Which diagnostic imaging modality relies on the precession and relaxation of hydrogen protons (Hard) in a strong external magnetic field?
Answer and explanation
Correct answer: C. Magnetic Resonance Imaging (MRI)
- Step 1: Water and fat contain abundant hydrogen nuclei (single protons) with non-zero magnetic spin. Step 2. In a strong magnetic field (1.5-3.0 Tesla), protons align with the field; radiofrequency excitation pulses tip their magnetization, and emitted relaxation signals generate soft-tissue MRI images. Answer: Magnetic Resonance Imaging (MRI). Why not the others: CT uses rotating ionizing X-ray beams; PET uses positron-emitting radiotracers; Conventional X-ray uses projection radiography.
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