Initial Clinical Experience Using 14-fold Accelerated Whole-Chest, Equilibrium Phase Contrast-Enhanced bT1RESS for Evaluation of the Heart and Great Vessels

Background: Breath-hold (1) and free-breathing (2) versions of equilibrium phase bT1RESS (balanced T1 relaxation-enhanced steady-state) allow diagnostic contrast-enhanced MRA to be acquired for tens of minutes after contrast administration, providing a similar benefit to ferumoxytol infusion but using a standard gadolinium-based contrast agent. We recently improved the temporal resolution of free-breathing bT1RESS using a fourteen-fold scan acceleration factor, substantially larger than prior versions. Given the very short scan (< 2 minutes) and reconstruction times (< 1 minute) provided by this highly-accelerated technique, we were able to incorporate it into our routine CMR workflow and report our clinical experience.

Methods: The study was approved by the hospital IRB. The recruitment goal is 50 patients with 10 subjects scanned to date. Clinical indications included aortic aneurysm, cardiomyopathy, cardiac mass and thrombus. Imaging was performed on 1.5 T scanners (MAGNETOM Avanto^fit or Aera, Siemens Healthineers, Forchheim, Germany) using a standard CMR protocol which was modified by acquiring free-breathing bT1RESS during the 5-minute waiting period between resting perfusion and the TI scout. Gadobutrol dose was 0.15 mmol/kg. bT1RESS was acquired in a 30-degree coronal oblique orientation using a field-of-view of 385-mm, TE = 1.1 msec, asymmetric readout with sampling bandwidth ~1495 Hz/px, SPAIR for fat suppression, and 14-fold scan acceleration (3x3 GRAPPA + 6/8 (slice) x 7/8 (phase) partial Fourier). Temporal resolution was 146 msec and reconstructed spatial resolution was 2-mm x 1-mm x 1-mm.

Results: Image quality was good-to-excellent with delineation of normal myocardial morphology and the proximal-to-mid coronary arteries (Fig. 1). bT1RESS provided clinically useful information that was not obtained using the standard CMR protocol in patients with abnormal cardiac morphology (Fig. 2), intracardiac masses (Fig. 3), valvular calcification, and extracardiac masses (thyroid gland, liver, kidneys).

Conclusion: While recruitment for this study is ongoing, preliminary results suggest that 14-fold accelerated free-breathing whole-chest bT1RESS can be routinely incorporated into a standard CMR protocol without prolonging total exam time or disrupting workflow. To date, there have been no apparent drawbacks to the routine use of this technique. bT1RESS enabled rapid diastolic volumetric assessment of the heart, thoracic aorta, and pulmonary arteries and veins, which is not available with our standard CMR protocol. Moreover, it provided useful additional information by virtue of its capability for isotropic volumetric evaluation of the heart and extracardiac structures. Further enhancements to the spatial and temporal resolution are in progress and will be incorporated into the study protocol as they become available.

Research support, NIH grants 1R01CA263091and 1R21CA273280.

1. Multiplanar reformations (MPRs) from whole-chest bT1RESS (scan time of 1 min 14 sec) in a 58-year-old female depict normal cardiac and vascular morphology and demonstrate the proximal and mid segments of the right (blue arrow) and left (red arrow) coronary arteries.
2. Apical-variant hypertrophic cardiomyopathy in a 62-year-old female. MPRs from whole-chest bT1RESS (scan time of 1 min 19 sec) demonstrate the full length of a false tendon that extends from the apical lateral segment to the basal interventricular septum, and which was incompletely depicted in standard cine views. Thickened apical lateral myocardium (solid blue arrow) and an enhancing liver mass (open green arrow) are also shown.
3. 80-year-old male with a right atrial mass (red arrow). MOCO 2D LGE 4-chamber (top left) and short-axis (bottom left) views, with each scan plane acquired in approximately 2 minutes. By comparison, volumetric depiction of the mass was obtained using whole-chest bT1RESS in only 51 seconds.