Subjective Evaluation of a Novel Method of X-ray Dose Reduction by Optical Re-Exposure of Conventional Radiographs with a Multi-Observer R.O.I. Evaluation

A procedure been previously described that has an effect on the image quality and radiation dose of conventional radiographs already at the time of acquisition. This development is using X-ray sensitization by optical re-exposure. Aim of this study was to establish if the results of optical re-exposure measured with SNR and MTF also meant that the subjective quality of 50% dose reduced and re-exposed radiographs of bony structures was equal or better than conventional full dose radiographs of the same area. Freshly slaughtered anterior shoulders of lambs with preserved soft-tissue mantles and natural water content served as the animal model. A comminuted fracture in the middle of the shaft was artificially produced. After taking a normal exposed reference image, dose-reduced, five underexposed images were prepared by reducing the mAs product by exactly 50% with constant anode voltage. A conventional radiograph was taken in a single plane standard position from the object, which served as the reference image. These underexposed X-rays were then optically re-exposed for a defined period of time before development. In all images different osseous structures were defined as Regions of Interest (ROI). On the basis of these ROI`s, the subjective changes in image quality (information loss or gain) of images 2-6 were compared to the reference image 1 and evaluated by 16 physicians with large experience in diagnosis of orthopaedic radiographs. The evaluation of the observers scoring showed a significant decrease in subjective image quality regarding the detail recognition in all images apart from the images re-exposed for 60 sec. Comparing image 5 with the reference image, detail recognition of the ROI A was also evaluated as insignificantly improved (p = 0.31) even with a score of +0.06 above the level of the reference image. In conclusion, there is a possibility of reducing the collective radiation dose whilst keeping a high degree of diagnostic reliability. Film sensitization provides a technically simple and inexpensive procedure, which can be easily integrated into common film development processes and could considerably reduce patient radiation exposure as well as improve image quality and thus detail recognition.