Heat-resistant electrocardiogram cable

Abstract

The present disclosure provides an electrocardiograph cable for use in an MRI system, the electrocardiograph cable including a cable jacket and a plurality of leads extending through the cable jacket, each of the plurality of leads including a first end segment coupled to a monitoring electrode, a second end segment coupled to a monitoring device, an electrically insulating core extending from the first end segment to the second end segment, a conductive wire having a plurality of turns wound around the electrically insulating core from the first end segment to the second end segment, and an electrically insulating sleeve covering the conductive wire wound around the electrically insulating core. TIFF2025512983000002.tif92170

Description

[Technical field]

[0001] Field The present disclosure relates to electrocardiograph cables, and more particularly to electrocardiograph cables used in monitoring devices in magnetic resonance imaging (MRI) systems. [Background technology]

[0002] background In the medical field, MRI systems are routinely used to obtain anatomical images of patient tissues and organs. A typical device for an MRI system includes an electromagnetic scanner to generate a strong magnetic field, e.g., 1.5 Tesla or more, and to apply radio frequency (RF) pulses to a patient, who is usually placed on a table surrounded by the MRI scanner. The MRI scanner typically applies rapidly changing magnetic field gradients that vary linearly through space, which allows a processing device to selectively obtain slice images of the patient's tissues and organs. MRI systems typically include a monitoring room shielded from the MRI scanner, where an operator console receives and processes signals transmitted from the MRI scanner's sensors to generate anatomical images of the patient.

[0003] Typically, the patient's physiological state is monitored during an MRI procedure, during which the patient's physiological data is transmitted from the monitoring device to an operation console. For example, the patient's electrocardiogram signal is monitored by placing electrodes on the patient's torso and electrically connecting the electrodes to a patient monitor via leads. The patient monitor collects and transmits the electrocardiogram signal to the operation console.

[0004] However, the leads of electrocardiograph monitoring units are typically exposed to dynamic magnetic field gradients and pulsed RF waves applied by MRI scanners. This exposure can induce significant temperature rise in the leads (e.g., above 31° C.), which can damage or burn exposed patient skin, ultimately compromising patient safety. For example, MRI scanners typically excite the generated magnetic field with 50 kW of RF power, thereby creating a magnetic field strength of over 1500 V / M. Moreover, the moving magnetic field gradients can induce the generation of electrical currents in exposed conductive materials. These rapidly changing magnetic field gradients and strong RF fields induce eddy currents in the conductive material of the leads, which often heat the leads sufficiently to cause third-degree burns.

[0005] Therefore, there is a need for improved leads in electrocardiogram cables that can reduce the heating typically induced by the RF pulses emitted during MRI procedures. Summary of the Invention

[0006] Quick Overview The present disclosure includes various embodiments of an electrocardiograph cable for reducing heating induced by pulsating RF waves applied by an MRI scanner. In some embodiments, the electrocardiograph cable includes a cable jacket. In some embodiments, the electrocardiograph cable includes a plurality of leads extending through the cable jacket. In some embodiments, each of the plurality of leads includes a first end segment configured to be coupled to a monitoring electrode, a second end segment configured to be coupled to a monitoring device, an electrically insulating core extending from the first end segment to the second end segment, a conductive wire having a plurality of turns wound around the electrically insulating core from the first end segment to the second end segment, and an electrically insulating sleeve covering the conductive wire wound around the electrically insulating core. In some embodiments, the pitch between adjacent turns of the conductive wire remains substantially uniform along a longitudinal axis of the electrically insulating core. In some embodiments, the pitch between adjacent turns of the conductive wire is within a range of about 0.0020 inches to about 0.0001 inches.

[0007] In some embodiments, the conductive wire comprises a metal alloy-based material having a resistivity in the range of about 650 ohm-cir-mil / foot to about 850 ohm-cir-mil / foot.

[0008] In some embodiments, the metal alloy-based material of the conductive wire is non-magnetic.

[0009] In some embodiments, the conductive wire comprises a diameter within the range of about 0.00176 inches to about 0.00250 inches.

[0010] In some embodiments, the electrically insulative core comprises a fiberglass-based material.

