Ashok Srinivasan MD, Presenter: Nothing to Disclose

Ellen Grace Hoeffner MD, Abstract Co-Author: Nothing to Disclose

Gaurang V. Shah MD, Abstract Co-Author: Nothing to Disclose

Mohannad Ibrahim MD, Abstract Co-Author: Nothing to Disclose

Suresh K. Mukherji MD, Abstract Co-Author: Consultant, Koninklijke Philips Electronics NV

1. To evaluate the utility of virtual keV images (gemstone spectral imaging) in metal artifact reduction in the post-fusion spine 2. To compare the CT dose indices between spine CTs performed with and without gemstone spectral imaging

This IRB approved retrospective study included included consecutive post-fusion spine CTs from 2009-2012 performed as clinical studies on a 64 slice dual energy Gemstone spectral CT (Discovery CT750 HD, GE Medical Systems, Milwaukee, WI). Studies were post processed on the GE-AW workstation version 4.4 by a board certified neuroradiologist. The monochromatic feature was used to create virtual images from 40 keV to 140 keV. Our preliminary experience had shown that keVs higher than 100 were helpful in reducing metal artifact; hence, the reader used these higher energy levels to analyze the scans. Each transpedicular screw was analyzed on a 4 point scale for artifacts at the standard 70keV and at higher virtual keVs (100 to 140) :- 1- Poor visualization and/or significant artifact 2- Fair visualization and/or moderate artifact  3- Good visualization and/or mild artifact  4- Excellent visualization and/or minimal artifact The grading of the screws were compared using the non-parametric Wilcoxon signed rank test to detect if there were any significant differences in visualization between standard keV and virutal higher keVs. In addition, the CT dose indices of the scans performed with GSI were compared with 10 randomly chosen spine CTs in patients with spinal hardware performed in the same time period without GSI. Mann whitney test was used for this purpose.

89 transpedicular screws in 9 patients were identified (mean age:54 yrs): 18 C, 12 T, 49 L and 10 S. The mean scores for images at virtual high keVs was significantly higher than the scores at 70 keV (p <0.000) using the non-parametricx Wilcoxon matched pairs signed rank test: Virtual high keV: 3.26 (+ 0.67); 70 keV: 2.25 (+ 0.85).  The average CTDI for the GSI scans was 29.5 mGy compared to 42 mGy for non-GSI spine CTs performed in the same period (p=0.03).     

Virtual high keVs generated on GSI help in artifact reduction and better hardware assessment in the post fusion spine

Metal artifact reduction using gemstone spectral CT imaging in the spine helps in better visualization of the hardware and its complications with a lower CTDI.

Srinivasan, A, Hoeffner, E, Shah, G, Ibrahim, M, Mukherji, S, Optimizing Hardware Visualization in the Post-Fusion Spine: Early Experience with Gemstone Spectral Dual Energy CT.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12022272.html