Magnetically assisted remote-controlled endovascular catheter for interventional MR imaging: in vitro navigation at 1.5 T versus X-ray fluoroscopy.

PURPOSE: To compare in vitro navigation of a magnetically assisted remote-controlled (MARC) catheter under real-time magnetic resonance (MR) imaging with manual navigation under MR imaging and standard x-ray guidance in endovascular catheterization procedures in an abdominal aortic phantom. MATERIALS AND METHODS: The 2-mm-diameter custom clinical-grade microcatheter prototype with a solenoid coil at the distal tip was deflected with a foot pedal actuator used to deliver 300 mA of positive or negative current. Investigators navigated the catheter into branch vessels in a custom cryogel abdominal aortic phantom. This was repeated under MR imaging guidance without magnetic assistance and under conventional x-ray fluoroscopy. MR experiments were performed at 1.5 T by using a balanced steady-state free precession sequence. The mean procedure times and percentage success data were determined and analyzed with a linear mixed-effects regression analysis. RESULTS: The catheter was clearly visible under real-time MR imaging. One hundred ninety-two (80%) of 240 turns were successfully completed with magnetically assisted guidance versus 144 (60%) of 240 turns with nonassisted guidance (P < .001) and 119 (74%) of 160 turns with standard x-ray guidance (P = .028). Overall mean procedure time was shorter with magnetically assisted than with nonassisted guidance under MR imaging (37 seconds ± 6 [standard error of the mean] vs 55 seconds ± 3, P < .001), and time was comparable between magnetically assisted and standard x-ray guidance (37 seconds ± 6 vs 44 seconds ± 3, P = .045). When stratified by angle of branch vessel, magnetic assistance was faster than nonassisted MR guidance at turns of 45°, 60°, and 75°. CONCLUSION: In this study, a MARC catheter for endovascular navigation under real-time MR imaging guidance was developed and tested. For catheterization of branch vessels arising at large angles, magnetically assisted catheterization was faster than manual catheterization under MR imaging guidance and was comparable to standard x-ray guidance.

System architecture for a magnetically guided endovascular microcatheter.

Magnetic resonance imaging (MRI) guided minimally invasive interventions are an emerging technology. We developed a microcatheter that utilizes micro-electromagnets manufactured on the distal tip, in combination with the magnetic field of a MRI scanner, to perform microcatheter steering during endovascular surgery. The aim of this study was to evaluate a user control system for operating, steering and monitoring this magnetically guided microcatheter. The magnetically-assisted remote control (MARC) microcatheter was magnetically steered within a phantom in the bore of a 1.5 T MRI scanner. Controls mounted in an interventional MRI suite, along with a graphical user interface at the MRI console, were developed with communication enabled via MRI compatible hardware modules. Microcatheter tip deflection measurements were performed by evaluating MRI steady-state free precession (SSFP) images and compared to models derived from magnetic moment interactions and composite beam mechanics. The magnitude and direction of microcatheter deflections were controlled with user hand, foot, and software controls. Data from two different techniques for measuring the microcatheter tip location within a 1.5 T MRI scanner showed correlation of magnetic deflections to our model (R(2): 0.88) with a region of linear response (R(2): 0.98). Image processing tools were successful in autolocating the in vivo microcatheter tip within MRI SSFP images. Our system showed good correlation to response curves and introduced low amounts of MRI noise artifact. The center of the artifact created by the energized microcatheter solenoid was a reliable marker for determining the degree of microcatheter deflection and auto-locating the in vivo microcatheter tip.

Parallel determination of phenotypic cytotoxicity with a micropattern of mutant cell lines.

This work presents a novel tool, the Continuous Flow Microspotter (CFM) and its use in patterning cellular microarrays of multiple cell types into the bottom of a tissue culture well. The CFM uses a system of isolated microfluidic channels to make an array of localized microspots of adhesion dependent cells in the bottom of a conventional tissue culture well. With this device we have created micropatterns of multiple cell lines in a single tissue culture well and used this system to conduct simultaneous cytotoxicity tests and recover dose survival curves in a parallel study. This mechanism of parallel testing allows the researcher to employ the use of positive and negative controls, as well as compare the chemical response of phenotypes in a tightly controlled microenvironment. For the experiments presented in this paper we have fabricated a CFM with a set of ten microchannels (five inlet channels and five outlet channels) to pattern a row of five microspots consisting of four cellular microspots and one empty spot for background measurements. Micropatterns containing a set of four different Chinese hamster ovarian cell (CHO) mutant phenotypes were deposited into the bottom of commercially available tissue culture wells then interrogated with mitomycin C, a chemotherapeutic agent. This study shows statistically significant (P < 0.05) hypersensitivity of the UV20 CHO mutant to a DNA interstrand cross-linking agent (mitomycin C). Because the CFM is also capable of depositing proteins and other biomolecules to the individual microspots of the array we foresee capabilities of the 48 microspot CFM to multiplex 48 cell types with 48 chemical reagents all within the confines of a 60 mm(2) area.