Chemical shift artifact in MRI: the dark and bright bands at fat-water borders
Fat and water are placed a few pixels apart along the frequency direction. Bandwidth and field strength decide how far.
Chemical shift (misregistration)
A dark line on one side and a bright line on the other side of fat-water borders (kidney, bladder, orbit, vertebral endplates), along the frequency direction.
Fat protons precess about 220 Hz slower than water at 1.5 T (440 Hz at 3 T), so fat is mapped a few pixels away from its true position.
- Increase receiver bandwidth
- Use fat suppression
- Swap frequency direction to move the line away from the interface you need
- Smaller pixels reduce the shift in millimetres only if bandwidth per pixel is kept
Wider bandwidth lowers SNR.
This page is one entry from the MRI Technologist Reference
The full reference has 31 protocols, 9 dynamic study timelines, 19 artifacts, 16 scanner problems and 15 safety topics, as a PDF in English and Arabic plus an interactive tool.
Educational reference. It does not replace your site protocols, the radiologist's instructions, the MR safety officer, or the manufacturer's instructions for any implant, device or contrast agent. Parameter values are typical starting points at 1.5 T and must be adapted to the scanner, coil and patient.