Non-invasive assessment of hepatic iron stores by MRI.
BACKGROUND
MRI has been proposed for non-invasive detection and quantification of liver iron content, but has not been validated as a reproducible and sensitive method, especially in patients with mild iron overload. We aimed to assess the accuracy of a simple, rapid, and easy to implement MRI procedure to detect and quantify hepatic iron stores.


METHODS
Of 191 patients recruited, 17 were excluded and 174 studied, 139 in a study group and 35 in a validation group. All patients underwent both percutaneous liver biopsy with biochemical assessment of hepatic iron concentration (B-HIC) and MRI of the liver with various gradient-recalled-echo (GRE) sequences obtained with a 1.5 T magnet. Correlation between liver to muscle (L/M) signal intensity ratio and liver iron concentration was calculated. An algorithm to calculate magnetic resonance hepatic iron concentration (MR-HIC) was developed with data from the study group and then applied to the validation group.


RESULTS
A highly T2-weighted GRE sequence was most sensitive, with 89% sensitivity and 80% specificity in the validation group, with an L/M ratio below 0.88. This threshold allowed us to detect all clinically relevant liver iron overload greater than 60 micromol/g (normal value <36 micromol/g). With other sequences, an L/M ratio less than 1 was highly specific (>87%) for raised hepatic iron concentration. With respect to B-HIC range analysed (3-375 micromol/g), mean difference and 95% CI between B-HIC and MR-HIC were quite similar for study and validation groups (0.8 micromol/g [-6.3 to 7.9] and -2.1 micromol/g [-12.9 to 8.9], respectively).


CONCLUSIONS
MRI is a rapid, non-invasive, and cost effective technique that could limit use of liver biopsy to assess liver iron content. Our MR-HIC algorithm is designed to be used on various magnetic resonance machines.
Gandon
Y
Y
Fédération d'Imagerie Médicale, CHU Pontchaillou, Rennes, France. yves.gandon@chu-rennes.fr
Olivié
D
D
Guyader
D
D
Aubé
C
C
Oberti
F
F
Sebille
V
V
Deugnier
Y
Y
D000465:Algorithms; D001706:Biopsy; D005260:Female; D006801:Humans; D007501:Iron / Q000032:analysis*; D019190:Iron Overload / Q000175:diagnosis*; D008099:Liver / Q000737:chemistry* / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D012372:ROC Curve; D012680:Sensitivity and Specificity
D007501:Iron