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|Title||Biexponential R2* Relaxometry for Estimation of Liver Iron Concentration in Children: A Better Fit for High Liver Iron States.|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||Barrera CA, Khrichenko D, Serai SD, Hartung HD, Biko DM, Otero HJ|
|Journal||J Magn Reson Imaging|
|Date Published||2019 Apr 05|
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.
|Alternate Journal||J Magn Reson Imaging|