A radiologist from a well$-$known research hospital recently attended a medical conference at which a system that could transmit $4096409612-$bit digitized X$-$ray images over standard T$1(1\mathrm{.}544M\frac{b}{s})$ phone lines was exhibited. The system transmitted the images in a compressed form using a progressive technique in which a reasonably good approximation of the $x-$ray was first reconstructed at the viewing station and then refined gradually to produce an error$-$free display. The transmission of the data needed to generate the first approximation $100k$ approximately $5$ or $6s.$ Refinements were made every $5$ or $6s($on the average$)$ for the next $1$min, with the first and last refinements having the most and least significant impact on the reconstructed $x-$ray, respectively. The physician