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Keywords:
Liver, MR, Computer Applications-General, Haematologic diseases
Authors:
A. Casaleggio, C. Conforti, F. Paparo, L. Bacigalupo, D. Zefiro, C. M. viberti, G. Forni, G. A. Rollandi; Genoa/IT
DOI:
10.1594/ecr2015/C-1580
Aims and objectives
The quantification and monitoring of body iron burden play a pivotal role in the clinical management of patients affected by inherited hemoglobin disorders,
including thalassemia,
hereditary hemochromatosis and sickle cell disease.
The total amount of iron deposited in the organs well correlates with serum ferritin levels (expressed in ng/mL); however,
serum ferritin lacks of specificity,
since it may be affected by other factors such as fever or inflammation.
Liver iron content (LIC),
expressed as mg Fe/g dry tissue,
is considered a reliable biomarker of the total iron stored in the body [Angelucci 2000]; therefore,
direct or indirect methods for measuring LIC are used as surrogates for assessing the whole-body iron burden.
Currently,
chemical analysis of percutaneous liver biopsy specimens remains the reference standard for the diagnosis and quantification of LIC,
but its routine clinical application for purposes of screening,
treatment monitoring,
and epidemiologic studies is limited by the significant risk of bleeding,
infection and sampling errors,
due to the heterogeneous distribution of iron deposits throughout the liver [Butensky 2005].
In the last decade,
magnetic resonance imaging (MRI) has become an effective alternative for the noninvasive assessment of liver iron overload [Wood 2011].
MRI is able to produce LIC estimates over the entire range of clinically relevant values.
MRI quantifies iron indirectly,
by detecting the paramagnetic effects of the interactions between iron,
stored as ferritin and hemosiderin,
and nearby hydrogen nuclei.
MRI–based methods to provide estimates of LIC include signal intensity ratios,
based on T2 or T2*–weighted imaging,
and relaxometry,
based on T2 or T2* relaxation times (or R2 and R2* relaxation rates).
Relaxometry methods calculate T2 or T2* by fitting a decay model to the average signal intensity at various echo times (TEs); these methods have been proven to be more robust than signal intensity ratios.
The St Pierre method is a T2–based technique marketed with the name of FerriScanTM [Figure 1].
It is an FDA–approved technique that is currently used as surrogate of liver biopsy in different clinical trials.
The aim of this work was to compare the T2–derived LIC measurements (FerriScanTM) with LIC values obtained by T2* relaxometry using three different commercial software programs.