Exhibit Hall | Forum 3
Purpose: For breast Intrabeam (Carl Zeiss Meditec) IORT dose to the bone (ribs) for lumpectomy cavities close to the chest wall is very high as expected with 50 kV X-rays. It can reach 200% of the prescription dose in simulated calculations using the Radiance Monte Carlo based planning system in conjunction with pre-op CT scans. A sterile flexible shield placed between the Intrabeam applicator and the chest wall could protect the ribs from receiving this large unnecessary dose. Unfortunately, shields for protection of critical organs during IORT are currently not commercially available. Ten candidate materials were evaluated dosimetrically for their shielding capacities.
Methods: Radiation reducing gloves and apron materials by PROTECH Medical and Emerson & Co and tungsten based functional paper (TFP) were evaluated using EBT3 radiochromic film and a PTW 34013 chamber in a specially designed Solid Water phantom placed into a modified Intrabeam water tank (without water) for proper measurement setup and radiation protection. Film was calibrated for absolute dosimetry using a calibrated I-125 seed in a Solid Water calibration phantom and TG-43. Films and chamber were irradiated using a 30 mm flat applicator in contact with evaluated materials.
Results: While TFP provides superior protection per layer, attenuating 81.9% (single layer) or 94.1% (two layers) at depth 5 mm, it is less flexible and not sterile, compared to the gloves of all studied brands, which are sterile and much more flexible, attenuating on average 68.6% (single layer) or 85.7% (two layers). Apron materials attenuating on average 87.0% are thick like two glove layers and not sterile.
Conclusion: Several lead-free and latex-free commercially available materials were identified and classified according to their attenuation characteristics and convenience of use. Glove materials placed into sterile pouches to prevent shreds are used at our institution for protection of critical organs during IORT.
Funding Support, Disclosures, and Conflict of Interest: Partial funding and material support were provided by Carl Zeiss Meditec, Oberkochen, Germany A calibrated high activity I-125 seed was provided by Eckert & Ziegler BEBIG GmbH, Berlin, Germany
IORT, Low Energy X-rays, Shielding