Comparison of Bolus Materials to Highly Absorbent Polypropylene and Rayon Cloth

This study assesses the utility of a highly absorbent polypropylene and rayon cloth (HAPRC) as a bolus material in radiation therapy. A comparison of various bolus materials used clinically at our center to the test bolus material, water-saturated HAPRC, was conducted. The reproducibility of the physical density was assessed by computerized tomography (CT) scanning the water-saturated HAPRC on a uniform density block phantom on multiple occasions, allowing the cloth to dry fully between subsequent CT scans. The cloth was found to have a consistent physical density between 0.8 and 1.0 g/cm³. To evaluate the dosimetric impact of the various bolus materials, metal oxide semiconductor field effect transistor dosimetry measurements were performed for a 6 MV treatment beam on the anterior surface of an anthropomorphic thorax phantom. The ability of the bolus material to conform to an irregular surface was assessed by CT scanning the various bolus materials overlaying the nose of an anthropomorphic head phantom and another irregularly shaped test object. The HAPRC conforms well to irregular contours and is relatively inexpensive compared to Superflab and thermoplastic sheets. Before implementing the material into the clinical setting, an appropriate process for laundering the material should be determined, for hygienic reasons.