2385 - Evaluation of Cardiac Implantable Electronic Devices-Induced Distortion on 0.35T and 3.0T MR Scanners

A. Omidi¹, E. Weiss¹, M. Al Khalifa², and S. Kim¹; ¹Virginia Commonwealth University Health System, Department of Radiation Oncology, Richmond, VA, ²Virginia Commonwealth University, Department of Radiation Oncology, Richmond, VA

Purpose/Objective(s): Evaluation of the extent of signal distortion (i.e., the distance from which the complete signal loss and/or ring artifacts are formed) and geometrical distortion (i.e., geometrical displacement of image components) in magnetic resonance (MR) images of cardiac implantable electronic devices (CIEDs) (e.g., pacemaker/defibrillator) on a 0.35T MR-Linac and a 3.0T Canon MR simulator. Materials/

Methods: A custom water-filled plastic phantom and a MagPhan phantom (RT 820) comprising approximately 500 spheres of 1 cm diameter were used to measure the extent of signal distortion and quantitative geometrical distortion, respectively. The pacemaker/defibrillator (Boston Scientific, Marlborough, MA) with lead wires were positioned at the center of the phantoms. A 3D TrueFISP scan (TR: 3 ms, TE: 1.27 ms, flip angle: 60°, slice thickness: 3 mm) and a 3D T1 scan (TR: 5 ms, TE: 2.2 ms, flip angle: 9°, slice thickness: 2 mm) were performed on 0.35T and 3.0T scanners, respectively. The extent of signal distortion in the water-filled phantom was manually measured in the commercially available software. For quantitative geometrical distortion measurement, the spheres in the MagPhan phantom were manually contoured and registered to their manufacturing positions in the commercially available software. Geometrical distortion was calculated by subtraction of center of volume for each sphere between the acquired MR images and the manufacturing position.
Results: Symmetrical distortion maps were observed in the water-filled phantom measurements from both pacemaker and defibrillator in 0.35T and 3.0T. The maximum extent of signal distortion with the defibrillator was 20.7 cm at 0.35T and 10.3 cm at 3.0T. Similarly, pacemaker showed a 9.3 cm and a 5.7 cm signal distortion at 0.35T and 3.0T, respectively. Quantitative geometrical distortion measurements showed maximum defibrillator distortion of 12.0 mm at both 0.35T and 3.0T. The pacemaker maximum distortion was 7.4 mm and 5.0 mm at 0.35T and 3.0T, respectively. Table 1 shows the maximum magnitude of distortion at various distances from the CIEDs.
Conclusion: Defibrillator caused more distortion than pacemaker (due to a larger electronic size). Larger distortion was observed at 0.35T (due to formation of Moiré fringes in the TrueFISP sequence) except for the defibrillator at close vicinity of the device (<15 cm) where the larger electronic size and the greater magnet strength (3.0T vs 0.35T) outweighed Moiré fringes induced distortion. Further studies with various devices and MRI units are necessary for validation. Abstract 2385 – Table 1: Maximum geometrical distortion at various distances from CIEDs

Distance from the CIED (cm)	0-5	5-10	10-15	15-20
Distortion due to pacemaker at 0.35T (mm)	7.4	3.6	3.1	3.5
Distortion due to pacemaker at 3.0T (mm)	5	3.6	1.9	1.9
Distortion due to defibrillator at 0.35T (mm)	12	7.1	3.6	3.6
Distortion due to defibrillator at 3.0T (mm)	12	10.8	10.2	3.4