In this paper, we investigated <sup>18</sup>F-THK5351 PET/CT image of normal Thai population for the optimized time of radioactive tracer PET/CT. Twenty-five volunteers without neurological or psychiatric illnesses and all of them have no abnormalities detected on neurologic examination. All subject were underdiagnosed on <sup>18</sup>F-THK5351 PET/CT and 3.0 Tesla MR imaging. THK5351 PET/CT were operated on the co-registered MRI comprised for drawing an ROI. The DICOM file was converted to .img file, .hdr file and then merge with each other for obtaining an fmridata.mat. Position of ROI and fmridata.mat were used to plot graph showing the relationship between quantitative uptake with the frame of image. The optimized time of <sup>18</sup>F-THK5351 PET/CT in normal Thai population is 50 to 70 minutes.