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Evaluation of Epidural and Peripheral Nerve Catheter Heating during Magnetic Resonance Imaging
Abstract Number: S-25
Abstract Type: Original Research
Background: Many epidural and peripheral nerve catheters contain a polymer bound wire that could heat to unsafe levels when exposed to magnetic resonance imaging (MRI). As MRI is the gold standard for diagnosing epidural hematoma following placement of an epidural catheter, it is important to determine whether such catheters should be removed during MRI 1-3.
Methods: The six catheters we studied included three from Arrow International, Inc. (MultiPort Epidural with FlexTip Plus, Epidural with FlexTip Plus, and StimuCath Peripheral Nerve Catheter), two from B. Braun Medical Inc. (Contiplex Polyamide PNC, and Perifix FX Epidural), and one from Smiths Medical/Portex (Epifuse Nylon Epidural). Two of the six selected catheters, the Arrow International, Inc. StimuCath Peripheral Nerve Catheter and the B. Braun Medical Inc. Perifix FX Epidural, were found to be magnetic, attracted by the MRI magnetic field, and thus were excluded from radio frequency (RF) heat testing. Four catheters were placed in a standard human torso- sized phantom in clinical 1.5T and 3T MRI scanners in an epidural configuration, extending 5cm parallel to the main magnetic field. An MRI pulse sequence was applied with a maximum scanner allowed RF specific absorption rate (SAR) for 15 min 4. Temperature and SAR exposure were sampled during MRI using multiple fiberoptic temperature sensors at reference and catheter locations in the phantom.
Results: At 3T, exposure to the scanner’s maximum RF exposure produced anomalous heating to 47°C in the two Arrow catheters (MultiPort Epidural with FlexTip Plus, Epidural with FlexTip Plus ), with greatest heating occurring at the entry point for all devices. Temperature increases for the other catheters at 3T and all catheters at 1.5T were <1.5°C. When normalized to an applied average SAR exposure of 4W/kg, maximum temperature increases were 0.12.5°C at 1.5T, and 0.72.7°C at 3T for all catheters except the Arrow device at 3T whose maximum projected heating was 14°C.
Conclusions: Heating of <3°C during MRI for most catheters is not expected to be injurious. While heating was lower at 1.5T vs. 3T, performance variations between different manufacturer’s devices underscore the need for safety testing prior to performing MRI.
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2. Gilbert A, Owens BD, Mulroy MF. Epidural hematoma after outpatient epidural anesthesia. Anesth Analg 2002; 94:778.
3. Otsu I, Merrill D. Epidural hematoma after epidural anesthesia: A case report of nonsurgical management. Acute Pain 2003; 4:11720.
4. Guidance for Industry and FDA Staff Criteria for Significant Risk Investigations of Magnetic 15 Resonance Diagnostic Devices. US Dept of Health and Human Services, FDA, Center for Devices and Radiological Health. (http://www.fda.gov/downloads/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/UCM072688.pdf, 7/14/2003).