Purpose-To apply a magnetic resonance (MR) arterial spin labeling (ASL) technique to evaluate kidney perfusion in native and transplanted kidneys.Materials and Methods-This study was compliant with the Health Insurance Portability and Accountability Act (HIPAA) and approved by the institutional review board. Informed consent was obtained from all subjects. Renal perfusion exams were performed at 1.5 T in a total of 25 subjects: 10 with native and 15 with transplanted kidneys. A flow-sensitive alternating inversion recovery (FAIR) ASL sequence was performed with respiratory triggering in all subjects and under free-breathing conditions in five transplant subjects. Thirty-two control/tag pairs were acquired and processed using a single-compartment model. Perfusion in native and transplanted Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript kidneys was compared above and below an estimated glomerular filtration rate (eGFR) threshold of 60 ml/min/1.73m 2 and correlations with eGFR were determined.Results-In many of the transplanted kidneys, major feeding vessels in the coronal plane required a slice orientation sagittal to the kidney. Renal motion during the examination was observed in native and transplant subjects and was corrected with registration. Cortical perfusion correlated with eGFR in native (r=0.85, p=0.002) and transplant subjects (r=0.61, p=0.02). For subjects with eGFR≥60 ml/min/1.73m 2 , native kidneys demonstrated greater cortical (p=0.01) and medullary (p=0.04) perfusion than transplanted kidneys. For subjects with eGFR<60 ml/min/ 1.73m 2 , native kidneys demonstrated greater medullary perfusion (p=0.04) compared to transplanted kidneys. Free-breathing acquisitions provided renal perfusion measurements that were slightly lower compared to the coached/triggered technique, although no statistical differences were observed.Conclusion-In conclusion, FAIR-ASL was able to measure renal perfusion in subjects with native and transplanted kidneys, potentially providing a clinically viable technique for monitoring kidney function.

Purpose-To examine the reproducibility of quantitative magnetic resonance (MR) methods to estimate hepatic proton density fat-fraction (PDFF) at different magnetic field strengths. Materials and Methods-ThisHealth Insurance Portability and Accountability Act (HIPAA)-compliant study was approved by the Institutional Review Board. Following informed consent, 25 severely obese subjects (mean body mass index [BMI]: 45 ± 4, range: 38-53 kg/m 2 ) were scanned at 1.5T and 3T on the same day. Two confounder-corrected multiecho chemical shift-encoded gradient-echo-based imaging methods were acquired to estimate PDFF over the entire liver: 3D complex-based (MRI-C) and 2D magnitude-based (MRI-M) MRI. Single-voxel MR spectroscopy (MRS) was performed in the right liver lobe. Using linear regression, pairwise comparisons of estimated PDFF were made between methods (MRI-C, MRI-M, MRS) at each field strength and for each method across field strengths. Conclusion-This study demonstrates that PDFF estimation is reproducible across field strengths and across two confounder-corrected MR-based methods. Results HHS Public AccessNonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease, affecting between 20% to 30% of the U.S. population 1,2 and an even greater percentage of the obese population. 3 NAFLD can progress to liver inflammation, fibrosis, and eventually cirrhosis with complications including liver failure, portal hypertension, and hepatocellular carcinoma. 4 Recent studies have shown that hepatic fat content demonstrates a strong link to metabolic complications in the obese population, 5,6 and individuals with elevated liver fat are at higher risk of heart disease and diabetes. 7 Unfortunately, definitive diagnosis of NAFLD currently requires biopsy, which is expensive, carries some risk, and most important suffers from sampling variability. 8,9 Noninvasive, whole-liver fat quantification is critical for early detection and grading of NAFLD, and holds considerable potential to facilitate early intervention to prevent or reverse progression, as well as monitor treatment.In recent years, confounder-corrected chemical-shift-encoded quantitative magnetic resonance imaging (MRI) methods have shown promise as a noninvasive biomarker of hepatic steatosis. [10][11][12][13][14] These methods exploit the fact that hydrogen protons in water precess at a different resonance frequency than hydrogen protons in triglycerides. When all confounding factors are addressed (vide infra), the proton density fat-fraction (PDFF), an inherent property of tissue, can be quantified. 15 The first MR technique to demonstrate good correlation of hepatic fat content with tissue reference standards was MR spectroscopy (MRS), [16][17][18] and it is widely accepted as the noninvasive reference standard for fat-quantification in tissue. In recent years, the most common approach has combined a stimulated echo acquisition mode (STEAM) acquisition scheme with T 2 correction and spectral modeling that accounts for the mu...

Established as a method to study anatomic changes, such as renal tumors or atherosclerotic vascular disease, magnetic resonance imaging (MRI) to interrogate renal function has only recently begun to come of age. In this review, we briefly introduce some of the most important MRI techniques for renal functional imaging, and then review current findings on their use for diagnosis and monitoring of major kidney diseases. Specific applications include renovascular disease, diabetic nephropathy, renal transplants, renal masses, acute kidney injury and pediatric anomalies. With this review, we hope to encourage more collaboration between nephrologists and radiologists to accelerate the development and application of modern MRI tools in nephrology clinics.