Theoretical evaluation of moderately focused spherical transducers and multi-focus acoustic lens/transducer combinations for high intensity focused ultrasound thermal therapy

grantor: University of TorontoImpractically long treatment times are required for highly focused spherical transducers [HF] to destroy tumours because thermal lesions generated by these transducers are small and a large number of such lesions are required. Moderately focused spherical transducers [MF] and multi-focus acoustic lens/transducer combinations [LTC] can generate larger lesions compared to those produced by highly focused spherical transducers, and therefore shorter treatment times are expected. The degree of improvement in total treatment time by the use of MFs and LTCs was quantified in this study. A 3-D ultrasound thermal model and a target model were developed to calculate treatment times required for various ultrasound transducers, under identical treatment conditions. A LTC design method was developed to determine the thickness of lens elements for production of specified multi-focus fields. The simulation results show for the treatment of a 2 x 2 x 2 cm3 tumour, a HF, MF and LTC require 150, 42 and 30 min respectively.M.Sc