Low-profile lenses for ultrasound surgery.
Several flat lens designs have been simulated that focus a planar transducer at various depths and angular deflections. The use of flat lenses with planar phased arrays to create multiple focus patterns has also been explored. The simulations have shown that the discrete element size is practical to machine. Simulations predict that a flat polystyrene lens with an f number of 1.0 can produce a focal peak intensity that is 80% that of a geometrically focused transducer with the same focal depth, including the attenuation through the lens, by utilizing four discrete phase steps. These predictions were verified with a simplified experimental lens utilizing only two phase steps. Simulations predicted an attenuation within the lens of 18% and a focal peak intensity of 38%. Measurements resulted in an attenuation of 30% and a focal peak intensity of 30%. Experimental lens studies have indicated that sufficient power can be transmitted through the lenses for these designs to be feasible for use in ultrasound surgery.