Which imaging modality is described as producing medical images of soft tissue structures using high-frequency sound waves?

• A. Fluoro
• B. Sonography
• C. MRI
• D. CT

Answer: (B)

The concept being tested is identifying an imaging method that uses high-frequency sound waves to visualize soft tissues. This is ultrasound, also called sonography. It works by emitting high-frequency acoustic waves from a transducer; these waves travel through tissues and are reflected back at interfaces. The returning echoes are converted into real-time images, making it especially good for soft-tissue structures and for dynamic assessment. Ultrasound has the advantage of no ionizing radiation and can image a range of soft tissues like liver, kidneys, muscles, thyroid, breasts, or a fetus. The frequency can be adjusted: higher frequencies give better detail for superficial structures, while lower frequencies penetrate deeper tissues. The other modalities rely on different physics (X-rays for fluoroscopy and CT, magnetic fields for MRI) and do not use high-frequency sound waves.