High intensity focused ultrasound characterization of deep bleeder acoustic coagulation cuffs

Research prototype therapeutic ultrasound “cuffs” have been recently constructed to demonstrate the feasibility of cauterizing bleeding (acoustic hemostasis) of deep limb wounds, such as those from military combat or other penetrating trauma. The deep bleeder acoustic coagulation (DBAC) cuffs required a variety of HIFU power and acoustic beam assessments to assure safety and efficacy. The cuff, capable of > 1000 W acoustic power, comprised multiple two-dimensional (2-D) HIFU arrays that surrounded the limb and could dose with multiple arrays simultaneously. Each array was capable of high power (>170 W), significant electronic steering (solid angle = 57×34 deg), and depth focusing (5–20 cm). Device characterization required both individual array power measurements, and “integrated” whole cuff multiarray dosing assessment. The single array characterizations included (a) low-power beam plots, (b) high power focused power assessment in “apertured” radiation force balance tests, and (c) Schlieren beam pattern assessment. The integrated (whole cuff) behavior was evaluated using (1) integrated tissue mimicking material (TMM) phantoms replicating limbs, which included soft tissues, blood vessels, pulsatile arterial and “bleeder” blood flows, and were able to measure HIFU closed-loop targeting accuracy; and (2) TMM HIFU phantoms (measuring full power heating to 100 °C). [This research was sponsored by U.S. DARPA Contract No. HR0011-08-3-0004].