There has been increased interest in minimally invasive ablative treatments that typically require precise placement of the ablator tool to meet the predefined planning, and lead to efficient tumor destruction. Standard ablative procedures involve free hand transcutaneous ultrasonography (TCUS) in conjunction with manual tool positioning. Unfortunately, existing TCUS systems suffer from many limitations and results in failure to identify nearly half of all treatable liver lesions. Freehand manipulation of the ultrasound (US) probe and ablator tool critically lacks the level of control, accuracy, stability, and guaranteed performance required for these procedures. Freehand US results in undefined gap distribution, anatomic deformation due to variable pressure from the sonographer's hand, and severe difficulty in maintaining optimal scanning position. In response to these limitations, we developed a dual robotic arm system that manages both ultrasound manipulation and needle guidance. We have performed a comparative performance study between robotic vs. freehand systems for both US scanning and needle placement in mechanical and animal tissue phantoms.