Mathematics Colloquia and Seminars

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The estimation of single-kidney extraction fraction (EF) and glomerular filtration rate (GFR) using magnetic resonance imaging (MRI) is based on the intravenous injection of a standard MRI contrast agent, such as Gd-DTPA, which is freely filtered by the renal glomeruli but not reabsorbed by the renal tubular system. We have developed a technique for estimating single-kidney EF and GFR based upon a rapid single-shot echo planar imaging (EPI) sequence that is able to detect differences in blood concentration of Gd-DTPA between renal artery and renal vein. Potentially, the technique can provide continuous EF and GFR estimates with a temporal resolution of two seconds, and may ultimately be used in fundamental laboratory investigations of kidney function as well as clinical diagnosis of kidney disease. Our investigations have revealed specific image distortions and significant errors in the EF and GFR estimates resulting from imperfections in the physical realization of the EPI sequence, blood flow pulsatility, small renal vessel size, tortuousness and motion, Gd-DTPA biodistribution, and the assumptions of required curve fitting procedures. Unique computer simulations and data processing algorithms have been developed to understand and reduce these image distortions and errors. I will describe the pulse sequences, simulations and algorithms that have been developed, and strategies to further improve accuracy and precision of the estimates.