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.

Magnetic catheter manipulation in the interventional MR imaging environment.

PURPOSE: To evaluate deflection capability of a prototype endovascular catheter, which is remotely magnetically steerable, for use in the interventional magnetic resonance (MR) imaging environment. MATERIALS AND METHODS: Copper coils were mounted on the tips of commercially available 2.3-3.0-F microcatheters. The coils were fabricated in a novel manner by plasma vapor deposition of a copper layer followed by laser lithography of the layer into coils. Orthogonal helical (ie, solenoid) and saddle-shaped (ie, Helmholtz) coils were mounted on a single catheter tip. Microcatheters were tested in water bath phantoms in a 1.5-T clinical MR scanner, with variable simultaneous currents applied to the coils. Catheter tip deflection was imaged in the axial plane by using a "real-time" steady-state free precession MR imaging sequence. Degree of deflection and catheter tip orientation were measured for each current application. RESULTS: The catheter tip was clearly visible in the longitudinal and axial planes. Magnetic field artifacts were visible when the orthogonal coils at the catheter tip were energized. Variable amounts of current applied to a single coil demonstrated consistent catheter deflection in all water bath experiments. Changing current polarity reversed the observed direction of deflection, whereas current applied to two different coils resulted in deflection represented by the composite vector of individual coil activations. Microcatheter navigation through the vascular phantom was successful through control of applied current to one or more coils. CONCLUSIONS: Controlled catheter deflection is possible with laser lithographed multiaxis coil-tipped catheters in the MR imaging environment.

Comparing Occlusive Balloon Performance Using 3-Dimensional Printed Models of Intracranial Aneurysmal Defects.

OBJECTIVE: Balloon remodeling microcatheters are essential in assisting endovascular coiling of brain aneurysms, but the performance and pressure requirements of different balloon types when used in aneurysmal defects are currently unknown. METHODS: We used Tinkercad (Autodesk, Montreal, Quebec) to create model vessels with aneurysmal defects and 3-dimensionally printed these designs with polylactic acid using the Ultimaker2 (Ultimaker, Geldermalsen, Netherlands). We constructed a pressurized box capable of reaching physiologic pressures that housed our vessels and then tested compliant remodeling balloons under fluoroscopy from 3 manufacturers: Hyperglide (Medtronic, Minneapolis, Minnesota, USA), Transform (Stryker Neurovascular, Fremont, California, USA), and Scepter C (Microvention, Tustin, California, USA). Each balloon was inflated to a nominal and supranominal point at each defect, and at each inflation the maximum diameter of the balloon and internal balloon pressure were recorded. The Phillips Intellivue (Phillips, Amsterdam, The Netherlands) monitor was adapted for internal balloon pressure monitoring. A multivariate linear regression analysis was performed to model balloon compliance (balloon diameter divided by pressure). RESULTS: Multivariate regression modeling demonstrated the Scepter balloon had significantly greater compliance compared with both the Hyperglide and Transform balloons (P < 0.001). In addition, we found that Scepter balloons had higher compliance in larger defects compared with the other types of balloons and performance differences based on vessel size. CONCLUSIONS: Scepter balloons require less pressure compared with their counterparts to adequately deform through model defects, specifically in larger aneurysm necks in smaller vessel diameters. This result could inform operators of optimal balloon type and size when trying to minimize balloon pressure in fragile brain aneurysms.

Clinical Evaluation of a COVID-19 Antibody Lateral Flow Assay using Point of Care Samples.

