Christoph Amadeus Agten MD, Presenter: Nothing to Disclose

Filippo Del Grande MD, MBA, Abstract Co-Author: Nothing to Disclose

Sandro F. Fucentese MD, Abstract Co-Author: Nothing to Disclose

Samuel Blatter, Abstract Co-Author: Nothing to Disclose

Christian W. A. Pfirrmann MD, MBA, Abstract Co-Author: Advisory Board, Siemens AG Consultant, Medtronic, Inc

Reto Sutter MD, Abstract Co-Author: Nothing to Disclose

To evaluate the impact of slice-encoding for metal artifact correction (SEMAC) on image quality, findings, and therapy decision in patients with unicompartmental knee arthroplasty (UKA).

Forty-five painful UKAs were examined (1.5T-MRI, coronal STIR, sagittal proton-density (PD)-weighted sequence, each with SEMAC and high-bandwidth). Artifact size on each sequence was measured (1 reader). Image quality, anatomic depiction, and clinically relevant findings were compared between SEMAC and high-bandwidth sequences (2 readers). In 30 patients therapy decision and confidence (0=unsure, 10=sure) were retrospectively assessed by two orthopedic surgeons without MRI, with MRI using high-bandwidth, and with MRI using SEMAC. Wilcoxon test, McNemar test, Cochran’s Q, and Friedman Test were employed for statistics.

SEMAC reduced mean artifact size for STIR (11.8cm2 vs. 37.7cm2; P<.0005) and PD (16.8cm2 vs. 18.9cm2; P<.0005). SEMAC showed more blurring than high-bandwidth (P<.0005). STIR-SEMAC was better in depiction of anatomic structures around the UKA (P≤.003 and P≤.034 for reader 1 and 2, respectively), except for the anterior meniscal root for reader 2 (P=.987). PD-SEMAC was inferior in depiction of meniscal roots and cartilage (P<.0005). STIR-SEMAC revealed significantly more bone marrow edema (29 vs. 18 patients, P=.001 for reader 1 / 30 vs. 13 patients, P<.0005 for reader 2). PD-SEMAC was substantially worse in detecting meniscal lesions (6 missed, P=.031 / 9 missed, P=.004, by reader 1 and 2, respectively). Revision-surgery was the chosen therapy in 12 and 11 patients for orthopedic surgeon 1 and 2 without MRI. With high-bandwidth MRI revision-surgery was chosen in 15 and 14 patients, and with SEMAC-MRI in 19 and 14 patients (P=.005 for surgeon 1, P=.05 for surgeon 2). Mean confidence increased from 6.97 without MRI to 7.57 with SEMAC-MRI (surgeon 1; P=.01) and 6.90 to 6.93 (surgeon 2; P=.257).

STIR-SEMAC was useful for detection of bone marrow edema and influenced the orthopedic surgeons’ decisions and confidence towards surgery. PD-SEMAC was of inferior image quality and led to missed meniscal lesions in some cases.

In patients with unexplained painful unicompartmental knee arthroplasty, STIR-SEMAC may reveal bone marrow edema as a potential source of pain and is therefore useful in a knee MRI protocol.

Agten, C, Del Grande, F, Fucentese, S, Blatter, S, Pfirrmann, C, Sutter, R, Unicompartmental Knee Arthroplasty MRI: Impact of Slice-Encoding for Metal Artifact Correction MRI on Image Quality, Findings, and Therapy Decision.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14013074.html