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Artefacts in MRI are image features that do not represent true anatomy/pathology, arising due to limitations of physics, hardware, patient, or technique.
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They can mimic, obscure, or distort pathology.
The artefacts flowchart. Start by identifying the symptoms on the degraded image, then ask yourself the questions in the boxes. Follow the green arrows if the answer is ‘yes’ and the red ones if it’s ‘no’. You should arrive at one of the blue boxes, which will tell you the most likely cause of your artefact.
McRobbie DW, Moore EA, Graves MJ, Prince MR. MRI from Picture to Proton. 3rd ed. Cambridge University Press; 2017.
| Artefact | Properties | Solution |
|---|---|---|
| Chemical shift artefact | Due to different resonance frequencies of fat vs water (≈3.5 ppm). |
• Type I (frequency shift): misregistration at fat–water interfaces → dark/light bands. • Type II (India ink/black boundary): signal cancellation when fat & water are in same voxel, out-of-phase. | Fat suppression, in-phase TE, higher bandwidth | | Magnetic susceptibility artefact | Due to local field inhomogeneities at tissue–air/metal interfaces. • Appearance: signal loss + distortion, especially in echo-planar imaging (EPI). • Sites: sinuses, skull base, surgical clips. | Spin-echo sequences, shorter TE, higher bandwidth, MAR software | | Magic angle artefact | - Occurs when collagen fibres are oriented at ~55° to B₀.
Chemical shift artifact of the first and second kind. Chemical shift of the first kind (left) on the T1w in-phase GRE image (TR 100 ms, TE 4.4 ms) shows a dark rim in the posterior kidney-fat interface. Frequency encoding direction is anterior-posterior. Chemical-shift artifact of the second kind: T1w opposed-phase GRE image (right) (TR 100 ms, TE 2.2 ms) shows a surrounding dark rim at the fat-tissue interface, independent of the frequency encoding direction
Stadler, A., Schima, W., Ba-Ssalamah, A. et al. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 17, 1242–1255 (2007). https://doi.org/10.1007/s00330-006-0470-4
Metal-artefact-reduction scans on an example of hip screws. (a) High-bandwidth TSE; (b) SEMAC; (c) MAVRIC. Note that both SEMAC and MAVRIC offer similar reduction of artefact compared with conventional TSE, in this particular example.
McRobbie DW, Moore EA, Graves MJ, Prince MR. MRI from Picture to Proton. 3rd ed. Cambridge University Press; 2017.
Patient-related artefacts
| Artefact | Properties | Solution |
|---|---|---|
| Motion artefact | • From voluntary (movement) or involuntary (breathing, cardiac pulsation, CSF pulsation). | |
| • Appearance: ghosting, blurring, smearing along phase-encoding direction. | Patient instruction, faster sequences, gating, triggering, navigator echoes | |
| Flow artefact | • From flowing blood/CSF. | |
| • Appearance: ghosting, bright or dark flow voids, misregistration. | Flow compensation (gradient moment nulling), gating, saturation bands |
Motion artifact. More random respiratory motion (left) shows more general blurring of the T2 weighted TSE image (TR 2200 ms, TE 103 ms, ETL 21), periodic breathing leads to ghost artifacts (right)
Stadler, A., Schima, W., Ba-Ssalamah, A. et al. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 17, 1242–1255 (2007). https://doi.org/10.1007/s00330-006-0470-4
Scanner / acquisition-related artefacts
| Artefact | Properties | Solution |
|---|---|---|
| Aliasing (wrap-around) artefact | • When anatomy outside FOV is undersampled and folds back into image. | |
| • Appearance: superimposed structures. | Increase FOV, use oversampling, swap phase/frequency axes. | |
| Zipper artefact | • Due to RF interference or hardware leak. | |
| • Appearance: bright line(s) across the image. | Service shielding, equipment check. | |
| Gibbs (truncation) artefact | • Occurs from finite sampling of high-contrast edges. | |
| • Appearance: alternating dark/bright lines near sharp interfaces (e.g., spinal cord in CSF). | Increase matrix size, filtering. | |
| Nyquist ghosting (N/2 artefact) | • Due to phase-encoding errors in EPI sequences. | |
| • Appearance: ghosting at half-FOV shift. | Hardware calibration, correction algorithms. | |
| Dielectric effect (B1 inhomogeneity) | • At high-field MRI (≥3T), due to standing wave effects in body cavities. | |
| • Appearance: regional bright/dark shading. | Dielectric pads, parallel transmission. |
(a) Tissue outside the field of view (FOV) in the phase-encode direction wraps into the image. (b) With phase oversampling the reconstructed image is larger than the required FOV, and the computer just throws away the unwanted regions.
