Clay as thermoluminescence dosemeter in diagnostic radiology applications

As part of efforts to isolate and utilize local and naturally occurring materials for development of thermoluminescece dosemeters and other technologies, an earlier report had shown that Nigerian clay showed prospects of utility as a thermoluminescence dosemeter (TLD). This paper reports the investigation of the basic thermoluminescence properties of clay at x-rays in the diagnostic radiology range, including dose monitoring in abdominal radiography.

Clay sourced from Calabar, Nigeria, was tested for thermoluminescence response after irradiation at diagnostic radiology doses, including application in abdominal radiography dose monitoring in a clinical setting.

Results show that thermoluminescence (TL) output in natural clay is very low, but demonstrates enhanced performance with the addition of common salt. Specific TL characteristics of good repeatability for individual and batched pellets (variability index of 3.08%) and a high degree of trap emptying were observed. It had a glow curve peak at 275 degrees C; with traces of spurious thermoluminescence emission at the reader anneal temperature. There was evidence of good batch homogeneity (< 30%) and a similar pattern of dose absorption in abdominal radiography with commercial Lithium Fluoride (LiF TLD-100). A high fading rate (over 30% in twelve hours) and low sensitivity (12 times less than LiF TLD-100) however, signal the unacceptability of clay as a TLD in diagnostic radiology in the forms studied.

Clay demonstrates poor TL response at diagnostic radiology doses. However, it's water absorbing property offers a means of overcoming the hygroscopic nature of common salt. This could be explored to improve the use of sodium chloride as a radiation detector.