Acoustic focal characteristics of a transrectal phased array under heterogeneity and weak nonlinearity

This study evaluates how physical factors, nonlinearity and tissue heterogeneity, and technical factors, input power and focal length, influence the acoustic field in high intensity focused ultrasound treatment for prostate cancer. Combining acoustic holography with 3D numerical simulations based on segmented anatomical models, the investigation reveals how physiological variability and modeling assumptions affect focal pressure, acoustic field spatial distribution, and focal shifting. A reliable numerical source modeling required input correction through experimental correlation between electrical power and acoustic output. Results indicate that neglecting tissue heterogeneity and nonlinear propagation leads to significant deviations in focal characteristics. Neglecting the nonlinear propagation, represented here by the second harmonic, can have a significant impact on the simulated total deposited heat rate, depending on anatomical geometry and tissue properties. Additionally, phase correction model-based strategies substantially improve focal alignment, but without focal broadening or peak loss compensation. These findings reinforce the necessity of balancing model complexity with computational efficiency to enable accurate, patient-specific treatment planning. Importantly, no secondary lobes were observed in the simulations, suggesting a favorable safety profile when the focus is precisely controlled.