Detection of infratentorial lesions is important for diagnosis of multiple sclerosis. However, infratentorial lesions are hard to detect on conventional FLAIR protocols. In this work, we optimized the refocusing flip angle in the turbo spin echo readout of 3D FLAIR to enhance infratentorial lesion contrast in individual patients. T1, T2, and proton density measured in the brain stem and cortical gray matter were used to calculate the refocusing angle that maximizes the contrast-to-noise ratio. The patient-specific approach was assessed in 8 MS patients. Improved infratentorial lesion contrast was achieved in most of the cases.