In vivo inductive phase shift measurements to detect intraperitoneal fluid.

Four different volumes of physiological saline were infused into the abdominal cavity of rats and the resulting inductive phase shift in the bulk of the abdomen was measured with a noncontact electrical induction system, built to measure phase shift in the bulk of the body in the frequency range from 1 MHz to 8.5 MHz. This experimental study shows that inductive bulk measurements of phase shift have the potential to detect changes in intraperitoneal fluid in vivo with measurements made at frequencies higher than approximately 1 MHz. The experiments also show that the bulk phase shift increases as a function of frequency and fluid volume in a way that is qualitatively consistent with earlier theoretical predictions.