Evaluating noncontrast MRA protocols for lower extremity peripheral arterial disease
Magnetic resonance angiography (MRA) with gadolinium-based contrast is used to diagnose and characterize peripheral artery disease. Noncontrast angiography protocols for 3T magnetic resonance imaging (MRI) scanners have been developed, the most studied of which are electrocardiogram-gated fast spin echo (ECG-FSE) and quiescent-interval single-shot (QISS). A newer technique, quadruple inversion-recovery (QIR), has been developed for the abdominopelvic station to reduce high blood-flow artifacts found with the other techniques.
Researchers at the University of Utah in Salt Lake City conducted a small, 20-patient study to compare noncontrast angiography protocols with each other and with gadolinium-enhanced MR angiography protocols in evaluating peripheral artery disease (PAD). They found noncontrast protocols to be comparable, and that both are viable alternatives to conventional MRA with contrast. Their findings were published in the November 2018 issue of the Journal of Vascular and Interventional Radiology.
The patients underwent peripheral MRA using non-Gd protocols QISS and quadruple inversion-recovery (QIR)/ECG-FSE, as well as one using bolus-chase gadolinium-based contrast. Two body radiologists interpreted three image datasets per patient, including abdominopelvic QIR and 2-station ECG-FSE, 3-station QISS, and 3-station gadolinium MRA. The radiologists independently evaluated vessel segments using a Likert scale from 1-5 for vascular stenosis, graded the most severe stenosis, and noted the presence/absence of collateral vessel reconstitution and graft presence. They noted occlusions, technical artifacts, and/or metal artifacts. They also ranked Trans-Atlantic Inter-Society Consensus (TASC) II classification for each station. In total, the radiologists evaluated 1,143 QIR/ECG-FSE and 1,111 QISS segments.
Of 573 vascular segments imaged with gadolinium MRA, 17% demonstrated hemodynamically significant abnormalities in 19 patients. Diagnostic accuracy of QISS and ECG-FSE was calculated based on results from 564 segments (127 for the abdominopelvic station, 120 segments for the thigh station, and 317 for the calf station). Led by Christopher J. Hanrahan, MD, PhD, a musculoskeletal radiologist at the Utah Center for Advanced Imaging Research, the researchers found no significant differences in sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), or accuracy between the two protocols.
The authors reported that while both noncontrast angiography protocols showed strong agreement with gadolinium MRA in stations classified as TASC A/B, they underestimated disease severity in stations classified as TASC C/D. They also noted that abdominopelvic QISS imaging showed lower sensitivity than QIR, which they attributed to artifacts. ECG-FSE was “particularly affected” by motion in the thigh station. Slow-flow and/or flow reversal was also problematic with the non-gadolinium protocols. Image acquisition time was longer, and sensitivities and specificities were also lower.
“Improvements in both noncontrast methods may be necessary to make [the non-gadolinium protocols] as useful as Gd MR angiography for all patients with PAD,” they wrote. “Non-GD MR angiography with QISS or QIR/ECG-FSE at 3T is an alternative to Gd MR angiography or digital subtraction angiography in patients with contraindications to Gd.”
REFERENCE
- Hanrahan CJ, Lindley MD, Mueller M, et al. Diagnostic Accuracy of Noncontrast MR Angiography Protocols at 3T for the Detection and Characterization of Lower Extremity Peripheral Arterial Disease. J Vasc Interv Radiol. 2018;29(11):1585-1594.