Learning objectives
We present a review of different approaches and MRI sequences used for reducing metal associated artifacts to obtain clinically relevant information.We discuss a systematic approach to interpret MRI scans with metallic implants.
Background
Metal associated artifacts arise due tothe differencein magnetic properties of the tissues in the body (muscle,
ligaments,
fat,
bone- that are diamagnetic and contain variable water protons) and metal (that are markedly paramagnetic or ferromagnetic and typically do not contain water protons).
Types of metal associated artifacts
Geometric Distortion
The effect of the metal prosthesis in the magnetic field leads to geometric distortion,
that in the frequency encoding direction leads to in-plane distortion,
(curved appearance of straight lines) while that in the slice-selective direction leads...
Findings and procedure details
Systematic Approach to readMRI images with metal associated artifacts
1.
Don’t Panic
2.
Look at the signal on two different planes
If it seen on only one plane,
and not the other,
it might be artefactual.
If it is seen on two planes,
it is more likely real.
(fig 3)
3.
Look at the signal on two different sequences
Bright signal on STIR,
bright signal on T1 implies an artefact
Bright signal on STIR,
dark signal on T1 implies real signal abnormality.
(Fig 3)
4....
Conclusion
Tips and tricks for acquisition anda consistentproblem solving approach helps in imaging.
A systematic approach to interpretation of MRI scans with metal associated artifacts (including looking at two planes,
and looking at atleast two different image contasts) helps in finding the cause of symptoms.
Lastly,
but not the least,
Don't Panic!
References
Astary,
Garrett W.,
Marcus K.
Peprah,
Charles R.
Fisher,
et al. 2013 MR Measurement of Alloy Magnetic Susceptibility: Towards Developing Tissue-Susceptibility Matched Metals.
Journal of Magnetic Resonance (San Diego,
Calif.: 1997) 233: 49–55.
Briant-Evans,
T.
W.,
N.
Lyle,
S.
Barbur,
et al.
2015.
A Longitudinal Study of MARS MRI Scanning of Soft-Tissue Lesions around Metal-on-Metal Total Hip Arthroplasties and Disease Progression.
The Bone & Joint Journal 97-B(10): 1328–1337.
Jungmann,
Pia M.,
Christoph A.
Agten,
Christian W.
Pfirrmann,
and Reto Sutter 2017Advances in MRI around Metal....