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A breath-hold R2 mapping pulse sequence detects a decrease in myocardial ferritin iron after one-week of iron chelation
© Kim et al; licensee BioMed Central Ltd. 2010
Published: 21 January 2010
In transfusional iron overload, almost all the excess iron is sequestered intracellularly as ferritin iron, a dispersed, soluble and rapidly mobilizable fraction, and hemosiderin iron, an aggregated, insoluble fraction that is a long-term reserve. The effective transverse relaxation rate (R2*) of myocardium is predominantly influenced by hemosiderin iron and, even with intensive iron-chelating therapy, changes only slowly over several months . Intracellular ferritin iron is evidently in equilibrium with the low molecular weight cytosolic iron pool  that can decrease rapidly with iron chelation. We propose to use a new breath-hold fast spin-echo (FSE)  pulse sequence that permits calculation of RR2 , a "reduced transverse relaxation rate" as a measure of myocardial ferritin iron that is largely independent of hemosiderin iron.
To use RR2 measurements to detect short-term changes in myocardial ferritin iron produced by iron-chelating therapy.
We imaged 10 patients with thalassemia major (New York; mean age = 26.9 ± 10.3 years) on a 1.5 T MR scanner (Siemens-Avanto), and another 8 patients with thalassemia (Hong Kong; mean age = 29.3 ± 8.6 years) on a 3 T scanner (Phillips-Achieva). Both sets of patients were imaged in a mid-ventricular short-axis plane of the heart at mid-diastole, initially after discontinuing iron-chelation for one week, and subsequently after resuming their usual therapy (group 1: deferasirox; group 2: deferoxamine and/or deferiprone), for one week. Three different sets of FSE data were acquired in separate breath-holds with different echo spacings (ESP). For details on the pulse sequence and its parameters, please see references [3, 5]. A standard R2* mapping pulse sequence was also performed.
For data analysis, the septum was segmented manually. R2* was calculated by non-linear least square fitting of the mono-exponential relaxation curve. The RR2 was calculated by non-linear least square fitting of the three sets of non-monoexponential relaxation curves with different ESPs .
R2* and RR2 values of two groups after 1 week off and thereafter 1 week on iron chelation
Difference in R2* (1/s)
Difference in RR2 (1/s)
62.3 ± 27.6
61.1 ± 30.6
1.2 ± 7.8
24.5 ± 4.8
22.0 ± 5.3
2.5 ± 1.8
74.1 ± 39.0
71.9 ± 43.3
2.2 ± 9.9
22.1 ± 5.4
20.0 ± 5.6
2.0 ± 2.2
Grant sposor: AHA 0730143N; NIH R01-HL083309, NIH R01-DK069373, NIH R01-EB000447-07A1, NIH R01-DK069373, NIH R01-DK066251, NIH R37-DK049108, NIH R01-DK049108, GRF7794/07M, HK Children Thalassaemia Foundation (No. 2007/02).
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