Amit Gupta MD, Presenter: Nothing to Disclose

Naveen Subhas MD, Abstract Co-Author: Research Grant, Siemens AG

Sahar Shiraj MD, Abstract Co-Author: Nothing to Disclose

Joshua Matthew Polster MD, Abstract Co-Author: Nothing to Disclose

Nancy A. Obuchowski PhD, Abstract Co-Author: Research Consultant, Siemens AG Research Consultant, Hologic, Inc Research Consultant, CVUS Research Consultant, Elucid Bioimaging Inc

Andrew Primak PhD, Abstract Co-Author: Employee, Siemens AG

Joseph Iannotti, Abstract Co-Author: Consultant, Johnson & Johnson Consultant, Zimmer Holdings, Inc Consultant, Tornier, Inc Royalties, Johnson & Johnson Royalties, Zimmer Holdings, Inc Royalties, Tornier, Inc Royalties, Biomet, Inc Royalties, MTF Royalties, Wolters Kluwer nv Royalties, Reed Elsevier

To compare a new prototype CT reconstruction technique for reduction of artifacts from metal implants called Iterative Metal Artifact Reduction (IMAR) with standard filtered back projection (FBP), both quantitatively and qualitatively.

40 patients undergoing total shoulder arthroplasties were enrolled in a prospective study. Preoperative CT scans were performed with varying standard clinical protocols with FBP reconstructions. All postoperative scans were performed on one of three CT scanners (Definition Flash, Definition Edge or Definition AS+, Siemens, Erlangen, GE) with a standard protocol (140 kVp, 300 mAs, 0.6 mm collimation, effective pitch 0.5 - 0.9). FBP and IMAR images reconstructed using same kernel (B30 - smooth), slice thickness (2 mm) and slice interval (2 mm). After randomization and blinding, 2 musculoskeletal radiologists independently evaluated the bone (glenoid), bone metal interface and soft tissue (supraspinatus and subscapularis tendons) structures in each case. Using a 10 point scoring system, each structure was evaluated for the degree of streak artifact (1=none to 10=marked) and diagnostic confidence (1=no confidence to 10=high confidence). The accuracy and variance of attenuation near hardware was also measured quantitatively in the bone (glenoid), soft tissue (deltoid muscle) and subcutaneous fat as the absolute difference between the mean HU within a region of interest (ROI) near hardware on the postoperative scan and the mean HU within a ROI in the same location on the preoperative scan.

Qualitatively, both readers graded IMAR images with significantly lower streak artifact and significantly higher diagnostic confidence scores than FBP images for all of the structures (p<0.001) (Table 1a). Quantitatively, the attenuation near hardware was statistically significantly closer to preoperative attenuation for IMAR than FBP (p<0.001) (Table1b) and the variance between preop and postop attenuation was significantly lower for IMAR than FBP.

IMAR was superior to FBP in reducing metal artifact both qualitatively and quantitatively in patients with total shoulder arthroplasties with more accurate and less variable attenuation, less streak artifact and improved diagnostic confidence.

IMAR is a promising new CT metal artifact reduction technique that improves visualization of tissues near hardware compared to standard CT technique.

Gupta, A, Subhas, N, Shiraj, S, Polster, J, Obuchowski, N, Primak, A, Iannotti, J, Comparison of New CT Metal Artifact Reduction Technique to Filtered back Projection for Evaluation of Shoulder Arthroplasties: A Prospective Study.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14007193.html