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Hypospray and non-invasive surgery
McCoy's "Hypospray," which allowed for instantaneous, bloodless, and needle-free liquid injections, hasn't quite made it in terms of handheld portability yet to every medical office, but a real-life equivalent for use in mass-dosage scenarios exists as the jet injector, and is used for vaccinations by the Department of Defense and other government and relief agencies around the world.
While the truly non-invasive surgery employed on the original Star Trek and TNG shows for generalized use still remains largely science fiction, some procedures such as Stereotactic Radiosurgery for treating specific types of tumors, allow for non-invasive surgery on brain tissue using focused radiation beams.
And while the hand-held directed energy "Phaser" guns used for combat against hostile aliens still remain a fantasy, LASIK surgery using focused low-wattage lasers to correct vision is now well on its way to making eye glasses and contact lenses obsolete.