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A model for hepatic fibrosis: the competing effects of cell loss and iron on shortened modified Look‐Locker inversion recovery T 1 (shMOLLI‐ T 1 ) in the liver
Author(s) -
Tunnicliffe Elizabeth M.,
Banerjee Rajarshi,
Pavlides Michael,
Neubauer Stefan,
Robson Matthew D.
Publication year - 2017
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.25392
Subject(s) - fibrosis , liver biopsy , biopsy , extracellular fluid , chemistry , nuclear magnetic resonance , medicine , gastroenterology , nuclear medicine , extracellular , physics , biochemistry
Purpose 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) T 1 measurements. Liver T 1 values have shown sensitivity to inflammation and fibrosis, but are also affected by hepatic iron content. Modified Look‐Locker inversion recovery (MOLLI) T 1 measurements are biased by the lower T 2 associated with high iron. Materials and Methods 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‐ T 1 for a given ECF fraction and iron content. The LUT was used to calculate ECF(shMOLLI‐ T 1 ), assuming normal hepatic iron content (HIC), and ECF(shMOLLI‐ T 1 , T 2 * ), accounting for HIC determined byT 2 * , for 77 patients and compared to fibrosis assessed by liver biopsy. Results Simulations showed that increasing HIC decreases shMOLLI‐ T 1 , with an increase in HIC from 1.0 to 2.5 mg/g at normal ECF fraction decreasing shMOLLI‐ T 1 by 160 msec, while increasing ECF increased ShMOLLI‐ T 1 , with an increase of 20% ECF at normal iron increasing shMOLLI‐ T 1 by 200 msec. Calculated patient ECF(shMOLLI‐ T 1 ) showed a strong dependence on Ishak score (3.3 ± 0.8 %ECF/Ishak stage) and 1 / T 2 *(–0.23 ± 0.04 %ECF/Hz). However, when iron was accounted for to produce ECF(shMOLLI‐ T 1 , T 2 * ), it was independent of HIC but retained sensitivity to Ishak score. Conclusion Use of this multicompartment model of the liver with Bloch‐McConnell simulation should enable compensation of iron effects when using shMOLLI‐ T 1 to assess fibrosis. Level of Evidence: 1 J. Magn. Reson. Imaging 2017;45:450–462.