Qualitative and Quantitative Analysis of a Spiral Gradient Echo Sequence for Contrast-Enhanced Fat-Suppressed T1-Weighted Spine Magnetic Resonance Imaging

Abstract

Objectives: Pulse sequences with non-Cartesian k-space sampling enable improved imaging in anatomical areas with high degrees of motion artifacts. We analyzed a novel spiral 3-dimensional (3D) gradient echo (GRE) magnetic resonance imaging (MRI) sequence ("spiral," 114.7 ± 11 seconds) and compared it with a radial 3D GRE ("vane," 216.7 ± 2 seconds) and a conventional Cartesian 2D turbo spin echo (TSE) sequence ("TSE," 266.7 ± 82 seconds) for contrast-enhanced fat-suppressed T1-weighted spine imaging. Materials and Methods: Forty consecutive patients referred for contrast-enhanced MRI were prospectively scanned with all 3 sequences. A qualitative analysis was performed by 3 readers using 4-or 5-point Likert scales to independently grade images in terms of overall image quality, occurrence of artifacts, lesion conspicuity, and conspicuity of nerve roots. The numbers of visible nerve roots per sequence and patient were counted in consensus. Coefficient of variation measurements were performed for the paravertebral musculature (CV PM ) and the spinal cord (CV SC ). Results: Spiral (median [interquartile range], 5 [4-5]) exhibited improved overall image quality in comparison to ) and vane (4 [4-5]; both P < 0.001). Vane surpassed TSE in terms of overall image quality (P < 0.001). Spiral (4 [3.75-4]) and vane (3.5 [3-4]) presented with less artifacts than ]; both P < 0.001). ) outperformed vane (4 [3-5]; P = 0.01) and ; P = 0.04) in terms of lesion conspicuity. Conspicuity of nerve roots was superior on spiral (3 [3-4]) and vane (4 [3-4]) when compared with TSE (1.5 [1-2]; both P < 0.001). Readers discerned significantly more nerve roots on spiral (4 [2.75-8]) and vane (4 [3.75-7.25]) images when compared with TSE (2 [0-4]; both P < 0.001). Interreader agreement ranged from moderate (α = 0.639) to almost perfect (α = 0.967). CV PM and CV SC were significantly lower on spiral as compared with vane and TSE (P < 0.001, P = 0.04). Vane exhibited lower CV PM and CV SC than TSE (P < 0.001, P = 0.01). Conclusions: A novel spiral 3D GRE sequence improves contrast-enhanced fatsuppressed T1-weighted spinal imaging qualitatively and quantitatively in comparison with a conventional Cartesian 2D TSE sequence and to a lesser extent with a radial 3D GRE sequence at shorter scan times.

Contrast-Enhanced T1-Weighted Head and Neck MRI: Prospective Intraindividual Image Quality Comparison of Spiral GRE, Cartesian GRE, and Cartesian TSE Sequences

“…The percentage reduction achieved by spiral GRE compared with the other two sequences was computed. Interreader agreement of qualitative scores was assessed using Krippendorff's alpha coefficient, with the following scale to indicate the level of agreement: 0.0 to 0.20, poor agreement; 0.21 to 0.40, fair agreement; 0.41 to 0.60, moderate agreement; 0.61 to 0.80, substantial agreement; and 0.81 to 1.00, almost perfect agreement [13]. Qualitative metrics were summarized using the median and interquartile range and compared between spiral GRE and both Cartesian GRE and Cartesian TSE sequences using Wilcoxon signed-rank tests.…”

“…The parameters for the Cartesian GRE and TSE sequences were selected based on longstanding institutional clinical protocols. The parameters for the spiral GRE sequence were selected based on the vendor's recommendation after in-house and external optimization [1,13].…”

“…Readers were blinded to the sequence type or acquisition parameters or other imaging or clinical information. Readers were allowed to freely adjust window and level settings and to scroll through the images of the given sequence [13].…”

“…The readers subjectively assessed image quality using 5-point Likert scales, based on earlier studies [1,3,13]. The following qualitative measures were recorded: overall image quality (scores provided for the whole head and neck; only the neck, from clavicle to mandible; and only head, from mandible to orbits; 1, nondiagnostic; 2, severely limited; 3, moderately limited; 4, minimally limited; 5: excellent image quality); conspicuity of the a priori specified lesion (scores provided for the whole head and neck, only the neck, and only the head; 1: virtually unable to visualize; 2: blurry but visualized; 3: acceptable visualization; 4: good visualization; 5: excellent visualization); quality of fat suppression (1: inhomogeneous with definite diagnostic interference; 2: inhomogeneous with probable diagnostic interference; 3: inhomogeneous but probably no diagnostic interference; 4: incomplete but without diagnostic interference; 5: complete and homogeneous); artifacts, including from motion, pulsation, dental material (e.g., filling or implant; not evaluated in patients without dental material), flow, and signal foldover (1: markedly prominent artifact with definite diagnostic interference; 2: prominent artifact with probable diagnostic interference; 3: prominent artifact but probably no diagnostic interference; 4: minimal artifact without diagnostic interference; 5: no artifact); delineation of muscular contours (1: insufficient delineation to evaluate; 2: prominently reduced discrimination; 3: moderately reduced discrimination; 4: minimally and only focally reduced discrimination; 5: ubiquitous excellent discrimination); delineation of vessel contours, based on large vessels such as the internal carotid arteries and jugular veins (1: insufficient delineation to evaluate; 2: prominently reduced discrimination; 3: moderately reduced discrimination; 4: minimally and only focally reduced discrimination; 5: ubiquitous excellent discrimination); and differentiation between mucosa and pharyngeal muscles at the level of the oropharynx (1: insufficient to evaluate; 2: prominently…”

“…Spiral sequences offer high k-space sampling efficiency and central k-space oversampling, thus enabling artifact-robust imaging at even shorter scan times than for conventional T1W sequences [6,7]. Spiral sequences have previously shown promise for anatomic and functional imaging of various regions [6][7][8][9][10][11][12][13][14]. However, to our knowledge, the utility of spiral sequences has not been systematically explored for clinical head and neck MRI.…”