Amorphous silicon, flat-panel, x-ray detector versus storage phosphor-based computed radiography: contrast-detail phantom study at different tube voltages and detector entrance doses.

Rationale and Objectives: Evaluation of the contrast-detail performance of an active-matrix flat-panel x-ray detector in comparison with a storage phosphor system with special regard to the potential of dose reduction.
Methods: A digital x-ray detector based on cesium iodide (CsI) and amorphous silicon (a-Si) technology was compared with a fifth-generation storage phosphor system. A lucite plate with 36 drilled holes of varying diameters and depths was used as contrast-detail phantom. At 45 kVp, 70 kVp, and 113 kVp, images at 8 different detector entrance doses ranging between 0.3 microGy and 40 microGy were obtained. On soft-copy displays, 3 masked observers evaluated the detectability of each aperture in each image according to a 5-point scale. The mean sum scores of corresponding images were compared.
Results: For all tube voltages and detector entrance doses, the images obtained with the CsI/a-Si detector resulted in better observer contrast-detail performance as compared with the images of the storage phosphor system. The CsI/a-Si system allowed a calculated dose reduction of 39% at 45 kVp, 68% at 70 kVp, and 81% at 113 kVp as compared with the storage phosphor system, without loss of contrast-detail detectability.
Conclusions: Under the conditions of the chosen experimental design, the CsI/a-Si system provided a superior contrast-detail performance as compared with the storage phosphor system. The potential of dose reduction increased with rising tube voltage.