Metal artifact reduction sequence
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At the time the article was created Jan Frank Gerstenmaier had no recorded disclosures.
View Jan Frank Gerstenmaier's current disclosuresAt the time the article was last revised Ammar Haouimi had no recorded disclosures.
View Ammar Haouimi's current disclosures- MARS (metal artifact reduction sequence)
- WARP
- MAVRIC (Multiacquisition variable-resonance image combination)
- SEMAC (Slice-Encoding for Metal Artifact Correction)
- Metal artifact reduction sequence
- Metal artifact reduction sequences
- Metal artifact reduction sequences
- Metal artifact reduction sequence
A metal artifact reduction sequence (MARS) is intended to reduce the size and intensity of susceptibility artifacts resulting from magnetic field distortion.
A variety of techniques are used for reducing metal artifacts at MRI, both for addressing artifacts due to the presence of metal in the image plane (in-plane artifacts) and for artifacts due to metal in an adjacent plane (through-plane artifacts).
In-plane artifact reduction
A number of simple changes to the scan protocol can greatly reduce artifacts. Examples are 1:
- lower magnetic field strength: 1.5 T rather than 3 T
- increase bandwidth during slice selection and readout
- increase matrix: 512 pixel
- maintain good signal to noise ratio by increasing number of excitations (NEX)
- spin echo instead of gradient echo where possible
- STIR for fat suppression (spectral frequency selective fat suppression performs better in a homogeneous field)
- shorter echo spacing
- smaller water-fat shift
- thinner slices
- view-angle-tilting (VAT)
Through-plane artifact reduction
Multiacquisition variable-resonance image combination (MAVRIC) is a specialized sequence designed by GE to minimize metallic artifact around metallic prostheses 3. It relies on 3D FSE sequences, using multiple different overlapping volumes at different frequency offsets.
Another technique developed by Siemens used for addressing through-plane metal artifacts is Slice-Encoding for Metal Artifact Correction (SEMAC), where an additional slice-encoding gradient is added to a standard fast-spin echo sequence 4. The combination of the MAVRIC and SEMAC technique is known as MAVRIC-SL 5.
See also
References
- 1. Hargreaves BA, Worters PW, Pauly KB et-al. Metal-induced artifacts in MRI. AJR Am J Roentgenol. 2011;197 (3): 547-55. doi:10.2214/AJR.11.7364 - Pubmed citation
- 2. Hartley KG, Damon BM, Patterson GT et-al. MRI techniques: a review and update for the orthopaedic surgeon. J Am Acad Orthop Surg. 2012;20 (12): 775-87. J Am Acad Orthop Surg (full text) - doi:10.5435/JAAOS-20-12-775 - Pubmed citation
- 3. Hayter CL, Koff MF, Shah P et-al. MRI after arthroplasty: comparison of MAVRIC and conventional fast spin-echo techniques. AJR Am J Roentgenol. 2011;197 (3): W405-11. doi:10.2214/AJR.11.6659 - Pubmed citation
- 4. Sutter R, Ulbrich EJ, Jellus V, Nittka M, Pfirrmann CW. Reduction of metal artifacts in patients with total hip arthroplasty with slice-encoding metal artifact correction and view-angle tilting MR imaging. Radiology. 2012;265(1):204-14. doi:10.1148/radiol.12112408 - Pubmed citation
- 5. Choi SJ, Koch KM, Hargreaves BA, Stevens KJ, Gold GE. Metal artifact reduction with MAVRIC SL at 3-T MRI in patients with hip arthroplasty. AJR Am J Roentgenol. 2015;204(1):140-7. doi:10.2214/AJR.13.11785 - Pubmed citation
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