Washington (CNN) -- The head of the Transportation Security Administration defended his agency's security procedures Wednesday, telling lawmakers it is "using technology and protocols to stay ahead of the [terrorist] threat and keep you safe." John Pistole's testimony before the Senate Committee on Commerce, Science and Transportation follows a controversy that broke out over the past week about the agency's full body scans and pat-downs. "We've adjusted our pat-down policy that is informed by the latest intelligence," Pistole told lawmakers, acknowledging that the procedures "may challenge our social norms." "Security is a shared responsibility," the TSA chief said. "We are trying to detect the next generation of non-metallic devices" used in explosives, he added.
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NEW: GAO March report says it is unclear if scanners would have stopped attempted Christmas day attack
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NEW: TSA chief John Pistole says agency needs to be "more thorough in our screening technology"
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NEW: Pistole expects 1000 scanners nationwide by the end of 2011
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Pistole says the safety procedures are meant to "keep you safe, "but methods "may challenge our social norms"
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Critics say the searches are invasive
But some passengers and pilots have expressed objections to @placeholder's too-close-for-comfort pat-downs.