Relaxation-Enhanced Angiography Without Contrast and Triggering (REACT) for Fast Imaging of Extracranial Arteries in Acute Ischemic Stroke at 3 T

Abstract

Purpose To evaluate a novel flow-independent 3D isotropic REACT sequence compared with CE-MRA for the imaging of extracranial arteries in acute ischemic stroke (AIS). Methods This was a retrospective study of 35 patients who underwent a stroke protocol at 3 T including REACT (fixed scan time: 2:46 min) and CE-MRA of the extracranial arteries. Three radiologists evaluated scans regarding vessel delineation, signal, and contrast and assessed overall image noise and artifacts using 5-point scales (5: excellent delineation/no artifacts). Apparent signal- and contrast-to-noise ratios (aSNR/aCNR) were measured for the common carotid artery (CCA), internal carotid artery (ICA, C1 segment), and vertebral artery (V2 segment). Two radiologists graded the degree of proximal ICA stenosis. Results Compared to REACT, CE-MRA showed better delineation for the CCA and ICA (C1 and C2 segments) (median 5, range 2–5 vs. 4, range 3–5; P < 0.05). For the ICA (C1 and C2 segments), REACT provided a higher signal (5, range 3–5; P < 0.05/4.5, range 3–5; P > 0.05 vs. 4, range 2–5) and contrast (5, range 3–5 vs. 4, range 2–5; P > 0.05) than CE-MRA. The remaining segments of the blood-supplying vessels showed equal medians. There was no significant difference regarding artifacts, whereas REACT provided significantly lower image noise (4, range 3–5 vs. 4 range 2–5; P < 0.05) with a higher aSNR (P < 0.05) and aCNR (P < 0.05) for all vessels combined. For clinically relevant (≥50%) ICA stenosis, REACT achieved a detection sensitivity of 93.75% and a specificity of 100%. Conclusion Given its fast acquisition, comparable image quality to CE-MRA and high sensitivity and specificity for the detection of ICA stenosis, REACT was proven to be a clinically applicable method to assess extracranial arteries in AIS.

Clinical application of free-breathing 3D whole heart late gadolinium enhancement cardiovascular magnetic resonance with high isotropic spatial resolution using Compressed SENSE

“…Recently, Compressed SENSE was introduced, which combines compressed sensing and parallel imaging using SENSitivity Encoding (SENSE) [29][30][31]. Compressed SENSE enables image-acquisition acceleration currently not achievable by compressed sensing or parallel imaging alone and has shown promising results in musculoskeletal and cardiovascular imaging [29][30][31][32][33][34][35][36].…”

Free-breathing non-contrast flow-independent cardiovascular magnetic resonance angiography using cardiac gated, magnetization-prepared 3D Dixon method: assessment of thoracic vasculature in congenital heart disease

“…Furthermore, flow artifacts were present in 10/70 patients (14 %) on REACT- and steady-state-CMRA, respectively, but not on first-pass-CMRA. Fat-water separation artifacts were observed on REACT-CMRA in 11/70 cases (16 %), which are specific to chemical shift encoding sequences and Dixon methods [ 21 , 22 ]. However, some of these artifacts are known to appear on water- and fat-only images and can be circumvented by the additional reconstruction of in- and opposed-phase images.…”

“…REACT-CMRA can be used in a variety of applications, e.g. for imaging of the pelvic veins, extracranial arteries, or the thoracic vasculature [ 22 , 31 , 32 ]. To compensate for cardiac and respiratory motion artifacts, respiratory navigator- and ECG-gating was applied in this study.…”

Imaging of the extracranial internal carotid artery in acute ischemic stroke: assessment of stenosis, plaques, and image quality using relaxation-enhanced angiography without contrast and triggering (REACT)

“…The details of the applied extracranial MRA sequences have been described in detail elsewhere (30). In brief, a nontriggered flow-independent 3D isotropic REACT sequence was used for non-CE-MRA.…”

“…By providing a concurrent delineation of arteries and veins, it has demonstrated promising results in the imaging of the thoracic vasculature (26)(27)(28) and other vascular territories (29). While the REACT sequence cannot depict the intracranial arteries (25,30), it has also shown a comparable image quality to CE-MRA for extracranial arteries in a recent study at 3T while providing a high sensitivity and specificity for the detection of stenosis of the extracranial ICA (30). However, given the small sample size of aforementioned study (n=35), the validity of these findings remains questionable, especially the sensitivity of vessel stenosis detection.…”