New Aspects concerning X-ray Protection - Dose Reduction versus Diagnostic Information?

In comparison to conventional screen-film combinations Digital Radiography (DR) offers several advantages, i.e. reduction of the x-ray exposure and the further option of image processing. It is an obvious controversy that collimated film areas provide information for cephalometric analyses. One of the most interesting side effects of DR is the possibility to perform a complete analysis of the entire scull in typically collimated lateral cephalograms.The aim of this prospective study was to determine the validity of this special image processing method developed by the Department of Orthodontics, University of Muenster.Out of 400 digital radiographs taken for orthodontic diagnosis, 100 lateral head films were randomly selected. The routine radiographs were taken from the Department of Radiology, University of Muenster. For each patient the facial cranium exclusively was faded in and exposed at 77kV/12 mAs with an anode to film distance of 350 cm.The digital image acquisition included laser-scanning (pre-read) of the storage phosphor plates, individual processing of every image (Pattern Recognition for Iris of Exposure Field - algorithm) and storing of the original and processed images using the DICOM - format.The intra-individual reproducibility of the landmarks defined by DELAIRE who proposed a cranial and craniofacial analysis was examined using the NIH-Image 1.62 analysis program.The results show that it is possible to attain information from collimated areas (cranial vault, cervical vertebra) using DR combined with special image processing methods. This is due to the x-ray scatter and the various contrast enhancements possible in different film areas of the same image.The information attained from these areas with very low x-ray load is sufficient for a complete cranial analysis proposed by DELAIRE, so that an increase of field size can be avoided in many clinical cases.For the first time since 1987 the gold standard of head film acquisition for the DELAIRE-Analysis proposed by PRECIOUS and MILES has been redefined. Parole chiave: Digitale Fernröntgenseitenbilder, digitale Lumineszenzradiographie, Strahlenreduktion, Delaire-Analyse