The security of medical images is very important to maintain the confidentiality and privacy of patient information. Medical practitioners are required to adopt policies for the security of the access of patient’s electronic information. This paper provides the security analysis of the Medical Images based on Elliptic curve cryptography. Elliptic curve cryptography (ECC) is a complex method and involves intense computation which makes it robust for the intruder attack. In this paper, ECC based Medical Image Encryption algorithm is performed on varieties of medical images like MRI, CT scan and X-ray. Security analysis is presented based on Histogram, Entropy, NPCR and UACI measures and compared with traditional method RSA. Histogram after encryption using ECC has uniform distribution which reflects that the information of original medical image is hidden properly. Entropy and NPCR achieved are 7.86 – 7.99 and 99.62 – 99.64 % respectively which are very close to their ideal values. Results reveal that ECC is more powerful and useful for medical image authentication and key distribution. However, it can be used for exchange of secret key rather than encryption.