Adeel Shahid MD, Presenter: Nothing to Disclose

Linda Chi Hang Chu MD, Abstract Co-Author: Nothing to Disclose

Saman Nazarian MD, Abstract Co-Author: Scientific Advisor, Johnson & Johnson Research funded, Johnson & Johnson

Ihab R. Kamel MD, PhD, Abstract Co-Author: Nothing to Disclose

Stefan L. Zimmerman MD, Abstract Co-Author: Nothing to Disclose

Bolus timing is critical to optimal magnetic resonance angiography (MRA) acquisitions but can be challenging in some patients. Our purpose was to evaluate whether contrast-enhanced time-resolved interleaved stochastic trajectories (TWIST), a dynamic multiphase sequence that does not rely on bolus timing, is a viable alternative method to three-dimensional fast-long angle shot (FLASH) in patients with atrial fibrillation. 

Coronal subtracted MRA images from 20 patients with TWIST MRA performed for vascular mapping prior to atrial fibrillation ablation were compared to 20 patients with 3D FLASH MRA. The default TWIST protocol was modified to maximize spatial resolution at the expense of temporal resolution (7.4 sec). In-plane spatial resolution for both TWIST and FLASH was 1.0 x 1.0 mm. TWIST slice thickness was 1.5 mm; FLASH was 1.2 mm. Contrast dose was 0.2 mmol/kg, injected at 5 mL/sec for TWIST and 2 mL/sec for FLASH MRA. Left atrial signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured for the FLASH MRA and for the phase of the TWIST MRA demonstrating the best atrial enhancement. Quality was assessed in a blinded fashion on a 1-5 scale for relative left atrial opacification, left atrial contrast uniformity and overall study quality. 

TWIST SNR was significantly higher than that of 3D FLASH MRA (13.7 ± 3.3 vs 8.5 ± 2.1, p<0.001). TWIST CNR was not different than that of 3D FLASH MRA (p=0.08). Qualitative uniformity of left atrial enhancement was significantly higher with TWIST than FLASH MRA (4.8 ± 0.4 vs 4.2 ± 0.4, p<0.001), whereas relative atrial opacification (4.7 ± 0.5 vs 4.1 ± 1.3, p=0.06) and overall study quality were not different between TWIST and FLASH MRA (p=0.17).

TWIST modified to maximize spatial resolution offers an alternative method for performing high quality MRA examinations in patients with atrial fibrillation. TWIST offers greater signal-to-noise ratio and improved left atrial enhancement compared to traditional FLASH MRA techniques, without the challenges of proper bolus timing. 

TWIST can be used instead of traditional 3D MRA to image patients undergoing vascular mapping prior to atrial fibrillation ablation. Without the need for proper bolus timing, TWIST offers a straightforward push-button method for capturing optimal left atrial opacification due to its dynamic multiphase acquisition. 

Shahid, A, Chu, L, Nazarian, S, Kamel, I, Zimmerman, S, Utility of TWIST Magnetic Resonance Angiography for Pre-ablation Planning in Patients with Atrial Fibrillation: Comparison with Traditional Techniques.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017577.html