Use of magnetic resonance spectroscopy in the evaluation of skin flap circulation.

The assessment of events that occur in elevated skin flaps has been largely by indirect methods. A method was sought that gives direct, reproducible, and accurate data about physiological and biochemical changes that occur during flap elevation and during periods of altered blood flow. Because of its ability to monitor changes in the levels of high energy phosphorus metabolites (ATP or adenosine triphosphate, PCr, or phosphocreatin, Pi, or inorganic phosphate), 31p magnetic resonance spectroscopy (MRS) holds promise of providing direct assessment of the metabolic status and biochemical changes that occur during skin flap elevation. MRS monitoring was performed on raised abdominal skin flaps of 12 rats. Abdominal flaps in 4 animals served as controls with and without total vascular occlusion while arterial blood flow was manipulated in 4 flaps and venous flow in 4 flaps. The results have validated the ability of MRS to determine cellular levels of ATP, PCr, and Pi in skin flaps, and to measure intracellular pH through the chemical shift of the Pi resonance.