Figure 3.

Illustrative controlled hyperthermia by focused ultrasound

Real-time thermometry data (trace) captured after infusion of lyso-thermosensitive liposomal doxorubicin (LTLD) and during focused ultrasound exposure in moving beam (linear) mode for patient I.05. This trace was acquired at a 10 ms resolution by use of a calibrated Medtronic thermocouple, with custom LabView data-acquisition setup. Shaded regions represent the period when focused ultrasound was being applied. From approximately 30 s to 33 min, a 90·9 cm³ prescribed target tumour volume was exposed to focused ultrasound at 115 W (8·7 MPa peak rarefactional in situ pressure) at 70% duty cycle in linear mode. Although the release threshold was reached within 5 min of focused ultrasound exposure, heating in the first 30 min was deemed slightly suboptimal because of prolonged cooling periods between treatment cycles. Subsequently, by removing the outermost slices from the prescribed treatment volume, resulting in a smaller 68·3 cm³ tumour volume, and increasing power to 125 W (9·0 MPa derated) and duty cycle to 77%, optimal hyperthermia was achieved for 35–80 min. Once focused ultrasound stopped, the tumour was allowed to cool before the thermocouple was removed from the patient at 85 min, and a tumour biopsy sample was subsequently taken. The dotted curve is a fourth order polynomial fit, which is probably more representative of the bulk temperature in the prescribed tumour volume than the rapidly fluctuating point temperature recorded by the sensitive region of the intratumoural thermometry device (trace).