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Feasibility of noninvasive quantitative measurements of intrarenal R 2 ′ in humans using an asymmetric spin echo echo planar imaging sequence
Author(s) -
Zhang Xiaodong,
Zhang Yudong,
Yang Xuedong,
Wang Xiaoying,
An Hongyu,
Zhang Jue,
Fang Jing
Publication year - 2013
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.2823
Subject(s) - dephasing , furosemide , nuclear magnetic resonance , chemistry , reproducibility , spin echo , nuclear medicine , magnetic resonance imaging , medicine , physics , radiology , chromatography , organic chemistry , quantum mechanics
The purpose of this study was to demonstrate the feasibility of an asymmetric spin echo (ASE) single‐shot echo planar imaging (EPI) sequence for the noninvasive quantitative measurement of intrarenal R 2 ′ in humans within 20 s. The reproducibility of R 2 ′ measurements with the ASE‐EPI sequence was assessed in nine healthy young subjects in repeated studies conducted over three consecutive days. Moreover, we also evaluated whether the ASE‐EPI sequence‐measured R 2 ′ reflected the intrarenal oxygenation changes induced by furosemide in another group of normal human subjects ( n = 10). Different flow attenuation gradients ( b = 0, 40 and 80 s/mm 2 ) were utilized to examine the impact of the intravascular signal contribution on the estimation of intrarenal R 2 ′. In the absence of flow dephasing gradients ( b = 0 s/mm 2 ), the computed coefficient of variation (CV) of R 2 ′ was 21.31 ± 4.52%, and the estimated R 2 ′ value decreased slightly, but not statistically significantly ( p > 0.05), after the administration of furosemide in the medullary region. However, CV of R 2 ′ was much smaller in the presence of flow dephasing gradients (9.68 ± 3.58% with b = 40 s/mm 2 and 10.50 ± 3.62% with b = 80 s/mm 2 ). Moreover, a significant reduction in R 2 ′ in the renal medulla was obtained ( p < 0.05 for both b = 40 s/mm 2 and b = 80 s/mm 2 ) after the administration of furosemide, reflecting an increase in oxygen tension in the medullary region. In addition, R 2 ′ measurements did not differ between the b = 40 s/mm 2 and b = 80 s/mm 2 scans, suggesting that small diffusion gradients were sufficient to minimize the intravascular signal contribution. In summary, we have demonstrated that renal R 2 ′ can be obtained rapidly using an ASE‐EPI sequence. The measurement was highly reproducible and reflected the expected intrarenal oxygenation changes induced by furosemide. Copyright © 2012 John Wiley & Sons, Ltd.