X-Ray Trends Exposure Calculator (late 1970s)

This slide rule was developed by the US Food and Drug Administration for use in their Nationwide Evaluation of X-Ray Trends (NEXT) program. Since the copyright date on the calculator is 1976, I assume that it was probably manufactured in the late 1970s. The rule body is plastic while the slide is cardboard.

The NEXT Program compiles X-ray exposure data on an annual basis, and has been doing so since 1973. In 1983, the program began using specially developed human phantoms for these studies, and they also began limiting each years study to a specific type of medical examination.  

One side of this calculator (the one shown above) concerns the exposures due to medical X-rays. The other side deals with dental X-ray exposures. For example, given the current (mAs), the distance from the source, and the tube voltage (kVp), the calculator estimates the exposure in mR.

Size: ca. 3.1" x 8.4"