Acquisition Efficiency and Technical Repeatability of Dual‐Frequency 3D Vector MR Elastography of the Liver

Abstract

BackgroundMR elastography (MRE) at 60 Hz is widely used for staging liver fibrosis. MRE with lower frequencies may provide inflammation biomarkers.PurposeTo establish a practical simultaneous dual‐frequency liver MRE protocol at both 30 Hz and 60 Hz during a single examination and validate the occurrence of second harmonic waves at 30 Hz.Study TypeRetrospective.SubjectsOne hundred six patients (48 females, age: 50.0 ± 13.4 years) were divided as follows: Cohort One (15 patients with chronic liver disease [CLD] and 25 healthy volunteers) with simultaneous dual‐frequency MRE. Cohort Two (66 patients with CLD) with second harmonic MRE.Field Strength/Sequence3‐T, single‐ or dual‐frequency MRE at 30 Hz and 60 Hz.AssessmentLiver stiffness (LS) in both cohorts was evaluated with manually placed volumetric ROIs by two independent analyzers. Image quality was assessed by three independent readers on a 4‐point scale (0–3: none/failed, fair, moderate, excellent) based on the depth of wave propagation with 1/3 incremental penetration. The success rate was derived from the percentage of nonzero quality scores.Statistical TestsMeasurement agreement, bias, and repeatability of LS were assessed using intraclass correlation coefficients (ICCs), Bland–Altman plots, and repeatability coefficient (RC). Mann–Whitney U tests were used to evaluate the differences in image quality between different methods. A P‐value <0.05 was considered statistically significant.ResultsSuccess rate was 97.5% in Cohort One and 91% success rate for the second harmonic MRE in Cohort Two. The second harmonic and conventional MRE showed excellent agreement in LS (all ICCs >0.90). The quality scores for the second harmonic wave images were lower than those from the conventional MRE (Z = −4.523).Data ConclusionCompared with conventional and second harmonic methods, simultaneous dual‐frequency had better image quality, high success rate and the advantage of intrinsic co‐registration, while the second harmonic method can be an alternative if custom waveform is not available.Evidence Level3Technical EfficacyStage 1