[0011] In some embodiments, the electrically insulative core comprises a diameter within the range of about 0.250 inches to about 0.035 inches.

[0012] In some embodiments, each of the leads is configured to maintain an outer surface of the electrically insulating sleeve at a temperature in the range of about 26° C. to about 15° C. when subjected to a time-varying magnetic field having a magnetic flux density in the range of about 3 Tesla to about 10 Tesla.

[0013] In some embodiments, the electrically insulating sleeve comprises an elastomeric material.

[0014] In some embodiments, each of the leads has a distributed resistance of about 10,000 Ω / ft.

[0015] In some embodiments, the multiple leads are twisted along the interior passage of the cable jacket.

[0016] The present disclosure includes various embodiments of a lead in an electrocardiograph cable for reducing heat induced by pulsed radio frequency waves applied by an MRI scanner. In some embodiments, the lead includes a first end segment configured to be coupled to a monitoring electrode, a second end segment configured to be coupled to a monitoring device, an electrically insulating core extending from the first end segment to the second end segment, a conductive wire having multiple turns wound around the electrically insulating core from the first end segment to the second end segment, and an electrically insulating sleeve covering the conductive wire wound around the electrically insulating core. In some embodiments, the electrically insulating core includes a diameter in the range of about 0.250 inches to about 0.035 inches. In some embodiments, the conductive wire includes a thermal capacitance configured to maintain an outer surface of the electrically insulating sleeve at a temperature in the range of about 26° C. to about 15° C. when subjected to a time-varying magnetic field having a magnetic flux density in the range of about 3 Tesla to about 10 Tesla.

[0017] The present disclosure includes various embodiments of a method for controlling the temperature of a lead in an electrocardiograph cable during an MRI procedure. In some embodiments, the method includes providing an electrically insulating core of the lead having a diameter within a range of about 0.250 inches to about 0.035 inches. In some embodiments, the method includes providing a conductive wire of the lead having a resistance within a range of 650 Ω circular mils / ft to about 850 Ω circular mils / ft. In some embodiments, the method includes winding the conductive wire into a plurality of turns around the electrically insulating core from a first end segment of the lead to a second end segment of the lead. In some embodiments, the method includes maintaining a pitch within a range of about 0.0020 inches to about 0.0001 inches between adjacent turns of the conductive wire uniformly along a long axis of the electrically insulating core. In some embodiments, the method includes covering the conductive wire wound around the electrically insulating core with an electrically insulating sleeve of the lead. In some embodiments, the method includes subjecting the lead to a pulsed radio frequency wave and a time-varying magnetic field having a magnetic flux density in the range of about 3 Tesla to about 10 Tesla. In some embodiments, the method includes dissipating heat from the conductive wire to maintain an outer surface of the electrically insulating sleeve at a temperature in the range of about 26° C. to about 15° C. [Brief description of the drawings]

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the aspects and, together with the detailed description, serve to explain the principles of the aspects and to enable one skilled in the art to make and use the aspects.

[0019] [Figure 1] FIG. 1 is a schematic diagram of an MRI system for acquiring anatomical images of a patient and transmitting physiological data of the patient. [Diagram 2] FIG. 2 is a schematic diagram of an electrocardiograph cable according to some embodiments of the present disclosure for use in the MRI system of FIG. [Figure 3A]FIG. 3 is a perspective view of an electrically conductive wire and an electrically insulating core of a lead used in the electrocardiograph cable of FIG. 2 according to some embodiments of the present disclosure. [Figure 3B] 3A is an enlarged detailed view of the conductive wires and electrically insulating core of a lead used in the electrocardiograph cable of FIG. 2, taken along dashed line 3-3 in FIG. 3A, according to some embodiments of the present disclosure. [Figure 4A] FIG. 3 is a perspective view of an electrically conductive wire and an electrically insulating core of a lead used in the electrocardiograph cable of FIG. 2 according to some embodiments of the present disclosure. [Figure 4B] 4A is an enlarged detailed view of the conductive wires and electrically insulating core of a lead used in the electrocardiograph cable of FIG. 2, taken along dashed line 4-4 in FIG. 4A, according to some embodiments of the present disclosure. [Diagram 5] 1 is a table listing materials and dimensional parameters of lead wires according to some aspects of the present disclosure. [Figure 6] FIG. 1 is a block diagram illustrating a method for controlling a surface temperature of a lead according to an aspect of the present disclosure. [Figure 7] 8 is a cross-sectional view of the electrocardiograph cable of FIG. 2 taken along dashed line 8-8 of FIG. 2 according to some embodiments of the present disclosure.

