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RF induced heating of pacemaker/ICD lead-tips during MRI Scans at 1.5T and 3T: evaluation in cadavers
Journal of Cardiovascular Magnetic Resonance volume 18, Article number: O121 (2016)
Studies about the safety of MRI exams for patients with pacemakers/ICDs at 1.5T have been reported [Nazarian S., et al. Annals of internal medicine 155.7 (2011): 415-424.]. Of most concern is possible heating of the lead-tips in contact with the myocardium. Little is known about the relative safety of 3T MRI exams for these patients and in vivo lead-tip heating data is difficult, if not impossible, to obtain. Our objective was to measure lead-tip heating directly in human cadavers with pacemakers/ICDs at both 3.0T and 1.5T.
Cadavers (N = 5, 3 male, Table 1, part 1) with existing pacemakers had fiberoptic temperature probes implanted adjacent to right atrial (RA), right ventricular (RV) and/or abandoned lead-tips under x-ray guidance. Whole-body CT was used to estimate lead-tip to probe-tip distances. Cadavers were exposed to 15-minutes of 4 W/kg whole body SAR at both 1.5T and 3T (Siemens Avanto and Prisma) for five isocenter positions: 6 cm superior to the chin (LM1) and in four 15 cm increments inferior to LM1 (LM2 to LM5) in order to evaluate lead-tip heating as a function of the device's position relative to isocenter (i.e. different MRI exams). Maximum temperature increases at the lead-tip were reported as △TMax (temperature difference between the baseline before the MRI sequence and peak heating after 15-minutes).
All temperature probes were ≤10 mm from the lead-tip (Table 1, part 2). Figure 1 shows △TMax for 1.5T and 3T for each probe. Maximum heating was observed at the LM2 and LM3 isocenter positions for which the whole implant was inside the body transmit coil. △TMax was >2C for 7 of 25 cases at 1.5T and for 12 of 25 cases at 3T, but never exceeded 4C.
These data do not indicate a substantial difference between lead-tip heating at 1.5T and 3T, nor do they indicate △TMax>4C despite the lack of cooling due to tissue perfusion. Continued evaluation is warranted and on-going.
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Acikel, V., Magrath, P., Parker, S.E. et al. RF induced heating of pacemaker/ICD lead-tips during MRI Scans at 1.5T and 3T: evaluation in cadavers. J Cardiovasc Magn Reson 18, O121 (2016). https://doi.org/10.1186/1532-429X-18-S1-O121
- Temperature Difference
- Right Ventricular
- Tissue Perfusion
- Temperature Probe
- Human Cadaver