NONMAGNETIC HYPERBARIC CHAMBER FOR INVIVO NMR-SPECTROSCOPY STUDIES OFSMALL ANIMALS

A description is given of the design, construction, and initial use of a polycarbonate resin hyperbaric chamber for in vivo NMR spectroscopy studies of anesthetized, ventilated rats in a horizontal bore 4.7 Tes la magnet. The chamber and its associated equipment, initially used fo r hyperbaric studies of rats in states of extreme hypercapnia, are als o well suited for conventional hyperbaric studies, such as those relat ed to hyperbaric oxygen therapy, oxygen toxicity, and diving. Basic te chnical challenges that required innovations involved: a) preservation of magnetic field homogeneity; b) avoidance of a metallic chamber bod y that would overload gradient and RF coils; c) physiological monitori ng; and, d) remote control and stabilization of electromagnetic and ph ysiologic factors (especially ventilatory stability) during pressure c hanges. A small paramagnetic bulk magnetic susceptibility shift from c hamber-associated hyperbaric oxygen was observed when chamber oxygen t ensions were only one atmosphere. High-quality NMR imaging and spectro scopy were demonstrated during hyperbaric conditions.