B G Akdeniz1, H-G Gröndahl. 1. Department of Oral Diagnosis and Radiology, School of Dentistry, Ege University, Izmir, Turkey. bgunb@yahoo.com
Abstract
OBJECTIVE: To evaluate the degradation of storage phosphor images relative to scanning delay. METHODS: A series of exposures of an aluminium step-wedge with five 2 mm incremental steps were made using blue Digora storage phosphor plates (SPPs). After the first exposure the plates were immediately scanned. After the second the plates were scanned after a half hour delay, after the third after a 1 h delay and so on until a final delay of 8 h. Mean grey values (MGVs) of each step of the wedge and its background were compared using repeated measures analysis of variance (ANOVA). Difference between group means was assessed using Bonferroni/Dunn multiple comparison test (P<0.05). RESULTS: MGVs increased with the increase in scan delay. Repeated measures ANOVA revealed that MGVs of the background and each step of the wedge were significantly different from each other for all scan delays (P<0.0001). Bonferroni/Dunn test showed that MGVs from plates scanned half an hour after exposure were not significantly different from those scanned immediately (P>0.05). Longer delays gave rise to significant differences in MGVs (P<0.05). CONCLUSION: Digora SPPs show statistically significant degradation of grey level values and contrast in plates scanned half an hour or longer after exposure.
OBJECTIVE: To evaluate the degradation of storage phosphor images relative to scanning delay. METHODS: A series of exposures of an aluminium step-wedge with five 2 mm incremental steps were made using blue Digora storage phosphor plates (SPPs). After the first exposure the plates were immediately scanned. After the second the plates were scanned after a half hour delay, after the third after a 1 h delay and so on until a final delay of 8 h. Mean grey values (MGVs) of each step of the wedge and its background were compared using repeated measures analysis of variance (ANOVA). Difference between group means was assessed using Bonferroni/Dunn multiple comparison test (P<0.05). RESULTS: MGVs increased with the increase in scan delay. Repeated measures ANOVA revealed that MGVs of the background and each step of the wedge were significantly different from each other for all scan delays (P<0.0001). Bonferroni/Dunn test showed that MGVs from plates scanned half an hour after exposure were not significantly different from those scanned immediately (P>0.05). Longer delays gave rise to significant differences in MGVs (P<0.05). CONCLUSION: Digora SPPs show statistically significant degradation of grey level values and contrast in plates scanned half an hour or longer after exposure.