The Global Rigid Registration Of The B - Scan Sequence Image Eliminates The Interference Of The Carotid Pulse Displacement Estimation

With the year-to-year increase of the cardiovascular disease incidence and the risk of the disability and mortality due to them, it is well known that the most common pathological basis of the cardiovascular disease is the atherosclerosis which attracts the interest of many researches and has become research hotspots. The clinical and experimental studies have shown that the augments of the hardness and thickness of the arterial wall leading to the decreases of their elastic can be observed at the early stage of cerebrovascular disease. Then the arterial diameter and the fluctuating displacement of the vessel intima, membrane as well as outer membrane throughout the cardiac cycle can be employed as the crucial factors in the clinical diagnosis of vessel diseases at the early phase. Therefore, a method employed to measure the arterial diameter and the fluctuating displacement accurately is essential for prediction and diagnose of cardiovascular disease.One of the regularly employed methods to noninvasively assess the pulsation displacement of arterial wall in clinical practice is ultrasound detection through B-mode imaging, M-mode imaging and echo tracking, among which B-mode ultrasonic imaging has been frequently applied to receive not only the length but also the additional spatial information of the artery. However, the measurement correctness of the pulsation displacement of arterial wall can be achieved under the ideal environment which is impossible due to the influence of casual movements of transducer holding by the operator and breathe of the subjects and so on. In order to improve the measurement accuracy, an algorithm based on the global rigid-registration of ultrasound B-mode images is proposed in this thesis to weaken that interference from both the operator and subject during the estimation of artery pulsation displacement.It is widely known that image registration is a radical task in medical image processing for finding the optimal spatial transformation to achieve better alignment of serious images. In the thesis, the optimal spatial transformation is confirmed at firstly and employed to map ultrasonic images to the reference one for attenuating the casual interference during detection. During this process, it is fully taken into account the low contrast, speckle noise and low echo areas of the ultrasound B-mode images whose intensity and gradient are regularly employed in traditional image registration algorithm probably leading to the inaccuracy of image registration. So Monogenic Signal local phase characteristics of ultrasonic images are employed in the global rigid-registration algorithm proposed in this thesis for realizing more positive and accurate non-rigid registration of medical image. After that, the speckle tracking algorithm is employed to deal with the mapping ultrasonic images to achieve the artery pulsation displaments with improving accuracy.In order to evaluate the performance of the proposed method, simulation and clinical trials are carried out. The experimental results demonstrate that casual interferences are removed out and the estimation accuracy of the artery pulsation displacement are enhanced significantly. It can be concluded that a promising approaches is proposed in this thesis for improving the accuracy of diagnosis of vascular stenosis disease at an early stage.