This is a single-center drug distribution and pharmacokinetic study of a single microdose of 18F-raltegravir given to 10 HIV-infected subjects who are either taking or not taking a raltegravir-containing ART regimen. After administration of IV 18F-raltegravir, subjects will undergo PET/MRI in order to determine the distribution of radiolabeled drug through the lymphoreticular system and other tissues throughout the entire body.