KEYWORDS: 3D image processing, Tumors, Computed tomography, Ultrasonography, Liver, 3D metrology, 3D acquisition, 3D modeling, Radiofrequency ablation, Microwave radiation
Image-guided percutaneous ablation is the standard treatment for focal liver tumors deemed inoperable and is commonly
used to maintain eligibility for patients on transplant waitlists. Radiofrequency (RFA), microwave (MWA) and cryoablation
technologies are all delivered via one or a number of needle-shaped probes inserted directly into the tumor.
Planning is mostly based on contrast CT/MRI. While intra-procedural CT is commonly used to confirm the intended
probe placement, 2D ultrasound (US) remains the main, and in some centers the only imaging modality used for needle
guidance. Corresponding intraoperative 2D US with planning and other intra-procedural imaging modalities is essential
for accurate needle placement. However, identification of matching features of interest among these images is often
challenging given the limited field-of-view (FOV) and low quality of 2D US images. We have developed a passive
tracking arm with a motorized scan-head and software tools to improve guiding capabilities of conventional US by large
FOV 3D US scans that provides more anatomical landmarks that can facilitate registration of US with both planning and
intra-procedural images. The tracker arm is used to scan the whole liver with a high geometrical accuracy that facilitates
multi-modality landmark based image registration. Software tools are provided to assist with the segmentation of the
ablation probes and tumors, find the 2D view that best shows the probe(s) from a 3D US image, and to identify the
corresponding image from planning CT scans. In this paper, evaluation results from laboratory testing and a phase 1
clinical trial for planning and guiding RFA and MWA procedures using the developed system will be presented. Early
clinical results show a comparable performance to intra-procedural CT that suggests 3D US as a cost-effective
alternative with no side-effects in centers where CT is not available.
KEYWORDS: 3D image processing, Tumors, Computed tomography, 3D metrology, Liver, Transducers, 3D scanning, 3D modeling, Image segmentation, Medium wave
Two-dimensional ultrasound (2D US) imaging is commonly used for diagnostic and intraoperative guidance of
interventional abdominal procedures including percutaneous thermal ablation of focal liver tumors with radiofrequency (RF) or microwave (MW) induced energy. However, in many situations 2D US may not provide enough anatomical detail and guidance information. Therefore, intra-procedural CT or MR imaging are used in many centers for guidance purposes. These modalities are costly and are mainly utilized to confirm tool placement rather than guiding the insertion. Three-dimensional ultrasound (3D US) has been introduced to address these issues. In this paper, we present our integrated solution to provide 3D US images using a newly developed mechanical transducer with a large field-ofview and without the need for external tracking devices to combine diagnostic and planning information of different modalities for intraoperative guidance. The system provides tools to segment the target(s), plan the treatment, and detect the ablation applicators during the procedure for guiding purposes. We present experimental results used to ensure that our system generates accurate measurements and our early clinical evaluation results. The results suggest that 3D US used for focal liver ablation can provide a more reliable planning and guidance tool compared to 2D US only, and in many cases offers comparable measurements to other alternatives at significantly lower cost, faster time and with no harmful radiation.
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