| Author: | Li, Shuai |
| Title: | A novel 3D transcranial color doppler system : towards stroke risk assessment |
| Advisors: | Zheng, Yongping (BME) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Cerebrovascular disease -- Ultrasonic imaging Transcranial Doppler ultrasonography Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Biomedical Engineering |
| Pages: | 121 pages : color illustrations |
| Language: | English |
| Abstract: | Stroke, being the second most prevalent cause of mortality on a global scale, presents a significant threat to approximately one-quarter of the world's population, potentially posing risks of crippling and lasting disability. The Circle of Willis (CoW) is an essential anatomical structure that plays a crucial role in maintaining a consistent and uninterrupted blood flow to the brain, hence serving as a protective mechanism against the occurrence of stroke. Among the available imaging modalities, transcranial color-coded Doppler (TCCD) has gained increasing popularity in clinical settings owing to its cost-effective and radiation-free nature for assessing potential obstructions inside the CoW. Recently, 3D TCCD was developed to address the inherent limitations of 2D TCCD; examples include 3D power Doppler imaging and 3D color flow imaging. Nevertheless, these existing 3D approaches still suffer from certain limitations, either in terms of a deficient rate of vascular recognition or the lack of hemodynamic information. Besides, the issue of color overrepresentation is a significant obstacle to achieving anatomical precision in 3D TCCD. On top of that, there exist scarce studies on 3D TCCD reporting any quantitative difference in transcranial 3D reconstruction, which might indirectly imply a lack of confidence in the accuracy of the reconstructed objective. All of them are crucial in the context of precision medicine. In Chapter 2, we developed a novel 3D TCCD imaging system, called ultrasound brain angiography (UBA), using a commercial single-crystal phased array transducer to improve the Doppler sensitivity and an advanced color mode of directional color power imaging (dCPI) that integrates good sensitivity and the directional information. Subsequently, this new system was adopted for the following three chapters, with an overall objective to determine the feasibility and clinical values of UBA. In Chapter 3, the developed UBA system was tested on vascular phantoms, where the UBA system was used to investigate the influences of several factors, including vascular diameter, flow velocity, Doppler interrogation depth, and settings of color gain and velocity scale, on the occurrence of color overrepresentation in 3D displays. In Chapter 4, the developed UBA system was evaluated on healthy older adults in aspects of CoW vascular detection rate and its capacity to capture hemodynamics. In Chapter 5, the structural similarity of the reconstructed UBA images was compared against the gold standard of magnetic resonance angiography (MRA) on human subjects. In summary, the UBA system was successfully developed and tested on phantoms and human subjects. It was found to outperform the existing 3D TCCD techniques in aspects of vascular detection rate, with a high structural similarity agreement of CoW compared with the standard MRA. Apart from this, it offers CoW hemodynamic information, including blood flow direction and velocity, potentially assisting clinicians in assessing the presence of blood flow abnormalities. Overall, the findings of this study are of great value in enhancing the diagnostic performance of current 3D TCCD ultrasound imaging for assessing CoW integrity and, hence, pave the way towards stroke risk assessments in patients in the long run. |
| Rights: | All rights reserved |
| Access: | open access |
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