Image compression addresses the problem of reducing the amount of data required to represent a digital image. There are some areas of medicine where it is sufficient to maintain high image quality only for diagnostically significant regions, for example, tumor section of the brain MRI. This paper represents a compression method based on ROI and its performance analysis focusing on Discrete Cosine Transform technique. It is used for reducing the redundancy that is nothing but avoiding the replica data. The DCT is a mathematical function that transforms digital image data from the spatial domain to the frequency domain.