MRI uses magnetic fields and radio waves to interact with tissues.

• A. Magnetic fields and radio waves
• B. Gamma rays and neutrons
• C. Sound waves and heat
• D. X-rays and electrons

Answer: (A)

MRI works by using magnetic fields and radiofrequency energy to interact with tissues. In a strong magnetic field, hydrogen protons align with the field. A radiofrequency pulse tips these protons, and as they relax back, they emit signals that are detected and used to construct images. This approach exploits magnetic fields and radio waves, not ionizing radiation. Other imaging methods rely on different phenomena—gamma rays and neutrons in nuclear techniques, sound waves in ultrasound, or X-rays and electrons in X-ray/CT—so they don’t match how MRI creates its images.