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Purpose:To assess the reproducibility and the distribution of intravoxel incoherent motion (IVIM) and diffusion-tensor (DT) imaging parameters in healthy renal cortex and medulla at baseline and after hydration or furosemide challenges. Materials and Methods:Using an institutional review board-approved HIPAAcompliant protocol with written informed consent, IVIM and DT imaging were performed at 3 T in 10 volunteers before and after water loading or furosemide administration. /msec, P = .0094). Urine output correlated with cortical ADC with furosemide (r = 0.7, P = .034) and with medullary l 1 (r = 0.83, P = .0418), l 2 (r = 0.85, P = .0301), and MD (r = 0.82, P = .045) with hydration. Conclusion:Diffusion MR metrics are sensitive to flow changes in kidney induced by diuretic challenges. The results of this study suggest that vascular flow, tubular dilation, water reabsorption, and intratubular flow all play important roles in diffusion-weighted imaging contrast.q RSNA, 2012

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