Saudi Cultural Missions Theses & Dissertations
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Item Restricted Role of Tissue Doppler Ultrasonography for Emergency Assessment of Stroke(Saudi Digital Library, 2023-12-01) Almudayni, Alanoud; Chung, Emma; Lecchini-Visintini, AndreaBackground: The primary aims of my PhD project were to explore the feasibility of acquiring high quality brain tissue pulsation (BTP) measurements from stroke patients. The impact of artefacts on BTP estimates, and potential differences in BTP amplitude between patients and healthy controls are explored. My secondary aim was to better understand the impact of middle cerebral artery blood flow velocity (MCAv) changes on BTP amplitude. Methods: A systematic review was conducted to explore existing methods of investigating BTPs using MR techniques. A reduction in MCAv, induced in healthy volunteers through ingestion of caffeine, was used to explore the impact of lowering MCAv on BTP amplitude (measured using a transcranial tissue Doppler [TCTD] system) under controlled conditions. TCTD and physiological measurement data were obtained from stroke patients to investigate the quality of recordings, impact of artefacts on BTP estimates, and impact of stroke on BTP amplitude. Results: The systematic review confirmed that brain motion varies regionally within the brain, and that BTPs may be altered in the presence of pathology (e.g. Chiari I malformation). The physiological measurement study showed that BTP amplitude increases in response to caffeine. Analysis of healthy volunteer and patient data showed that artefacts tended to increase estimates of BTP amplitude. Analysis of the first 20 gates (which show limited penetration) from 18 ischaemic stroke patients and control subjects suggested a median (IQR) BTP amplitude in ischaemic stroke patients measured through the forehead of 8 μm (5.7, 13.6) compared to 16.2 μm (10.6, 24) in 24 age-matched control subjects. Waveform shapes appeared qualitatively similar to control subjects. Conclusions: BTP amplitude appears to be lower in stroke patients compared to healthy controls but increases in response to caffeine, which lowers MCAv. Further work is required to better understand the relationship between BTPs and cerebrovascular physiology.20 0Item Restricted Evaluation of Tomographic 3D Ultrasound for the Assessment of Vascular Pathology(2023-05-31) ALZAHRANI, Adel; Aslam, MTomographic 3D ultrasound (t3DUS) is a promising imaging technique for quantifying vascular diseases by measuring the degree of stenosis and plaque volume. However, its accuracy and reliability for the assessment of vascular diseases need to be investigated. Therefore, this thesis aims to assess the accuracy and reproducibility of t3DUS for quantifying vascular diseases, including grading stenosis and measuring plaque volume in-vitro and in-vivo. A literature review was performed to evaluate the use of three-dimensional ultrasound (3DUS) for assessing carotid stenosis in patients with carotid diseases showing that 3DUS is more accurate in quantifying carotid diseases and has a low level of inter and intra-observer variability when compared to 2DUS. However, it requires prolonged time for images to be reconstructed into 3DUS, which may currently limit its use in clinical practice. The analysis from the in-vitro study on the vascular phantom, including channels with different grades of stenosis, demonstrated that t3DUS has an excellent inter-operator agreement with low variability and is more accurate than 2DUS for grading stenosis when compared to the reference values with an Intra-Class Correlation (ICC) value of 0.96 (95% confidence interval (CI) 0.90 – 0.98, p <0.001. Based on these findings, two clinical studies were conducted investigating the reproducibility and accuracy of t3DUS for measuring carotid plaque volume (CPV) within the internal carotid artery (ICA) in patients undergoing carotid endarterectomy (CEA) (n=25), and the potential benefits of t3DUS in providing more precise measurement of stenosis in the superficial femoral artery (SFA) in patients with the peripheral arterial disease (PAD) (n=50). The results showed an excellent agreement level between t3DUS and reference test (i.e., Ex-vivo carotid plaque volume from carotid endarterectomy specimen) and intra-observer agreement in measuring carotid plaque volume. This result demonstrates that t3DUS can measure the disease severity of SFA in patients with lower limb arterial disease with a correlation value (r) = 0.99, p<0.001. The findings of this thesis indicated that t3DUS is a reliable and reproducible method for quantifying vascular diseases, including grading stenosis and measurements of CPV. Further research investigating the potential of the added value of t3DUS in assessing the different ranges of vascular diseases, including aneurysms, arteriovenous fistula (AVF) for haemodialysis access, and venous mapping, should be considered.25 0