Moving focused ultrasound reorganizes coupled heat and solute transport near a pulsatile blood vessel

Near a large vessel, axial convection competes with heat diffusion and the retention of released solute. This study examines how translating a focused-ultrasound source changes the spatial distribution of heating and drug exposure under pulsatile flow. A three-dimensional transient model couples a prescribed moving Gaussian intensity field, attenuation-based heating and radiation force, Carreau–Yasuda blood flow, porous-tissue heat transfer, and temperature-dependent liposome release and free-drug transport. For an 8-mm vessel with a mean inlet speed of 0.020 m s−1, the nominal Reynolds and Womersley numbers are 48.5 and 5.52; and the thermal and free-drug Péclet numbers are 1.21 × 103 and 3.20 × 105. Compared with a static focus, scanning with a 15-mm amplitude increases the tissue volume above 315 K from 32 to 108 mm3 and reduces the peak temperature from 319.1 to 318.2 K. The strongest intensity–drug co-localization occurs near 1 Hz within the sampled frequency range. This response is consistent with competition among focal dwell, revisit, and convective washout: dwell decreases from 1.18 s at 0.25 Hz to 0.074 s at 4 Hz, while mean-flow transit across the 24-mm focal length takes ∼1.20 s. A matched force-on/force-off calculation shows that the prescribed radiation force can materially reorganize lumen flow and scalar transport. Source translation therefore redistributes thermal exposure and solute transport along the vessel–tissue interface. The prescribed acoustic field, fixed scan–cardiac timing, and the 3-s observation window limit the frequency response to the simulated configuration; a phase-independent optimum is not established.