PROJECT SUMMARY Breast cancer, the second-leading cause of cancer deaths among women, affects millions of Americans. Early cancer detection and accurate tumor diagnosis are crucial for favorable clinical outcomes. Ultrasonography (US) is an important imaging modality adjunct to mammography as it is noninvasive, cost-effective, and widely available. However, the low specificity of US limits its diagnosis accuracy, even in combination with mammography. The resultant unnecessary benign biopsies substantially increase patients’ cost and anxiety. Tumor angiogenesis can be used as a valuable biomarker for better breast tumor US differentiation. However, conventional Doppler imaging has insufficient vessel detection sensitivity. We have recently developed a novel 2-dimensional ultra-sensitive ultrasound microvessel imaging (2D-UMI) technology, which demonstrates significantly increased vessel detection sensitivity over conventional Doppler methods without the need of using contrast agents. In our preliminary study, the diagnosis accuracy of combining US with 2D-UMI was improved by 15% compared to using conventional US alone. However, 2D tumor vascularity evaluation may be incomprehensive as most tumors are heterogeneous. In the proposed research, the 2D-UMI technique will be advanced to 3D imaging, and further enhanced to provide a comprehensive tumor vessel investigation to improve breast tumor classification accuracy and reduce unnecessary benign biopsies. In light of clinical need and our recent diagnostic development, this proposal has two specific aims: Specific Aim 1: Develop and enhance the 3D-UMI scanning sequence. We will develop the UMI sequence in 3D imaging using a Verasonics Vantage research scanner. We will apply multiple coded plane wave transmissions to ensure sufficient incident acoustic energy and ultrasound penetration. We will also develop new tissue clutter filters to eliminate the banding side-lobe artifacts caused by strong reflectors in breast imaging. We will then use a custom flow phantom to test and enhance the technology, and pave the way for the clinical study in Aim 2. Specific Aim 2: Conduct a pilot clinical study of 3D-UMI on patients with breast masses. We will study 42 patients with breast tumors to assess the 3D-UMI’s efficacy in improving breast tumor classification. An experienced radiologist will evaluate the results. We will then compare the diagnosis accuracy (using pathology as the gold standard) between the combined diagnosis of conventional US plus 3D-UMI versus use of conventional US alone. Successful completion of the proposed research will lead to a novel ultra-sensitive 3D Doppler technology to facilitate diagnosis of breast tumors with high accuracy.