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The macromolecular proton fraction (MPF) is a quantitative MRI parameter determining the magnetization transfer (MT) effect in tissues, and is defined as the relative amount of immobile macromolecular protons involved in magnetization exchange with mobile water protons. MPF has the potential to provide a quantitative assessment of fibrous tissue because of the intrinsically high MPF specific for collagen. The goal of this study was to investigate the relationship between histologically determined fibrosis stage and MPF in the liver parenchyma measured using a recently developed fast single-point clinically targeted MPF mapping method. Optimal saturation parameters for single-point liver MPF measurements were determined from the analysis of liver Z spectra in vivo based on the error propagation model. Sixteen patients with chronic hepatitis C viral infection underwent 3-T MRI using an optimized liver MPF mapping protocol. Fourteen patients had prior liver biopsy with histologically staged fibrosis (METAVIR scores F0-F3) and two patients had clinically diagnosed cirrhosis (score F4 was assigned). The protocol included four breath-hold three-dimensional scans with 2 × 3 × 6-mm(3) resolution and 10 transverse sections: dynamic acquisition of MT-weighted and reference images; dynamic acquisition of three images for variable flip angle T1 mapping; dual-echo B0 map; and actual flip angle imaging B1 map. The average liver MPF was determined as the mode of the MPF histograms. MPF was significantly increased in patients with clinically significant fibrosis (scores F2-F4, n = 6) relative to patients with no or mild fibrosis (scores F0-F1, n = 10): 6.49 ± 0.36% versus 5.94 ± 0.26%, p < 0.01 (Mann-Whitney test). MPF and fibrosis scores were strongly positively correlated, with a Spearman's rank correlation coefficient of 0.80 (p < 0.001). This study demonstrates the feasibility of fast MPF mapping of the human liver in vivo and confirms the hypothesis that MPF is increased in hepatic fibrosis and associated with fibrosis stage. MPF may be useful as a non-invasive imaging biomarker of hepatic fibrosis., (Copyright © 2015 John Wiley & Sons, Ltd.)

Objectives: We evaluated whether commercially available, computerized "brain-training" games can be used to identify subtle cognitive impairments in patients with cirrhosis., Methods: We compared patients with cirrhosis who did not have overt encephalopathy (n=31), patients with pre-cirrhotic chronic liver disease (n=28), and normal controls without liver disease (n=16) with respect to their scores on the number connection test-A (NCT-A), the Inhibitory Control Test (ICT), and five, short (∼2.5 min), brain-training games that were administered on an Apple iPad and tested different cognitive domains., Results: Patients with cirrhosis had similar scores to patients with pre-cirrhotic liver disease and slightly worse scores than normal controls in the NCT-A and the ICT, although these differences were not statistically significant. In contrast, patients with cirrhosis had significantly worse scores than patients with pre-cirrhotic liver disease and even more so than normal controls in all five of the brain-training games. After adjustment for age and educational attainment, these differences remained significant for two of the tests, "Color Match" which is a version of the Stroop test and measures selective attention, and "Memory Matrix", which measures visuospatial memory. The area under the receiver operating characteristic curve discriminating cirrhosis from pre-cirrhotic liver disease was 0.56 (95% confidence interval (CI) 0.41-0.72) for the ICT and 0.58 (95% CI 0.43-0.73) for the NCT-A, indicating no discrimination, while it was 0.75 (95% CI 0.63-0.87) for "Color Match" and 0.77 (95% CI 0.64-0.90) for "Memory Matrix", indicating good discrimination., Conclusions: Short, brain-training games administered on an iPad can be used as psychometric tests to detect subtle cognitive impairments in patients with cirrhosis without overt encephalopathy that could not be detected by the NCT-A or the ICT.