Heat delivery and thermometry in clinical hyperthermia

This chapter has discussed some recent technical developments and trends in clinical hyperthermia. Several techniques for the treatment of tumours within 3-4 cm of the body surfaces were described. Each technique has its minor advantages and disadvantages; all techniques employing a single applicator produce temperature distributions with considerable gradients. The introduction of microwave and ultrasound techniques using multiple applicators in which there is some control of the pattern of the energy deposition within the treatment area should improve superficial treatments in this respect. A number of electromagnetic devices for regional hyperthermia are being developed and evaluated. The theoretical predictions of their performances are beginning to suggest restrictions to their use; the limited clinical experience is in general agreement with these predictions. Scanned and focussed ultrasound beams may offer the unique possibility of non-invasive, deep, yet localised hyperthermia in some locations. Such systems are at an early stage of their development; if they prove successful, their controlled and safe use will require detailed information of the temperature distributions produced. Invasive methods for inducing hyperthermia can produce relatively good temperature distributions. The development of 'constant temperature seeds' is promising. Both RF and microwave interstitial systems offering individual control of power to several channels should lead to improved temperature distributions. In general, non-invasive thermometry in clinical hyperthermia remains a distant goal, although developments in microwave radiometry may lead to systems with suitable spatial, temporal and temperature resolutions for use in superficial treatments. Invasive thermometry techniques can provide temperature measurements from several points or from along tracks within the treatment volume. The development of computer models to infer temperature distributions from the limited information available will be a major step in quantifying hyperthermal treatments.