Whole-body R2∗ mapping to quantify tissue iron in iron storage organs: reference values and a genotype.

ABSTRACT

AIM: To define reference values for the transverse relaxation rate (R2∗) in iron storage organs and to investigate the role of human haemochromatosis protein (HFE) genotype on iron storage. MATERIALS AND METHODS: Whole-body magnetic resonance imaging (MRI) including a five-echo gradient-echo sequence was performed in 483 volunteers (269 men, mean age 59.3 ± 12.2 years) without clinical evidence of an iron storage disease at 1.5 T. R2∗ values were assessed for liver, spleen, pancreas, heart, bones, and brain parenchyma. The HFE genotype was determined regarding the single nucleotide polymorphisms (SNPs) rs74315324, rs1799945, rs41303501, rs1800562, rs1800730. R2∗ values were compared among participants without and with at least one mutation. R2∗ reference values were defined using volunteers without any mutation. RESULTS: Three hundred and one participants had no mutations in any HFE SNP, 182 had at least one mutation. HFE gene mutations were distributed as (heterozygous/homozygous) rs1799945132/9, rs180056233/1, and rs180073011/0. Mean R2∗ values ± SD (per second) in the group without mutation were liver 33.4 ± 12.7, spleen 24.1 ± 13.8, pancreas 27.2 ± 6.6, heart 32.7 ± 11.8, bone 69.3 ± 21.0, brain parenchyma 13.9 ± 1.2. No significant difference in R2∗ values were found between participants with and without the HFE gene mutation for any examined iron storage organ (pliver=0.09, pspleen=0.36, ppancreas = 0.08, pheart = 0.36, pbone = 0.98, pbrain=0.74). CONCLUSION: Reference values of R2∗ in iron storage organs are feasible to support the diagnosis of iron storage diseases. Non-specific mutations in HFE SNPs appear not to affect the phenotype of tissue iron accumulation.