Educational Exhibit at the European Congress of Radiology, Vienna, 2019
(Note: images here are for representation only. Please write to us in case you would like the actual images)
Learning objectives
We present a review of different MRI sequences used for reducing metal associated artifacts. We discuss a systematic approach to interpret MRI scans with metallic implants.
Coronal T1 W and MAVRIC sequences representing both artifacts (red arrows) and infection (black arrows)
Background
Metal associated artifacts can be due to the presence of metal in the image plane (in-plane artifacts) or due to metal in an adjacent plane (through-plane artifacts). The techniques used for reduction of metal artifacts include high bandwidth sequences non-frequency selective fat suppression sequences like STIR (MARS), 2-point and 3- Point Dixon techniques and dedicated sequences like Multiacquisition variable-resonance image combination (MAVRIC) and Slice-Encoding for Metal Artifact Correction (SEMAC). The combination of the MAVRIC and SEMAC technique is known as MAVRIC-SL.
Coronal MAVRIC of knee joint shows regular fluid cleft under tibial platform suggestive of prosthetic loosening
Findings and procedure details
The systematic approach includes
Don’t Panic
Look at the signal a) Bright on STIR/MAVRIC/SEMAC and Dark on T1- Abnormal b) Bright on STIR/MAVRIC/SEMAC and bright on T1- Artifact c) Dark on STIR/MAVRIC/SEMAC and Dark on T1- Metal or Air/metallosis
The pathologies to exclude include a) Infection b) Loosening c) Synovitis d) Injury to adjacent ligaments e) Adverse reaction to metal debris f) Nerve and vascular injuries
Linear dark areas on Sagittal MAVRIC of knee inside joint seen in metallosis
Conclusion
A systematic approach to interpretation of MRI scans with metal associated artifacts can be systematic. Correlation with other imaging modalities like CT and ultrasound can be helpful in difficult cases.
Coronal MAVRIC of femur reveals Break of hypo-intense continuity seen in a stress fracture
