POSITION-DEPENDENT VASCULAR IMAGING WITH TILTABLE MRI
Jordy van Zandwijk is a PhD student in the department Magnetic Detection and Imaging. (Co)Promotors are prof.dr.ir. B. ten Haken, prof.dr. R.H. Geelkerken and dr.ir. F.F.J. Simonis from the faculty of Science & Technology.
Cardiovascular diseases (CVDs) cause over 18 million deaths annually, making them a major global health concern alongside their 500 million cases. Although external forces, including gravity, have long been acknowledged to influence the vascular system and blood circulation, their diagnostic and treatment implications remain largely unexplored. While tiltable MRI is predominantly used for musculoskeletal imaging to consider gravity's effect on joints and bones, its potential impact on the vascular system remains underinvestigated. There is a notable gap in comprehensive research on position-dependent vascular imaging, which holds significant promise for cardiovascular disease diagnosis, treatment, and understanding vascular behavior in various body positions. This thesis is dedicated to exploring position-dependent vascular imaging using low-field MRI, with a focus on assessing its added value and feasibility.
In this context, we conducted a scoping review to identify knowledge gaps in position and posture-dependent vascular imaging. While the majority of studies have utilized ultrasound in position-dependent investigations, tiltable MRI has been employed in approximately 25% of cases, proving valuable in assessing parameters like blood vessel curvature and tortuosity. These findings hold clinical significance in areas such as diagnosis, surgical planning, and stent placement, as well as postoperative follow-up.
Furthermore, clinical studies from this thesis encompassed both healthy volunteers and patients, focusing on both the venous and arterial systems. Our research demonstrated the utility of tiltable low-field MRI in evaluating the geometry of neck veins and alternative vascular pathways that manifests in more upright positions. Alongside a higher prevalence of collapsed vessels, we observed a decrease in the average diameter of non-collapsed vessels with increasing inclination angles for both the left and right internal jugular veins (IJVs). Notably, patients with impaired venous return to the heart stand to benefit from improved 3D visualization techniques under varying inclination angles.
Additionally, we conducted a clinical study involving patients with abdominal aneurysms who had undergone stent placement. Our investigation aimed to uncover the added value of tiltable MRI in examining stent leakages, particularly those that were previously unexplained and suspected to be position-dependent. While our results indicated limited additional value of upright MRI for leak detection, we identified specific scenarios where upright MRI can offer benefits. Patients suspected of stent leakages can now undergo examinations using this novel technique, whose feasibility was explored in this thesis.
Furthermore, this thesis contributed to the enhancement of tiltable MRI by studying and optimizing the concentration of a new contrast agent specifically designed for MRI with lower magnetic field strengths, as utilized in this research.
In summary, as research continues to advance and more evidence accumulates regarding the clinical advantages of this technology, tiltable MRI holds the promise of integration into vascular imaging and patient care. Despite the limitations posed by the low-field MRI technology underpinning tiltable MRI, the current work has established a foundation for a deeper understanding of how body position influences vascular system (patho)physiology.
