Realtime Three Dimentional Imaging Of Coronary Artery Bypass Grafting Using High-frequency Epicardial Ultrasound
Kiyotoshi Oishi, Katsuhiro Ouchi, Tomohiro Mizuno, Tatsuki Fujiwara, Hirokuni Arai.
Tokyo Medical and Dental University, Tokyo, Japan.
Objective The validity of the high-frequency epicardial ultrasound (ECUS) in coronary artery bypass graft (CABG) has been described. However, the echo image is a partial cross section and is insufficient for the evaluation of three-dimensional structure. So, we intended for visualization and evaluation of CABG anastomosis by performing the real time 3D construction of the ECUS images. Methods ECUS we have chosen was VeriQ C (MEDISTIM, Oslo, Norway) to obtain the ultrasound images, and attached the electromagnetic position-tracking sensor (trakSTAR, Ascension Technology Corp., Sherburne, Vermont, USA) to ECUS probe. We implemented the function for integrating scanned ultrasound images with positional information and making them 3D in real time with the open-source 3D Slicer application (www.slicer.org), SlicerIGT extension (www.slicerigt.org) and PLUS toolkit (www.plustoolkit.org). We evaluated this system using CABG anastomosis model, which was made with extracted pig heart. Harvested RCA was anastomosed to LAD, and normal saline was injected from the graft continuously. We scanned CABG anastomosis model and created the 3D images (Fig.A). Results Bypass graft and anastomosis evaluation using ECUS is valuable, because it describes the vessel lumen and anastomotic form more exactly. The anastomotic 3D construction was possible by volume rendering of the ultrasound images merging image stack on the z-axis with general-purpose software, but it needs too much editing time and it is unsuitable for intraoperative use. On the other hand, our method becomes able to edit the 3D image in a few minutes (Fig.B) and we can evaluate the anastomotic quality instantly. Furthermore, indications by 3D viewer or write output into 3D printer are possible. It is useful to view the anastomotic form from multidirectional angles. Conclusion Real time evaluation of the anastomotic form was enabled by 3D building of ECUS images by combining a position sensor. And it may be used for intraoperative graft evaluation in future by improving precision. LEGEND Figure.1: Real time three-dimensional imaging of coronary artery bypass graft anastomosis. (A) The system which built 3D image by the combination of ECUS and positional information sensor. (B) Scanned ECUS along LAD and made a provided image 3D in real time. 
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