# Blockchain-Based Distributed Patient-Centric Image Management System
## 6 Discussion  
The blockchain technology in PCIM system cryptographically protects the state of transactions of medical images and provides higher efficiency in terms of cost, event storage and image access overhead as discussed in the previous section. The use of IPFS allows constructing a high-throughput content-based storage model with content-addressed hyperlinks. In addition, the medical image migration time and retrieval time is faster compared to the conventional cloud based PACS. Furthermore, in Table 2 we provide a summarized comparison between the proposed framework using the ISN [16]  
Figure 11: Average Time Taken to Record the PCAC-SC Events by using Five Patients’ Ethereum Address. Figure 12: Gas Consumption and Block Size versus Number of Transaction of the PCAC-SC functions. and alternative blockchain-based medical health record management frameworks [22; 23; 24]. From this table, it can be seen that the proposed PCIM system has greater advantages comparing with the existing alternatives. Among them, studies [16; 22; 23] are based on centralized frameworks in which one central node failure causes a fail of the whole system. In contrast, in the framework proposed in this paper, every node is independent of each other, which ensures robust and efficient data access. The MedChain [24] uses a mutable P2P storage network and their patient data are maintained manually by the healthcare providers, which has a high risk of data attacks and data duplication. The proposed PCIM system overcomes these disadvantages by using an IPFS-based storage in which hashed medical images with the same content cannot be duplicated. This allows users to have full control of their medical images by ensuring guaranteed security, transparency, and data integrity. If the contents in a file stored within the IPFS network are not peered or active for a period of time, it is recycled by the garbage collector. Therefore, a participant of the healthcare ecosystem must pin the encrypted image content to ensure that the content never gets deleted by the garbage collector. The image stays up indefinitely, as long as it is pinned on the IPFS network. Protocol labs understood this limitation of IPFS and build Filecoin as a complementary component, that turns cloud storage into an algorithmic market [36]. Using the IPFS and blockchain system has the advantage of replacing current expensive storage systems (PACS) and centralized databases and of eliminating the recovery cost in the event of data breaches. However, we note some limitations for a broader concern, due to the decentralized nature of our system, such as losing private keys. In some studies [37; 38], the researchers introduced an efficient recovery mechanism using biometric data to create key pairs. This technique helps patient to securely store keys on their devices and recover the key in case they are lost. Furthermore, the medical images are not protected once the sensitive image is decrypted. It is difficult to identify the authorized recipients who attempt to tamper or manipulate the decrypted medical image. To overcome this issue, there are several data hiding techniques, i.e., watermarking, reported in the literature [39; 40; 41]. However, these data hiding techniques have not yet been clinically employed. In our future work, we will address the aforementioned limitations by considering the biometric signature [37] and steganography techniques [41]. Another limitation is that the encryption and the decryption of original medical images are performed manually on the IPFS network by the participants. Thus, in the future, the complexity underlying this action will be improved with a user-friendly application interface for emergency access. In the end, it is important to consider the Health Insurance Portability and Accountability Act (HIPPA) privacy rule [42] are relevant to incorporate the proposed approach within healthcare services.