Which modality allows differentiation between solid and cystic structures?

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

Answer: (B)

The ability to distinguish solid from cystic structures hinges on how ultrasound interacts with different tissues. Fluid-filled cysts are anechoic, meaning they appear completely dark on the image, and they produce posterior acoustic enhancement because sound waves pass through fluid with little attenuation and then brighten the area behind the cyst. In contrast, solid structures generate internal echoes and may show complex architecture or vascularity on Doppler imaging. This real-time assessment of echogenicity and posterior enhancement makes ultrasound particularly effective at telling apart solid from cystic lesions. Other modalities can characterize tissue in different ways (CT via density values, MRI via signal patterns, radiographs via general contrast), but they don’t provide this straightforward, immediate solid-versus-cyst distinction in the same way.