Self-Gated Cardiac MRI for Free-Breathing Simultaneous Cine, T1 Map and LGE Acquisition

Heart failure (HF) is a major and growing public health problem in the United States. Currently, approximately six million Americans live with heart failure. Cardiac magnetic resonance (CMR) imaging provides important diagnostic and prognostic utility in HF. It has become the gold standard for accurately measuring left ventricular ejection fraction (LVEF) using cine imaging, and for characterizing myocardial scarring using late gadolinium enhancement (LGE) images. More recently developed parametric mapping techniques of myocardial native T1 and extracellular volume fraction (ECV) have further extended the unique diagnostic and prognostic information provided by CMR to characterize cardiomyopathy.

In a current clinical practice, a stack of 10-12 2D slices of short-axis cine images are typically acquired with breath-holding (BH) and electrocardiograph (ECG)-gating. In a separate set of acquisitions, T1 maps are typically acquired before and after contrast injection with a Modified Look-Locker-Inversion recovery (MOLLI) technique. MOLLI acquires single-shot images intermittently in diastole during 3 to 5 heartbeats after the inversion recovery (IR) pulses using breath-holding and ECG-gating. Alternatively, the SAturation-recovery single-SHot Acquisition (SASHA) sequence uses saturation recovery (SR) pulses. Ten minutes following contrast administration, a stack of 10-12 short-axis LGE images are acquired to characterize fibrosis. This approach to CMR image acquisition is inefficient and subject to artifacts related to poor ECG-gating and breath-hold. It also requires patient to complete 40+ breath-hold maneuvers during a 40+ minute acquisition. Recently advanced CMR techniques have been proposed to obtain multi-contrast cardiac imaging. Those methods either require ECG synchronization or breath-holds, or separate map for B1 correction. In this dissertation we propose to develop techniques to perform free-breathing (FB) cine, T1 mapping and LGE (post-contrast) imaging in a single acquisition without the need of ECG synchronization, and validate the proposed techniques in phantoms, normal human subjects and clinical patients including the ones with cardiomyopathy.

Specific Aim #1 is to develop free-breathing cine imaging using spiral acquisition with respiratory correction and cardiac self-gating (SPARCS). (a) Develop an automatic heart detection algorithm and extract respiratory motion around the heart to perform motion correction (MC) on k-space data. (b) Design a continuously acquired golden-angle (GA = 137.51°) spiral pulse sequence and perform a cardiac self-gated and respiratory motion-corrected reconstruction. (c) Evaluate image quality and compare the quantification of LVEF as compared to standard breath-holding and ECG-gating balanced steady state free-precession (bSSFP) cine imaging.

Specific Aim #2 is to develop simultaneous acquisition of cine images, T1 maps and LGE images under free-breathing and cardiac self-gating (CAT-SPARCS). (a) Design a spiral pulse sequence with intermittent IR pulses and relaxation time to obtain cine and T1 maps in a single free-breathing acquisition. (b) Design a continuous IR-based spiral pulse sequence with two excitation flip angles to measure T1 while correcting for B1 effects and slice profile (CAT-SPARCS 2FAs). (c) Develop a free-breathing Bloch-Siegert B1 mapping acquisition and incorporate it to the continuous IR-based spiral acquisition pipeline with one excitation flip angle (1FA+B1).

Specific Aim #3 is to validate the CAT-SPARCS 2FAs and 1FA+B1 techniques in phantom, normal human subjects and clinical patients including the ones with cardiomyopathy. (a) Acquire data using CAT-SPARCS 2FAs and 1FA+B1, and the standard clinical-used T1 maps including MOLLI and SASHA results during experiments. (b) Validate the proposed T1 measurements as compared to MOLLI and SASHA results.