Perimeter encoding for teleradiology

Perimeter encoding is a technique of data compression that is done simply by outlining the area of interest on an examination. In a sample of 92 emergency room examinations (excluding chest, abdomen, and pelvic exams), 304 films were interpreted by a resident radiologist who indicated the area of interest by marking four corners of a rectangle. The adequacy of the area of interest was determined by a staff osteoradiologist during subsequent review of the films. The amount of data reduction was measured by determining the ratio of the area of interest inside a rectangle to the area of the film (compression ratio). The overall average compression ratio was 3 to 1. This preliminary study suggests that further evaluation of perimeter encoding is warranted.