Final answer:
In medical imaging, artifacts appearing as fine, grainy echoes within cystic structures are often due to calcifications or stones that create reflections of ultrasound waves, and are observed in conditions like neurocysticercosis on CT scans.
Step-by-step explanation:
The type of artifact that appears as a collection of fine, grainy echoes distributed along the inside of cystic structures in medical imaging, particularly in ultrasound, is known as acoustic shadowing or echoes. This phenomenon is often seen in cases where there are calcifications or stones within the cyst, which create reflections of the ultrasound waves leading to the appearance of these echoes. When observing cysts on a CT scan, such as in the case of neurocysticercosis (as illustrated in the provided brain CT scans), numerous cysts may be visible, which can contain calcifications that result in grainy echoes. These structures can sometimes offer clues about the nature of the cystic lesion, helping clinicians in diagnosis and treatment planning.