Divergencies between chemical shift measurements of temperature and directly measured values using optical sensors have been studied in vivo in human peripheral muscle with the assistance of a variety of experimental and theoretical techniques. These include the modelling of both thermal and susceptibility changes using two- and three-dimensional finite element methods, as well as the use of multi-wavelength near-infrared observations. The conclusion of these studies is that a simple temperature calibration is not accessible, with results affected by the complex response of the tissue itself.

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An RF coil, made by twisting a conventional wire loop, was tuned to form an extended sensor to provide an effective method of showing the track of a catheter. A twisted‐pair coil can be made small enough in diameter to pass through needles in common clinical use. The coil has a very small field of view and in transmit/receive operation has minimal effect on the magnetization of the surrounding tissue. Magn Reson Med 41:636–638, 1999.  © 1999 Wiley‐Liss, Inc.

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A novel brushless ac permanent-magnet motor is described. This is intended for use as a highly efficient machine for a propeller-driven stratospheric aircraft. The machine is lightweight because of the use of plastics for the structural elements. A form of modeling is described in which the parameters for a decoupled equivalent circuit are calculated by three-dimensional finite-element analysis of a module of the machine. Matlab is then used to simulate the equivalent circuit action. It is shown that the fundamental component of the current waveforms agrees closely with a simple analysis approach.