Magnetically-assisted remote control (MARC) steering of endovascular catheters for interventional MRI: a model for deflection and design implications.
Current applied to wire coils wound at the tip of an endovascular catheter can be used to remotely steer a catheter under magnetic resonance imaging guidance. In this study, we derive and validate an equation that characterizes the relationship between deflection and a number of physical factors: theta/sin(gamma-theta) = nIABL/EI(A) where theta is the deflection angle, n is the number of solenoidal turns, I is the current, A is the cross-sectional area of the catheter tip, B is the magnetic resonance (MR) scanner main magnetic field, L is the unconstrained catheter length, E is Young's Modulus for the catheter material, and I(A) is the area moment of inertia, and y is the initial angle between the catheter tip and B. Solenoids of 50, 100, or 150 turns were wound on 1.8 F and 5 F catheters. Varying currents were applied remotely using a DC power supply in the MRI control room. The distal catheter tip was suspended within a phantom at varying lengths. Images were obtained with a 1.5 T or a 3 T MR scanner using "real-time" MR pulse sequences. Deflection angles were measured on acquired images. Catheter bending stiffess was determined using a tensile testing apparatus and a stereomicroscope. Predicted relationships between deflection and various physical factors were observed (R2 = 0.98-0.99). The derived equation provides a framework for modeling of the behavior of the specialized catheter tip. Each physical factor studied has implications for catheter design and device implementation.
Settecase
Fabio
F
Department of Medical Imaging and Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.
Sussman
Marshall S
MS
Wilson
Mark W
MW
Hetts
Steven
S
Arenson
Ronald L
RL
Malba
Vincent
V
Bernhardt
Anthony F
AF
Kucharczyk
Walter
W
Roberts
Timothy P L
TP
D002404:Catheterization; D002406:Catheterization, Peripheral / Q000295:instrumentation*; D004548:Elasticity; D004867:Equipment Design; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation* / Q000379:methods*; D008280:Magnetics; D019047:Phantoms, Imaging