Improved neuronal tract tracing using manganese enhanced magnetic resonance imaging with fast T(1) mapping.
There has been growing interest in using manganese-enhanced MRI (MEMRI) to detect neuronal activation, neural architecture, and neuronal connections. Usually Mn(2+) produces a very wide range of T(1) change. In particular, in neuronal tract tracing experiments the site of Mn(2+) injection can have very short T(1) while distant regions have small T(1) reductions, primarily due to dilution of Mn(2+). Most MEMRI studies use T(1)-weighted sequences, which can only give optimal contrast for a narrow range of T(1) changes. To improve sensitivity to the full extent of Mn(2+) concentrations and to optimize detection of low concentrations of Mn(2+), a fast T(1) mapping sequence based on the Look and Locker technique was implemented. Phantom studies demonstrated less than 6.5% error in T(1) compared to more conventional T(1) measurements. Using center-out segmented EPI, whole-brain 3D T(1) maps with 200-microm isotropic resolution were obtained in 2 h from rat brain. Mn(2+) transport from the rat olfactory bulb through appropriate brain structures could be detected to the amygdala in individual animals. The method reliably detected less than 7% reductions in T(1). With this quantitative imaging it should be possible to study more extensive pathways using MEMRI and decrease the dose of Mn(2+) used.
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, Maryland 20892-1065, USA.
Kai-Hsiang
KH
Chuang
Alan
A
Koretsky
D000818:Animals; D001921:Brain / Q000033:anatomy & histology; D002712:Chlorides; D003287:Contrast Media; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008345:Manganese; D017895:Manganese Compounds; D009420:Nervous System / Q000033:anatomy & histology*; D019047:Phantoms, Imaging; D051381:Rats; D017207:Rats, Sprague-Dawley
D002712:Chlorides; D003287:Contrast Media; D017895:Manganese Compounds; D008345:Manganese; C025340:manganese chloride