Acoustic Signature: A focused ultrasound guidance technique with sub-millimeter accuracy

Abstract

Accurate targeting is paramount for focused ultrasound (FUS) procedures. Here we describe a method for targeting FUS dubbed acoustic signature, which uses acoustic feedback from a target’s unique reflection patterns to guide the transducer to a previously defined orientation. We demonstrate convergence to the desired target in a 3 degree of freedom (DOF) water tank scenario and a 5 DOF robotic arm scenario. We also tested the acoustic signature technique for targeting with a phantom skull on a 3 DOF motor stage and a 5 DOF manual stereotactic frame designed for transcranial FUS procedures in an MRI environment. In both the water tank and the robotic arm convergence tests, the method converges to the target. The convergence was sufficiently smooth for automated gradient descent. In the 3-DOF test, the net targeting error was 0.30 ± 0.27 mm (n = 10). In the stereotactic frame 5-DOF test, the targeting error was 2.11 ± 0.99 mm and 3.2 ± 2.2° (n = 10) summed rotational error. The accuracy of this technique is limited by the positioning apparatus. This method may enable precise and repeatable FUS targeting for therapies which require multiple FUS sessions at the same target.