Analysis of digital images acquired using different phosphor storage plates (PSPs) subjected to varying reading times and storage conditions

Objectives: To assess, both objectively and subjectively, the effects of different combinations of storage conditions and varying delays in reading on digital images captured using phosphor storage plates (PSPs). Method: Standardized images were obtained of an aluminium step wedge and a dry mandible in acrylic using GE 1000 and PSPs from the Digora((R)) (Soredex) and DenOptix((R)) (Gendex) digital systems. Twelve plates from each system were exposed and immediately scanned to produce the baseline gold standard. The plates were re-exposed and stored using three different storage combinations, (A) ambient temperature, (R) refrigeration and (S) low humidity, and then scanned after 6 h, 12 h, 18 h, 24 h, 48 h or 72 h. Objective analysis was carried out by pixel density measurements and the data were analysed statistically using analysis of variance. Subjective analysis was carried by three oral radiologists and the results were analysed using Mann-Whitney U-test. Results: For the DenOptix((R)) system there were no differences either objectively or subjectively in the images obtained from all the plates using different storage conditions and after varying time intervals. For Digora((R)), objective analysis showed loss of pixel density after 6 h using all storage conditions. This loss of density was also evident subjectively after 6 h on plates stored under certain storage conditions. Conclusion: Storage of DenOptix((R)) PSPs for up to 72 h in different conditions does not affect the quality of the digital images. However, there is a loss of image density within 6 h when using Digora((R)) PSPs, which may affect clinical image interpretation.o TEXTO COMPLETO DESTE ARTIGO, ESTARÁ DISPONÍVEL À PARTIR DE AGOSTO DE 2015.32318619

Reproducibility of pixel values for two photostimulable phosphor plates in consecutive standardized scannings Reprodutibilidade dos valores de "pixels" de duas placas de fósforo fotoestimuláveis em leituras padronizadas consecutivas

The objective of the present study was to determine the reproducibility of the pixel values obtained with the Digora system (Soredex, Finland). Exposures were standardized, with variation in exposure and scanning time of two photostimulable phosphor plates containing a stepwedge image. The smallest variation in pixel values ranged from 50 to 75%, with the widest variations being observed in less dense steps. A significant difference in pixel values was observed in terms of X-ray exposure and scanning times and between the two plates themselves (ANOVA, p < 0.01). Using the present methodology, the reproducibility of pixel values was not satisfactory for the tested white photostimulable plates. This wide variation in digitalization might be influenced by the amount of X-rays that sensitized the plates. It may be important to establish the reproducibility of the pixel values in quantitative studies using digital image.<br>O objetivo do presente trabalho foi determinar a reprodutibilidade dos valores de "pixels" obtidos com o sistema Digora (Soredex, Finlândia). As exposições foram padronizadas, com variação no tempo de exposição e leitura de duas placas de fósforo fotoestimuláveis contendo a imagem de um penetrômetro. A menor variação nos valores de "pixels" foi de 50 a 75%, sendo as maiores variações oriundas nas faixas mais claras. Uma diferença significante nos valores de "pixels" foi observada em relação ao tempo de exposição e leitura das placas e entre as duas placas (ANOVA, p < 0,01). Utilizando a presente metodologia, a reprodutibilidade dos valores de "pixels" das placas testadas do sistema Digora não foi satisfatória. Essa grande variação na digitalização pode ter sido influenciada pela quantidade de Raios X que sensibilizou as placas. Isso pode ser importante para estabelecer a reprodutibilidade dos valores de "pixels" em estudos quantitativos usando imagem digital