Quantitative MRI for measuring cardiac-induced brain tissue pulsations in humans

Abstract

Our brain is a richly vascular organ, with a complex network of small blood vessels. These blood vessels pulsate with the heartbeat, briefly increasing the blood volume in our brains. These pulsations result in local deformation of the brain tissue. Damage to these small blood vessels from disease leads to problems such as gait disturbances, cognitive decline, dementia and mood disorders, depending on the severity of the disease. Unfortunately, it is not possible to directly image the small vessels in our brains, which limits our ability to understand how disease processes lead to damage.

This thesis focuses on the use of an advanced MRI technique adapted to investigate the pulsation of the cerebral microcirculation. This method, called DENSE, can measure the very small displacements of the brain tissue and the volumetric strain due to the changing blood volume. In this way, the condition of the small vessels in the brain can be assessed indirectly.

This thesis shows that DENSE is effective in measuring pulsatile movements in brain tissue and that differences in volumetric strain can be detected in different tissue types. In patients with vascular disease and brain tissue damage, abnormal volumetric strain patterns were observed, indicating that DENSE may be useful for investigating brain vascular disease.

This work highlights that DENSE is a powerful tool for measuring heart rate-related volume changes in the human brain, providing a basis for further research into the biomechanics of blood vessels in the brain. It also opens up new possibilities for understanding neurodegeneration in aging, which may eventually lead to new applications in diagnostics.