[0020] Features and advantages of the embodiments will become more apparent from the following detailed description read in conjunction with the drawings, in which like reference numbers identify corresponding elements throughout the drawings, where like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Detailed Description The embodiments of the present disclosure will now be described in detail with reference to the embodiments thereof as illustrated in the accompanying drawings. References such as "one embodiment," "an embodiment," "several embodiments," and the like indicate that the described embodiments may include a particular feature, structure, or characteristic, but each embodiment may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is believed to be within the knowledge of one of ordinary skill in the art to operate such feature, structure, or characteristic in connection with other embodiments (whether or not explicitly described).

[0022] The following examples are illustrative of the present embodiments and are not intended to be limiting. Other suitable modifications and adaptations of the variety of conditions and parameters normally encountered in the art which will be obvious to those skilled in the art are within the spirit and scope of the disclosure.

[0023] The present disclosure presents an electrocardiograph cable configured to reduce the risk of overheating typically induced by pulsed RF waves applied by an MRI scanner in an MRI system, such as MRI system 100 shown diagrammatically in FIG. 1. According to an embodiment described in more detail below, the electrocardiograph cable includes multiple leads for carrying electrocardiogram signals from monitoring electrodes. Each lead includes a sufficient amount of surface area and conductive material to enhance the rate of heat transfer through the lead while providing a sufficient amount of distributed resistance along the lead to minimize the generation of eddy currents typically induced by pulsed RF waves emitted during an MRI procedure.

[0024] The MRI system 100 may include any device suitable for acquiring anatomical images of the patient 10 and monitoring the physiological condition of the patient 10. For example, the MRI system 100 may include an MRI scanner 110 configured to examine the patient 10 in an examination area 112. The MRI system 100 may include a patient bed 120 configured to move the patient 10 through the examination area 112 of the MRI scanner 110. The MRI system 100 may include a monitoring device 130 configured to monitor the physiological condition of the patient 10. The MRI system 100 may include a transmitter 140 configured to transmit physiological parameters of the patient 10 monitored during the imaging session to a recording device.

[0025] The MRI scanner 110 may include any components suitable for generating a magnetic field and applying RF pulses to the examination area 112 to obtain an anatomical image of the patient 10. For example, the MRI scanner 110 may include a magnet, e.g., a superconducting magnet, configured to generate a static magnetic field in the examination area 112 having a magnetic flux density of at least 1.5 Tesla (e.g., a magnetic flux density of 3.0 Tesla). The MRI scanner 110 may include an RF antenna configured to apply RF pulses, such as a gradient echo sequence, to the examination area 112 to excite the nuclei of the body of the patient 10. The repetition rate of the RF pulses may range from about 10 Hz to 5 KHz. The RF pulses may be excited with an RF power of 50 kW to create a magnetic field strength of at least 1500 V / M. The MRI scanner 110 may include a gradient coil configured to generate a gradient of the magnetic field, e.g., a linear change in the magnetic field. The magnetic field gradient may be used for selective slice excitation as well as phase and frequency encoding of the measurement signals.

[0026] The monitoring device 130 may be configured to detect one or more physiological signals, such as an electrocardiogram, a respiratory signal, and / or a plethysmographic signal, of the patient 10. These signals may be used as reference values ​​for the acquired images by correlating the physiological signals with each image slice. For example, in cardiac imaging, accurate detection of the "R" wave peak of the electrocardiogram signal may ensure that each image slice is acquired when the heart is in the same relative position.

[0027] In some embodiments, the monitoring device 130 may include a set of monitoring electrodes 132 configured to detect electrocardiogram signals of the patient 10, attached to the patient's body (e.g., the patient's torso). In some embodiments, the electrodes 132 may be constructed of a carbon fiber material. The monitoring device 130 may include an electrocardiograph cable 200 coupled to the electrodes 132. The electrocardiograph cable 200 may be configured to direct the patient's electrocardiogram signals detected by the electrodes 132 to the transmitter 140 or any other suitable patient monitoring device, thereby allowing the patient's electrocardiogram signals to be tracked during the MRI procedure.

