Conventional screen/film vs reduced exposure photostimulable phosphor plate imaging in lower extremity venography: an ROC analysis.

Half-exposure phosphor plates used in venography substantially reduce the total X-ray exposure to a patient while increasing the chance that all images will be of excellent diagnostic quality. Simultaneous half-exposure phosphor plate and full-exposure conventional screen/film venograms were obtained of 35 patients and compared by using receiver operating characteristic (ROC) analysis. The area under the ROC curve ranged from 0.67 to 0.78 for conventional films and 0.68 to 0.91 for phosphor plates. Group performances on conventional films vs phosphor plates were not statistically different. No statistically significant difference in individual performance with the two techniques was seen in seven of the eight interpreters at the 95% confidence level. The eighth interpreter performed significantly better with phosphor plates than with conventional films. Interpreters with and without specific experience in phosphor plate venography were grouped separately, and performance of the two groups was compared in each technique. No difference in performance was found between the groups when interpreting conventional venograms, but, when interpreting phosphor plate venograms, the group with specific experience performed significantly better than they had with conventional venograms, and significantly better than the other group did at interpreting either conventional or phosphor plate venograms. We conclude that phosphor plate venograms made at a 50% reduction in X-ray exposure are equal to, and may surpass, conventional screen/film venograms for diagnosing acute venous thrombosis of the calf and thigh. We recommend expanding the indications for phosphor plate radiography to include contrast venography of the lower extremities.