Project Summary Approximately 12% of women in the United States will develop breast cancer in their lifetime, including an estimated 276,480 new cases of invasive breast cancer, 48,350 new cases of non-invasive (in-situ) breast cancer, and 42,170 deaths in 2020. Breast cancer is the second most diagnosed cancer in women, with a death rate second only to lung cancer. Although mammography is the gold standard for initial breast cancer screening, 10-30% of breast cancers can be missed at mammography. Despite several underlying explanations, including dense breast tissue, slow growing lesions, perception error, and incorrect interpretation of suspect findings, errors in positioning the breast are common and have a profound effect on mammography's accuracy as a diagnostic modality. Further, positioning errors are the primary reason breast centers fail reaccreditation. These problems stem from the fact that experience in breast positioning is limited during a mammography technologist's training. To address these issues, One World DMG is developing the MammoVest Simulator System, a device and curriculum designed to provide expanded initial training to mammography students and continuing education on proper positioning to practicing mammography technologists, ultimately to increase the efficacy of mammography screening. MammoVest will be a wearable vest with life-like female breasts and realistic elastic skin. The filler will mimic the real feel and response of breast tissue during manipulation and under compression. In this Phase I SBIR program we will first modify the initial design of the MammoVest, originally designed for mammography equipment demonstrations, to be wearable and have the optimal mobility and anatomy for breast positioning training. This first `Standard' MammoVest will provide mammography technologists with a dependable, standardized resource for beginner- level training. We will conduct a Face (or Content) Validity study in which expert mammography technologists will evaluate the realism of the `Standard' MammoVest with additional effort allotted to making any design modifications discovered to be necessary in the Validation study. Finally, we will develop and outline a downloadable curriculum for training breast positioning using MammoVest in collaboration with our expert mammography technologist. The curriculum will include videos of proper positioning, metrics for success, and common errors. This Phase I SBIR will demonstrate that MammoVest can be a complete, validated training system for mammography and breast positioning. In Phase II multiple MammoVests with diverse breast morphologies, including those most challenging to position (very large, very small, augmented, etc.), will be built, the curriculum expanded, and further Validation studies completed. Ultimately, MammoVest will provide standardized and validated breast positioning training to mammography technologists and radiologists, potentially improving the accuracy of mammography throughout the world.