[0028] FIG. 2 shows a schematic diagram of an electrocardiograph cable 200 according to some embodiments for carrying electrocardiogram signals from the monitoring electrodes 132 to a monitoring device (e.g., transmitter 140). The electrocardiograph cable 200 is configured to reduce heating typically induced by pulsed RF waves applied during an MRI session to prevent patient burns. The electrocardiograph cable 200 includes multiple leads 210A-D, each coupled to a respective monitoring electrode 132 and a monitoring device, e.g., transmitter 140. The electrocardiograph cable 200 may include a cable jacket 220 that bundles the multiple leads 210A-D. For example, as shown in FIG. 7, each of the leads 210A-D may extend through an internal passage 222 of the cable jacket 220. In some embodiments, the multiple leads 210A-D may be twisted along the internal passage of the cable jacket 220. In some embodiments, multiple leads 210A-D may extend parallel to one another along the interior passage of the cable jacket 220.

[0029] In some embodiments, the cable jacket 220 may be constructed of an electrically insulating material, such as polyvinyl chloride, polyethylene, chlorinated polyethylene, ethylene propylene diene monomer, nitrile rubber, or combinations thereof. In some embodiments, the cable jacket 220 may be constructed of a thermoplastic elastomer (TPE), such as Teknor Apex Medalist® medical grade TPE (e.g., Teknor Apex Medalist® MD-585). The cable jacket 220 may be formed by any method suitable for bundling the leads 210A-D, such as blow molding, injection molding, compression molding, and thermoforming. As shown in FIG. 7, in some embodiments, the cable jacket 220 may include a paper wrap liner 224 disposed along an inner surface of the cable jacket 220.

[0030] 2, each of the leads 210A-D may include a first end segment 212 configured to couple to a monitoring electrode, such as electrode 132. For example, in some embodiments, the first end segment 212 may include an electrode connector configured to clamp the electrode 132. Each of the leads 210A-D may include a second end segment 214 configured to couple to a monitoring device, such as a transmitter 140 or a patient monitor. In some embodiments, the second end segment 214 may include a metal terminal pin configured to be inserted into the transmitter 140 or a patient monitor.

[0031] 3A-4B show perspective views of the internal designs of the leads 210A-D according to some embodiments. The internal designs of the leads 210A-D provide tight control of electrical resistance per unit length while increasing the thermal capacity of the leads to reduce the amount of heat typically induced by RF waves applied during an MRI session. To reduce RF induced heating, the internal designs of the leads 210A-D are configured to increase the rate of heat transfer from the internal conductive material of the leads 210A-D to the outer surface and to minimize the generation of eddy currents in the conductive material of the leads 210A-D.

[0032] Each of the leads 210A-D may include an electrically insulating core 310, 410; an electrically conductive wire 320, 420; and an outer electrically insulating sleeve 330.

[0033] The electrically insulating core 310, 410 may extend from the first end segment 212 to the second end segment 214 of the leads 210A-D. The electrically insulating core 310, 410 may be comprised of any material suitable for preventing the conduction of electrical current while providing a suitable combination of strength and flexibility. For example, in some embodiments, the electrically insulating core 310, 410 may be comprised of a fiberglass-based material. The electrically insulating core 310, 410 may include a diameter within a range of about 0.20 inches to about 0.40 inches, such as a diameter within a range of about 0.25 inches to about 0.35 inches. These core diameter ranges allow the insulating core 310, 410 to have a sufficient amount of exterior surface area to accommodate additional conductive material, such as conductive wires, while providing the leads 210A-D with the flexibility necessary to reach the electrodes 132 and monitoring devices. In some embodiments, the electrically insulating core 310, 410 may include a fiberglass core having a diameter of about 0.034 inches. In some embodiments, the electrically insulative core 310, 410 may comprise a fiberglass core having a diameter of about 0.025 inches.

