Jaman Son, Jin Dong Cho, Seongmoon Jung, Chang Heon Choi, Jong Min Park, Jung-in Kim
Contact lens-type ocular in vivo dosimeters (CLODs) were recently developed as the frst in vivo dosim eter that can be worn directly on the eye to measure the dose delivered to the lens during radiotherapy. However, it has an inherent uncertainty because of its curved shape. Newton’s ring efect inevitably occurs because the spacing between the glass window and the active layer is not constant. Furthermore, it involves a large uncertainty because the objective of the CLOD with such morphological characteristics is to measure the dose delivered to an out-of-feld lens. In this study, we aimed to investigate the efects of various compensating materials on the sensitivity, accuracy, and uniformity of analysis using a curved CLOD. We developed a new scanning methodology that involves applying a compensating material to reduce the uncertainty caused by the air gap.
Four compensating materials—Dragon Skin™ 10 (DS), a transparent silicon material, SORTA-Clear™ 40 (SC), optical grease (OG), and air (no compensating material)—were used in this study. The CLOD was scanned in the refective mode and transmission mode using each compensating material. We then examined the sensitivity, accu racy, and scan uniformity to evaluate the scanning methodology using compensating materials.
The increase in sensitivity was the highest for OG compared to that for air in the refective mode. On aver age, the sensitivity in the refective mode was higher than that in the transmission mode by a factor of 2.5 for each dose. Among the four compensating materials, OG had the smallest uncertainty. Therefore, the best scan uniformity was achieved when OG was used.
Scanning methodology was proposed in which a compensating material is applied for a curved lens type dosimeter. Our results show that OG is the most suitable compensating material to obtain the best accuracy of dose analysis. Following this methodology, the scan uncertainty of curved dosimeters significantly decreased.