ULTRASOUND PHASED ARRAYS FOR HYPERTHERMIA: NEW TECHNIQUES BASED ON THE FIELD CONJUGATION METHOD.

Phased arrays, which can be focused and steered electronically, offer an alternative to the mechanically scanned focused systems currently in use. This could be attributed to the speed and flexibility of electronic control systems which, while complex, can be implemented remotely from the applicator aperture. However, both electrical and mechanical scanning require intense focal spots, which could increase the risk of unwanted nonthermal effects, e. g. , cavitation. Hot spots proximal to the tumor might occur because of near-field beam overlapping due to scanning. A method is proposed to allow scanning at reduced spatial-peak temporal-peak (SPTP) intensity compared to approaches used in conventional scanning techniques. The method permits the direct synthesis of the more diffuse heating patterns useful in hyperthermia without the need for mechanical or electrical scanning.