Which of the following techniques uses a combination of a large magnet and radio waves to visualize the organs and structures inside our bodies?

Magnetic Resonance Imaging

The correct answer is option 4. Magnetic Resonance Imaging.

The technique that uses a combination of a large magnet and radio waves to visualize the organs and structures inside our bodies is Magnetic Resonance Imaging (MRI).

MRI is a non-invasive medical imaging technique that produces detailed images of the body's internal structures. It works by generating a strong magnetic field and then using radio waves to manipulate the hydrogen atoms in the body. These atoms emit signals that are detected by the MRI machine and processed into high-resolution images.

Computed Tomography (CT) uses X-rays to produce cross-sectional images of the body, Fluoroscopy is a technique that uses continuous X-ray beams to create real-time images of internal structures, and Positron Emission Tomography (PET) involves injecting a radioactive tracer into the body and detecting the emitted positrons to create images of metabolic activity. While these techniques are valuable in medical imaging, they do not rely on a combination of a large magnet and radio waves like MRI does.