Vector Doppler Using Aperture Domain Data

Studies have shown that hemodynamic dysfunction is an important factor in the development of cardiovascular diseases, including atherosclerotic plaques, aneurysms and aortic dissection. Therefore, noninvasive imaging methods that reveal hemodynamic information have great scientific significance as well as potential clinical value. Color Doppler Flow Imaging is a mature modality in clinical practice, but it can only detect one vector component of blood flow along the direction of the ultrasound beam, and is only accepted as a qualitative tool in general. Vector Doppler encompasses a number of detection and imaging methods that provide 2D or even 3D vector estimation of blood flow velocity. After decades of R&D effort, however, vector Doppler still has not gained clinical acceptance due to system complexity and other factors.In the current generation ultrasound imaging systems, up to 128 channels of RF data is digitized but this data is beamformed, or combined, by hardware into one channel of RF data before it is available for analysis by software algorithm. Recently, more advanced data acquisition systems provide capability to acquire and store the full 128-channel preeamformed RF data, which is more benefit for aperture domain data analysis in software. Based on previously reported ultrafast imaging methods, we developed novel vector Doppler imaging methods using unfocused transmit beams and all-channels receive. Softtware beamforming is then performed and axial and lateral displacements between firing events are measured. A theoretical investigation of the principle of the two-dimensional Doppler effect was made. A simulation study using the Field II platform was performed in explore different imaging approach. An experimental study was performed using the S-Sharp Prodigy ultrasound system and a self-made rotational phantom.In this thesis a novel approach to obtain two dimensional vector Doppler imaging was proposed and tested experimentally. Flow vector estimation by the proposed method, when compared with reference(physical) measurements, revealed maximal error range of less than 30%, and typical error range of less than 10%. It is expected that with further development and verification, especially on living animal and human subjects, this method has the potential to bring vector Doppler imaging to clinical trials.