While X-Ray's are a form of ionization radiation that is potentially hazardous,levels used to check hand baggage are relatively 'very' low. Levels in the region of (aprox) 0.05 mR(millirem) per inspection are about average. . . Put into perspective you receive 3mR in about 4 days of exposure from radiation received naturally from the sun ! and about 4 mR from background radiation when you fly coast to coast in the US !.. . The max annual dose (not STD's !!) for US & Canadian radiation workers is 5000mR !.. . So you can see that a second head growth spurt is unlikely !!.