A multiple focused probe approach for high intensity focused ultrasound based surgery

To produce deep-seated surgical lesions using ultrasound requires high powe r and intensity levels at the target sites. Conventionally, large transduce rs are used which require big apertures and so are generally suitable only for extra-corporeal access. Such transducers also result in strong off-focu s maxima, where the resulting hot spots can destroy normal tissue whilst de ep-seated large tissue volumes are being ablated. This paper describes a ne w approach in which it is proposed that multiple probes are used simultaneo usly, each at a relatively low power, to result in an overlapping focused r egion of high temperature without strong off-focus hot spots. Robotic techn iques could be used to move the individual probes in coordination to sweep out the desired region of tissue ablation. Simulation and planning are the key to quality prediction for high intensit y focused ultrasound (HIFU). Simplified two-dimensional and three-dimension al models of HIFU probes have been developed to study the characteristics o f various multi-probe configurations. Preliminary simulation results show t hat the multi-probe system can be arranged successfully to minimise off-foc us hot spots. Experimental results are presented which validate the modalit y and confirm this positive finding. Further prediction studies and plannin g will be necessary to achieve the most appropriate desired treatment, by v arying the pulse duration and spacing. (C) 2001 Elsevier Science B.V. All r ights reserved.