Breath-Hold, Whole-Chest, Equilibrium Phase Contrast-Enhanced MR Angiography Using Highly Accelerated Nonselective Balanced T1 Relaxation-Enhanced Steady-State (bT1RESS) (RF_SA_500)

Saturday, February 1, 2025

11:00 AM – 11:10 AM East Coast USA Time

Location: Blue Room PreFunction

Presenting Author(s)

Robert R. Edelman, MD

Chairman
NorthShore University HealthSystem

Primary Author(s)

Robert R. Edelman, MD

Chairman
NorthShore University HealthSystem

Co-Author(s)

AP

Amit Pursnani, MD

Advanced Imaging Cardiology Program Director
NorthShore University HealthSystem
NL

Nondas Leloudas, BA, RT

Research technologist
NorthShore University HealthSystem
IK

Ioannis Koktzoglou, PhD

MRI Scientist
NorthShore University HealthSystem

Background: Both CTA and CEMRA require that scanning be performed during the first pass of contrast agent to obtain adequate vessel conspicuity and image quality, with substantial image degradation if scans are delayed until the equilibrium phase. Recently, we reported a paradigm-shifting approach for CEMRA called equilibrium phase bT1RESS (balanced T1 relaxation-enhanced steady-state), which extends the useful angiographic window to as long as 30 minutes after administration of a standard gadolinium-based contrast agent [1]. While the original version used a modest degree of scan acceleration and a slab-selective RF excitation, we recently implemented a highly accelerated version using a spatially nonselective excitation. A pilot study was performed to evaluate technical feasibility in patients undergoing CMR.

Methods: The study was approved by the hospital IRB. 6 adult patients and 1 healthy volunteer were imaged at 1.5 Tesla from 4 to 15 minutes after infusion of gadobutrol (0.15 mmol/kg). Slab-selective bT1RESS used up to 9-fold acceleration, while nonselective bT1RESS used up to 15-fold acceleration (combination of parallel acceleration and partial Fourier). Nonselective bT1RESS was acquired in an oblique coronal plane. Both techniques used breath-holding, fat suppression, and reconstructed voxel dimensions of 1.1-mm.

Results: Comparing slab-selective with nonselective bT1RESS, respective slab coverage was 79.2-mm vs. whole chest. Vessel conspicuity was excellent for both techniques (Figures 1 - 3). With the nonselective version, multiplanar reconstructions (MPRs) of the entire heart and great vessels could be obtained in arbitrary orientations. The coronary origins were routinely visible, while the absence of off-resonance or flow artifacts was particularly helpful for depicting the pulmonary vein origins. Minor artifacts (possibly from aliasing and/or gradient nonlinearities) were sometimes present in portions of the nonselective bT1RESS images, but did not significantly interfere with cardiovascular evaluation.

Conclusion: The excellent SNR provided by equilibrium phase bT1RESS enables very high acceleration factors, which in turn allows the use of a nonselective RF excitation for breath-hold imaging with full volume coverage. The nonselective excitation minimizes off-resonance effects and improves temporal resolution because of the very short TR/TE (2.2 ms/1.1 ms). Since the entire chest can be imaged in a single breath-hold and images can be acquired for many minutes after contrast administration, the technique can be routinely incorporated into a standard CMR protocol. Arteries and veins are well evaluated, as is cardiac morphology. The technique could prove especially useful for the anatomic display of complex vascular anomalies in congenital heart disease. Future efforts will be directed towards further increasing scan acceleration, eliminating residual artifacts, and clinical validation.