Pre‐Scan Breathing Pattern and Image Quality in Respiratory‐Triggered T2 ‐Weighted Liver MRI : Radial Versus Cartesian Fast Spin Echo

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.