The study is to produced a brain phantom simulating corpus striatum, which can evaluate the progression of parkinson s disease, to investigate possibility of reducing the brain exposure dose to CT while maintaining opti-mal image quality during PET-CT examinations. CT scans were performed by varying tube voltage (100, 120 kVp) and tube current (80, 140, 200 mAs) with 18F FP-CIT injected into the phantom s hot sphere and back-ground (radioactivity ratio 3:1)(reference condition; 120 kVp, 140 mAs). Estimated effective dose was calculated by using conversion factor according to each condition, and image quality was evaluated by setting SNR and CRChot image evaluation factors. Experimental results showed that the predicted effective dose below the CT imaging reference condition was reduced by at least 10% and by up to 60%, and the predicted effective dose beyond the reference condition was increased by 40%. In addition, there was no significant difference between SNR and CRChot of PET images, and it was confirmed that brain dose decreased with decrease of tube voltage and tube current. At the same time, there was no significant change in the quality of the image in terms of SNR and CRChot despite the change in scan conditions. This fact suggests that the quality of the images ac-quired under the existing dose conditions can be obtained even at low dose conditions and it is expected that it will be possible to use the brain PET-CT scan as a basic data for the research on reduction of dose and improvement of image quality.