# Blockchain-Based Distributed Patient-Centric Image Management System
###### Abstract
To solve the problem of decentralized storage, the Protocol Labs [10] created a distributed web called Inter Planetary File System (IPFS). IPFS was designed to enable a content-addressable, peer-to-peer (P2P) technology to share and store hypermedia in a distributed file system. Several other decentralized storage systems were developed, such as storj, swarm, and sia [11]. IPFS has an advantage of being compatible with other blockchain networks by offering an off-chain storage solution. IPFS provides permanent, smarter, and faster web services to distributed data access systems. However, several obstacles exist in terms of storing sensitive medical images over these distributed storage solutions, such as unauthorized access and privacy concerns with regard to patient images. Namely, the ability to manage big data across general practitioners, hospitals, patients, and medical institutions without significant exposure to the risk of privacy breaches is essential. Another important aspect of a confidential and secure storage system is the ability to reduce the cost and restrictions of medical image acquisition by eliminating the need in centralized parties [12]. Therefore, the following research question is formulated:  
\"How can we design a patient-centric distributed architecture for the purpose of medical image storage and sharing, while simultaneously addressing the concerns about privacy, security, access flexibility, and costs?\"  
To answer this question, we propose a proof-of-concept (POC) design for a distributed framework called a patient-centric image management (PCIM) system that is a blockchain-based architecture designed to facilitate secured patient-centric access and storage of encrypted medical images within an open distributed network. The contributions of this paper are as follows:  
1. We provide a brief overview on the structure of the proposed PCIM system and illustrate interactions among different components of the system. 2. We propose a patient-centric access control protocol using a smart contract (PCAC-SC). Specific functions are considered to transmit information in and out of the Ethereum blockchain and give access privileges between entities. We implement a framework to test feasibility of the concept. To this end, we have developed a PCAC-SC prototype on an Ethereum test network. We have published the related source codes online. 4. We verify the functionality using test cases and analyzed the capabilities of the proposed framework based on the following performance parameters: image access time, cost for executing functions, time taken to record PCAC-SC events in the blockchain, average block size, and average gas consumption. The rest of the paper is organized as follows: in Section 2, we discuss the state of medical image sharing. The system components of the proposed framework are described in Section 3. An overview of the proposed PCIM system and PCAC-SC is presented in Section 4. Implementation, verification and analysis of the proposed system are described in Section 5. Section 6 discusses the advantages, limitations, and future research directions. Finally, Section 7 concludes the work.