Purpose: To determine normative R2* values in the liver and heart at 3T, and establish the relationship between R2* at 3T and 1.5T over a range of tissue iron concentrations. Materials and Methods:A total of 20 healthy control subjects and 14 transfusion-dependent patients were scanned at 1.5T and 3T. At each field strength R2* imaging was performed in the liver and heart.Results: Normative R2* values in the liver were estimated from the control group to be 39.2 ± 9.0 second −1 at 1.5T and 69.1 ± 21.9 second −1 at 3T. Normative cardiac values were estimated as 23.4 ± 2.2 second −1 at 1.5T and 30.0 ± 3.7 second −1 at 3T. The combined R2* data from patients and control subjects exhibited a linear relationship between 3T and 1.5T. In the liver, the line of best fit to the 3T vs. 1.5T data had a slope of 2.00 ± 0.06 and an intercept of −11 ± 4 second −1 . In the heart, it had a slope of 1.88 ± 0.14 and an intercept of −15 ± 4 second −1 . Conclusion:These preliminary data suggest that the iron-dependent component of R2* scales linearly with field strength over a wide range of tissue iron concentrations. The incidence of susceptibility artifacts may, however, also increase with field strength. KeywordsMRI; R2*; T2*; iron overload; thalassemia; 3T PATIENTS WITH CERTAIN HEREDITARY anemias such as thalassemia major require regular blood transfusions to maintain adequate hemoglobin levels. However, the body has limited capacity to excrete iron, so frequent transfusions result in iron accumulation, particularly in the liver, spleen, endocrine organs, and heart. Iron is sequestered within

To assess the global and segmental left ventricular (LV) native T1 and extracellular volume fraction (ECV) in children and young adults with hypertrophic cardiomyopathy (HCM) compared to a control cohort. The study population included 21 HCM patients (mean 14.1 ± 4.6 years) and 21 controls (mean 15.7 ± 1.5 years). Native modified Look-Locker inversion recovery sequence was performed before and after contrast injection in 3 short axis planes. Global and segmental LV native T1 and ECV were quantified and compared between HCM patients and controls. Mean native T1 in HCM patients and controls was 1020.4 ± 41.2 and 965.6 ± 30.2 ms respectively (p < 0.0001). Hypertrophied myocardium had significantly higher native global T1 and global ECV compared to non-hypertrophied myocardium in HCM (p < 0.0001, = 0.14 and 0.048, = 0.01 respectively). In a subset of patients, ECV was higher in LV segments with LGE compared to no LGE (p < 0.0001). No significant correlation was identified between global native T1 and ECV and parameters of LV structure and function. Native T1 cut-off of 987 ms provided the highest sensitivity (95 %) and specificity (91 %) to separate HCM patients from controls. Global and segmental native T1 are elevated in HCM patients. LV segments with hypertrophy and/or LGE had higher ECV in a subset of HCM patients. LV native T1 and ECV do not correlate with parameters of LV structure and function. T1 in children and young adults may be used as a non-invasive tool to assess for HCM and related fibrosis.

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