Neurological monitoring cable for magnetic resonance environments
An electrode system includes an electrode, a connector, and a cable with an in-line radio-frequency filter module comprising resistors and inductors without any deliberately added capacitance. The resistors are arranged in an alternating series of resistors and inductors, preferably with resistors at both outer ends, and connected electrically in series. The in-line module is located at a specific location along the wire, chosen through computer modeling and real-world testing for minimum transfer of received RF energy to a patient's skin, such as between 100 cm and 150 cm from the electrode end of a 240 centimeter cable. The total resistance of the resistors plus cable, connectors and solder is 1000 ohms or less; while the total inductance is roughly 1560 nanohenries. The inductors do not include ferrite or other magnetic material and are, together with the resistors, stock components thereby simplifying manufacture and reducing cost.
1. A neurological monitoring device for magnetic resonance environments, comprising:
a neurological electrode, wherein the neurological electrode is configured to monitor neurological electrical signals;
a connector operable to attach to an amplifier; and
a cable having a first end and a second end, said first end of said cable being in electrical connection to said neurological electrode and said second end of said cable being in electrical connection to said connector, said cable including an inline radio frequency filter module without lead wires and having miniature, surface-mounted components including at least one resistor and at least one inductor in series with said at least one resistor, and without capacitors.
2. The device of claim 1 , wherein said at least one resistor is a plurality of resistors.
3. The device of claim 1 , wherein said at least one inductor is a plurality of inductors.
4. The device of claim 1 wherein said at least one inductor is a number N of inductors, and said wherein at least one resistor is a number N+1 of resistors.
5. The device of claim 1 , wherein said at least one resistor alternates with said at least one inductor.
6. The device of claim 1 , wherein said at least one resistor is a plurality of resistors and wherein a resistor of said plurality of resistors has the same resistance as another resistor of said plurality of resistors.
7. The device of claim 1 , wherein said at least one inductor is a plurality of inductors and wherein an inductor of said plurality of inductors has the same inductance as another inductor of said plurality of inductors.
8. The device of claim 1 , wherein said at least one inductor has a total inductance between one and two microhenries.
9. The device of claim 1 , wherein said at least one inductor has a total inductance between 1370 and 1800 nanohenries.
10. The device of claim 1 , wherein said at least one resistor has a total resistance between 1 and 1000 ohms.
11. The device of claim 10 , wherein said at least one resistor has a total resistance between 10 and 60 ohms.
12. The device of claim 1 , wherein said in-line filter module has a first end and a second end, and wherein said first end of said in-line filter module includes a first contact and said second end of said in-line filter module includes a second contact.
13. The device of claim 12 , wherein said first contact and said second contact are non-magnetic.
14. The device of claim 1 , wherein said in-line filter module has an outer layer or housing made from a nonconductive polymer.
15. The device of claim 14 , wherein said nonconductive polymer is selected from the group consisting of epoxy, silicone rubber, polyvinyl chloride, polyethylene and polypropylene.
16. The device of claim 1 , wherein said in-line filter module contains a plurality of resistors and a plurality of inductors arranged in an alternating, electrical series relationship that begins and ends with resistors.
17. The device of claim 1 , wherein said at least one resistor and said at least one inductor are selected in number, in component value, and in arrangement to reduce and spread resistive heating in said cable during a magnetic resonance procedure, thereby to minimize resistance heating.