title: Influence of the analysis technique on estimating hepatic iron content using MRI.
abstract: To investigate the effect of the analysis technique on estimating hepatic iron content using MRI.
  
  
  
  We evaluated the influences of single-exponential (EXP), bi-exponential (BEXP), and exponential-plus-constant (CEXP) models; and pixel-wise (MAP), average (AVG), and median (MED) signal calculation methods on T2* measurement using numerical simulations, calibrated phantoms, and nine patients scanned on 3 Tesla MRI, based on regression, correlation, and t-test statistical analysis.
  
  
  
  The T2* measurement error varied from 9 to 51% in the numerical simulations (T2*: 5-20 ms), depending on signal-to-noise ratio (SNR; range: 8-233) with significant (P < 0.05) difference between actual and predicted values. The MAP method performed well (error < 10%) at high SNR (>100), but resulted in severe estimation errors at low SNR (<50). The EXP model resulted in significant measurement differences (P < 0.05) compared with all other methods, irrespective of SNR. In vivo T2* values ranged from 3.1 to 53.6 ms, depending on the amount of iron overload and implemented analysis method. The BEXP (range: 3.7-50 ms) and CEXP (range: 3.8-53.6 ms) models, and the AVG (range: 3.2-38.8 ms) and MED (range: 3.1-38.5 ms) methods provided more accurate measurements than the EXP model (range: 3.1-18.3 ms) and MAP (range: 3.8-53.6 ms) method, respectively (P < 0.05). The BEXP and CEXP models provided very similar measurements (P > 0.87). Similarly, the AVG and MED methods provided very similar results (P > 0.97), with slightly better performance of the AVG method.
  
  
  
  Different analysis techniques show different performances based on the fitting model and signal calculation method. Based on this study, the CEXP model and AVG method are recommended due to simpler implementation and less influence by the selected analysis region. J. Magn. Reson. Imaging 2016;44:1448-1455.
authors.affiliation: Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: El-Sayed H
authors.initials: EH
authors.lastname: Ibrahim
authors.affiliation: Department of Biomedical Engineering, Helwan University, Cairo, Egypt.
authors.forename: Ayman M
authors.initials: AM
authors.lastname: Khalifa
authors.affiliation: Department of Biomedical Engineering, Helwan University, Cairo, Egypt.
authors.forename: Ahmed K
authors.initials: AK
authors.lastname: Eldaly
mesh_terms: D000328:Adult; D000465:Algorithms; D000755:Anemia, Sickle Cell / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007501:Iron / Q000378:metabolism*; D008099:Liver / Q000000981:diagnostic imaging* / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D057054:Molecular Imaging / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007501:Iron
keywords: T2*; exponential modeling; iron overload; liver; signal calculation