Introduction: The ongoing SARS-CoV-2 pandemic has spurred the development of numerous point of care (PoC) immunoassays. Assessments of performance of available kits are necessary to determine their clinical utility. Previous studies have mostly performed these assessments in a laboratory setting, which raises concerns of translating findings for PoC use. The aim of this study was to assess the performance of a lateral flow immunoassay for the detection of SARS-CoV-2 antibodies using samples collected at PoC. Method: One lateral flow immunoassay (Humasis® COVID-19 IgG/IgM) was tested. In total, 50 PCR RT-PCR positive and 52 RT-PCR negative samples were collected at PoC. Fifty serum specimens from Dec 2018 to Feb 2019 were used as controls for specificity. Serum samples collected between Dec 2019 to Feb 2020 were used as additional comparators. Clinical data including symptom onset date was collected from patient history and the medical record. Results: The overall sensitivity for the kit was 74% (95% CI: 59.7% - 85.4%). The sensitivity for IgM and IgG detection >14 days after date of onset was 88% (95% CI: 68.8% - 97.5%) and 84% (95% CI: 63.9% - 95.5%), with a negative predictive value (NPV) of 94% for IgM (95% CI: 83.5% - 98.8%) and 93% for IgG (95% CI: 81.8% - 97.9%). The overall specificity was 94% (95% CI: 83.5% - 98.8%). The Immunoglobulin specific specificity was 94% for IgM (95% CI: 83.5% - 98.8%) and 98% for IgG (95% CI: 89.4% - 100.0%), with a positive predictive value (PPV) of 88% for IgM (95% CI: 68.8% - 97.5%) and 95% for IgG (95% CI: 77.2% - 99.9%) respectively for samples collected from patients >14 days after date of onset. Specimen collected during early phase of COVID-19 pandemic (Dec 2019 to Feb 2020) showed 11.8% antibody positivity, and 11.3% of PCR-negative patients demonstrated antibody positivity. Discussion: Humasis® COVID-19 IgG/IgM LFA demonstrates greater than 90% PPV and NPV for samples collected 14 days after the onset of symptoms using samples collected at PoC. While not practical for the diagnosis of acute infection, the use of the lateral flow assays with high specificity may have utility for determining seroprevalence or seroconversion in longitudinal studies.

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.

Current trends in endovascular management of traumatic cerebrovascular injury.

BACKGROUND: The role of catheter angiography in the diagnosis and management of traumatic cerebrovascular injury has evolved rapidly with advances in CT and MR angiography and continued development of endovascular techniques. OBJECTIVE: To identify the modern spectrum of traumatic arterial injury encountered during catheter neuroangiography and to examine current patterns of endovascular treatment. METHODS: Records of trauma patients undergoing catheter neuroangiography over a 4 year period at two high volume centers were retrospectively reviewed. The sample comprised 100 separate arterial lesions that were classified according to mechanism, location, acuity, and endovascular treatment. Follow-up imaging and clinical notes were reviewed to identify procedural complications. RESULTS: Of 100 arterial lesions, 81% were related to blunt trauma. Distribution of lesions by location was 42% intracranial, 39% cervical, and 19% extracranial. The most common injuries were pseudoaneurysm (38%), fistula (29%), and dissection (19%). In total, 41% of lesions underwent endovascular treatment, with trends favoring treatment of non-acute, penetrating, non-cervical, and high grade lesions. Therapy involved coil embolization for 89% of treated lesions. There were a total of two immediate neurovascular complications and one delayed neurovascular complication; one of these resulted in a permanent neurological deficit. CONCLUSIONS: Our experience in a large cohort of patients suggests that a relatively high proportion of traumatic arterial lesions identified by catheter angiography are treated by endovascular means, with a low rate of immediate and delayed neurovascular complications.

Magnetically-Assisted Remote Controlled Microcatheter Tip Deflection under Magnetic Resonance Imaging.

X-ray fluoroscopy-guided endovascular procedures have several significant limitations, including difficult catheter navigation and use of ionizing radiation, which can potentially be overcome using a magnetically steerable catheter under MR guidance. The main goal of this work is to develop a microcatheter whose tip can be remotely controlled using the magnetic field of the MR scanner. This protocol aims to describe the procedures for applying current to the microcoil-tipped microcatheter to produce consistent and controllable deflections. A microcoil was fabricated using laser lathe lithography onto a polyimide-tipped endovascular catheter. In vitro testing was performed in a waterbath and vessel phantom under the guidance of a 1.5-T MR system using steady-state free precession (SSFP) sequencing. Various amounts of current were applied to the coils of the microcatheter to produce measureable tip deflections and navigate in vascular phantoms. The development of this device provides a platform for future testing and opportunity to revolutionize the endovascular interventional MRI environment.