Educational Exhibit at the European Congress of Radiology, Vienna, 2019
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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.
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.
Findings and procedure details
The systematic approach includes
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
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.