# Blockchain-Based Distributed Patient-Centric Image Management System
###### Abstract  
In recent years, many researchers have focused on developing a feasible solution for storing and exchanging medical images in the field of health care. Current practices are deployed on cloud-based centralized data centers, which increase maintenance costs, require massive storage space, and raise privacy concerns about sharing information over a network. Therefore, it is important to design a framework to enable sharing and storing of big medical data efficiently within a trustless environment. In the present paper, we propose a novel proof-of-concept design for a distributed patient-centric image management (PCIM) system that is aimed to ensure safety and control of patient private data without using a centralized infrastructure. In this system, we employed an emerging Ethereum blockchain and a distributed file system technology called Inter-Planetary File System (IPFS). Then, we implemented an Ethereum smart contract called the patient-centric access control protocol to enable a distributed and trustworthy access control policy. IPFS provides the means for decentralized storage of medical images with global accessibility. We describe how the PCIM system architecture facilitates the distributed and secured patient-centric data access across multiple entities such as hospitals, patients, and image requestors. Finally, we deployed a smart contract prototype on an Ethereum testnet blockchain and evaluated the proposed framework within the Windows environment. The evaluation results demonstrated that the proposed scheme is efficient and feasible. blockchain; distributed storage; medical image sharing; healthcare system; smart contract; IPFS +
Footnote †: 2021: 11, 196. [[https://dx.doi.org/10.3390/app11010196](https://dx.doi.org/10.3390/app11010196)]([https://dx.doi.org/10.3390/app11010196](https://dx.doi.org/10.3390/app11010196))
to have full access control over their medical images and can monitor it online without relying on any centralized infrastructure. The shift towards the concept of decentralized technologies such as blockchain [4] became a significant trend that has the potential to lay new groundwork for decreasing the aforementioned barriers and encourage more widespread adoption for a patient-centric system. Recently, blockchain technology, e.g., Bitcoin [5] and Ethereum [6], has become one of the most important research topics, not only in the finance industry, but broadly across the field of information technologies due to its decentralized nature. Healthcare-based blockchain applications have been gaining particular attention in terms of applying them to enable interoperable sharing the real-time data among providers, payers, and patients [4,7]. Public blockchain technology is an open distributed ledger that stores all transaction details in blocks [5]. A typical blockchain consists of a directed acyclic graph (DAG) structure, where each block is linked with the previous block by a hash. Information stored in each block is public and cannot be easily deleted nor modified. Therefore, a blockchain is considered to be a decentralized method to facilitate verifiable exchanges of transactions between any two entities efficiently and permanently. Timely verification and recording of transactions are possible without the necessity in a centralized intermediary. A blockchain has such advantages as being tamper-proof and capable of protecting information against integrity-based attacks. A significant problem with regard to storing medical images and records in a blockchain is the size of the content. For example, as of November 2020, the size of the Bitcoin blockchain reached 362.51 GB [8]. This is the result of data accumulation over the past ten years at a growth rate of 1 MB every 10 min since Bitcoin was launched in 2009. There are approximately 1000 transactions in a block. Thereby, a single transaction has the order of 1 KB. The size of medical images corresponds to the orders of magnitude larger than those a public blockchain can offer [9].