Biophan Cardiovascular Technologies - Magnetic Resonance Imaging Compatibility of Cardiovascular Devices

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Citation
ICR 2007;2007:2(1):1-2
Magnetic Resonance Image Compatibility Overview

Biophan Europe GmbH is a subsidiary of Biophan Technologies Inc., Rochester, New York, and develops proprietary technologies with the goal of making biomedical devices capable of safely and successfully working with magnetic resonance imaging (MRI). The current focus of research and development (R&D) is concentrated on the area of vascular implants See RSNA 2006 Educational Exhibition, www.biophan.com
Vascular implants, and some types of catheters and guide wires, are not safe for use with MRI but have limited MRI image compatibility and visibility. Others have properties that interfere with the MRI image by causing an image artefact in the area in and around the device, limiting the effectiveness of MRI for assisting placement or diagnostic follow-up on these implants. Biophan is developing solutions to these limitations, which will apply to a wide range of medical devices. Biophan currently has developed solutions for limited image compatibility with MRI for the following devices.

MRI Visible Stents

When imaged under MRI, the magnetic characteristics of the metal cause in-homogenity of the magnetic field and create a large image artefact Even stents made of non-magnetic metal act as a Faraday cage (shielding radio-frequency (RF) signals). MRI image of the stent is obscured because of the magnetic characteristics (susceptibility) of the metal and shielding generated by the Faraday cage effect. Biophan’s resonator technology allows for accurate visualisation inside a stent. This is caused by the fact that a metallic stent behaves as a Faraday Cage due to its geometry and material, and the stent additionally creates a magnetic susceptibility artefact due to the material of manufacture of the stent. Biophan has developed a solution to this problem – the active MRI stent (aMRI). To overcome this limitation, Biophan has developed a patented resonator technology, which uses tuned circuits to increase the RF signal, making it possible to image within and around a stent. Figure 1 shows the principle of the resonant circuit.
Figure 2 shows a standard vascular stent made of 316L imaged under 1.5 Tesla MRI. The image artefact (the large dark area) prevents visualisation of the critical area in and around the stent. Biophan’s technology allows accurate imaging of the blood clot within the stent. This technology could also be used to check for restenosis (re-narrowing of a coronary artery) within the stent. Currently, measuring restenosis within a stent requires either an angiography or an intravenous ultrasound – both of which require a complex, costly and invasive catheterisation procedure and have a higher chance of complications to the patient than does a simple, non-invasive MRI scan.

MRI Visible Vena Cava Filters

The MRI image (see Figure 3) illustrates a commercial nitinol filter showing that the image of the filter is disrupted and the physician cannot see within the filter. This is a commercial nitinol filter, without Biophan’s patented resonator technology.
Figure 3 is a standard MRI image of a vena cava filter, showing that the filter interferes with the MRI image. The lumen is shielding a thombus clot that cannot be visualised. Biophan’s resonator technology allows for visualising inside the vena cava filter and timing of retrieval (University Aachen, Spuentrup et al.)
Biophan’s resonator technology overcomes the MRI interference. In the MRI image (see Figure 3), the material is effectively imaged within the vena cava filter due to the application of Biophan’s proprietary resonator technology. This is a resonant-frequency circuitry tuned to the exact MRI frequency. Developed by the Biophan Europe division, based in Germany, this technology has significant implications for the future of medical imaging. The ability to effectively visualise allows a physician to easily determine the degree of clotting within the filter and to know whether it is safe to remove the device, or if it is necessary to take other actions. This kind of vital, accurate information will lead to better diagnosis and safer procedures for patients.
Viewing interventional devices, such as catheters and guidewires, under MRI is a challenge. Often, the objects are smaller or thinner than the resolution of the MRI system, or are made of materials that are less well-contrasted under MRI. Biophan’s patented technologies overcome these challenges, enabling surgical procedures under MRI that would have been difficult or impossible to perform previously.

MRI Visualisation of Catheters

In another example of enhanced MRI visibility, Biophan’s resonator bands can be applied to a catheter tip and imaged under MRI. Resonator bands on the catheter tip allow for accurate placement in MRI-guided intervention. These bands use Biophan’s proprietary resonator technology – resonant-frequency circuitry, tuned to the exact MRI frequency, which makes the catheter clearly visible under MRI, allowing accurate placement in MRI-guided interventional procedures.

Cardiovascular Assist Device

Biophan Technologies, Inc. is developing the Myotech Circulatory Support System (CSS) – a simple-to-install, single-use device that can restore full cardiac output to a failing or arrested heart in three minutes. All other circulatory support devices on the market are blood pumps, and come into direct contact with circulating blood. The Myotech CSS is a heart pump that directly compresses and expands the patient’s heart, without coming into contact with circulating blood (see Figure 5).
The Myotech CSS is a comprehensive circulatory support system that will provide safer and more effective support for a wide array of heart failure conditions. The technology employed in the Myotech CSS has already saved human lives.
The Myotech CSS offers the following major competitive advantages:
• it powers both the systolic and diastolic cycles of the heart, for both the right and left ventricles. Current devices typically provide only systolic support to the left ventricle; • there is no contact with circulating blood, which eliminates or significantly reduces the problems of clotting, stroke, bleeding, repeat surgery and blood-borne infection – problems that plague existing circulatory support devices; • installation is rapid (three minutes) and does not require highly specialised facilities or specialised surgical expertise (it can be installed by a general surgeon); • once introduced, the CSS can be available at virtually every hospital, not just a limited number of transplant or specialised cardiac centres; • it can be installed via an incision between the ribs (thoracotomy), and does not require perforation of the heart or great vessels. The installation procedure is less invasive than for most alternative devices; and • it is available in multiple sizes to treat a broad spectrum of heart failure patients, including women and children, who are not well served by existing circulatory support products.
Biophan’s unique value proposition for the Myotech CSS is a lower total procedure cost compared with existing device therapies, combined with a simpler, safer and more effective product design that can be installed quickly and in more hospitals without the need for specialised cardiothoracic surgical facilities or personnel. ■
For further information please contact John Lanzafame CEO Biophan Technologies Inc. johnl@biophan.com or Andreas Melzer, CEO Biophan Europe GmbH, amelzer@biophan.com
Copyright© Biophan Technologies, Inc., 2007. All rights reserved.