In order to establish the potential of 51/52MnCl2 as safe PET brain tracers, the radiation effective dose (ED) of 51Mn- and 52Mn-chloride has been assessed by using biokinetic models in anthropomorphic phantoms. Results showed that 52Mn-chloride releases one hundred thirty times more radiation dose (ED = 1.35 mSv/MBq) than 51Mn-chloride (ED = 1.02E-02 mSv/MBq). Although the maximum positron energy of 52Mn allows a PET image resolution similar to that of 18F, activities below 15 MBq should be administered. •51Mn-chloride is a safe PET brain agent due to its low radiation effective dose.•52Mn-chloride produces effective doses one hundred-fold greater than 18F (e.g., 18FFDG).•52Mn-chloride produces effective doses 2.7-fold greater than 89Zr (e.g., 89ZrTrastuzumab).