This Small Business Innovation Research (SBIR) Phase I project will prove the feasibility of a low-dose 4D cone beam tomosynthesis reconstruction algorithm for use in medical image-guided interventions. Despite the availability of highly accurate 3D guidance systems, most image-guided interventions are still performed under 2D fluoroscopy. 3D guidance is significantly more complex and expensive, as it requires the combination of 3D imaging (like CT) with surgical navigation, both expensive and complex technologies. A system capable of reconstructing a 4D scene would provide accurate and easy to use guidance for the medical professional, at lower costs. This research will develop a 3D reconstruction algorithm with quasi real-time performance (4D) that does not increase exposure to x-rays when compared to 2D fluoroscopy. The proposed technology will combine the most recent advancements in tomosynthesis, iterative reconstruction and compressed sensing and fundamentally change image-guided interventions. The broader impact/commercial potential of this project is that advanced medical procedures, like minimally invasive surgery, will be significantly improved in workflow and accessibility, reducing healthcare costs, improving outcomes and improving quality of life for patients. In the U.S. alone, a 10% shift to minimally invasive spine surgeries can reduce healthcare costs by $180M while reducing patient trauma and providing faster recoveries to 45,000 patients. This technology could be applied in other clinical areas like oncology and interventional radiology, improving a broad array of procedures and bringing a new level of excellence in medical interventions. 4D systems would compete in the intra-operative x-ray medical imaging market, a $1B market that is growing 6% annually, and in the Surgical Navigation market, a $400M market that is growing 9% annually. The proposed concept has the potential to disrupt both these markets by replacing pairs of intra-operative 3D imaging and surgical navigation systems with one 4D system that is more cost effective and easier to use.