Intraindividual comparison of MR-renal perfusion imaging at 1.5 T and 3.0 T

The purpose of this study was to intraindividually compare fast gradient-echo semiquantitative renal perfusion measurements at 1.5 Tesla (T) and 3.0 Tesla.

Fifteen healthy male volunteers underwent renal perfusion measurements at 1.5 T and 3.0 T after the bolus injection of 7 mL of Gd-BOPTA. At both field strengths a Saturation-Recovery-fast gradient echo sequence (SR-TurboFLASH) with a temporal resolution of 4 (1.5 T) and 5 (3.0 T) simultaneously acquired slices per second was used. At 3.0 T, a parallel-imaging factor 2 was applied. For postprocessing, semiquantitative perfusion parameters including mean transit time (MTT), time to peak (TTP), and maximal signal intensity (SMax) were determined. The signal-to-noise ratios (SNR) of kidneys and aorta were determined precontrast and after enhancement. The image quality was rated by 2 radiologists. After Bonferroni correction paired t-tests were performed for statistical analysis.

All measurements were successfully performed. At 3.0 T, a significant 63% increase in the baseline SNR (P = 0.00005) of the kidneys was found, the peak SNR was also increased though not statistically significant. Because of the higher SNR, the SMax was also significantly (P = 0.005) increased from 406 A.U. to 522 A.U., whereas MTT and TTP were not significantly changed. The image quality was rated very good to good for the 3.0 T images but only good to moderate at 1.5 T.

Renal perfusion measurements at 3.0 T are feasible and directly benefit from the inherently higher SNR at 3.0 T. The higher SNR also translates into an increased SMax, whereas MTT and TTP are independent of the field strength.