Which imaging technique primarily uses magnetic fields?

The imaging technique that primarily uses magnetic fields is magnetic resonance imaging, commonly known as MRI. This method employs strong magnetic fields and radio waves to generate detailed images of the organs and tissues within the body.

The magnetic fields in MRI affect the alignment of hydrogen atoms, which are abundant in body tissues. When the magnetic field is applied, these hydrogen atoms align in a certain way, and upon the application of radiofrequency pulses, they emit signals that are captured to create images. This process enables MRI to produce high-resolution images with exceptional contrast between different types of soft tissues, making it particularly useful for visualizing the brain, muscles, and joints.

In contrast, X-rays use ionizing radiation to create images and are typically utilized for examining bone structures. CT scans, or computed tomography scans, combine X-ray technology with computer processing to produce cross-sectional images but do not use magnetic fields. Ultrasound employs high-frequency sound waves to generate images of soft tissues and organs, making it a different modality altogether. Therefore, MRI stands out as the only imaging technique among the choices that predominantly utilizes magnetic fields for its operation.