Implant detectibility of intervertebral disc spacers in post fusion MRI: evaluation of the MRI scan quality by using a scoring system--an in vitro study.
BACKGROUND
Intervertebral spacers for anterior spine fusion are made of different materials, such as titanium and cobalt chromium alloys and carbon fiber-reinforced polymers. Implant-related susceptibility artifacts can decrease the quality of MRI scans. The aim of this cadaveric study was to demonstrate the extent that implant-related MRI artifacting affects the postfusion differentiation of determined regions of interest (ROIs).


METHODS
In six cadaveric porcine spines, we evaluated the postimplantation MRI scans of a titanium, cobalt-chromium and carbon spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into ROIs to characterize the spinal canal as well as the intervertebral disc space. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists the artifact-affected image quality of the median MRI slice was rated on a score of 0-3. A maximum score of 18 points (100%) for the determined ROIs was possible.


RESULTS
Turbo spin echo sequences produced the best scores for all spacers and the control. Only the control achieved a score of 100%. For the determined ROI maximum scores for the cobalt-chromium, titanium and carbon spacers were 24%, 32% and 84%, respectively.


CONCLUSIONS
By using favored T1 TSE sequences the carbon spacer showed a clear advantage in postfusion spinal imaging. Independent of artifact dimensions, the scoring system used allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.
Ernstberger
Thorsten
T
Department of Orthopaedic Surgery, University of Göttingen, Robert-Koch-Strasse 40, 37075 Göttingen, Germany. ternstberger@med.uni-goettingen.de
Heidrich
Gabert
G
Schultz
Wolfgang
W
Grabbe
Eckhardt
E
D000497:Alloys; D000818:Animals; D016477:Artifacts; D002102:Cadaver; D002244:Carbon; D000077482:Carbon Fiber; D002858:Chromium Alloys; D004867:Equipment Design; D016268:Internal Fixators; D008279:Magnetic Resonance Imaging; D013123:Spinal Fusion / Q000295:instrumentation*; D013552:Swine; D013904:Thoracic Vertebrae; D014025:Titanium
D000497:Alloys; D000077482:Carbon Fiber; D002858:Chromium Alloys; C031462:titanium alloy (TiAl6V4); D002244:Carbon; D014025:Titanium