title: A model for hepatic fibrosis: the competing effects of cell loss and iron on shortened modified Look-Locker inversion recovery T1(shMOLLI-T1) in the liver.
abstract: To propose a simple multicompartment model of the liver and use Bloch-McConnell simulations to demonstrate the effects of iron and fibrosis on shortened-MOLLI (shMOLLI) T1measurements. Liver T1values have shown sensitivity to inflammation and fibrosis, but are also affected by hepatic iron content. Modified Look-Locker inversion recovery (MOLLI) T1measurements are biased by the lower T2associated with high iron.
  
  
  
  A tissue model was generated consisting of liver cells and extracellular fluid (ECF), with iron-dependent relaxation rates. Fibrosis was imitated by increasing the ECF proportion. Simulations of the shMOLLI sequence produced a look-up table (LUT) of shMOLLI-T1for a given ECF fraction and iron content. The LUT was used to calculate ECF(shMOLLI-T1), assuming normal hepatic iron content (HIC), and ECF(shMOLLI- T1,T2*), accounting for HIC determined by T2*, for 77 patients and compared to fibrosis assessed by liver biopsy.
  
  
  
  Simulations showed that increasing HIC decreases shMOLLI-T1, with an increase in HIC from 1.0 to 2.5 mg/g at normal ECF fraction decreasing shMOLLI-T1by 160 msec, while increasing ECF increased ShMOLLI-T1, with an increase of 20% ECF at normal iron increasing shMOLLI-T1by 200 msec. Calculated patient ECF(shMOLLI-T1) showed a strong dependence on Ishak score (3.3 ± 0.8 %ECF/Ishak stage) and 1/T2* (-0.23 ± 0.04 %ECF/Hz). However, when iron was accounted for to produce ECF(shMOLLI- T1,T2*), it was independent of HIC but retained sensitivity to Ishak score.
  
  
  
  Use of this multicompartment model of the liver with Bloch-McConnell simulation should enable compensation of iron effects when using shMOLLI-T1to assess fibrosis.
  
  
  
  1 J. Magn. Reson. Imaging 2017;45:450-462.
authors.affiliation: University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Tunnicliffe
authors.affiliation: University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Rajarshi
authors.initials: R
authors.lastname: Banerjee
authors.affiliation: University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.|Translational Gastroenterology Unit, University of Oxford, Oxford, UK.
authors.forename: Michael
authors.initials: M
authors.lastname: Pavlides
authors.affiliation: University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Stefan
authors.initials: S
authors.lastname: Neubauer
authors.affiliation: University of Oxford Centre for Clinical Magnetic Resonance Research (OCMR), Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Robson
mesh_terms: D000328:Adult; D017209:Apoptosis; D003198:Computer Simulation; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007501:Iron / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D007501:Iron
keywords: T1 mapping; liver MRI; liver disease