Device and method for preventing magnetic-resonance imaging induced damage

Abstract

An electromagnetic shield has a first patterned or apertured layer having non-conductive materials and conductive material and a second patterned or apertured layer having non-conductive materials and conductive material. The conductive material may be a metal, a carbon composite, or a polymer composite. The non-conductive materials in the first patterned or apertured layer may be randomly located or located in a predetermined segmented pattern such that the non-conductive materials in the first patterned or apertured layer are located in a predetermined segmented pattern with respect to locations of the non-conductive materials in the second patterned or apertured layer.

Description

CROSS-REFERENCE TO RELATED US PATENT APPLICATIONS [0001] This application is a divisional of co-pending U.S. patent application Ser. No. 10 / 405,154, filed on Apr. 2, 2003. The entire contents of U.S. patent application Ser. No. 10 / 405,154 are hereby incorporated by reference.FIELD OF THE PRESENT INVENTION [0002] The present invention relates generally to a device and method for preventing magnetic-resonance imaging induced damage. More particularly, the present invention is directed to medical assist systems, which may include leads and other implantable or non-implantable components, that are shielded by segmented shielding to hardened or immune the systems from electromagnetic interference or insult, namely electromagnetic interference or insult in a magnetic-resonance imaging environment and to a modifiable magnetic-resonance imaging, which is, automatically or manually, responsive to sensed tissue temperature changes or known localized specific energy absorption ratios. CROSS RE...

AI Technical Summary

Problems solved by technology

The use of the magnetic-resonance imaging process with patients who have implanted or non-implanted medical assist devices; such as, but not limited to, cardiac assist devices, implanted insulin pumps, catheter guide wires, leads for neurostimulation probes, intraluminal coils, guided catheters, temporary cardiac pacemakers, temporary esophageal pacemakers; often presents problems.

Since the sensing systems and conductive elements of these medical assist devices are responsive to changes in local electromagnetic fields, the medical assist devices are vulnerable to external sources of severe electromagnetic noise, and in particular, to electromagnetic fields emitted during the magnetic-resonance imaging (magnetic-resonance imaging) procedure.

A common implantable pacemaker can, under some circumstances, be susceptible to electrical interference such that the desired functionality of the pacemaker is impaired.

Such electrical interference can damage the circuitry of the cardiac assist systems or cause interference in the proper operation or functionality of the cardiac assist systems.

For example, damage may occur due to high voltages or excessive currents introduced into the cardiac assist system by voltages or currents induced in the cardiac assist system circuitry or on the wire leads leading to and from the cardiac assist system circuitry.

Therefore, it is required that such voltages and currents be limited at the input of such cardiac assist systems, e.g., at the interface.

However, such protection, provided by zener diodes and capacitors placed at the input of the medical device, increases the congestion of the medical device circuits, at least one zener diode and one capacitor per input / output connection or interface.

This is contrary to the desire for increased miniaturization of implantable medical devices.

Further, when such protection is provided, interconnect wire length for connecting such protection circuitry and pins of the interfaces to the medical device circuitry that performs desired functions for the medical device tends to be undesirably long.

The excessive wire length may lead to signal loss and undesirable inductive effects.

Additionally, the radio frequency (radio-frequency) energy that is inductively coupled into the wire causes intense heating along the length of the wire, and at the electrodes that are attached to the heart wall.

A further result of this ablation and scarring is that the sensitive node that the electrode is intended to pace with low voltage signals becomes desensitized, so that pacing the patient's heart becomes less reliable, and in some cases fails altogether.

Additionally, the switching of the gradient magnetic fields may also induce unwanted voltages causing problems with the circuitry and potential pacing of the heart.

Another problem associated with magnetic-resonance imaging is the temperature change in tissue regions caused by using conventional magnetic-resonance imaging techniques.

The constant changing of alignment of the magnetic moments of the spins in the tissue causes the tissue's temperature to increase, thereby exposing the tissue to possible magnetic-resonance imaging induced thermal damage.

Although, conventional medical assist devices provide some means for protection against electromagnetic interference, these conventional medical assist devices require much circuitry and fail to provide fail-safe protection against radiation produced by magnetic-resonance imaging procedures.

Moreover, the conventional medical assist devices fail to address the possible damage that can be done at the tissue interface due to radio-frequency-induced heating.

Furthermore, the conventional medical assist devices fail to address the unwanted tissue region stimulation that may result from radio-frequency-induced electrical currents.

Lastly, conventional magnetic-resonance imaging processes fail to provide a proper safeguard against potential magnetic-resonance imaging induced thermal damage due to the tissue's exposure to the switching magnetic field gradients and the circularly polarized Radio Frequency Field of the magnetic-resonance imaging process.

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