Author: Arash Bedayat, Jason Bradfield, Minsong Cao, Robert K Chin, Huiming Dong, J Paul Finn, Fei Han, Justin Hayase, Shu-Fu Shih, Xiaodong Zhong 👨🔬
Affiliation: Cardiac Electrophysiology, University of California, Los Angeles, Department of Radiation Oncology, University of California, Los Angeles, Department of Radiology, University of California, Los Angeles, Siemens Healthineers 🌍
Purpose: Cardiac SBRT is a promising treatment for ventricular tachycardia (VT). Success depends on accurate target delineation, for which 2D narrowband late gadolinium-enhanced (LGE) MRI offers valuable assist in identifying VT-inducing scars. However, hyperintense artifacts from patients’ implantable cardioverter devices (ICDs) often compromise the MR images, being confounded with the contrast-enhanced signals from targets. This study aims to implement a 3D wideband (WB) LGE MR sequence, and investigate its geometric distortion and hyperintense artifact mitigation for VT SBRT.
Methods: The 3D WB-LGE sequence was implemented using a 3D gradient-echo readout with ECG and respiratory navigator gating for motion management. A non-selective hyperbolic secant WB-inversion pulse with a 4kHz bandwidth (vs. conventional narrowband=1.1kHz) was utilized to reduce ICD-induced hyperintensity. Imaging was performed on a 1.5T Siemens MR simulator. The sequence-associated geometric distortion was investigated in a MagPhan. The reduction of ICD-induced hyperintense artifacts was evaluated in an ACR phantom, two healthy participants and a VT patient. The ICD was positioned near the phantom, or on the skin surface near the heart of the healthy participants to reproduce ICD locations in patients.
Results: Geometric distortion associated with the WB-LGE sequence was well within the clinical tolerance in MagPhan. The maximum distortion was 0.62mm (tolerance=1mm) at 200mm diameter spherical volume (DSV), and it increased to 0.85mm (tolerance=2mm) at 350mm DSV. Hyperintense artifacts were effectively reduced in the ACR phantom and two healthy participants with the 3D WB LGE technique compared to the conventional narrowband LGE technique. In the VT patient, the VT-inducing scars were successfully identified using the proposed 3D WB-LGE sequence and well correlated to the electroanatomic mapping.
Conclusion: A 3D WB-LGE MR sequence was introduced for cardiac SBRT, demonstrating minimal distortion and effective mitigation of ICD-induced hyperintensity, allowing more accurate target identification using MRI during the treatment planning for VT radioablation.