Reproducibility of liver iron concentration measured by R2* method based on 1.5-T MRI: a meta-analysis

Objectives: To explore the reproducibility of the 1.5-T MR imaging (MRI)-based R2* method in measuring the liver iron concentration (LIC) across different MRI scanners, scan parameters, and postprocessing techniques.

Materials and methods: We performed a systematic search of the PubMed, Embase, Medline, Cochrane Library, and Web of Science databases and identified studies that used the 1.5-T MRI-based R2* method to measure the LIC. The original data were extracted from the selected studies. Reproducibility was assessed in terms of the ability to replicate the measured LIC with the 1.5-T MRI-based R2* method across different scanning instruments, scan parameters, and postprocessing techniques. We used the scanner equipment, scan parameters, and postprocessing technique as random effects to determine whether the R2* values obtained in the different studies were significantly different after the effects of the measured LIC were excluded. The calibration curve that best fit the R2* value to the LIC was estimated via univariate regression.

Results: Twenty-one studies (1147 participants) were included. The seven studies (435 participants) in which the initial TE was ≤ 1.0 ms and the TE spacing was ≤ 1.4 ms did not have significant differences in the measured R2* value in pairwise comparisons (p > 0.05). Calibration of R2* to LIC was as follows: LIC (mg/g) = 0.042 + 2.85 × 10^-2 R2* (s^-1) (R² = 0.79).

Conclusion: The 1.5-T MRI-based R2* method in estimating LIC was reproducible across different MRI scanners, scan parameters, and postprocessing techniques.

Key points: Question The R2* method is widely used to quantify LIC, but the reproducibility of R2*-based LIC estimation remains unknown. Findings In scan sequences with an initial echo time (TE) ≤ 1.0 ms and a TE spacing ≤ 1.4 ms, the R2*-based LIC quantification at 1.5 T achieved good reproducibility. Clinical relevance The 1.5-T MRI-based R2* method enables reproducible quantification of the LIC; its reproducibility spares patients from unnecessary trauma and economic burdens while promoting the extensive clinical dissemination of R2*-based LIC quantification methods.