A Patient-Mounted, Telerobotic Tool for CT-Guided Percutaneous Interventions

Abstract

This paper describes Robopsy, an economical, patient-mounted, telerobotic, needle guidance and insertion system, that enables faster, more accurate targeting during CT-guided biopsies and other percutaneous interventions. The current state of the art imaging technology facilitates precise location of sites within the body; however, there is no mechanical equivalent to then facilitate precise targeting. The lightweight, disposable actuator unit, which affixes directly to the patient, is composed primarily of inexpensive, injection molded, radiolucent, plastic parts that snap together, whereas the four micromotors and control electronics are retained and reused. By attaching to a patient, via an adhesive pad and optional strap points, the device moves passively with patient motion and is thus inherently safe. The device’s mechanism tilts the needle to a two degree-of-freedom compound angle, toward the patient’s head or feet (in and out of the scanner bore) and left or right with respect to the CT slice, via two motor-actuated concentric, crossed, and partially nested hoops. A carriage rides in the hoops and interfaces with the needle via a two degree-of-freedom friction drive that both grips the needle and inserts it. This is accomplished by two rubber rollers, one passive and one driven, that grip the needle via a rack and pinion drive. Gripping is doctor controlled; thus when not actively being manipulated, the needle is released and allowed to oscillate within a defined region so as to minimize tissue laceration due to the patient breathing. Compared to many other small robots intended for medical applications, Robopsy is an order of magnitude less costly and lighter while offering appropriate functionality to improve patient care and procedural efficiency. This demonstrates the feasibility of developing cost-effective disposable medical robots, which could enable their more widespread application.