Early experience of a commercial scanned focused ultrasound hyperthermia system

Preliminary experiences of the Sonotherm 6500 scanned focused ultrasound (SFUS) system in the hyperthermic treatment of bulky tumours in breast, superficial sites and within the pelvis in 22 patients are reported. Tumour volumes ranged from 235 to 603 cm3 (breast), 105 to 209 cm3 (superficial sites) and 24 to 905 cm3 (pelvis). Temperature distributions in 58 evaluable treatments were analysed in terms of temporal peak and time-averaged temperatures (highest and lowest temperatures, percentage of sensors exceeding index temperatures, etc.) achieved within scanned volumes. Mean number of sensors implanted into tumour was 14 in breast and superficial tumours and approximately 11 in pelvic tumours. Mean time-averaged maximum and minimum temperatures for the best treatments (i.e. for each patient, that with the highest percentage of sensors recording time averaged temperatures greater than or equal to 42 degrees C) administered to patients with tumours in the breast and superficial sites were 44.6 +/- 1.7 degrees C and 39.7 +/- 1.1 degrees C, respectively and the mean number of sensors exceeding 42 degrees C was 58 +/- 19%. In the case of pelvic tumours these figures were 41.6 +/- 0.9 degrees C, 40.0 +/- 0.6 degrees C and 8 +/- 12%, respectively. Patient tolerance to treatments was, in general, good. Areas where technical improvement of the system is appropriate and further research and development are required are identified; these should lead to a better realization of the potential of the SFUS technique, particularly for pelvic tumours.