A bioscan is a process in which an organism's biological structure – both external and internal – is scanned, normally for medical purposes.
A bioscan of Nadet by Phlox revealed that she was ill with lung cancer. (ENT: "Terra Nova")
While aboard the ECS Fortunate, a bioscan conducted by T'Pol using a scanner picked up a Nausicaan life sign aboard the freighter. The bioscan was able to determine that the Nausicaan was also injured. (ENT: "Fortunate Son")
Doctor Beverly Crusher performed several bioscans on Susanna Leijten and Geordi La Forge when they were affected by the Tarchannen III species. Each scan proved inconclusive and no infections were detected. A short time later however, both were transformed by the disease into Tachannen III lifeforms. (TNG: "Identity Crisis")
Doctor Crusher ran a bioscan on Berlinghoff Rasmussen to verify his identity. The readings indicated that he was perfectly Human. (TNG: "A Matter of Time")
Geordi La Forge checked the bioscans of himself, Captain Picard, and Deanna Troi in 2369 after Troi told the others about her unusual experience seeing the others "frozen in time". (TNG: "Timescape")
Captain Kathryn Janeway ordered full bioscans on Harry Kim and Derran Tal after Kim began exhibiting symptoms of olan'vora in 2375. (VOY: "The Disease")