Digital twin technology for precision medicine

Healthcare digital twin (HDT) technology originated in spaceflight planning before becoming a major driver of Industry 5.0 and precision medicine. Unlike traditional static models, HDT systems leverage cyber-physical integration via a bidirectional closed-loop between physical patients and their digital counterparts. AI systems process vast amounts of heterogeneous data from the "virtual" patient - electronic health records, genomics, radiomics, and wearable sensor outputs- to simulate and predict patient outcomes across multiple scales-from molecular interactions to population-wide health. Indeed, the current landscape of HDT applications spans key issues in patient-care and clinical trial optimization. Yet, technical, regulatory, and ethical challenges remain. This chapter explores the foundational concepts, technical frameworks, and current applications of digital twins, outlining both their transformative potential and the obstacles that must be navigated to fully realize their role in precision medicine.