A study on evaluation of surface contamination activity of 67 Ga, 99m Tc and 131 I used in nuclear medicine using wipe-test samples measured by a surface contamination monitor based on ZnS(Ag) scintillator

In general, radioactive materials can be removed from surfaces by non-destructive means, e.g., wiping or washing. In order to decide if removable contamination is present through wiping the surface with a dry or wet material, this needs the wipe material surface activity to be evaluated by a validated method. Hence the aim of this study is to perform verification of the two-step calibration procedure of a surface contamination monitor(SCM), and thenit is apply this this method to evaluate the measured surface removable activity measurement (Bq∙cm ^− 2 ) through dry wipe materials contaminated with some nuclear medicine radioisotopes like ^99m Tc, ¹³¹ I, and ⁶⁷ Ga. In this study, a commercially available ZnS(Ag) based LB 124 Scint-300 SCM device was used to measure the surface activity of the cotton textile samples. Reference plate sources of 10cmx10cm size ( ²⁴¹ Am, ⁹⁰ Sr/ ⁹⁰ Y, and ¹³⁷ Cs) in accordance with ISO 8769 were used for the calibration of the SCM according to the requirements of ISO 7503-3 standard To this end, the direct method was chosen to obtain a calibration factor(CF)in which the countrate(cps) was converted to Bq∙cm ^− 2 by taking in consideration the particle emergence factor and effective window area. For the surface activity evaluation, cotton textile pieces with an area of 100 cm ² and 345 cm ² were respectively contaminated by droplets of ^99m Tc, ¹³¹ I, and ⁶⁷ Ga with known activities prepared from their liquid solutions. The obtained activity results were presented for the parameters affecting the accurate measurement of surface activity of the wipe material as an indirect method, in which the employed SCM method and the results obtained for alpha and beta/gamma surface contamination measurements were discussed in detail.