Measuring renal tissue relaxation times at 7 T

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics
• Renal Physiology

Background:

• Ultra-high-field (UHF) MRI, particularly at 7 Tesla (7 T), presents new possibilities for renal imaging.
• Accurate characterization of renal tissue requires understanding T1 and T2 relaxation times.
• Developments in RF coils and management strategies make UHF renal imaging feasible.

Purpose of the Study:

• To measure T1 and T2 relaxation times in the human kidney at 7 T.
• To compare these measurements with those obtained at 3 T.
• To assess the feasibility and reproducibility of UHF renal imaging for tissue characterization and quantitative analysis.

Main Methods:

• A magnetization-prepared single-breath-hold fast spin echo imaging method was employed.
• Studies were conducted on 11 healthy volunteers at 7 T, with comparative measurements at 3 T.
• Challenges of B1+ inhomogeneity and specific absorption rate (SAR) limits were addressed.

Main Results:

• At 7 T, mean T1 values were 1661±68 ms (cortex) and 2094±67 ms (medulla), and T2 values were 108±7 ms (cortex) and 126±6 ms (medulla).
• Measurements at 3 T yielded different values: T1 of 1261±86 ms (cortex) and 1676±94 ms (medulla), and T2 of 121±5 ms (cortex) and 138±7 ms (medulla).
• T1 and T2 estimations at 7 T demonstrated robustness, with reproducibility within 4%.

Conclusions:

• Renal T1 and T2 values measured at 7 T differ significantly from those at 3 T.
• These findings are crucial for optimizing MRI sequences and enabling quantitative functional renal imaging at UHF.
• The study confirms the feasibility and reproducibility of 7 T renal MRI for tissue characterization.