[0034] The conductive wire 320, 420 may be spirally wound around the electrically insulating core 310, 410. The conductive wire 320, 420 may be composed of any material suitable for conducting electrical current while including a sufficient amount of resistance (e.g., at least 100 Ω / ft) to prevent the generation of eddy currents from RF waves applied by the MRI scanner. For example, in some embodiments, the conductive wire 320, 420 may include a metal alloy-based material having a resistance within a range of about 650 Ω circular mils / ft to about 850 Ω circular mils / ft. This resistance range provides a sufficient amount of conductivity to transfer electrical charges, such as electrocardiogram signals, from the electrodes 132 while having sufficient resistance to reduce the possibility of eddy currents generating during an MRI session. In some embodiments, the metal alloy of the conductive wire 320, 420 may include a combination of nickel and chromium (e.g., nichrome). The conductive wire 320, 420 may be free of any iron-based material so as to be non-magnetic. In some embodiments, the conductive wires 320, 420 may be iron-free resistive wires.

[0035] The conductive wire 320, 420 may include multiple turns 322, 422 wound around the electrically insulating core 310, 410 from the first end segment 212 to the second end segment 214 of the leads 210A-D. The spatial arrangement of the multiple turns 322, 422 of the conductive wire 320, 420 along the longitudinal axis A of the electrically insulating core 310, 410 is configured to increase the total conductor surface area of ​​the leads 210A-D, thereby increasing the thermal capacity of the leads 210A-D and ultimately improving the heat transfer performance of the leads 210A-D. For example, the pitch P between adjacent turns 322, 422 of the conductive wire 320, 420 may remain substantially uniform along the longitudinal axis A of the electrically insulating core 310, 410 such that the spacing between each pair of adjacent turns 322, 422 along the electrically insulating core 310, 410 is equal. The pitch P between adjacent turns 322, 422 of the conductive wire 320, 420 can range from about 0.0020 inches to about 0.0001 inches, for example, the pitch P ranges from about 0.00138 inches (e.g., design 25 of table 500 of FIG. 5) to about 0.00026 inches (e.g., design 17 of table 500 of FIG. 5). For example, in some embodiments, the pitch P between adjacent turns 322, 422 of the conductive wire 320, 420 can be about 0.0011 inches (e.g., design 15 of table 500 of FIG. 5). If the electrically insulating core 310, 410 has a larger diameter (e.g., greater than about 0.030 inches), the pitch P between adjacent turns 322, 422 of the conductive wire 320, 420 can be reduced to a smaller value within this range (e.g., from about 0.0011 inches to 0.00026 inches). In the context of the present disclosure, pitch P corresponds to the distance measured from a point (e.g., radial center or edge) on one wire turn to a corresponding point (e.g., radial center or edge) on an adjacent wire turn, as shown in Figures 3B and 4B. The total number of turns 322, 422 of the conductive wire 320, 420 provides a distributed resistance along the longitudinal axis A of the electrically insulating core 310, 410 of approximately 10,000 Ω / ft.

[0036] This range of pitch P between adjacent turns 322, 422 of the conductive wire 320, 420 provides a sufficient amount of conductive surface area within the interior of the lead 210A-D to enhance the rate of heat transfer from the conductive wire 320, 420 to the exterior of the lead 210A-D, while also ensuring sufficient spacing between adjacent turns 322, 422 to avoid unintentional contact by the turns 322, 422 and to facilitate ease of manufacture of the lead 210A-D. The heat transfer rate of the conductive wire 320, 420 achieved by this range of pitch P between adjacent turns 322, 422 ultimately prevents the lead wire 210A-D from overheating when subjected to typical MRI session operating conditions, e.g., a time-varying magnetic field having a magnetic flux density of at least 3 Tesla and pulses of RF waves generated at 50 kW RF power.

[0037] The conductive wires 320, 420 may include a diameter ranging from about 0.0012 inches to about 0.0030 inches, for example, from about 0.00176 inches (e.g., 45 gauge wire) to about 0.00250 inches (e.g., 42 gauge wire). In some embodiments, the conductive wires 320, 420 include 45 gauge metal alloy wire having a diameter of about 0.00176 inches. This diameter range of the conductive wires 320, 420 provides a sufficient amount of conductive material within the leads 210A-D while maintaining a fine structure that reduces the likelihood of eddy currents occurring in the conductive material. If the conductive wire 320, 420 has a larger number of turns, for example, if the pitch P between adjacent turns 322, 422 is in the range of approximately 0.0011 inches to 0.00026 inches, the diameter of the conductive wire 320, 420 may be reduced to a smaller value within this range (e.g., from 0.0012 inches to approximately 0.0018 inches).

