Safety: Epidural CathetersCan patients with epidural or perineural catheters be safely scanned?
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It depends. Obviously those catheters made entirely of nylon or polyurethane but no metal components are by definition MR Safe.
The problem is that a substantial number of epidural catheters are reinforced with a metallic spring or wire. This core may be made of titanium or non-ferromagnetic stainless steel, but in some cases is made of martensitic (ferromagnetic) steel. Relatively few peer reviewed studies have been performed to test the catheters of today, and manufacturer's literature is often obtuse or lacking with regard to MR safety. The major risks include movement/dislodgment of the catheter and RF-induced heating of the catheter tip via the antenna effect. Since the catheter may lie just a millimeter or two away from the spinal cord or trunk of a major nerve, this latter risk is often the dominant consideration.
The problem is that a substantial number of epidural catheters are reinforced with a metallic spring or wire. This core may be made of titanium or non-ferromagnetic stainless steel, but in some cases is made of martensitic (ferromagnetic) steel. Relatively few peer reviewed studies have been performed to test the catheters of today, and manufacturer's literature is often obtuse or lacking with regard to MR safety. The major risks include movement/dislodgment of the catheter and RF-induced heating of the catheter tip via the antenna effect. Since the catheter may lie just a millimeter or two away from the spinal cord or trunk of a major nerve, this latter risk is often the dominant consideration.
MR Unsafe metal-reinforced epidural catheter (courtesy Telemed)
Perhaps it is simplest to first list the reinforced catheters generally considered to be MR Unsafe (by independent testing or per the manufacturer):
- Medline Reinforced Epidural Catheter (Medline)
- Perifix® FX Springwound Epidural Catheter (B. Braun)
- StimuCath® Peripheral (Teleflex)
- DuraFlex® and DuraFlex® Plus (Smiths Medical)
- Epilog® Soft Epidural Catheter (Pajunk)
- Racz®-type Catheters — Brevi-XL® series, G21®, Feth-R-Kath®, NeoKath®, Tun-L-Cath®, VersaKath®, and Spirol® — (Epimed)
Several popular wire-reinforced catheters are generally considered to be MR Conditional (although in some cases MR compatibility has been assumed based on relatively limited phantom data and bench testing):
- Arrow TheraCath®, FlexTip®, FlexTip® Plus, and FlexBlock® Peripheral (Teleflex) — Conditional at 1.5T and 3.0T using transmit-receive head coil only
- Contiplex® Polyamide Peripheral (B. Braun) — no significant heating at 1.5T or 3.0T with body coil
- Smith/Portex Epifuse® Nylon Epidural Catheter (Smiths Medical) — no significant heating at 1.5T or 3.0T with body coil
References
Maralani PJ, Schieda N, Hecht EM, et al. MRI safety and devices: an update and expert consensus. J Magn Reson Imaging 2019; 51:657-674. [DOI LINK]
Owens S, Erturk A, Ouanes J-P, et al. Evaluation of epidural and peripheral nerve catheter heating during magnetic resonance imaging. Reg Anesth Pain Med 2014; 39:534-539. [DOI LINK]
Shellock FG. Biomedical implants and devices: assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Reson Imaging. 2002; 16:721–723. [DOI LINK]
Toledano RD, Tsen LC. Epidural catheter design. History, innovations, and clinical implications. Anesthesiology 2014; 121:9-17.
Maralani PJ, Schieda N, Hecht EM, et al. MRI safety and devices: an update and expert consensus. J Magn Reson Imaging 2019; 51:657-674. [DOI LINK]
Owens S, Erturk A, Ouanes J-P, et al. Evaluation of epidural and peripheral nerve catheter heating during magnetic resonance imaging. Reg Anesth Pain Med 2014; 39:534-539. [DOI LINK]
Shellock FG. Biomedical implants and devices: assessment of magnetic field interactions with a 3.0-Tesla MR system. J Magn Reson Imaging. 2002; 16:721–723. [DOI LINK]
Toledano RD, Tsen LC. Epidural catheter design. History, innovations, and clinical implications. Anesthesiology 2014; 121:9-17.
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