title: Imaging Renal Urea Handling in Rats at Millimeter Resolution using Hyperpolarized Magnetic Resonance Relaxometry.
abstract: In vivospin spin relaxation time (T2) heterogeneity of hyperpolarized [13C,15N2]urea in the rat kidney was investigated. Selective quenching of the vascular hyperpolarized13C signal with a macromolecular relaxation agent revealed that a long-T2component of the [13C,15N2]urea signal originated from the renal extravascular space, thus allowing the vascular and renal filtrate contrast agent pools of the [13C,15N2]urea to be distinguished via multi-exponential analysis. TheT2response to induced diuresis and antidiuresis was performed with two imaging agents: hyperpolarized [13C,15N2]urea and a control agent hyperpolarized bis-1,1-(hydroxymethyl)-1-13C-cyclopropane-2H8. LargeT2increases in the inner-medullar and papilla were observed with the former agent and not the latter during antidiuresis. Therefore, [13C,15N2]urea relaxometry is sensitive to two steps of the renal urea handling process: glomerular filtration and the inner-medullary urea transporter (UT)-A1 and UT-A3 mediated urea concentrating process. Simple motion correction and subspace denoising algorithms are presented to aid in the multi exponential data analysis. Furthermore, aT2-edited, ultra long echo time sequence was developed for sub-2 mm3resolution 3D encoding of urea by exploiting relaxation differences in the vascular and filtrate pools.
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA; Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA.
authors: Galen D
authors: GD
authors: Reed
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA.
authors: Cornelius
authors: C
authors: von Morze
authors: Departments of Medicine and Physiology, University of California San Francisco, San Francisco, California, USA.
authors: Alan S
authors: AS
authors: Verkman
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA; Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA.
authors: Bertram L
authors: BL
authors: Koelsch
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA.
authors: Myriam M
authors: MM
authors: Chaumeil
authors: Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA; Department of Electrical Engineering and Computer Sciences, University of California Berkeley, Berkeley, California, USA.
authors: Michael
authors: M
authors: Lustig
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA; Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA.
authors: Sabrina M
authors: SM
authors: Ronen
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA.
authors: Robert A
authors: RA
authors: Bok
authors: Department of Medicine, Renal Division, Emory University, Atlanta, Georgia, USA.
authors: Jeff M
authors: JM
authors: Sands
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA; Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA.
authors: Peder E Z
authors: PE
authors: Larson
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA.
authors: Zhen J
authors: ZJ
authors: Wang
authors: GE Healthcare, Brøndby, Denmark; Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
authors: Jan Henrik Ardenkjær
authors: JH
authors: Larsen
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA; Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA.
authors: John
authors: J
authors: Kurhanewicz
authors: Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, California, USA; Graduate Group in Bioengineering University of California San Francisco, San Francisco, California, USA, and University of California Berkeley, Berkeley, California, USA.
authors: Daniel B
authors: DB
authors: Vigneron