The concentration and total amount of iron in different tissues are critical parameters that determine clinical outcome in all forms of systemic iron overload, independent of whether the iron overload is caused by blood transfusion (i.e., transfusion-dependent thalassaemia, sickle cell disease, aplastic or sideroblastic anaemia, or myelodysplastic syndrome) or by up-regulated intestinal iron absorption (i.e., hereditary haemochromatosis, non-transfusion dependent thalassaemia, iron loading anaemia). The precise assessment of the size of the iron storage pool, which may also include organ volume,¹  is essential for the treatment of chronically transfused patients with iron chelators to avoid both toxicity from increased organ iron concentration and side-effects from an excessive chelator dose.²