Microstructural origins of gadolinium-enhanced susceptibility contrast and anisotropy.
OBJECTIVE
MR histology based on magnetic susceptibility can be used to visualize diamagnetic myelin (and its deterioration) in the central nervous system and is facilitated by the application of high magnetic field strengths and paramagnetic contrast agents. Characterizing the effect of these tools will aid in assessing white matter myelin content and microstructure.


METHODS
Image data from six gadolinium-perfused mouse brain specimens were acquired at 2.0, 7.0, and 9.4 Tesla. Magnetic susceptibility contrast was analyzed for its dependence on field strength, gadolinium concentration, and white matter fiber orientation. A model for this contrast is presented based on the three-pool model for white matter.


RESULTS
The specimen data illustrate that white-gray matter susceptibility contrast is field strength independent. White-gray matter contrast improves significantly as a function of gadolinium contrast agent in the tissue, i.e., white matter appears increasingly more diamagnetic relative to gray matter. The simulated data from the model suggest that susceptibility anisotropy of white matter fiber bundles increases nonlinearly as a function of gadolinium concentration due to contrast agent compartmentalization into the extracellular white matter water pool.


CONCLUSIONS
Using contrast agents in MR histology facilitates white-gray matter susceptibility contrast modulation and the probing of white matter microstructure and orientation.
Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina, USA; Biomedical Engineering, Duke University, Durham, North Carolina, USA.
Russell
R
Dibb
Wei
W
Li
Gary
G
Cofer
Chunlei
C
Liu
D000818:Animals; D016880:Anisotropy; D001921:Brain / Q000166:cytology* / Q000187:drug effects; D003287:Contrast Media / Q000008:administration & dosage; D056324:Diffusion Tensor Imaging / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D005682:Gadolinium / Q000008:administration & dosage; D066128:Gray Matter / Q000166:cytology* / Q000187:drug effects; D006571:Heterocyclic Compounds / Q000008:administration & dosage*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009942:Organometallic Compounds / Q000008:administration & dosage*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D066127:White Matter / Q000166:cytology* / Q000187:drug effects
D003287:Contrast Media; D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; C062402:gadoteridol; D005682:Gadolinium
anisotropic magnetic susceptibility; nonlinear contrast enhancement; quantitative susceptibility mapping; resonance frequency shift; tissue compartmentalization; white matter