| Less Invasive Surgical (LIS) techniques accomplish a desired surgical objective with greatly reduced body trauma, usually with catheter- or probe-based instruments. These procedures are desirable from the patient's perspective because of the reduction in trauma and pain, a faster return to function, and potentially reduced costs. As these techniques continue to evolve, control of the orientation and direction of the catheter's tip device will be of increasing importance, for improved function as well as safety.; This dissertation presents the design, development, and preliminary concept verification of a 3 French (1 mm OD) cardiac catheter system with a 4-way (2 DOF) controllable tip. Current small-diameter catheter systems for the cardiac vasculature are positioned using guidewires with soft, preshaped tips. Control of the tip direction is obtained by twisting the proximal end of the guidewire. These systems frequently require repeated attempts to negotiate sharp vessel bifurcations or bends due to the lack of precise in vivo control of the tip orientation. Active control of the catheter tip would increase the catheter steerability and also provide the capability to manipulate and position active tip elements such as lasers, ultrasound sensors, or mechanical devices.; The objectives of this research program were to: (1) determine the design and performance limitations of micro-actuation systems for control and manipulation of the distal tip of a long, small-diameter catheter for the cardiac arteries; (2) fabricate prototype catheters based on the results of part (1); and (3) complete preliminary functional evaluation in a biological model. Four different power approaches were considered: pneumatic, hydraulic, electrical, and mechanical. A theoretical analysis of the four approaches indicated that a tendon-based design was the only actuation method that could generate the forces required to bend the tip at the diameters required for coronary arteries while simultaneously maintaining the required shaft flexibility. Prototype catheters with a tendon-based steering design were fabricated. These catheters were used to actively select the direction of advancement in cardiac arteries (dog) with 60{dollar}spcirc{dollar} to 90{dollar}spcirc{dollar} bifurcations at penetration depths of up to 14 centimeters.; External control of the tip configuration increases the functionality and safety of catheter devices, and is a fundamental step in the development of systems capable of precise in vivo manipulation of active tip elements. |
