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Quantifying Axonal Injury , Demylination , and inflammation in Human MS Autopsy Specimens using Diffusion Basis Spectrum Imaging ( DBSI )
| Content Provider | Semantic Scholar |
|---|---|
| Author | Wang, Yong Wang, Qing Xie, Mingqiang Cross, Anne H. Song, Sheng-Kwei |
| Copyright Year | 2011 |
| Abstract | Introduction: To a first approximation, axon bundles have been considered as an aggregate of cylindrical tubes representing myelinated axon fibers. Such simplification has served the diffusion MRI community well in developing various techniques to resolve complications of crossing fibers and edema. In real life, typical axon bundles contain oligodendrocytes and other cells. During CNS pathology, cell components such as microglia and astrocytes may increase in numbers, and additional inflammatory cells, such as macrophages and lymphocytes, may enter from the blood. We contend that the presence of these cells significantly confounds white matter structure and pathology assessed using diffusion MRI. For example, the presence of a restricted diffusion component consisting of infiltrating cells will interfere with axonal fiber caliber estimation if not considered. The presence of infiltrating inflammatory cells will tend to reduce axial diffusivity leading to a false overestimation of axonal injury within white matter tracts. To address this issue, we have recently developed a new diffusion MRI method, diffusion basis spectrum imaging (DBSI) [1], demonstrating the capability to accurately quantify the extent of cellularity change as well as the axonal injury and demyelination in cuprizone treated mice. In the present study, autopsied spinal cord specimens of MS patients were examined to correlate DBSI with immunohistochemistry (IHC) findings. Method: Autopsy Spinal Cord Specimens: Ten autopsied human cervical spinal cords were fixed in 10% formalin and prepared for MRI scanning. MRI: Diffusion MRI of the autopsy spinal cord specimens was performed using an Agilent DirectDrive console equipped with a 4.7 T magnet and a 15cm inner diameter, actively shielded Magnex gradient coil (60 G/cm, 270 μs rise time). The tissue contained in a 3-ml syringe was placed in a custommade solenoid coil for data acquisition using the following parameters: repetition time (TR) 2s, spin echo time (TE) 39 ms, time between application of gradient pulses (Δ) 20 ms, diffusion gradient duration (δ) 8 ms, slice thickness 0.5 mm, number of slices 5, field-of-view 2.4 × 2.4 cm, number of average 1, data matrix 192 × 192, SNR = 200. Diffusion sensitizing gradients were applied in 99 directions with max b-value = 3200 s/mm [1]. In-plane resolution was 125 × 125 μm. Total acquisition time of diffusion weighted data was 5 hours and 20 minutes. DBSI Analysis: The Eq. [1] was solved by fitting the 99 diffusion weighted signals using a linear combination of diffusion basis set consisting of cylindrically symmetric diffusion tensors [1] with the freedom to vary λ|| and λ⊥ to estimate the number of anisotropic diffusion tensor components (Naniso) and the associated principal directions. After NAniso was computed, the number of |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://cds.ismrm.org/protected/12MProceedings/files/0466.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
