Blood brain barrier(BBB) leakage plays an important role in the patients with early Alzheimer disease. BBB is a collection of cells in brain that separates the blood from the brain parenchyma. When BBB is harmed, it loss it’s ability to keep substance influenced brain tissue, therefore would cause dementia. In this research, we take a series of MRI images, and use the difference of pixel intensity between images to calculate the leakage rate by Patlak approach, and plot the histogram to obtain the sum of the amount of leakage. Key words: BBB leakage, Patlak Graphical model, Alzheimer disease