The document discusses various medical imaging techniques, including their basic mechanisms and applications. Plain x-rays use x-ray beams to generate images based on tissue density. Computed tomography (CT) uses x-ray beams and computer processing to create cross-sectional images of the body. Magnetic resonance imaging (MRI) uses magnetic fields and radiofrequency pulses to generate images of anatomical structures without using ionizing radiation. Nuclear medicine techniques involve injecting radioactive tracers and using gamma cameras to assess organ function.