256 - ICD Artifacts Reduction for Radiotherapy of Ventricular Tachycardia Using 3D Wideband Late Gadolinium-Enhanced MRI: A Preliminary Study in Healthy Participants and Patient

03:40pm - 03:50pm PT

Room 155/157

Presenter(s)

Huiming Dong, PhD - University of California Los Angeles, Los Angeles, CA

H. Dong¹, S. F. Shih², F. Han³, R. K. Chin¹, J. Hayase⁴, J. Bradfield⁴, A. Bedayat², J. P. Finn², M. Cao^1,5, and X. Zhong²; ¹Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, ²Department of Radiology, University of California, Los Angeles, Los Angeles, CA, ³Siemens Medical Solutions, USA, Los Angeles, CA, ⁴Electrophysiology, University of California, Los Angeles, Los Angeles, CA, ⁵Department of Radiation Oncology, University of California San Francisco, San Francisco, CA

Purpose/Objective(s): Cardiac SBRT emerges as promising modality for treating refractory ventricular tachycardia (VT). One key element for successful outcome is target delineation accuracy, for which 2D late gadolinium-enhanced (LGE) MRI with narrowband (NB) inversion recovery (IR) pulses offers unique value in identifying VT-inducing myocardial scars. However, the presence of hyperintense image artifacts due to implantable cardioverter devices (ICDs) often impairs the NB LGE MR images. Additionally, limitations inherent in 2D MRI, such as thick slices, large slice gaps, and suboptimal spatial coverage further challenge target localization during treatment planning. To allow accurate VT scar delineation, this study aims to implement 3D LGE MRI using wideband (WB) IR pulses for reduction of ICD-induced hyperintense artifacts.

Materials/Methods: Pulse Sequence Design: Proposed 3D WB LGE sequence contains a non-selective hyperbolic secant WB IR RF pulse with a 4kHz bandwidth (vs. conventional narrowband=1.1kHz) to reduce ICD artifacts, followed by a 3D gradient-echo readout to acquire the volumetric k-space. ECG and respiratory navigator gating were employed for managing patient cardiorespiratory motion. In Vivo Study: Imaging was performed on a 1.5T technology company's MR simulator. MR sequence-associated geometric distortion was investigated in a MagPhan. Image quality and suppression of ICD artifact were evaluated in 3 healthy participants for whom an ICD was placed near the heart. The 3D WB LGE MRI was then performed in a 73 y.o. male ICD-dependent patient to delineate treatment targets for VT radioablation.

Results:

Geometric distortion of the 3D WB LGE sequence was well within the clinical tolerance (Table I). Maximum distortion was 0.62mm (tolerance=1mm) at 200mm diameter spherical volume (DSV), and it increased to 0.85mm (tolerance=2mm) at 350mm DSV.

The hyperintense artifacts were effectively suppressed in all participants using the 3D WB LGE technique compared to the conventional NB LGE MRI.

In the ICD-dependent VT patient, the electrophysiologists identified scars in segment 4, 5, 6 and 11 per the AHA 17-segment model. These targets were successfully localized for treatment planning by the 3D WB LGE MRI which correlated well to the electroanatomic mapping without artifacts.

Conclusion: A 3D WB LGE MR sequence was introduced for cardiac SBRT, demonstrating minimal distortion and successful ICD artifact suppression, allowing accurate target identification for VT radioablation treatment planning.

200mm Diameter Spherical Volume (Tolerance for Distortion=1mm)
	Max Distortion Magnitude (mm)	Max Distortion X Direction (mm)	Max Distortion Y Direction (mm)	Max Distortion Z Direction (mm)
T1 MPRAGE	0.22	0.16	0.02	0.25
WB LGE	0.62	0.39	0.40	0.40

350mm Diameter Spherical Volume (Tolerance for Distortion=2mm)
	Max Distortion Magnitude (mm)	Max Distortion X Direction (mm)	Max Distortion Y Direction (mm)	Max Distortion Z Direction (mm)
T1 MPRAGE	0.15	0.20	0.17	0.46
WB LGE	0.85	0.49	0.70	0.55