Abstract No. 281: 3D ultrasound-guided percutaneous microwave ablation of hepatocellular carcinoma tumors

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Microwave (MW) thermal ablation permits large, uniform burn volumes through synergistic placement of multiple probes; however, proper MW thermal induction requires that the probes be parallel and at equal insertion depth. Guidance and confirmation of the placement of multiple probes is difficult on 2D US and costly when performed entirely within the CT suite. We have designed and demonstrated a handheld 3D US system as an affordable volumetric imaging tool for accurate MW probe guidance. Our 3D US system is a convenient handheld device that incorporates mechanical translation and tilt sector sweeping of any standard 2D US probe to acquire volumetric images. Each mechanical function is operational independently or may be combined for compounded probe movements that allow for a wide field-of-view (FOV) acquisition. Ten patients with localized HCC were enrolled in our ethics board approved study. Each patient underwent percutaneous MW ablation of one or more lesions using both intra-operative 3D US and CT for probe guidance. Intra-operative 3D US and CT scans were acquired concurrently for direct geometric comparison and probe placement validation. A total of 11 tumors (diameter range: 1.0-4.1 cm) were successfully ablated without any requiring re-intervention. US volumes acquired with the compound scanner motion had a FOV of 17 cm in the direction orthogonal to the 2D US image plane at the depth of 16 cm. Assessment of the MW probe position under 3D US was similar to that of CT. For cases requiring multiple MW probes, assessment for probe parallelity was enhanced within our 3D US system, as oblique slicing of the 3D US image enabled visualization of multiple probes in a single US plane. The total volume acquisition time of <8 seconds was well tolerated in a single breath hold for all patients. We developed a handheld, compound motion 3D US system capable of wide FOV imaging and demonstrated its utility for MW probe guidance. The assessment of the relative parallelity and insertion depths for multiple MW probes with 3D US was comparable to that of CT. Therefore, 3D US guidance may provide a more affordable and non-ionizing alternative to CT probe guidance.