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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

The position of an atom passing through a standing light wave is localized by making a quadrature phase measurement on the light field. This localization can be thought of as the creation of a virtual slit (or slits) for the atom by the field measurement. Diffraction and interference behavior may be observed in the far field.

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Diffusion-weighted imaging (DWI) involves data acquisitions at multiple b values. In this paper, we presented a method of selecting the b values that maximize estimation precision of the biexponential analysis of renal DWI data. We developed an error propagation factor for the biexponential model, and proposed to optimize the b-value samplings by minimizing the error propagation factor. A prospective study of four healthy human subjects (eight kidneys) was done to verify the feasibility of the proposed protocol and to assess the validity of predicted precision for DWI measures, followed by Monte Carlo simulations of DWI signals based on acquired data from renal lesions of 16 subjects. In healthy subjects, the proposed methods improved precision (P = 0.003) and accuracy (P < 0.001) significantly in region-of-interest based biexponential analysis. In Monte Carlo simulation of renal lesions, the b-sampling optimization lowered estimation error by at least 20–30% compared with uniformly distributed b values, and improved the differentiation between malignant and benign lesions significantly. In conclusion, the proposed method has the potential of maximizing the precision and accuracy of the biexponential analysis of renal DWI.

In vivo DT imaging of patellar cartilage is feasible, has good test-retest reproducibility, and may be accurate in discriminating healthy subjects from subjects with OA. ADC and FA are two promising biomarkers for early OA.

Purpose:To estimate the reproducibility of BOLD MRI measurements in the evaluation of intrarenal oxygenation levels. Materials and Methods:In this study, the reproducibility of semiquantitative BOLD MRI measurements performed on a 1.5 T scanner with a multiple gradient-echo sequence in the renal medulla and cortex, and their response to furosemide and waterload, were assessed in eight healthy young subjects (25.6 Ϯ 4.1 years). Each subject underwent an identical experimental procedure on two separate days.Results: Renal R* 2 measurements were shown to be reproducible within ϳ12% from day to day based on a coefficient of variance (CV) analysis. The changes in R* 2 (⌬R * 2 ) following administration of furosemide were statistically significant, as shown by ANOVA and a paired Student's t-test, and were deemed reliable based on the reliable change index (RCI). However, ⌬R* 2 values following waterload were not statistically significant, and were not deemed reliable.Conclusion: R* 2 measurements were reproducible over 270 days within 12%. Furosemide produced a significant and reliable change (ϳ30%), and the magnitude of change (5.7 s Ϫ1) was reproducible and consistent with our previous data. The response to waterload, however, did not reach statistical significance, and the magnitude did not reach the level that we had previously reported.