The crossover surface coil is constructed with two turns of copper foil using a unique transposition construction which incorporates an explicit center tap ground of the widened bottom layer. The coil reduces dielectric and inductive losses by effective shielding of electric fields and uniform distribution of magnetic fields for minimum Q losses upon loading of the coil. Flexible, copper foil construction permits easy conformation to tissues of interest, enhancing coil performance. Construction details of the crossover coil and Q data for coils of various sizes operating at a number of frequencies are given.

An elongated, narrow, slotted crossover surface coil provides surface localization capable of resolving in vivo 31P NMR spectra from skin tissues. The shallow B1 field penetration achieves localization objectives while the probe length maintains signal-to-noise requirements. Dielectric and inductive losses are minimized via the crossover design (see T. L. Nagel et al., Magn. Reson. Med. 13, xxx (1990). In vivo spectra with millimeter depth resolution were acquired in 5 min at 2 T without pulse localization sequences. Preliminary 31P NMR spectra of normal and thermally injured rat skin were completed using a 25 X 3-mm slotted probe with a 3 X 2-cm surface region of excitation. Normal rat skin tissue PCr/Pi ratios ranged from 3.8 to 4.7 for 5-, 10-, and 30-mus pulse widths, while partial- and full-thickness scald injured tissues ranged from 0 to 2.8. Evaluation of a single minor partial thickness injury 1 to 5 h postburn shows evidence of a localized hypermetabolic response associated with hyperemia. Determination of burn depth and tissue viability appears feasible using: (1) PCr/Pi ratios and (2) observation of localized hypermetabolism.