Which imaging modality uses magnetic fields and radio waves to produce images without using X-rays?

• A. X-ray
• B. Ultrasound
• C. Computed Tomography
• D. Magnetic Resonance Imaging

Answer: (D)

Think of imaging methods by the energy they use. The one that uses magnetic fields and radio waves to create images without X-rays is Magnetic Resonance Imaging. It works by aligning the body's hydrogen protons with a strong magnetic field. A radiofrequency pulse then perturbs that alignment, and as the protons return to their original state, they emit signals captured by the scanner to form images. Because MRI relies on magnets and radio waves rather than ionizing radiation, there’s no X-ray exposure. Ultrasound uses sound waves, while X-ray and computed tomography rely on X-ray photons. MRI is especially helpful for detailed soft-tissue contrast, like the brain, spinal cord, muscles, and joints.