This paper presents design and development of an advanced image encryption/decryption system specifically used for maintaining and securing medical images which are ‘Digital Imaging and Communications in Medicine’ formatted. Proposed system is necessary in the field of healthcare to safeguard the sensitive patient data and medical information. It utilizes the ‘Advanced Encryption Standard’ algorithm along with a large key space of 256-bits which provides an enhanced security and randomness as compared to key spaces including 32-bits, 64-bits, and 128-bits. System’s novelty lies in encrypting the binary form of the medical image data resulting in assurance of the confidentiality specifically in DICOM format images. The performance of the system is observed using security parameters including average number of pixel change rate, average of unified average changing intensity, average of peak signal to noise ratio, and average of ratio of entropy indexes. These parameters are evaluated on experimenting over 4,620 DICOM format images. The average of number of pixel change rate between the original image data and its encrypted form resulted in 99.9% pixel change rate. Whereas, the decrypted image after one cycle of encryption-decryption highly resembled with its original form resulting in average of zero percent change in pixels rate, maintaining the data integrity.