[0038] As shown in FIG. 7, an electrically insulating sleeve 330 may cover the conductive wires 320, 420 wound around the electrically insulating cores 310, 410. The electrically insulating sleeve 330 may be composed of any material suitable for resisting the charge of the conductive wires 320, 420 and shielding the interior of the leads 210A-D. In some embodiments, the insulating sleeve 330 may include a polymer-based material, such as polyethylene, ethylene tetrafluoroethylene (ETFE), polyurethane, silicone resin, or any combination thereof. In some embodiments, the insulating sleeve 330 may include an elastomeric material, such as TPE, thermoset rubber, or combinations thereof, such as Santoprene™.

[0039] The diameter of the electrically insulating core 310, 410 and the internal resistance, diameter and pitch of the conductive wires 320, 420 are collectively configured to reduce heating induced by RF waves applied during an MRI session. The internal resistance, diameter and pitch of the conductive wires 320, 420 increase the thermal capacity of the leads 210A-D while reducing the likelihood of generating eddy currents typically induced in conventional leads during an MRI session. Thus, each of the leads 210A-D is configured to maintain the outer surface of the electrically insulating sleeve at a temperature (e.g., a temperature of about 26° C. or less) that will not cause burns or trauma to the patient 10 when subjected to MRI operating conditions, e.g., a time-varying magnetic field having a magnetic flux density of at least 3 Tesla and a train of pulsed RF waves generated by 50 kW of RF power. That is, the internal resistance, diameter and pitch of the conductive wires 320, 420 collectively prevent the insulating sleeve temperature from increasing significantly above the ambient temperature of the medical environment during MRI operating conditions, thereby ensuring patient safety.

[0040] FIG. 5 shows a table 500 listing various aspects of the leads that were tested during the development of the electrocardiograph cable 200. During testing, the leads listed in table 500, along with other conventional leads, were subjected to typical MRI session operating conditions to compare the thermal performance of the leads with the conventional leads. For example, during one scanning session of the testing procedure, a set of the newly developed leads and a set of conventional leads were placed side-by-side in the bay of an MRI scanner and subjected to a magnetic field having a magnetic flux density of 3 Tesla and an RF wave pulsed at the maximum operating power of the MRI scanner (e.g., 50 kW) for a predetermined period of time. After completing the scanning session, temperature measurements were performed on the newly developed leads and the conventional leads and used to measure the surface temperature of the insulating sleeves of the newly developed leads and the conventional leads.

[0041] Lead embodiments according to design numbers 11, 25, 13, 15, 27, 17, 19, and 21 in Table 500 each included a wire internal resistance, core diameter, wire diameter, and wire turn pitch that met the ranges described herein. By including the specific resistances, diameters, and pitches shown in Table 500, lead embodiments according to design numbers 11, 25, 13, 15, 27, and 17 demonstrated improved heat transfer performance, maintaining a lower sleeve surface temperature than other conventional leads during the testing procedures described herein. Lead embodiments according to design numbers 13, 15, 27, and 17 produced improved thermal performance (e.g., increased heat transfer rate and heat capacity) while providing sufficient resistance to prevent the generation of eddy currents.

[0042] FIG. 6 is an exemplary block diagram illustrating a method 600 according to an embodiment for controlling the temperature of leads 210A-D in an electrocardiograph cable 200 during an MRI procedure.

[0043] The method 600 may include step 610 of providing an electrically insulating core 310, 410 having a diameter within a range of about 0.250 inches to about 0.035 inches, and providing a conductive wire 320, 420 having a resistance within a range of 650 Ω circular mils / ft to about 850 Ω circular mils / ft. In some embodiments, step 610 may include providing a fiberglass core having a diameter of about 0.034 inches and a conductive wire having a resistance of about 800 Ω circular mils / ft.

