What type of imaging modality uses a magnetic field and radio waves?

The correct choice is MRI (Magnetic Resonance Imaging) because it uniquely employs a strong magnetic field and radiofrequency waves to generate detailed images of the body's internal structures. The process begins when the magnetic field aligns the protons in the body's hydrogen atoms. Then, radio waves are used to disturb this alignment, causing the protons to emit signals as they realign with the magnetic field. These signals are detected and converted into images by a computer, resulting in high-resolution images of soft tissues, organs, and other structures within the body. This method is particularly advantageous for neurological, musculoskeletal, and cardiovascular imaging due to its ability to provide contrast between different types of soft tissues without using ionizing radiation, which is a significant concern with other imaging modalities.