Measuring renal tissue relaxation times at 7 T

• Published in: NMR in biomedicine 2015-01, Vol.28 (1), p.63-69
• Main Authors: Li, Xiufeng, Bolan, Patrick J., Ugurbil, Kamil, Metzger, Gregory J.
• Format: Article
• Language: English
• Subjects: 7 T; Adult; Female; Humans; Kidney - metabolism; kidneys; longitudinal relaxation time (T1); Magnetic Resonance Imaging - methods; Male; Middle Aged; renal relaxation time; Reproducibility of Results; Time Factors; transverse relaxation time (T2); ultra-high field (UHF)
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.3195

As developments in RF coils and RF management strategies make performing ultra‐high‐field renal imaging feasible, understanding the relaxation times of the tissue becomes increasingly important for tissue characterization, sequence optimization and quantitative functional renal imaging, such as renal perfusion imaging using arterial spin labeling. By using a magnetization‐prepared single‐breath‐hold fast spin echo imaging method, human renal T1 and T2 imaging studies were successfully performed at 7 T with 11 healthy volunteers (eight males, 45 ± 17 years, and three females, 29 ± 7 years, mean ± standard deviation, S.D.) while addressing challenges of B1+ inhomogeneity and short‐term specific absorption rate limits. At 7 T, measured renal T1 values for the renal cortex and medulla (mean ± S.D.) from five healthy volunteers who participated in both 3 T and two‐session 7 T studies were 1661 ± 68 ms and 2094 ± 67 ms, and T2 values were 108 ± 7 ms and 126 ± 6 ms. For comparison, similar measurements were made at 3 T, where renal cortex and medulla T1 values of 1261 ± 86 ms and 1676 ± 94 ms and T2 values of 121 ± 5 ms and 138 ± 7 ms were obtained. Measurements at 3 T and 7 T were significantly different for both T1 and T2 values in both renal tissues. Reproducibility studies at 7 T demonstrated that T1 and T2 estimations were robust, with group mean percentage differences of less than 4%. Copyright © 2014 John Wiley & Sons, Ltd. Renal relaxometry measurements were made at 3 T and 7 T using a magnetization‐prepared single‐breath‐hold fast spin echo imaging method. Reproducibility of measured relaxometry parameters was demonstrated at 7 T while overcoming the challenges of B1+ and B0 inhomogeneity and limitation in peak available B1+ and short‐term SAR.