In electrical patient record system，
reference images are used for physicians，
not for primary diagnosis.
Lossy image compression method such as JPEG is often used for reference images. The purpose of this study is to develop a new image compression method to apply different compression ratio to the inside of ROIs according to normal JPEG scheme. ROIs can be often defined as more significant regions than others by radiologists. By using our method，two quantization matrices were used in the phase of encoding.
We studied the quantization matrix for outside of ROI to minimize the degradation of image quality. The image size was 7.3% smaller than the normal JPEG images. It is easy to introduce our method into PACS，
since any additional software was not required to decode image data compressed by the proposed method.