US Airports have unveiled new X-ray scanning machines, which will be used to screen more passengers with full-body imaging.

The USD$170,000 machines show images of passengers' bodies through their clothes to reveal hidden objects. Three of these machines were activated on Monday at Boston's Logan Airport. The US Department of Homeland Security hopes to deploy  450 advanced scanners at airports by year's end, using funds from last year's American Recovery and Reinvestment Act, also known as the stimulus. DHS has asked for another USD$214.7 million to buy 500 more advanced scanners, which coupled with previous orders would place the imaging machines in most of the country's largest airports. The new machines will replace the ubiquitous metal detectors for some randomly selected passengers. Officials said that passengers can choose a pat-down search instead, though in past tests nearly all preferred the imaging scanners. Logan airport has previously tested another imaging machine made by L-3 Communications that analysed natural "millimetre wave" energy radiated by travellers' bodies. The new machines, made by Rapiscan Systems, are known as "backscatter" machines and bounce low-energy X-rays off passengers.