Chest radiography with a digital flat-panel detector: Experimental receiver operating characteristic analysis

PURPOSE: To evaluate the influence of different detector radiation doses and peak kilovoltage settings on diagnostic performance and radiation dose at posteroanterior (PA) chest radiography performed with an amorphous silicon flat-panel detector (FPD). MATERIALS AND METHODS: All examinations were performed by using a digital FPD. PA chest radiographs of an anthropomorphic chest phantom were obtained with detector radiation doses of 2.50 μGy (system speed, 400), 1.56 μGy (speed, 640), and 1.25 μGy (speed, 800) and with peak kilovoltage values of 100, 120, and 140 kVp. Four types of simulated lesions - nodules of different sizes, polylobulated lesions, interstitial-nodular lesions, and interstitial-reticular lesions - were superimposed on the phantom. After four radiologists assessed all of the images, receiver operating characteristics analysis was performed. In addition, the entrance surface dose was measured and the effective dose was calculated. RESULTS: Reduced detector dose led to significantly decreased diagnostic performance in overall lesion detection (P < .05). However, over pulmonary areas only, this effect could not be seen. With use of the same kilovoltage values, reducing the detector dose, even to 1.25 μGy (speed, 800), did not lead to significantly decreased lesion detectability. In terms of diagnostic performance and effective dose, 120 kVp was the most effective. CONCLUSION: Standard PA chest radiographs should still be acquired at a detector dose of 2.50 μGy (speed, 400) with 120 kVp to yield the highest diagnostic performance. However, when the present analysis was focused on the lung fields only, no significant loss in diagnostic performance could be demonstrated, even after a 50% reduction in radiation dose.