chemical shift artifact
MRI artifact causing spatial misregistration of fat and water tissues due to different resonance frequencies, appearing as dark and bright bands at fat-water interfaces.
Full Definition
Chemical shift artifact arises from the inherent difference in resonance frequency between fat and water protons (approximately 3.5 parts per million). In frequency-encoding direction, this frequency difference is misinterpreted as spatial displacement by the MRI reconstruction algorithm, causing fat and water in the same anatomical location to appear spatially separated. The artifact manifests as characteristic dark and bright bands at tissue interfaces where fat and water are adjacent. Artifact severity increases at higher field strengths and with lower receiver bandwidth. Recognition is crucial for proper image interpretation, particularly in abdominal and musculoskeletal imaging where the artifact can simulate pathology.
Usage
Usage note: Distinguish from chemical shift imaging, which is an intentional technique.
In Context
- "The apparent signal dropout adjacent to the vertebral body represents chemical shift artifact rather than pathology." — Spine MRI interpretation
- "Chemical shift artifact was minimized by increasing the receiver bandwidth to 130 Hz/pixel." — Technical protocol optimization