Ultrasound (US) is commonly used to guide antenna placement for microwave ablation procedures into the tumor because of its direct, real-time visualization capability and lack of ionizing radiation. Following ablation, a contrast-enhanced biphasic CT (CECT) is required to verify the effectiveness of the ablation as ablation delineation is difficult with conventional B-mode US.
Recently our lab has developed an alternative US imaging modality for visualizing liver masses and ablated regions named electrode displacement elastography (EDE). However, comparison of EDE derived delineations of ablated regions with the current clinical gold-standard CECT is necessary to verify EDE viability in clinical settings. These in vivo datasets therefore require CT-US registration for a direct comparison of EDE with CECT. Recently our lab has developed a method for fusing intraoperative CT volumes with US B-mode for potentially evaluating the efficacy of EDE utilizing a concept named ‘CT virtual slicing’. The CT virtual slice is obtained from a 3D CT volume by co-locating to the US imaging plane and accounting for local deformations present due to physiological motion utilizing electrode and anatomical landmarks. This work paves the way for direct comparison of ablation areas determined using US based electrode displacement elastography to CECT, the current gold standard for assessing minimally invasive thermal ablation of tumors in patients.
(a) Transverse slice with the antenna region highlighted in blue. (b) CT volume as a stack of transverse slices with the antenna location highlighted within the blue cube. (c) Zoomed in region of the antenna location in the CT volume with the antenna shown in green. (d) US B-mode image from patient after ablation. (e) Zoomed in CT volume with the two vectors creating the virtual slice plane highlighted in green and blue for the vector along the direction of the antenna and the vector projected onto the xy-plane. (f) The resultant CT virtual slice after affine transformation in green transposed onto the red US B-mode image. (g) The entire CT virtual slice collected pre-ablation. (h) The CT virtual slice estimated post-ablation.
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