Biexponential R2* Relaxometry for Estimation of Liver Iron Concentration in Children: A Better Fit for High Liver Iron States.

TitleBiexponential R2* Relaxometry for Estimation of Liver Iron Concentration in Children: A Better Fit for High Liver Iron States.
Publication TypeJournal Article
Year of Publication2019
AuthorsBarrera CA, Khrichenko D, Serai SD, Hartung HD, Biko DM, Otero HJ
JournalJ Magn Reson Imaging
Date Published2019 Apr 05
ISSN1522-2586
Abstract

BACKGROUND: R2* relaxometry's capacity to calculate liver iron concentration (LIC) is limited in patients with severe overload. Hemosiderin increases in these patients, which exhibits a non-monoexponential decay that renders a failed R2* analysis.

PURPOSE/HYPOTHESIS: To evaluate a biexponential R2* relaxometry model in children with different ranges of iron overload.

STUDY TYPE: Retrospective.

POPULATION: In all, 181 children with different conditions associated with iron overload.

FIELD STRENGTH/SEQUENCE: 1.5T, T *-weighted gradient echo sequence.

ASSESSMENT: Bi- and monoexponential R2* relaxometry were measured in the liver using two regions of interest (ROIs) using a nonproprietary software: one encompassing the whole liver parenchyma (ROI-1) and the other only the periphery (ROI-2). These were drawn by a single trained observer. The residuals for each fitting model were estimated. A ratio between the residuals of the mono- and biexponential models was calculated to identify the best fitting model. Patients with 1) residual ratio ≥1.5 and 2) R2* ≥R2* were considered as having a predominant biexponential behavior.

STATISTICAL TESTS: Nonparametric tests, Bland-Altman plots, linear correlation, intraclass correlation coefficient. Patients were divided according to their LIC into stable (n = 23), mild (n = 58), moderate (n = 61), and severe (n = 39).

RESULTS: The biexponential model was more suitable for patients with severe iron overload when compared with the other three LIC categories (P < 0.001) for both ROIs. For ROI-1, 37 subjects met criteria for a predominant biexponential behavior. The slow component (5.7%) had a lower fraction than the fast component (94.2%). For ROI-2, 22 subjects met criteria for a predominant biexponential behavior. The slow component (4.7%) had a lower fraction than the fast component (95.2%). The intraobserver variability between both ROIs was excellent.

DATA CONCLUSION: The biexponential R2* relaxometry model is more suitable in children with severe iron overload.

LEVEL OF EVIDENCE: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019.

DOI10.1002/jmri.26735
Alternate JournalJ Magn Reson Imaging
PubMed ID30950562