Which artifact is characterized by intensity variations due to a lack of contrast agent?

The artifact characterized by intensity variations due to a lack of contrast agent is truncation. This phenomenon occurs primarily in magnetic resonance imaging (MRI) when the number of data points collected in the frequency domain is insufficient to fully portray the high-spatial-frequency components of the tissue being imaged. When this data is insufficient, it leads to inaccuracies in reconstructing the image, typically resulting in a pattern that suggests intensity variations and can cause the appearance of "gaps" in the image.

Truncation is often seen in regions with steep signal gradients, such as at the edges of structures with different signal intensities. When a suitable contrast agent is not available or used, the differences in tissue types or structures are not enhanced, exacerbating the truncation effects. This can make it more challenging to differentiate between adjacent tissues effectively.

The other artifacts—phase wrap, ring artifact, and banding—have different causes and manifestations. Phase wrap pertains to misinterpretation of a signal’s phase when the imaging parameters are not set correctly, leading to aliasing. Ring artifacts arise due to inconsistencies in the detector system, often producing circular patterns unrelated to contrast agent use. Banding, on the other hand, involves periodic intensity variations caused by systematic errors in the