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Feasibility of noninvasive quantitative measurements of intrarenal R2′ in humans using an asymmetric spin echo echo planar imaging sequence


J. Zhang, 5 Yiheyuan Rd., Peking University, College of Engineering, Beijing, 100871, China.


X. Wang, Department of Radiology, Peking University First Hospital, Beijing, China.



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 R2′ in humans within 20 s. The reproducibility of R2′ 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 R2′ 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/mm2) were utilized to examine the impact of the intravascular signal contribution on the estimation of intrarenal R2′. In the absence of flow dephasing gradients (b = 0 s/mm2), the computed coefficient of variation (CV) of R2′ was 21.31 ± 4.52%, and the estimated R2′ value decreased slightly, but not statistically significantly (p > 0.05), after the administration of furosemide in the medullary region. However, CV of R2′ was much smaller in the presence of flow dephasing gradients (9.68 ± 3.58% with b = 40 s/mm2and 10.50 ± 3.62% with b = 80 s/mm2). Moreover, a significant reduction in R2′ in the renal medulla was obtained (p < 0.05 for both b = 40 s/mm2 and b = 80 s/mm2) after the administration of furosemide, reflecting an increase in oxygen tension in the medullary region. In addition, R2′ measurements did not differ between the b = 40 s/mm2 and b = 80 s/mm2 scans, suggesting that small diffusion gradients were sufficient to minimize the intravascular signal contribution. In summary, we have demonstrated that renal R2′ 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.

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