High resolution (13)C MRI with hyperpolarized urea: in vivo T(2) mapping and (15)N labeling effects.
(13)C steady state free precession (SSFP) magnetic resonance imaging and effective spin-spin relaxation time (T2) mapping were performed using hyperpolarized [(13)C] urea and [(13) C,(15)N2] urea injected intravenously in rats. (15)N 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 [(13) C,(15) N2] urea giving T2 values of 6.3±1.3 s in the cortex and medulla, and 11±2 s in the renal pelvis. The measured T2 in the aorta was 1.3±0.3 s. [(13)C] 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 [(13)C,(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 [(13)C,(15) N2] urea giving a greater than four-fold increase in signal-to-noise ratio over [(13)C] urea.
Galen D
GD
Reed
Cornelius
C
von Morze
Robert
R
Bok
Bertram L
BL
Koelsch
Mark
M
Van Criekinge
Kenneth J
KJ
Smith
Hong Shang
Peder E Z
PE
Larson
John
J
Kurhanewicz
Daniel B
DB
Vigneron
D000792:Angiography / Q000379:methods*; D000818:Animals; D002247:Carbon Isotopes / Q000737:chemistry; D007668:Kidney / Q000098:blood supply; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009587:Nitrogen Isotopes / Q000737:chemistry; D019047:Phantoms, Imaging; D051381:Rats; D014508:Urea / Q000737:chemistry*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D014508:Urea