The number of bits required for storing the information contained in an x-ray image depends primarily on the x-ray exposure at the image plane and on the desired spatial resolution. This dependence has been determined from calculations of the maximum attainable signal-to-noise ratios for exposures and resolutions respectively in the regions from 10-2 to 102 milliroentgens and 10-4 to 1 cm2. The results show that for the different image sizes and exposures used in diagnostic radiology, the number of bits required for the storage of these images extends from approximately 105 to 108.
J. W. Motz,
"Information Storage Requirements In Radiology", Proc. SPIE 0206, Recent and Future Developments in Medical Imaging II, (26 December 1979); doi: 10.1117/12.958191; https://doi.org/10.1117/12.958191