The document discusses several medical imaging techniques: - X-rays use high energy electromagnetic waves emitted from accelerated electrons to generate images. CT scans take multiple X-ray images from different angles to construct 3D images. - Ultrasound uses piezoelectric transducers to generate and receive ultrasonic waves, which are reflected differently by tissues. This is used in A-scans and B-scans. - MRI uses strong magnetic fields and radio waves to excite hydrogen nuclei in the body, and detects their signals to construct images based on tissue density and fluid content.