The Focused Assessment with Sonography in Trauma (FAST) exam is the standard of care for rapid detection of abdominal free fluid in emergency medicine and trauma critical care. It is a point-of-care ultrasound exam that incorporates four views of the abdomen. In trauma, abdominal free fluid is assumed to be blood until proven otherwise. Timely detection is critical because if untreated abdominal hemorrhage can rapidly lead to hemorrhagic shock and death. In community hospitals, the FAST exam is underutilized due to limited access to physicians who are able to perform the exam (typically an emergency physician or trauma surgeon). In addition, the low cost and portability of ultrasound make it an ideal triage tool for prehospital settings including extreme environments like mass-casualty and combat zones. In these settings, detection of abdominal free fluid would impact medical transport prioritization and aid in the distribution of limited resources. BioSensics, in collaboration with Boston University School of Medicine, proposes to develop a portable ultrasound system to enable a minimally trained operator to perform and accurately interpret a FAST exam. The system will guide the operator through the image acquisition process and automatically compute a probability for abdominal free fluid. We have previously shown that image processing algorithms can detect free fluid with 100% sensitivity and 90% specificity in perihepatic (e.g., right upper quadrant) abdominal ultrasound views (J. Ultrasound in Medicine, In Press). In this Phase I SBIR project we will improve our image processing algorithms and validate them on FAST exams recorded using a portable ultrasound system. We will also develop a beta version of the system for usability testing and further clinical evaluation in Phase II. By the completion of Phase I the system will be able to concurrently record, and display in realtime, ultrasound images and ultrasound probe position and kinematics. Recording probe position and movement is important because it will assist the software in guiding a minimally trained operator through the image acquisition process. In Phase II we will develop operator guidance software and perform a randomized clinical trial to evaluate efficacy from the perspective of usability (can a minimally trained operator record a diagnostic quality exam) and performance (how much free fluid has to be present for the developed system to reliably detect it). The proposed technology has significant commercialization potential. Our first target market is emergency medical services including civilian ambulance companies and the U.S. military. Important use cases in this market include medical transport prioritization in mass-casualty and combat settings, as well as pre-hospital free-fluid assessment, particularly during longer transports. Our second target market is emergency departments with a focus on rural and community hospitals. Broader applications include use in resource limited global health medicine, as well as in many other specialties where non-trauma assessment of abdominal free fluid is necessary, such as the medically critically ill or to assess for ascites.