The relation of microvascular pulsatility and mechanical properties
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Recently, microvascular pulsatility received attention given its association with small vessel disease and the hypothesized role of volume pulsatility as a driver of cerebral solute transport. In response, multiple MRI techniques emerged to probe cerebral pulsatility in vivo. However, these techniques often lack specificity to distinguish volume pulsatility due to vessel wall deformation from velocity pulsatility, as well as vessel-size specificity. Additionally, they commonly yield relative pulsatility indices. Consequently, it remains challenging to interpret measured pulsatility and relate it to the underlying mechanistic behaviour. To enhance understanding of the relation of altered pulsatility and microvascular physiological changes, we developed a computational framework of the human cortical cerebrovascular hemodynamics. We conducted a sensitivity study to establish plausible baseline vessel wall parameters and assess effects of changes in wall thickness and young’s modulus on observed volume and velocity pulsatility across cortical depth. We find that vessel wall thickening (thinning) consistently decreases (increases) volume pulsatility and changes in young’s modulus correlate with local distensibility. Notably, venous stiffness has a pronounced effect on capillary volume distension. Velocity pulsatility decreases with cortical depth while volume pulsatility remains nearly constant. This work enhances the interpretability of MRI pulsatility measurements by disentangling contributions of pulsating blood volume and velocity across cortical depth and vessel size. The ability to simulate altered hemodynamics further allows to assess how ageing and diseaserelated changes affect microvascular pulsatility.
