MR Imaging of Joint Arthroplasty

Abstract

Imaging evaluation of the painful total joint arthroplasty has, in the past, been limited to conventional radiographs, arthrography, and nuclear scintigraphy. All three modalities provide some clinical information regarding the status of the prosthesis, adjacent bone, and surrounding soft tissues but are hampered by poor specificity, particularly nuclear scintigraphy. Magnetic resonance imaging, using optimized pulse sequences to reduce the susceptibility artifact generated by the arthroplasty, can provide clinically relevant information regarding the prosthesis as well as the surrounding bone, soft tissues, and neurovascular structures.

Magnetic resonance imaging of the postoperative hip

“…Technical options available on most MR units to reduce magnetic susceptibility include use of a wider receiver bandwidth, thereby increasing the strength of the readout gradient (16,17). Orienting the frequency-encoding direction along the longitudinal axis of the prosthesis will further subjectively minimize the susceptibility artifact from the surrounding anatomy (14).…”

“…Increasing the number of excitations will increase the scan time, but will also increase image signal-to-noise ratio (SNR). This will offset the SNR reducing effects of wider receiver bandwidths (16). Additionally, using a wide receiver bandwidth will reduce the interecho spacing, allowing longer echo train lengths and reduction in scan time, but at the cost of reduced SNR.…”

“…Imaging at lower field strength will directly reduce susceptibility artifact (8,16) and SNR. Susceptibility artifact is directly proportional to magnetic field strength and thus imaging at 3T should be avoided.…”

“…Fast spin echo (FSE) imaging is preferred over routine spin echo imaging in the presence of metallic hardware due to the increased efficiency encountered with these sequences compared to the standard spin echo (16). Gradient echo sequences should be avoided since they lack the 180 refocusing pulse of a spin echo sequence.…”

“…The rapid intravoxel dephasing of spins results in significant signal loss in the image and increased artifacts (18). When fat suppression is required, fast inversion recovery sequences are preferred, as they are less sensitive to local field inhomogeneities in the presence of metallic hardware, despite having a lower SNR (16).…”