Evaluation of Cryogenic Temperature Sensors for Use in Electromagnetic Fields

The establishment of organ banks for long-term storage could become feasible if rapid, uniform electromagnetic thawing of cryopreserved organs can be accomplished. Internal and external temperature measurements of the organ during thawing will be nec­ essary to provide real-time data on tissue heating rate and distribution. This information will be use­ ful for both optimization of thawing system design and as an input for system power control. But because conventional measurement techniques which are useful at cryogenic temperatures are not suitable for use with EM thawing systems, several alternative methods for making temperature measurements have been inves­ tigated. These alternative methods include techniques where temperature probes are implanted in the bio­ logical tissue and techniques employing non-invasive temperature sensors. From a clinical standpoint, a non-invasive temperature sensor would be the best alternative for measurements in cryopreserved organs. It would minimize introduction of foreign materials into the organ and would also reduce long term costs by eliminating the need to implant separate sensors in each organ. On the other hand, temperature probes can provide localized temperature data which a ■noninvasive measurement technique might not. Also, probes are more nearly feasible in the current measurement technology than are non-invasive techniques. In this paper, the requirements of a cryogenic temperature sensor suitable for use in the presence of an electro­ magnetic field will be discussed and both non-invasive and probe measurement techniques will be considered.