N × N Square-Element Ultrasound Phased-Array Applicator: Simulated Temperature Distributions Associated with Directly Synthesized Heating Patterns

Computer simulations are conducted to demonstrate the possibility of heating small tumors by appropriately driving the electronic control circuitry of an n × n square-element ultrasonic phased array. The synthesis method consists of simultaneously focusing the ultrasonic beam at different points uniformly distributed along the tumor periphery and, hence, involves no scanning. It is demonstrated that by combining the multiple focusing feature with a new field phasing concept, typical undesired hot spots can be eliminated. The tissue thermal response to this heating modality is investigated by iteratively solving the three-dimensional (3-D) steady-state bioheat equation. Temperature distributions associated with different directly synthesized power deposition patterns are simulated and discussed.