Abstract: A guidewire compatible for use with magnetic resonance systems is made from a non-metallic material with a high specific electric impedance, preferably constructed primarily of a glass body. Possible material selections for the glass body include quartz. Further enhancements to the present invention are as follows. Moreover, the glass body may be sheathed in a protective polymer layer, which is also non-metallic and tends to improve the physical characteristics of the guidewire. The sheath may preferably be reinforced with a number of reinforcing fibers, which may be made from carbon, borium, aramide and also various types of glass fibers. If necessary to obtain the desired physical performance of the guidewire, including high flexibility at the distal end, a distal portion of the guidewire may be constructed of metal components according to designs known in the art. Such a metal tip portion may be made of nitinol, and should be substantially shorter than the wavelength of the magnetic resonance field.

Abstract: An intravascular catheter having controllable stiffness or flexibility, and adapted for use with various contrast media. The stiffness of the catheter may be increased during the use of the catheter by applying a fluid under pressure at the proximal end of the catheter to thereby fill a cavity within the body of the catheter to thereby cause the region of the catheter defined by the cavity to become less flexible. When the fluid pressure is decreased, this region of the catheter becomes more flexible. The fluids to be applied inside the cavities may be a variety of types of contrast media, used with imaging techniques such as either MRI or X-ray fluoroscopy.