Pre-Scan Breathing Pattern and Image Quality in Respiratory-Triggered T2-Weighted Liver MRI: Radial Versus Cartesian Fast Spin Echo.
Abstract
Background
Respiratory-triggered T2-weighted imaging (T2WI) may use rectilinear sampling (respiratory-triggered fast recovery fast spin echo [RT-FRFSE]) or radial sampling (periodically rotated overlapping parallel lines with enhanced reconstruction [PROPELLER]). Their relative performance across breathing patterns is unclear.
Purpose
To compare image quality of PROPELLER and RT-FRFSE according to pre-scan breathing pattern. STUDY TYPE Retrospective. SUBJECTS 200 patients undergoing liver MRI (124 males; mean age, 58.1 ± 13.3 years). FIELD STRENGTH/SEQUENCE 1.5 T; fat-suppressed T2WI using PROPELLER and RT-FRFSE, both respiratory-triggered. ASSESSMENT Patients were stratified by pre-scan respiratory rate and regularity: Group A (regular, ≤ 14 breaths/min, n = 49), B (15-17, n = 57), C (≥ 18, n = 49), D (irregular, n = 45). Three radiologists, blinded to respiratory group, graded ghost artifacts, sharpness, noise, and overall quality on five-point scales. Liver signal-to-noise (SNR) and liver-to-gallbladder contrast-to-noise ratios (CNR) were measured. STATISTICAL TESTS Wilcoxon signed-rank test with Holm correction; Kruskal-Wallis analysis of within-patient difference scores and a linear mixed-effects model for SNR/CNR interactions; quadratic weighted kappa and intraclass correlation coefficient for interobserver agreement. p < 0.05 indicated significance.
Results
In Groups A and B, RT-FRFSE scored higher qualitatively, except ghost artifacts in Group A (p = 0.197). In Groups C and D, PROPELLER was superior (overall quality 3.96 vs. 3.41 and 3.93 vs. 3.01). Quantitatively (PROPELLER vs. RT-FRFSE), median SNR was 79.2 vs. 95.6 (A) and 70.0 vs. 58.6 (C), and median CNR 57.6 vs. 64.4 (A) and 55.5 vs. 42.7 (D); SNR did not differ in Groups B (p = 0.504) or D (p = 0.480), and CNR did not differ in Groups B or C (both p = 1.000). Interobserver agreement was substantial to almost perfect (kappa: 0.64-0.83; ICC: 0.89-0.93). DATA
Conclusion
RT-FRFSE performed better with slower, regular breathing and PROPELLER with faster or irregular breathing. Pre-scan respiratory assessment may inform sequence selection. EVIDENCE LEVEL 3. TECHNICAL EFFICACY Stage 1.