Several experiments have shown that electronic detectors (i.e. the CCD/CMOS detector in your camera), as well digital flash memory, degrade slowly after passing through checkpoint X-ray machines. Your data will not be ruined after 5 or 10 or 20 trips, much less one. But it's a good idea to copy your data to a different storage after arrival (if possible), and then rewrite it back to the flash card. I personally remove all flash storage and put it in my pocket (it will not set off any detectors) before going through security.