest wall. The brass mesh bolus increases the dose for the chest wall irradiation in the presence of a gas-filled expander. Compared with the standard tissue equivalent bolus, the brass mesh bolus eliminates the air gaps by conforming to the chestwall, thus dosimetrically improving the dose uniformity.


Breast, Dose Uniformity


TH- External beam- photons: Standard field experimental dosimetry

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