Common Questions

Rhythmlink's Instructions for Use state that the "electrodes can safely remain on a patient for 15 minutes of continuous scanning". Does that mean that the whole MRI procedure can only last for 15 minutes?

No. A scan is a single pulse sequence. Procedures are often longer than 15 minutes and are comprised of multiple pulse sequences with cool-down breaks in between.

Rhythmlink's Instructions for Use state that the "electrodes can safely remain on a patient for 15 minutes of continuous scanning". How can I perform a MRI procedure that lasts longer than 15 minutes?

A 'scan' is a single pulse sequence. Procedures are often longer than 15 minutes and are comprised of multiple pulse sequences with cool-down breaks in between.

End users may plan procedures so that they use a single, continuous scan (i.e. one pulse sequence) lasting no longer than 15 minutes. This scan must be performed at an SAR equal to or less than the 2 W/kg prescribed in the instructions for use.

Procedures lasting longer than 15 minutes are typically performed using multiple pulse sequences with cool-down breaks in between. When using Rhythmlink's MR Conditional Electrodes, it is essential that the SAR and duration of each pulse sequence be maintained at or below 2 W/kg and 15 minutes, respectively.

If, for some reason, a pulse sequence longer than 15 minutes is required, the machine must be run at a lower SAR. The new, lower SAR must be recalculated according to the hospital?s own validated protocols.

The method or combination of methods used to mitigate the temperature rise in the electrodes needs to be chosen by the hospital, and the lengths of the scan/sequence durations and/or the lengths of the breaks between pulse sequences must be determined using the hospital's own validated protocols.

I'd like to use a head coil, but the Instructions for Use only mention body coils. Can Rhythmlink's MR Conditional Electrodes safely remain on a patient when head coils are used?

Yes, as long as the SAR and pulse sequence duration limits of 2 W/kg and 15 minutes are observed.

What MRI system did Rhythmlink use for testing?

1.5 Tesla testing was performed using the following system:

Operating Frequency 64 MHz
Nominal Field Strength 1.5 T
Model Medical Implant Test System (MITS)
Manufacturer Zurich Medtech AG

Zurich, Switzerland

B 1 field strength max. <<20µT
Induced E 1 max. >>500 V/m
Polarization Circular 90
Pulse Repetition Rate 154.32 Hz
Duty Cycle 12.04
Frequency 63.51 MHz
Power Level 63.36 dBm
E-Field Level 1.3
Software MITS-DUALBAND 1.2.5.2
Coil Birdcage coil

Manufacturer's note: the Medical Implant Test System (MITS) is designed to simulate high precision worst-case incident fields as generated by commercial 1.5 Tesla MR scanners. MITS1.5 is compatible with the latest draft of the ISO/IEC Joint Working Group (JWG) Technical Specication1. It has been rigorously validated.

3 Tesla testing was performed using the following system:

Operating Frequency 123 MHz
Nominal Field Strength 3 T
Model Magnetom Trio
Manufacturer Siemens Medical Solutions
Erlangen, Germany
Static Magnetic Gradient Field <= 7 Tesla/meter
Static Magnetic Gradient Field Product <= 20 Telsa 2/meter
Gradient <= 40 mT/m
Slew Rate <= 200 mT/m/ms
Rise Time >= 0.2 ms
dB/dt <= 56 T/s acc. to IEC 60601-2-33
Software Numaris/4 syngo MR A30
Coil Body coil

Additional information regarding test systems and sequences are available upon request.

How did Rhythmlink obtain clearance for its MR Conditional Electrodes?

Rhythmlink worked extensively with scientists and consultants to achieve optimal safety and effectiveness for its Disposable MR Conditional Electrodes. To achieve clearance in both the 1.5 Tesla and 3.0 Tesla scanners, Rhythmlink conducted numerous simulations testing different electrode configurations and positions upon a phantom patient.

Through these test simulations Rhythmlink's electrodes were proven to be both safe and effective under those specific conditions which can be found in detail in the instructions for use of this product.

The data generated via the test simulations were submitted to the FDA for marketing clearance. Rhythmlink received FDA 510(k) clearance to market its Disposable MR Conditional Cup and Webbed™ Electrodes on May 30, 2013 and MR Conditional PressOn Electrodes on July 22, 2013.

Can I collect data while in the MR?

Rhythmlink's Disposable MR Conditional* Electrodes cannot be used for data collection while in the MR environment. While the electrodes can remain on the patient during the imaging and do not have to be removed and reapplied for each MR scanning session, the extension cables must be removed from the electrode prior to entering the MR environment. The extension cables are MRI Unsafe.


*Patent Pending
Webbed™ EEG Electrode; US Patent No. D644,738
Webbed EEG Electrode; European Design Patent No. 001893751-0001
PressOn™ Electrode, US Patent Nos. 8112131, 8185183, 8271065, 8428681, 8538502
PressOn Electrode, Chinese Patent No. CN101720202
PressOn Electrode, Japan Patent No. JP5226776
PressOn Electrode, European Patent No. EP2155056