Comparison of clinical MRI liver iron content measurements using signal intensity ratios, R 2 and R 2 .

PURPOSE: To compare three types of MRI liver iron content (LIC) measurement performed in daily clinical routine in a single center over a 6-year period.

METHODS: Patients undergoing LIC MRI-scans (1.5T) at our center between January 1, 2008 and December 31, 2013 were retrospectively included. LIC was measured routinely with signal intensity ratio (SIR) and MR-relaxometry (R 2 and R 2 *) methods. Three observers placed regions-of-interest. The success rate was the number of correctly acquired scans over the total number of scans. Interobserver agreement was assessed with intraclass correlation coefficients (ICC) and Bland-Altman analysis, correlations between LICSIR , R 2 , R 2 *, and serum values with Spearman's rank correlation coefficient. Diagnostic accuracies of LICSIR , R 2 and serum transferrin, transferrin-saturation, and ferritin compared to increased R 2 * (≥44 Hz) as indicator of iron overload were assessed using ROC-analysis.

RESULTS: LIC MRI-scans were performed in 114 subjects. SIR, R 2 , and R 2 * data were successfully acquired in 102/114 (89%), 71/114 (62%), and 112/114 (98%) measurements, with the lowest success rate for R 2 . The ICCs of SIR, R 2 , and R 2 * did not differ at 0.998, 0.997, and 0.999. R 2 and serum ferritin had the highest diagnostic accuracies to detect elevated R 2 * as mark of iron overload.

CONCLUSIONS: SIR and R 2 * are preferable over R 2 in terms of success rates. R 2 *'s shorter acquisition time and wide range of measurable LIC values favor R 2 * over SIR for MRI-based LIC measurement.