Increased radiographic contrast and dynamic range by combining a rapid multiple scanning beam device with a wide latitude receptor and digital enhancement

The Rotating Aperture Wheel (RAW) rapid multiple scanning beam device is demonstrating marked contrast improvement in initial clinical trials. Although the RAW device is well suited to the short exposure time requirements of chest radiography, such clinical application has not as yet been attempted because the RAW's efficient scatter reduction only accentuates the inherent dynamic range problem. If a large dynamic range receptor, such as very wide latitude film or a storage phosphor, were used in combination with the RAW and the resulting images were digitally contrast enhanced, a higher signal to noise ratio could be realized across the full range of required exposure in lung, subdiaphragmatic, and mediastinal fields. We have recently begun such a study using a system combining the RAW, wide latitute film, and film digitization with scanning microden-sitometer facilities for evaluating images of a chest phantom. Computer enhanced RAW images compared to those obtained using a conventional 12:1 grid show: a) no loss in feature identification in the lung field, b) better visualization of low contrast nodules as well as rib detail in the subdiaphragmatic region, and c) generally better contrast in the mediastinal region. The results clearly encourage further quantitative studies of phantoms as well as preparation for clinical application using larger image matrices.