An investigation was made to evaluate currently used subtraction radiography techniques. The first order subtraction technique was found to be adequate for conventional clinical use. However when using fine-grain high contrast films for the originals, the second order technique gave a more accurate subtraction image. The limiting factor in the sensitivity of the radiographic subtraction technique for detecting small contrast changes over an area of about 2 cm in diameter was found to be film noise and not quantum statistics. Extra-fine-grain films were compared with conventionally used films. While these extra-fine-grain films gave slightly better results, they also required x-ray exposures which would be too high for routine clinical use.
Michael G. Ort,
Earle C. Gregg,
"Characteristics and Limitations of Photographic Films Used in Subtraction Radiography," Optical Engineering 15(4), 154349 (1 August 1976). https://doi.org/10.1117/12.7971991