With the rapid development of information and communication technology, a vast amount of personal health data is generated, stored, and utilized in healthcare related services. However, there are many issues remained to be solved, such as data interoperability, security, and privacy concerns. On the other hand, blockchain, a decentralized peer-to-peer digital ledger, has attracted a lot of attention in recent years as a promising technology to protect privacy of personal data. By adopting blockchain, individuals can take advantage of personal health data for better healthcare. In this paper, after briefly summarizing the major features of blockchain, we describe blockchain-empowered solutions for utilization of personal health data in healthcare and discuss issues and challenges. We further propose i-Blockchain, an individual-centric framework for use of personal health data based on an extension of permissioned blockchain, present the basic architecture and protocols, and show several application scenarios.