Final answer:
The absorption of radio frequency waves in a patient is measured using MRI, which uses radio waves in a resonance process sensitive to the density of nuclei such as protons or hydrogen nuclei to produce detailed images.
Step-by-step explanation:
The absorption of radio frequency waves in a patient is measured using an MRI (Magnetic Resonance Imaging). During an MRI, radio waves are broadcast, absorbed, and reemitted by nuclei (usually protons or hydrogen nuclei) in a resonance process that is highly sensitive to the density of these nuclei. The resultant images are highly detailed and can provide two- or three-dimensional views, enabling precise localization and characterization of tissue structure and composition.