Effectiveness of shielding materials against 177Lu gamma rays and the corresponding distance relationship.

Abstract

The purpose of this study is to determine the dose reduction of different shielding materials at various distances from a 177Lu photon radiation source. Two protective aprons with lead equivalent thicknesses of 0.25mm and 0.35mm and tungsten-containing rubber (TCR) were used as shielding materials. A vial containing 177Lu was sealed in a lead container so that a narrow beam went out through a 3mm-diameter hole. The dose rate was measured at distances of 0, 10, 50, 100, and 200cm from the source using a NaI scintillation survey meter to obtain the rate of dose reduction. TCR was tested with thicknesses ranging from 0.3 to 1.0mm at 0.1mm intervals and from 1.0 to 4.0mm at 0.5mm intervals. At distances of 0, 10, 50, 100, and 200cm, the dose reduction for the lead equivalent thickness of 0.25mm were 32.7%, 54.5%, 93.1%, 97.9%, and 99.6%, respectively; and for the lead equivalent thickness of 0.35mm were 53.4%, 70.6%, 95.6%, 98.9%, and 99.6%, respectively. Without any shielding, the dose rate decreased by 34.4% at 10cm and by 88.8% at 50cm from the radiation source. The dose reduction for the TCR thickness of 3.5mm was 89.8% at 0cm and 93.3% at 10cm. The TCR thickness of 0.4mm provided a dose reduction comparable to or greater than that of the 0.25mm lead equivalent, whereas the TCR thickness of 1.0mm or greater provided a dose reduction comparable to that of the 0.35mm lead equivalent. Achieving a reduction of 95% or more requires the 0.25mm lead equivalent for a distance of 100cm, the 0.35mm lead equivalent for 50cm, the TCR thickness of 0.3mm for 100cm, or the TCR thickness of 0.9mm for 50cm. Without wearing a protective apron, a reduction of approximately 95% is observed at distances greater than 100cm. These findings would be useful for medical staff engaging in related activities.