Reduced transverse relaxation rate (RR2) for improved sensitivity in monitoring myocardial iron in thalassemia

Purpose: To evaluate the reduced transverse relaxation rate (RR2), a new relaxation index which has been shown recently to be primarily sensitive to intracellular ferritin iron, as a means of detecting short‐term changes in myocardial storage iron produced by iron‐chelating therapy in transfusion‐dependent thalassemia patients. Materials and Methods: A single‐breathhold multi‐echo fast spin‐echo sequence was implemented at 3 Tesla (T) to estimate RR2 by acquiring signal decays with interecho times of 5, 9 and 13 ms. Transfusion‐dependent thalassemia patients (N = 8) were examined immediately before suspending iron‐chelating therapy for 1 week (Day 0), after a 1‐week suspension of chelation (Day 7), and after a 1‐week resumption of chelation (Day 14). Results: The mean percent changes in RR2, R2, and R2* off chelation (between Day 0 and 7) were 11.9 ± 8.9%, 5.4 ± 7.7% and −4.4 ± 25.0%; and, after resuming chelation (between Day 7 and 14), −10.6 ± 13.9%, −8.9 ± 8.0% and −8.5 ± 24.3%, respectively. Significant differences in R2 and RR2 were observed between Day 0 and 7, and between Day 7 and 14, with the greatest proportional changes in RR2. No significant differences in R2* were found. Conclusion: These initial results demonstrate that significant differences in RR2 are detectable after a single week of changes in iron‐chelating therapy, likely as a result of superior sensitivity to soluble ferritin iron, which is in close equilibrium with the chelatable cytosolic iron pool. RR2 measurement may provide a new means of monitoring the short‐term effectiveness of iron‐chelating agents in patients with myocardial iron overload. J. Magn. Reson. Imaging 2011;33:1510–1516. © 2011 Wiley‐Liss, Inc.