Abstract
PurposeThis study develops a tracer kinetic model of xenon uptake in the human brain to determine the transfer rate of inhaled hyperpolarized 129Xe from cerebral blood to gray matter that accounts for the effects of cerebral physiology, perfusion and magnetization dynamics. The 129Xe transfer rate is expressed using a tracer transfer coefficient, which estimates the quantity of hyperpolarized 129Xe dissolved in cerebral blood under exchange with depolarized 129Xe dissolved in gray matter under equilibrium of concentration.Theory and MethodsTime‐resolved MR spectra of hyperpolarized 129Xe dissolved in the human brain were acquired from three healthy volunteers. Acquired spectra were numerically fitted with five Lorentzian peaks in accordance with known 129Xe brain spectral peaks. The signal dynamics of spectral peaks for gray matter and red blood cells were quantified, and correction for the 129Xe T 1 dependence upon blood oxygenation was applied. 129Xe transfer dynamics determined from the ratio of the peaks for gray matter and red blood cells was numerically fitted with the developed tracer kinetic model.ResultsFor all the acquired NMR spectra, the developed tracer kinetic model fitted the data with tracer transfer coefficients between 0.1 and 0.14.ConclusionIn this study, a tracer kinetic model was developed and validated that estimates the transfer rate of HP 129Xe from cerebral blood to gray matter in the human brain.
Highlights
IntroductionIt acts as a selectively permeable barrier, which allows molecules essential for brain function through the barrier, while restricting the passage of noxious or neuroactive substances, and is vital for maintaining normal
This study develops a tracer kinetic model to determine the transfer rate of HP 129Xe from the cerebral blood to gray matter by considering the mass transfer of 129Xe irrespective of its status of hyperpolarization, with the aim of quantitatively measuring the compartmental transfer dynamics in 2 | THEORY
Quantification of the spectral peaks for cerebral blood and gray matter is shown in Figure 3A along with the time course of the individual quantified spectral peaks
Summary
It acts as a selectively permeable barrier, which allows molecules essential for brain function through the barrier, while restricting the passage of noxious or neuroactive substances, and is vital for maintaining normal. Since the water molecules cross the intact BBB, this technique is being investigated for diagnosis of BBB diseases.[22,23,24] the technique has some limitations due to acquisition strategy (post labeling delay time, labeling plane) competing with physiology (longitudinal relaxation time, arterial transit time) and abundance of water molecules in the brain tissue (background noise, magnetization transfer).[19,25]
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