Anti-focus driving signals to mitigate bone heating during focused ultrasound ablation of uterine fibroids with phased arrays
Abstract
Objective. During magnetic resonance-guided focused ultrasound (MRgFUS) treatment of uterine fibroids, ablating tissue near the spine is challenging as unwanted far-field bone heating can cause pain and potentially injure nearby nerves. This study investigates an anti-focus (AF) scheme for minimizing bone heating when targeting fibroid tissue in proximity to the spine.Approach.Acoustic and thermal simulations were conducted using 3D MRI-derived anatomical models from ten patients who underwent MRgFUS for uterine fibroids using a low-frequency (0.5 MHz) 6144-element flat fully-populated modular phased array during a clinical trial (NCT03323905). AF points were distributed over patient spine surfaces with varying densities, transducer array element-wise phase and amplitude controls were obtained via Tikhonov regularization, and the resulting temperature fields were compared to those obtained via both conventional focusing (CF) and a transducer module partial blocking (PB) approach developed to mitigate far-field bone heating (Goudarziet al(2024Med. Phys.518670-87)). Optimal regularization parameter values were chosen to maximize the focal-to-bone heating ratio (ΔTratio) while maintaining focal integrity.Results. For high point densities (0.25 AF mm-2), AF driving signals provided significant improvements in ΔTratiocompared to CF (fold improvement: 13 ± 16,p= 0.0009) and the optimal PB approach (fold improvement: 11 ± 11,p= 0.0009), at the cost of more diffuse focusing (focal…
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Evidence Hub reads this as a clinical trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence.
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