An intraoperative 3D ultrasound system for tumor margin determination in breast cancer surgery

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The purpose of this study was to analyze the clinical utility of a portable three-dimensional ultrasound (3DUS) system to be used for surgical guidance of lumpectomy surgeries. In 11%-60% of lumpectomy surgeries, a second surgery is required to fully resect the tumor. Previous studies have used 3DUS as a guidance tool with the hope of more accuracy in resecting the entire tumor during the first surgery. However, they utilized larger systems, which are not easily integrated into the operating room. The portable 3DUS scanning system we developed consisted of a motorized "tilt" scanner coupled to a Terason t3000 portable ultrasound machine (Terason Ultrasound, Burlington, MA). The 3DUS system was evaluated by measuring agar "tumor" phantoms of known volumes and acquiring and segmenting images from nine patients undergoing lumpectomy. Experiments on simulated agar tumor phantoms have shown that our device could be used to measure objects with smooth, well-defined boundaries of known volume with an error of 3%. It was possible to view and segment estimated tumor margins from the clinical images in three dimensions. Correspondence between measurements obtained in the laboratory and the operating room varied with tumor geometry and the degree of spiculation in the ultrasound image. The measured values obtained by the system did not correspond closely with those obtained using histology. However, a more accurate histological measurement using 3D histology may provide a better basis for comparison. The results of imaging simulated agar tumor phantoms indicate the system's consistency in measuring objects of known volume and geometry. The system could be used for segmenting the approximate boundary of lumpectomy patients' breast tumors relative to inserted guide wires. The potential advantages of this system are a reduction in the number of re-excision surgeries required and a reduction in the operative time with the patient under anesthesia.