Computing adrenal uptakes with compact, fixed-size regions.

In planar nuclear medicine imaging of the adrenal gland, there are three requirements for an uptake determination: finding the region of interest, subtracting 'background', and converting cps to muCi. A computer program that covers each requirement is outlined. The region of interest is determined by a nearest-neighbor region-growing technique. It starts from an operator-chosen center, searches for the hottest pixels, and terminates when a fixed-size region is found. If the resulting region is unacceptable, recourse to a second level of searching, which produces a more compact region, is possible. Background from underlying and overlying tissue is estimated from the average counts/pixel in a narrow 'ring' surrounding the adrenal. Conversion to muCi is carried out by use of a calibration equation which requires a value for the adrenal depth. This value may be obtained from a lateral view. The program is available in listing form. For use with a Medical Data Systems A2 computer, files can be transferred directly. Parameters which should be changed for the use of the program with another camera-collimator system are noted.