McRobbie DW, Moore EA, Graves MJ, Prince MR. MRI from Picture to Proton. 3rd ed. Cambridge University Press; 2017.
Coronal gradient echo image (TR 13 ms, TE 5 ms) shows a so called zebra stripes artifact along the body wall, especially at areas of susceptibility borders (e.g., air-tissue). This artifact is caused by an interference of aliasing and field inhomogenity
Stadler, A., Schima, W., Ba-Ssalamah, A. et al. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 17, 1242–1255 (2007). https://doi.org/10.1007/s00330-006-0470-4
Zipper artifact. Coronal image (TR 53.7 ms, TE 7.4 ms) shows an RF ablation needle placed in the liver (left). After switching the radiofrequency on, zipper artifacts are produced (arrows, right image)
Stadler, A., Schima, W., Ba-Ssalamah, A. et al. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 17, 1242–1255 (2007). https://doi.org/10.1007/s00330-006-0470-4
Crisscross artifact. Loss of single data points or data lines in the acquisition process due to spike formed external interfering signals or to errors in the signal processing can lead to a variable degree of artifact, sometimes showing a “crisscross” or “herringbone” pattern
Stadler, A., Schima, W., Ba-Ssalamah, A. et al. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 17, 1242–1255 (2007). https://doi.org/10.1007/s00330-006-0470-4
(a) A low phase-encode matrix can cause Gibbs’ artefact, alternating light and dark bands near a high-contrast interface. (b) Increasing the phase-encode matrix avoids the artefact. (c) A line profile across the structure reveals the typical pattern of Gibbs’ ringing.
Truncation. Ringing artifact with bright and dark lines parallel to edges of abrupt intensity changes, in a T1 weighted SE image (TR 252 ms, TE 15 ms), with low matrix size (64 × 64). After increasing the matrix (256 × 256) the ringing artefact is not visible
Stadler, A., Schima, W., Ba-Ssalamah, A. et al. Artifacts in body MR imaging: their appearance and how to eliminate them. Eur Radiol 17, 1242–1255 (2007). https://doi.org/10.1007/s00330-006-0470-4
Summary Table
| Artefact | Cause | Appearance | Remedy |
|---|---|---|---|
| Chemical shift | Fat–water frequency difference | Dark/light bands or black boundary | Fat suppression, ↑bandwidth |
| Susceptibility | Tissue–air/metal interfaces | Signal void, distortion | Spin-echo, ↓TE |
| Magic angle | Collagen 55° to B₀ | ↑T2 signal in tendons | Change TE/position |
| Motion | Patient/physiologic motion | Ghosting, blurring | Gating, faster scan |
| Flow | Blood/CSF motion | Ghosts, flow voids | Flow comp, sat bands |
| Aliasing | Small FOV | Wrap-around anatomy | Oversampling, ↑FOV |
| Zipper | RF leak | Bright line(s) | Shielding, service |
| Gibbs (truncation) | Finite sampling | Ripple near edges | ↑Matrix, filtering |
| Nyquist ghosting | Phase errors in EPI | Ghosting at ½ FOV | Correction software |
| Dielectric shading | B1 inhomogeneity | Regional bright/dark | Pads, pTx |
Further reading: