During these periods of " sleep , " new horizons is powered by a single radioisotope thermoelectric generator , which uses less power than a pair of 100-watt household light bulbs .
This model train was mounted with a synthetic radioisotope ( a source of neutrons - or energy ) and sent on a continuous three-day loop on hobby train tracks to help inform other fusion experiments .
If looking at the liver is necessary to check for signs of disease , the doctor might order a computerized axial tomography ( cat ) scan , ultrasound , magnetic resonance imaging ( mri ) , or a scan of the liver using a radioisotope ( a harmless radioactive substance that highlights the liver ) .