Spleen R2 and R2* in iron-overloaded patients with sickle cell disease and thalassemia major.

Objective: To evaluate the magnetic properties of the spleen in chronically transfused, iron-overloaded patients with sickle cell disease (SCD) and thalassemia major (TM) and to compare splenic iron burdens to those in the liver, heart, pancreas, and kidneys.

Methods: A retrospective analysis of 63 TM and 46 SCD patients was performed. Spleen R2 and R2* values were calculated from spin-echo and gradient-echo images collected between April 2004 and September 2007.

Results: The spleen showed a different R2-R2* relationship than that previously established for the liver. At high iron concentrations (R2* > 300 Hz), spleen R2 was lower than predicted for liver. The proportion of splenic to hepatic iron content was greater in SCD patients compared with TM patients (23.8% vs. 13.8%). A weak association was found between splenic and liver iron-this association was stronger in SCD patients. Little correlation was found between splenic iron and extrahepatic R2* values.

Conclusions: For spleen and liver tissue with the same R2* value, splenic R2 was significantly lower than hepatic R2, particularly for R2* > approximately 300 Hz. Splenic iron levels have little predictive value for R2* values of heart, pancreas, and kidney.