Real-time imaging of cerebrospinal fluid flow physiology at 7T

Sammanfattning: Background The cerebrospinal fluid (CSF) is involved in several diseases and patho- physiological states, such as Alzheimer’s disease and hydrocephalus. Previous studies CSF dynamics in the brain show that the flow of the CSF depends on cardiac pulsation, time of day and respiration. Methods In this thesis, the validity of using real time phase contrast MRI in order to study CSF flow is evaluated in a phantom experiment. Furthermore, the same sequence is used in vivo in healthy volunteers (n = 7) to study CSF flow behaviour under differ- ent respiratory conditions. For the phantom experiment, fluid flow with two frequencies corresponding to cardiac pulsations and respiration was produced in tubes submerged in water. A comparison of the two frequency components between a real-time phase contrast protocol and a gated reference protocol was made. For the in vivo study, correlation be- tween respiratory behaviour during exercises and CSF flow was evaluated. Net volumes were acquired and CSF flow deceleration in breath hold intervals was studied. Results The frequency component comparison in the phantom study showed that high frequency amplitudes were underestimated in the real time protocol. Furthermore, it was shown that exploiting temporal sparsity allowed for a significantly better frequency ampli- tude estimation than ignoring temporal sparsity, as in conjugate gradient. For the in vivo study, there was a clear correlation between CSF flow curves and respira- tory curves, measured with respiratory bellows, with a mean R2 0.5 for the deep breath- ing exercise. The mean volume transported per breath for the deep breathing exercise was 1.6 ml (upward flow) for inspirations and 3.0 ml (downward flow) for expirations. A de- celeration of the CSF flow of 0.005 mls−2 was found for breath holding exercises. Conclusion This method is a viable option for studying CSF flow in real-time in phan- tom measurements and could be further developed to be a means of studying CSF flow in vivo in the future.