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Nuclear magnetic resonance (NMR) spectroscopy of small lesions is restricted by the difficulties of localizing the surface coil with respect to the lesion and the problem of ensuring that signal is only obtained from the lesion and not from surrounding tissue. A double-tuned coil has been developed that permits NMR proton images to be obtained from a region of interest, prior to carrying out 31P spectroscopy of the same region with the same coil, without the need for further adjustment. The coil provides a means of accurately localizing the region from which the 31P signal is obtained, whilst offering a means of accurately applying 31P signal localization methods, and the possibility of making corrections for the nonuniform sensitivity of a given surface coil. The coil makes use of two parallel resonant circuits, with independent rf connections, but sharing a common coil. Simulated shorted and open circuit lambda /4 cables are used, respectively, to open circuit each circuit at the resonant frequency of the other circuit and ensure that the simulated lambda /4 line is short circuited for each circuit at the circuit's resonant frequency. At 63.6 MHz, the Q of the coil was 190 unloaded and 90 loaded, and at 25.7 MHz the Q was 210 unloaded and 140 loaded, for a 4-cm-diam coil. The coil has been used to obtain proton images and 31P spectra. A circuit employing only one input was also developed.

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A novel type of solid-state laser with a tubular active element made of Nd:YAG is presented. Using the tube geometry, one can achieve higher efficiency and higher output power per laser crystal than by using a rod or slab geometry. Our tube laser is pumped from the inside by four flash lamps. The slope efficiency of 9% and the total efficiency of 7.5% at as much as 400 W of output power are, to our knowledge, the highest values reported for flash-lamp-pumped Nd:YAG lasers. At 15 kW, 75% of the maximum available pumping power, the output power is 1000 W. Thermal lensing is five times lower than for an equivalent rod laser.