A Hemispherical Sparse Phased Array Design For Low Frequency Transcranial Focused Ultrasound Applications Without Skull-Specific Phase Aberration Correction

摘要

A sparse large-element hemispherical phased array scheme was investigated for low frequency transcranial focused ultrasound applications without skull-specific phase aberration correction. The simulated transcranial focused beams in brain from the randomly distributed sparse array elements (0.25 MHz, 125 mm radius of curvature, 250 mm diameter, 50% sparsity of 953 square elements of 10 mm spacing) could be steered without skull specific aberration correction at 0.25 MHz. The 28 foci were on average 1.7±1.2 mm shifted from their intended locations. The average –3 dB beam width and length were 3.3±1.2 mm and 6.3±2.2 mm, respectively. The sidelobe levels ranged from 28% to 62% of the peak pressure values. The focal beam was steerable 35 mm laterally away from the transducer center axis and 30 mm axially in the transducer center axis when the sidelobe pressure values were 50% of or less than the peak pressure values. This allows the array to be mechanically aimed to one quarter of the brain and then electronically steered. The sparse array design offers a tradeoff between the best beam steering range and the manageable number of elements for a practical clinical system.