PURPOSE: To evaluate the safety and feasibility of 3-T magnetic
resonance (MR) imaging of
the brain in patients with implanted
cardiac pacemakers (PMs) by using a transmit-receive
head coil. MATERIALS AND METHODS: The study protocol was approved by the
institutional review board. Signed informed consent was obtained from all subjects. In vitro testing at 3 T was performed with 32 PMs and 45 PM leads that were evaluated for force and torque (by using a floating platform) and
radiofrequency (RF)-related heating by using a transmit-receive
head coil (maximum
specific absorption rate, 3.2 W/kg). Patient examinations at 3 T were performed in 44 patients with a
cardiac PM and a strong clinical need; patients underwent a total of 51 MR examinations of
the brain by using a transmit-receive
head coil to minimize RF exposure of the PM system. An
electrocardiograph and
pulse oximetry were used for continuous monitoring during MR imaging. The technical and functional PM status was assessed
prior to and immediately after MR imaging and at 3 months thereafter. Serum
troponin I level was measured before and 12 hours after imaging to detect
myocardial thermal injury. PM
reprogramming was performed
prior to MR imaging depending on the patient's intrinsic
heart rate (< 60 beats per minute, asynchronous pacing; > or = 60 beats per minute, sense-only mode). RESULTS: For in vitro testing, the maximum translational force was 2150 mN (
mean, 374.38 mN +/- 392.75 [
standard deviation]), and maximum torque was 17.8 x 10(-3) N x m (
mean, [2.29 +/- 4.08] x 10(-3) N x m). The maximum temperature increase was 2.98 degrees C (
mean, 0.16 degrees C +/- 0.45). For patient examinations, all MR examinations (51 of 51) were completed safely. There were no significant (P < .05) changes in lead
impedance, pacing capture threshold level, or serum
troponin I level. CONCLUSION: MR imaging of
the brain at 3 T in patients with a
cardiac PM can be performed safely when dedicated safety precautions (including the use of a transmit-receive
head coil) are taken.
