This question is about diagnostic medical ultrasound imaging of internal structures.
During a cardiac ultrasound (echocardiogram), a specialized acoustic coupling gel is applied directly to the patient's skin before placing the transducer. Explain, in terms of acoustic impedance, why this gel is necessary and describe the physical consequence of omitting it.
An A-scan (Amplitude scan) can be used to monitor patients with suspected pericardial effusion—an abnormal accumulation of fluid in the pericardial cavity surrounding the heart.
Using the diagram below, explain how an A-scan is used to determine the exact thickness of this fluid layer.