[0044] The method 600 may include step 620 of winding the conductive wire 320, 420 as a plurality of turns 322, 422 around the electrically insulating core 310, 410 from the first end segment 212 of the leads 210A-D to the second end segment 214 of the leads 210A-D. In some embodiments, step 620 may include winding a total number of turns 322, 422 that provides a distributed resistance of 10,000 ohms / foot along the leads 210A-D.

[0045] The method 600 may include step 630 of maintaining a pitch within a range of about 0.0020 inches to about 0.0001 inches between adjacent turns 322, 422 of the conductive wire 320, 420 uniformly along the longitudinal axis A of the electrically insulating core 310, 410. In some embodiments, step 630 may include maintaining a pitch of about 0.0011 inches between adjacent turns 322, 422 of the conductive wire 320, 420.

[0046] The method 600 may include step 640 of covering the conductive wire 320, 420 wound around the electrically insulative core 310, 410 with an electrically insulative sleeve of the leads 210A-D. In some embodiments, step 640 may include covering the conductive wire 320, 420 wound around the electrically insulative core 310, 410 using an elastomeric material.

[0047] Method 600 may include step 650 of subjecting leads 210A-D to pulsed RF waves and a time-varying magnetic field having a magnetic flux density in a range of about 1 Tesla to about 12 Tesla, e.g., a time-varying magnetic field having a magnetic flux density in a range of 3 Tesla to 5 Tesla. In some embodiments, step 650 may include connecting leads 210A-D to monitoring electrodes coupled to a patient 10 positioned in an examination area 112 of an MRI scanner 110. In some embodiments, step 650 may include generating the pulsed RF waves using 50 kW RF power by the MRI scanner 110.

[0048] Method 600 may include step 660 of dissipating heat from conductive wire 320, 420 to maintain a sleeve surface temperature of lead 210A-D below a maximum surface temperature. In some embodiments, step 660 may include a maximum surface temperature in the range of about 15° C. to about 26° C., e.g., 26° C., to prevent lead 210A-D from causing burns to the patient's skin. In some embodiments, step 660 may include controlling the rise in sleeve surface temperature above an ambient temperature of the medical environment (e.g., 20° C.) to be within a predetermined range. For example, if the ambient temperature of the medical environment is 20° C., conductive wire 320, 420 may be configured to dissipate sufficient heat during the operating conditions set in step 650 to maintain a maximum temperature rise of the sleeve surface in the range of about 2° C. to about 6° C. above the ambient temperature of the medical environment.

[0049] It should be understood that the Detailed Description section, unlike the Summary and Abstract sections, is intended to be used to interpret the appended claims. The Summary and Abstract sections may describe one or more exemplary embodiments contemplated by the inventors, but do not describe all exemplary embodiments and are therefore not intended to limit the scope of the present embodiments and the appended claims in any manner.

[0050] The foregoing description of specific embodiments sufficiently reveals the general nature of the invention so that others, by applying knowledge of the art, may, without undue experimentation, modify and adapt such specific embodiments to various uses without departing from the general concept of the disclosure. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. The phraseology or terminology herein is for the purposes of description and not limitation, and the terminology or terminology herein should be interpreted by those skilled in the art in light of the teaching and guidance.

[0051] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A cable jacket; a plurality of leads extending through said cable jacket; each of the plurality of leads a first end segment configured to be coupled to a monitoring electrode; a second end segment configured to be coupled to a monitoring device; an electrically insulating core extending from the first end segment to the second end segment; an electrically conductive wire having a plurality of turns wound around the electrically insulating core from the first end segment to the second end segment; an electrically insulating sleeve covering the conductive wire wound around the electrically insulating core; Including, a pitch between adjacent turns of the conductive wire remains substantially uniform along a longitudinal axis of the electrically insulative core, the pitch between adjacent turns of the conductive wire being within a range of about 0.0020 inches to about 0.0001 inches; Electrocardiograph cable for reducing heating induced by pulsating radio frequency waves applied by a magnetic resonance imaging (MRI) scanner.

2. 10. The electrocardiograph cable of claim 1, wherein the conductive wire comprises a metal alloy based material having a resistivity within a range of about 650 ohm-cir-mil / foot to about 850 ohm-cir-mil / foot.

