UBC Theses and Dissertations

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UBC Theses and Dissertations

Modelling inhomogeneous magnetization transfer in myelin water and intra-/extra-cellular water in normal and injured excised rat spinal cord Lam, Michelle H.


Inhomogeneous magnetization transfer (ihMT) and myelin water imaging (MWI) were combined to separate the ihMT signal in the myelin water (MW) and intra-/extra-cellular water (IEW). A bi-exponential was used to fit the T2 decays of each saturation type, to quantify the ihMT effect in the MW and IEW pool, separately. Here, we proposed a model that included the dipolar reservoirs to the original four pool model to better interpret our ihMTR, ihMTR-MW, and ihMTR-IEW values. We took data at 11 different levels of T1D filtering (11 Tswitch times) for 9 formalin-fixed rat spinal cords, 3 healthy and 6 injured cords. We were able to reasonably fit the ihMTR-MW decay curve but could not capture the early data points of the ihMTR-IEW decay in our model, which may have yielded an inaccurate T1D (non-myelin) measurement. Our T1D (myelin) values were relatively close to previously measured T1D values and we saw a significant drop in T1D (myelin) in the 3 weeks post-injury spinal cords in the fasciculus gracilis region. Thus, our results suggest that T1D (myelin) may be a potential marker for separating functional myelin from myelin debris; however, more studies are required to confirm this result. Additionally, modifications need to be made to the model to improve the fit of the ihMTR-IEW data points.

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