## 9 Challenges, Opportunities, Limitations, and Future Trends  
The integration of DT in the medical field is developing quickly and is transforming a number of businesses by improving consumer service, streamlining processes, and boosting general productivity. However, this integration also presents several challenges that can be stated as follows:  
1. Data Integration and Interoperability: It might be challenging to incorporate real-time information from real systems or objects into DTs for medical systems. For data integration to be easy, compatibility and interoperability across many data formats, protocols, and devices must be guaranteed. 2. Scalability and Performance: Developing DTs that can manage many concurrent users and complex interactions requires scalable infrastructure. Maintaining optimal performance, such as low latency and high responsiveness, is essential for a smooth user experience. 3. Security and Privacy: DTs frequently contain vulnerable information, requiring robust security measures to protect against unauthorized access, data breaches, and privacy violations. Implementing authentication, encryption, and access controls is essential to ensure data security and privacy for secure medical data. 4. User Experience and Interaction: Creating intuitive and participating person experiences within biomedical systems is crucial for user adoption. Seamless interactions between users and their DTs, as well as with other users, require thoughtful interface design, haptic feedback, natural language processing, and gesture recognition. 5. Standardization and Interoperability: Lack of standardization and interoperability among different platforms and devices can hinder seamless integration. Developing industry-wide standards and protocols is necessary to ensuring compatibility and a connected ecosystem. 6. Cost and Infrastructure Requirements: Creating and preserving medical-based digital twins can involve significant costs. Creating high-fidelity virtual environments, managing real-time data streams, and ensuring robust infrastructure requires substantial investments. 7. Ethical Considerations: As the use of the new technology increases, ethical considerations regarding data ownership, privacy, algorithmic bias, and the misuse of DT arise. DTs depend on private patient information, like health records, DNA data, and live health tracking from wearables. This brings up questions about who owns the data: does the patient own the data used to make their model? Patients should control their health info, but the use of these data by different doctors, scientists, and outside groups can make ownership unclear. Also, strict rules need to exist to keep patient information safe in systems, particularly in federated learning environments where data are decentralized. Patients need to agree to and understand how people will use their data and why. Thus, regulators must monitor these technologies to make sure they are used in the right way and to protect patients' rights. Establishing ethical guidelines and frameworks is crucial for governing their development and use. Addressing these challenges will contribute to successful healthcare-based digital twin solutions, unlocking their full potential in various industries while ensuring data security, positive user experience, and ethical practices. Regardless of its promising potential, federated learning (FL) in care faces various significant challenges:  
1. Data Heterogeneity: Medical data vary widely across institutions in terms of format, quality, and completeness. This heterogeneity can complicate model training and reduce the generalizability of FL models. 2. Computational and Communication Overhead: FL requires significant computational resources and efficient communication protocols. Ensuring that all participating devices and institutions can handle these demands is a challenge, especially in resource-constrained settings. 3. Privacy and Security Risks: While FL aims to enhance data privacy, there are still potential risks of data leakage and attacks.