3. 3. The electrocardiograph cable of claim 2, wherein the metal alloy-based material of the conductive wire is non-magnetic.

4. 10. The electrocardiograph cable of claim 1, wherein said conductive wire comprises a diameter within a range of about 0.00176 inches to about 0.00250 inches.

5. 10. The electrocardiograph cable of claim 1, wherein the electrically insulating core comprises a fiberglass-based material.

6. 10. The electrocardiograph cable of claim 1, wherein said electrically insulating core comprises a diameter within a range of about 0.250 inches to about 0.035 inches.

7. 10. The electrocardiograph cable of claim 1, wherein each of the leads is configured to maintain an outer surface of the electrically insulating sleeve at a temperature in the range of about 26° C. to about 15° C. when subjected to a time-varying magnetic field having a magnetic flux density in the range of about 3 Tesla to about 10 Tesla.

8. 10. The electrocardiograph cable of claim 1, wherein the electrically insulating sleeve comprises an elastomeric material.

9. 10. The electrocardiograph cable of claim 1, wherein each of said leads has a distributed resistance of about 10,000 ohms / foot.

10. 10. The electrocardiograph cable of claim 1, wherein the plurality of leads are twisted along an interior passage of the cable jacket.

11. a first end segment configured to be coupled to a monitoring electrode; a second end segment configured to be coupled to a monitoring device; an electrically insulating core extending from the first end segment to the second end segment, the electrically insulating core including a diameter within a range of about 0.250 inches to about 0.035 inches; an electrically conductive wire having a plurality of turns wound around the electrically insulative core from the first end segment to the second end segment; an electrically insulating sleeve covering the conductive wire wound around the electrically insulating core; Including, a thermal capacitance configured to maintain an outer surface of the electrically insulating sleeve at a temperature in the range of about 26° C. to about 15° C. when the electrically conductive wire is subjected to a time-varying magnetic field having a magnetic flux density in the range of about 3 Tesla to about 10 Tesla; Leads in electrocardiograph cables to reduce heating induced by pulsed radio frequency waves applied by a magnetic resonance imaging (MRI) scanner.

12. 12. The lead of claim 11, wherein the pitch between adjacent turns of the conductive wire remains substantially uniform along a longitudinal axis of the electrically insulating core.

13. The lead of claim 12, wherein the pitch between adjacent turns of the conductive wire is within a range of about 0.0020 inches to about 0.0001 inches.

14. The lead of claim 11, wherein the conductive wire comprises a metal alloy based material having a resistivity within a range of about 650 ohms circular mils / ft to about 850 ohms circular mils / ft.

15. 15. The lead of claim 14, wherein the metal alloy based material of the conductive wire is non-magnetic.

16. The lead of claim 11 , wherein the conductive wire comprises a diameter within the range of about 0.00176 inches to about 0.00250 inches.

17. 12. The lead of claim 11, wherein the electrically insulative core comprises a fiberglass-based material.

18. 12. The lead of claim 11, wherein the electrically insulating sleeve is or includes an elastomeric material.

19. 12. The lead of claim 11, further comprising a distributed resistance of about 10,000 ohms / foot.

20. A method for controlling temperature of leads in an electrocardiograph cable during a magnetic resonance imaging (MRI) procedure, comprising: providing an electrically insulating core of said lead having a diameter within the range of about 0.250 inches to about 0.035 inches; providing a conductive wire of said lead having a resistance within the range of 650 ohms circular mils / ft to about 850 ohms circular mils / ft; winding the conductive wire into a plurality of turns about the electrically insulating core from the first end segment of the lead to the second end segment of the lead; maintaining a pitch between adjacent turns of the conductive wire uniformly along a longitudinal axis of the electrically insulating core within a range of about 0.0020 inches to about 0.0001 inches; covering the conductive wire wound around the electrically insulating core with an electrically insulating sleeve of the lead; subjecting the lead to a pulsed radio frequency wave and a time-varying magnetic field having a magnetic flux density in the range of about 3 Tesla to about 10 Tesla; and Dissipating heat from the conductive wire to maintain the outer surface of the electrically insulating sleeve at a temperature within the range of about 26°C to about 15°C.

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