Cryoablation temperature monitoring with dense ultrasonic speed-of-sound shift imaging

Objective.To accurately monitor temperature during cryoablation, a minimally invasive technique that destroys tissue locally by forming an ice ball around an inserted cryoprobe.Approach.We present a dense slowness-shift imaging method that estimates local speed-of-sound changes from ultrasound (US) B-mode images using optical flow. This single-transducer, image-based approach enables mapping of spatial temperature change without requiring additional hardware. Cryoablation experiments were conducted in a tissue-mimicking phantom andex vivoturkey breast.Main results.Slowness deviation increased with decreasing temperature. In the phantom, the dependence was linear (α_a= - 20.70ηs·m^-1C°^-1), while in turkey breast it followed an exponential relationship (α_t= 34.04 × exp (0.075(-ΔT)-1)ηs·m^-1C°^-1). The algorithm detected sub-degree temperature variations and accurately tracked cooling down to -39.4 ± 5.6 °C.Significance.Accurate temperature monitoring is essential for effective and safe cryoablation. This work demonstrates the feasibility of US-based, noninvasive temperature monitoring during cryoablation, providing a scalable, real-time alternative to existing invasive or high-cost thermal assessment techniques.