Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Patent
1995-05-24
1998-10-06
Lateef, Marvin M.
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
600420, 424 93, A61B 05055
Patent
active
058170170
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetic imaging of insertable and implantable devices within or on a patient's body. More particularly, the present invention relates to the fabrication and use of such devices having properties which enhance their image when viewed by magnetic resonance imaging and other imaging techniques.
The ability to non-invasively image internal body structures and diseased tissues within a patient's body has become indispensable to the practice of modern medicine. A variety of such non-invasive imaging techniques exist, including x-ray imaging, ultrasonic imaging, x-ray computed tomography, emission tomography, and the like. Of particular interest to the present invention, magnetic resonance imaging can provide two-dimensional sectional images through a patient, providing color or gray scale contrast images of soft tissue, particularly for imaging tumors, edema, infarcts, infections, and the like. In addition to high quality, magnetic resonance images are desirable since they do not expose the patient to harmful radiation.
Patients undergoing magnetic resonance imaging often have catheters, tubes, implants, and other devices present within their bodies, and the precise anatomical locations of such devices can be of substantial clinical importance. Unfortunately, most catheters and many other devices are composed of materials, such as organic polymers, which do not produce adequate signals for detection by magnetic resonance imaging techniques. In particular, most polymeric catheters are not clearly discernible on magnetic resonance images unless they are surrounded by tissue that has a high signal intensity, in which case they leave a dark void on the image.
It would therefore be desirable to provide catheters and other medical devices having enhanced detectability when viewed using magnetic resonance imaging regardless of the nature of surrounding tissue. To this end, it has been proposed to incorporate ferromagnetic particles within the polymeric tubes which are employed in a variety of catheter devices. The ferromagnetic particles could be incorporated during the extrusion of such tubes, and would provide a high contrast image when viewed under magnetic resonance imaging. While the use of ferromagnetic particles in catheters would provide for improved visibility, such improvement is dependent on the relative orientation of the catheter relative to the magnetic field used in imaging. In particular, it has been found that the image enhancement occurs only when the catheter is oriented perpendicular to the main magnetic field. When oriented parallel to the magnetic field, there is no image enhancement. Image enhancement using ferromagnetic particles does not depend on an interaction with protons. Thus, further improvements in magnetic resonance image enhancement of catheters and other medical devices would be desirable.
It has also been proposed to introduce liquid solutions and gels containing paramagnetic material into catheter lumens. The paramagnetic material will provide contrast with surrounding tissue regardless of orientation relative to the magnetic field. Although this is an improvement in one sense over the use of ferromagnetic materials as discussed above, the need to incorporate a liquid or gel in the catheter is difficult from a manufacturing view, limits the flexibility of the catheter, and is generally inconvenient.
Direct incorporation of paramagnetic materials into the polymeric material of catheters and other medical devices, however, is difficult since paramagnetic materials, such as transition metal ions, require the proximity of water or other proton-bearing substance in order to provide a high contrast signal under magnetic resonance imaging. The introduction of hydrated transition metal ions into extruded materials is particularly problematic since the water of hydration will be readily lost during high temperature extrusion.
A method has been proposed for highlighting the magnetic resonance im
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Miller Richard A.
Young Stuart W.
Lateef Marvin M.
Pharmacyclics Inc.
Shaw Shawna J.
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