a method of comparing micro - electronic devices . the method includes : placing a first micro - electronic device in a sample chamber of a magnetic resonance imaging machine , subjecting the first micro - electronic device to a magnetic field and a radio frequency pulse , turning off or adjusting the magnetic field and detecting a first returned rf pulse from the first micro - electronic device and storing first data relating to the first returned rf pulse ; placing a second micro - electronic device in the sample chamber , subjecting the second micro - electronic device to the magnetic field and the radio frequency pulse , turning off or adjusting the magnetic field and detecting a second returned rf pulse from the second micro - electronic device and storing second data relating to the second returned rf pulse ; and comparing the first data to the second data and determining if the second micro - electronic device is essentially identical to the first micro - electronic device based on the comparing .