AMBIENT LIGHT EXPOSURE OF PHOTOSTIMULABLE PHOSPHOR PLATES: IS THERE A SAFE LIMIT FOR ACCEPTABLE IMAGE QUALITY?
Department of Oral Diagnosis, Division of Oral Radiology, Piracicaba Dental School, University of Campinas (UNICAMP), Piracicaba, São Paulo, Brazil
Introduction: Photostimulable phosphor (PSP) plates are widely used in dental routine and unsheathed or partially sheathed PSP plates can be unintentionally exposed to ambient light after X-ray exposure, leading to a demonstrated deterioration in quantitative metrics of image quality. Despite the importance of quantitative assessments, the clinical relevance related to the reported outcomes should be validated by human observers. Aim: To subjectively evaluate radiographs obtained with PSP plates exposed to clinical levels of ambient light prior to read-out to potentially set a safe limit for acceptable image quality.
Material and Methods: Six dental regions of a dry human skull were X-rayed using PSP plates from VistaScan and Express under four exposure times: 0.1, 0.2, 0.32, and 0.4 s. Before the read-out, the PSP plates were exposed to ambient light for 0, 5, 10, 30, 60, and 90 s. Six observers were asked to classify the 288 resulting radiographs as acceptable or unacceptable based on the identification of anatomical structures and global image quality. The number of answers classifying radiographs as unacceptable was used to calculate a rejection rate; a pairwise comparison for better image quality was further conducted among radiographs considered acceptable. Reproducibility was tested by having 25% of all experimental groups reassessed.
Results: Intra- and inter-observer agreement ranged from 0.87 to 1.00 and from 0.81 to 0.92, respectively. Exposure of PSP plates to light increased rejection rates mostly as of 10 s. In the pairwise comparison, subtle differences were observed between radiographs obtained with PSP plates not exposed and those exposed to light for 5 s.
Conclusions: A safe limit of ambient light exposure of 5 s for VistaScan and Express should be considered. Ambient light exposure of PSP plates within safe limits can avoid retakes and reduce unnecessary patient exposure to X-rays.