How does ultrasound differentiate between cystic and solid lesions?

Ultrasound differentiates between cystic and solid lesions primarily by relying on the different acoustic properties of fluids and tissues. Cystic lesions, which are filled with fluid, typically appear as anechoic (dark) on an ultrasound image because fluid does not reflect sound waves effectively. In contrast, solid lesions contain more tissue and can reflect sound waves, leading to varying echogenicities (brightness levels) in the images.

The fundamental principle at play here is the interaction of ultrasound waves with different tissues. When sound waves encounter a boundary between different types of tissues or substances, they will reflect or transmit differently based on the acoustic properties such as density and elastic properties. This contrast enables clinicians to distinguish between a cyst, which generally shows no internal echoes, and a solid lesion, which may show internal echoes and greater variability in appearance.

Other options involve techniques or methods not related to ultrasound imaging. For instance, using radioactive isotopes pertains to nuclear medicine rather than ultrasound. Analyzing vascularity, while useful in other contexts such as assessing blood flow with Doppler ultrasound, does not directly determine whether a lesion is cystic or solid. Measuring electrical conductivity relates to different medical imaging modalities and does not apply to ultrasound technology. Thus, understanding the role