MRI scan uses which physical principles to produce images of soft tissue?

MRI scan uses which physical principles to produce images of soft tissue?

• A. uses X-ray photons
• B. uses radio waves and a very strong magnetic field to produce images of the soft tissue
• C. uses sound waves
• D. uses radioactive tracers

Answer: (B)

MRI relies on how hydrogen protons behave in a strong magnetic field and when stimulated by radiofrequency energy. In the body, many protons are in water and fat; the external magnetic field causes their spins to align. A radiofrequency pulse at the right frequency tips this net magnetization away from alignment. When the protons relax back, they emit signals in the radiofrequency range, and the scanner detects these signals. The rate of relaxation (T1 and T2) and the proton density differ among tissues, giving high-contrast images of soft tissues. Gradient magnetic fields then encode spatial information to build detailed images. Because MRI uses only a very strong magnetic field and radio waves, it does not involve ionizing X-rays, acoustic ultrasound, or radioactive tracers.

MRI relies on how hydrogen protons behave in a strong magnetic field and when stimulated by radiofrequency energy. In the body, many protons are in water and fat; the external magnetic field causes their spins to align. A radiofrequency pulse at the right frequency tips this net magnetization away from alignment. When the protons relax back, they emit signals in the radiofrequency range, and the scanner detects these signals. The rate of relaxation (T1 and T2) and the proton density differ among tissues, giving high-contrast images of soft tissues. Gradient magnetic fields then encode spatial information to build detailed images. Because MRI uses only a very strong magnetic field and radio waves, it does not involve ionizing X-rays, acoustic ultrasound, or radioactive tracers.