Findings from an animal study suggest that a non-invasive imaging technique could, with further development, become a tool to assess immune system recovery in people receiving treatment for HIV infection. Researchers used single-photon emission computed tomography (SPECT) and a CD4-specific imaging probe to assess immune system changes throughout the bodies of macaques infected with SIV following initiation and interruption of antiretroviral therapy (ART). They evaluated pools of CD4+ T cells in tissues.