Positron emis­sion tomog­ra­phy (PET) uses small amounts of radioac­tive mate­ri­als called radio­trac­ers, a spe­cial cam­era and a com­put­er to help eval­u­ate your organ and tis­sue func­tions. By iden­ti­fy­ing body changes at the cel­lu­lar lev­el, PET may detect the ear­ly onset of dis­ease before it is evi­dent on oth­er imag­ing tests. Today, almost all PET scans are per­formed on instru­ments that are com­bined PET and CT scan­ners. The com­bined PET/CT scans pro­vide images that pin­point the anatom­ic loca­tion of abnor­mal meta­bol­ic activ­i­ty with­in the body. The com­bined scans have been shown to pro­vide more accu­rate diag­noses than the two scans per­formed separately.