Comparison Between Force and Ultrasound Image-Based Controllers for Autonomous Robotic Ultrasound Acquisition in Different Tissue Types

The main challenges in automatic robotic ultrasound (US) scanning include ensuring acoustic coupling between the tissue and the US probe, while minimizing tissue deformation. In this comparative study, a force controller, confidence-driven controller (CDC), and hybrid force-image controller are tested to perform automatic robotic ultrasound (US) scan. The controllers have been tested using a 7DoF robot equipped with a force sensor and a linear US transducer. Obtaining a robotic 3D US acquisition would increase the reproducibility and accuracy of the diagnostic, and at the same time, would simplify the registration of 3D US volumes with MRI images. The robot follows a reference trajectory which is adjusted by any of the controllers to ensure acoustic coupling. The CDC makes the corrections based on confidence maps. The force and hybrid controllers correct the probe contact based on the contact force of the end-effector with the tissue. The CDC and hybrid controller ensure normal orientation to the tissue by controlling in-plane rotations based on the confidence map. The three controllers are tested in three phantoms of different stiffness.