Which imaging modality does not use ionizing radiation?

Which imaging modality does not use ionizing radiation?

• A. Nuclear medicine scan
• B. Computed tomography (CT)
• C. Magnetic resonance imaging (MRI)
• D. X-ray radiography

Answer: (C)

Understanding who uses ionizing radiation is the key idea. Ionizing radiation has enough energy to remove electrons, and imaging methods that rely on X-ray photons or radioactive decays expose you to it. Magnetic resonance imaging, on the other hand, uses a strong magnetic field plus radiofrequency pulses to flip and detect the signal from hydrogen protons in the body. This process creates images without producing ionizing photons, so it is non-ionizing. Nuclear medicine scans depend on radiopharmaceuticals that emit gamma rays, CT uses X-ray beams, and X-ray radiography also relies on X-ray photons. All of these involve ionizing radiation. Therefore, the modality that does not use ionizing radiation is MRI. Keep in mind MRI avoids radiation exposure but has other considerations, such as longer exam times and compatibility issues with certain implants.

Understanding who uses ionizing radiation is the key idea. Ionizing radiation has enough energy to remove electrons, and imaging methods that rely on X-ray photons or radioactive decays expose you to it. Magnetic resonance imaging, on the other hand, uses a strong magnetic field plus radiofrequency pulses to flip and detect the signal from hydrogen protons in the body. This process creates images without producing ionizing photons, so it is non-ionizing.

Nuclear medicine scans depend on radiopharmaceuticals that emit gamma rays, CT uses X-ray beams, and X-ray radiography also relies on X-ray photons. All of these involve ionizing radiation. Therefore, the modality that does not use ionizing radiation is MRI. Keep in mind MRI avoids radiation exposure but has other considerations, such as longer exam times and compatibility issues with certain implants.