DIRECT P-31 IMAGING IN HUMAN LIMB AND BRAIN

Objective: This article describes two methods for direct imaging of th e P-31-metabolites phosphocreatine (PCr) and inorganic phosphate (P(i) ) and their application in human brain and muscle. Materials and Metho ds: All studies were performed on a 1.5 T whole-body GE Signa scanner, using bird cage resonators double-tuned to P-31 and H-1. The pulse se quence was based on a multiple slice, multiple echo imaging sequence. Selection of the PCr signal was achieved either by selective excitatio n or by the extensive chemical shift artifact in read direction. Exami nations were done in two diabetic patients, in four patients with cere bral neoplasms, and in several healthy subjects. Results: In calf musc le, images showed uniform distribution of PCr in normal muscle; defici ts corresponded to bony structures and neurovascular bundles. Repeated exercise (dorsiflexion of the foot) led to selective loss of PCr in t he anterior muscle compartment. A simultaneous increase in P(i) appear ed as a spatially distinct map. Diabetic patients showed more severe c hanges of PCr distribution in the calf muscle at rest and during much milder exercise. Direct imaging in the human brain with chemical shift selective excitation was completed in 5-30 min. In normal cerebral co rtex, PCr was uniformly distributed around deficits marking the latera l ventricles. Tumors exhibiting moderate to severe depletion of PCr ap peared as well defined deficits in the PCr image. Conclusion: Direct i maging of PCr and P(i), with or without selective excitation of PCr, w as effective in the human brain and limb. The methods described should lead to greatly improved fast phosphorus imaging. Clinical utility in peripheral ischemia and in localized energy deficits in the brain of patients with tumor, stroke, and other pathologies is anticipated.