MRSO Cardiac Implantable Electronic Devices (CIEDs) and MRI Safety

Question 1

Which ASTM/ISO designation applies to a pacemaker that may be used in MRI only when all specified conditions of field strength, SAR, and gradient slew rate are met?

Accepted Answer

MR Conditional

Answer

MR Conditional indicates the device poses no known hazards only within the specific MRI conditions defined in its labeling, unlike MR Safe, which implies safety in all MRI environments.

Question 2

Which mechanism is the primary source of cardiac injury risk from MRI in patients with implanted pacemaker leads?

Accepted Answer

RF-induced resistive heating concentrated at the electrode-tissue interface

Answer

RF energy is absorbed along the conductor and concentrates at the lead tip, producing resistive heating that can thermally damage myocardial tissue at the electrode-tissue interface.

Question 3

What was the central finding of the MagnaSafe Registry regarding MRI performed in patients with non-MR-conditional CIEDs?

Accepted Answer

Clinically significant adverse events were rare when a standardized monitoring protocol was followed

Answer

The MagnaSafe Registry demonstrated that MRI in patients with legacy (non-MR-conditional) CIEDs had a very low rate of device-related adverse events when performed under a rigorous, standardized protocol with continuous monitoring.

Question 4

Which whole-body average SAR limit is most commonly specified in MR-conditional pacemaker labeling to reduce the risk of RF-induced lead tip heating?

Accepted Answer

2.0 W/kg

Answer

Most MR-conditional pacemaker labels specify a whole-body average SAR limit of 2.0 W/kg, which aligns with the IEC normal operating mode threshold and limits RF deposition in implanted leads.

Question 5

Why are abandoned (non-functional) pacemaker leads considered particularly hazardous during MRI compared to connected leads?

Accepted Answer

Without a connected generator, RF-induced current concentrates entirely at the lead tip, maximizing heating

Answer

Abandoned leads without a proximal connection act as unloaded antennas; with no circuit path to dissipate current, all RF-induced energy concentrates at the electrode tip, producing greater heating than a connected lead.

MRSO - Magnetic Resonance Safety Officer Practice Test

MRSO - Magnetic Resonance Safety Officer Practice Test

MRSO Cardiac Implantable Electronic Devices (CIEDs) and MRI Safety