"If something is obstructing the flow of that radiation, for example a weapon, the device will highlight that object, " said Commissioner Raymond Kelly, who described the device Wednesday in a speech at the Waldorf-Astoria Hotel.

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In the past radiation was a clumsy and undiscriminating weapon, killing cancer cells and healthy cells in one sweep.

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It would add a potent weapon to the standard arsenal of cancer therapies--to chemotherapy, radiation and surgery.

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While 233U is an excellent fuel, its harsh radiation makes it nearly impossible to steal, and extremely difficult to use in a weapon.

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