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Published on: October 16, 2014
Dual-energy CT fusion imaging improves ice-ball visualization in bone during spinal cryoablation in porcine cadavers
Djamel Dabli1, Wissem Nabi2, Pierre Viala2
1IMAGINE UR UM 103, Montpellier University, Department of Medical Imaging, Nîmes University Hospital, Nîmes, France. Djamel.dabli@chu-nimes.fr.
Objective:
We evaluated ex vivo feasibility of ice-ball visualization during bone cryoablation using dual-energy computed tomography (DECT).
Materials And Methods:
This ex vivo study included three porcine cadavers on which cryoablation was performed on four vertebrae. Spectral DECT acquisitions were made at 0 and 10 min after ablation. Conventional images, virtual monoenergetic images (VMIs) at 50 keV, electron density (ED), effective atomic number (Zeff) and virtual non-calcium (VNCa) images were generated. Two radiologists assessed visibility and delineation of the ice-ball using a 4-point Likert scale. Quantitative analyses were made on HU VMI, VNCa noted HU*, ED, and Zeff in bone and adjacent tissues. Fused ED and VNCa images were assessed for each vertebra. For one pig, the fused ED and VNCa images were compared with post-ablation magnetic resonance imaging (MRI).
Results:
For each pig, the ice-ball was visible in soft tissues on all spectral images except on Zeff images. The best contour delineation was observed on ED images for soft tissues, whereas the ice-ball was detectable in bone only on VNCa images, with poorer but acceptable contour delineation. Significant (p ≤ 0.039; effect size (ES) ≥ 0.84) changes in HU and ED were observed for the adjacent soft tissue. For bone, significant (p ≤ 0.043; ES ≥ 0.073) changes were found of ED and HU* on VNCa. ED/VNCa fusion improved ice-ball delineation in bone, confirmed by comparison with MRI.
Conclusion:
The fusion of spectral ED and VNCa images could show potential in improving the visualization of the ice-ball during bone cryoablation.
Relevance Statement:
Fusion of electron density and virtual non-calcium images enhances the ice-ball visualization in bone during spinal cryoablation.
Key Points:
The lack of visibility of the ice-ball in the bone during cryoablation represents a limitation for the safety of adjacent structures at risk. In bone, the ice-ball was detectable only on virtual non-calcium (VNCa) images, but the quality of its contour delineation was poorer. Electron density and VNCa fusion images improved ice-ball visualization and delineation in bone, as confirmed by comparison with MRI.
