The early use of fracking to get at reserves previously thought of as unrecoverable, shortly after the turn of the 21st century, came about after exploration companies began examining geologic formations using x-ray computed tomography, or CT scanners.

FORBES: Old Technology Fuels New Energy Boom

The technique can provide excellent, detailed images of the body's soft tissue and is an alternative to using X-ray techniques such as computed tomography (CT).

BBC: Study into health impact of MRI

CT, which stands for computed tomography, builds up a more revealing picture than a simple x-ray by taking a series of cross-section pictures.

BBC: scanner