Rapid and motion-robust pediatric brain imaging: T2-weighted turbo-spin-echo PROPELLER acquisition with compressed sensing.

Abstract

Background: In pediatric magnetic resonance imaging (MRI), reducing the rate of non-diagnostic scans due to artifacts and shortening acquisition time are crucial not only for economic reasons but also to minimize sedation or general anesthesia.

Objective: Enabling faster and motion-robust MRI of the brain in infants and children using a novel, enhanced compressed sensing (CS) algorithm in combination with a turbo-spin-echo T2-weighted sequence utilizing the PROPELLER-technique (periodically rotated overlapping parallel lines with enhanced reconstruction; T2_{PROPELLER CS}).

Materials and methods: This prospective study included 31 patients (8.0 ± 4.7 years, 15 males) undergoing a clinically indicated MRI examination of the brain on a 3-T scanner. The T2_{PROPELLER CS} sequence was compared to a conventional, CS-accelerated Cartesian turbo-spin-echo T2-weighted sequence (T2_{Cartesian CS}). Apparent contrast-to-noise ratio (aCNR) and signal-to-noise ratio (aSNR) were calculated. Three blinded radiologists independently rated both sequences twice qualitatively on a 5-point Likert-scale from 1-5 (non-diagnostic-excellent) for artifacts, image sharpness, basal ganglia delineation, lesion conspicuity, and overall image quality. Statistical analysis was performed using the Wilcoxon signed-rank test and paired sample t test. Intra- and interrater reliability of qualitative image assessment was evaluated by computing Krippendorff's $\alpha$ reliability estimates.

Results: The average acquisition time of the T2_{PROPELLER CS} (189 ± 27 s) was 31% shorter than that of the T2_{Cartesian CS} sequence (273 ± 21 s; P < 0.001). aCNR (7.7 ± 4.6 vs. 6.2 ± 2.8; P = 0.004) and aSNR (24.8 ± 9.7 vs. 18.8 ± 5.5; P < 0.001) were higher for the T2_{Cartesian CS} compared to the T2_{PROPELLER CS} sequence. The T2_{PROPELLER CS} sequence significantly reduced (motion-)artifacts (P < 0.001) and increased image sharpness (P < 0.001), basal ganglia delineation (P<0.001), lesion conspicuity (raters 1 and 2, P < 0.001; rater 3, P = 0.004), and overall image quality (P < 0.001). Metal artifacts were prominent in both sequences, though slightly more pronounced in the T2_{PROPELLER CS} sequence.

Conclusion: The T2_{PROPELLER CS} sequence enables faster and motion-robust imaging of the brain in infants and children, reducing the rate of non-diagnostic scans and potentially allowing sedation or general anesthesia to be minimized in the future.