Highly accelerated time-of-flight magnetic resonance angiography using spiral imaging improves conspicuity of intracranial arterial branches while reducing scan time.

OBJECTIVE: To systematically compare time-of-flight magnetic resonance angiography (TOF-MRA) acquired with Compressed SENSE (TOF-CS) to spiral imaging (TOF-Spiral) for imaging of brain-feeding arteries.
METHODS: Seventy-one patients (60.2 ± 19.5 years, 43.7% females, 28.2% with pathology) who underwent TOF-MRA after implementation of a new scanner software program enabling spiral imaging were analyzed retrospectively. TOF-CS (standard sequence; duration ~ 4 min) and the new TOF-Spiral (duration ~ 3 min) were acquired. Image evaluation (vessel image quality and detectability, diagnostic confidence (1 (diagnosis very uncertain) to 5 (diagnosis very certain)), quantitative measurement of aneurysm diameter or degree of stenosis according to North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria) was performed by two readers. Quantitative assessments of pathology were compared to computed tomography angiography (CTA) or digital subtraction angiography (DSA).
RESULTS: TOF-CS showed higher image quality for intraosseous and intradural segments of the internal carotid artery while TOF-Spiral better depicted small intracranial vessels like the anterior choroidal artery. All vessel pathologies were correctly identified by both readers for TOF-CS and TOF-Spiral with high confidence (TOF-CS (4.4 ± 0.6 and 4.3 ± 0.8), TOF-Spiral (4.3 ± 0.7 and 4.3 ± 0.8)) and good inter-reader agreement (Cohen's kappa > 0.8). Quantitative assessments of aneurysm size or stenosis did not significantly differ between TOF-CS or TOF-Spiral and CTA or DSA (p > 0.05).
CONCLUSIONS: TOF-Spiral for imaging of brain-feeding arteries enables reductions in scan time without drawbacks in diagnostic confidence. A combination of spiral imaging and CS may help to overcome shortcomings of both sequences alone and could further reduce acquisition times in the future. KEY POINTS: • TOF-MRA with Compressed SENSE is superior in depicting arteries at the skull base while spiral TOF-MRA is able to better depict small intracranial vessels. • Both TOF-MRA with Compressed SENSE and TOF-MRA with spiral imaging provide high diagnostic confidence for detection of pathologies of brain-feeding arteries. • Spiral TOF-MRA is faster (by 25% for the sequence used in this study) than TOF-MRA with Compressed SENSE, thus enabling clear reductions in scan time for the clinical setting.