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

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.

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.

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) rs1799945:132/9, rs1800562:33/1, and rs1800730:11/0. 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 (p_liver=0.09, p_spleen=0.36, p_pancreas = 0.08, p_heart = 0.36, p_bone = 0.98, p_brain=0.74).

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.