What imaging technique is used to view the inside of the body using magnetic gradients?

Magnetic Resonance Imaging (MRI) is the correct choice because it utilizes powerful magnets and magnetic gradients to generate detailed images of the organs and tissues inside the body. Unlike other imaging techniques, MRI focuses on the magnetic properties of hydrogen atoms in the body, aligning them with the magnetic field before producing images based on the radio frequency signals emitted as these protons return to their original alignment. This makes MRI particularly effective for soft tissue contrast and is commonly used in various medical fields, including oncology and neurology.

In comparison, CT scans use X-ray technology and computer processing to create cross-sectional images, while X-rays primarily capture static images based on differential absorption of radiation by various tissues. Ultrasound employs high-frequency sound waves to create images, making it less effective for certain types of soft tissue contrast. Hence, MRI is the only technique listed that specifically uses magnetic gradients for imaging.