Article

High Resolution C-13 MRI With Hyperpolarized Urea: Mapping and N-15 Labeling Effects.

IEEE transactions on medical imaging 10/2013; 33(2). DOI: 10.1109/TMI.2013.2285120
Source: PubMed

ABSTRACT C steady state free precession (SSFP) magnetic resonance imaging and effective spin-spin relaxation time (T2) mapping were performed using hyperpolarized [13C]urea and [13C;15 N2]urea injected intravenously in rats. 15N labeling gave large T2 increases both in solution and in vivo due to the elimination of a strong scalar relaxation pathway. The T2 increase was pronounced in the kidney, with [13C;15 N2]urea giving T2 values of 6:31:3 s in the cortex and medulla, and 112 s in the renal pelvis. The measured T2 in the aorta was 1:3 0:3 s. [13C]urea showed shortened T2 values in the kidney of 0:23 0:03 s compared to 0:28 0:03 s measured in the aorta. The enhanced T2 of [13C;15 N2]urea was utilized to generate large signal enhancement by SSFP acquisitions with flip angles approaching the fully refocused regime. Projection images at 0.94 mm in-plane resolution were acquired with both urea isotopes, with [13C;15 N2]urea giving a greater than four-fold increase in SNR over [13C]urea.

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