Project Summary Ultrasound imaging is a critical tool for applications such as obstetric, abdominal and cardiac care. As a non- invasive, real-time, and cost-effective method, ultrasound is the preferred tool for many screening and diagnostic tasks used across the United States and around the world. The proliferation of pocket-sized point of care systems has furthered ultrasound's reach into all areas of healthcare. However, image quality is often inadequate for deep targets in difficult-to-image patients. A lack of resolution at depth and significant acoustic clutter (haze or distortion) lead to non-diagnostic results and high rates of recall or referral to other imaging modalities, increasing healthcare costs and putting patients at risk. Resolution directly depends on the size of the transducer, which is limited by ergonomics of the handheld probe and by system complexity (especially in point of care systems). Targets at large tissue depths also require lower imaging frequencies, exacerbating the degradation of resolution. This project builds on the previously demonstrated swept synthetic aperture (SSA) method to better image deep targets. Using precise knowledge of the position and orientation of the ultrasound array as it is quickly swept over a target, an effective array larger than the physical footprint can be constructed to improve lateral resolution by several times. This proposal focuses on the development of a platform for clinical translation of the SSA technique. Technology that enables a freehand sweep is required to apply SSA imaging to a diversity of body shapes and imaging targets in clinical and point of care settings. An optical tracking system will by synchronized with the ultrasound scanner to allow a sonographer to perform a freehand sweep without mechanical constraints. The position and ultrasound data will be combined with sub-wavelength positional accuracy to achieve images with improved resolution. The imaging system will be characterized using imaging phantoms to assess improvements in resolution and detectability of deep targets. Experimental parameters including the maximum sweep speed and extent as well as practical guidance for the sweep trajectory will be determined using this platform. This freehand SSA system will enable future assessment of the clinical impact of improved resolution on diagnostic tasks across several areas of care. It will also serve as a test platform for array- and image-based tracking to make the image improvements afforded by SSA imaging accessible without the cost or complexity of the external tracking hardware.