Master of Engineering Science
Dr. Terry M. Peters
In minimally invasive navigated mitral valve repair surgery, the spatial calibration of the trans-esophageal echocardiography (TEE) ultrasound probe to the magnetic tracking system is an essential requisite. The standard calibration approach requires scanning a specialized phantom prior to the surgery, which is associated with the scaling mismatch issue. Preoperative estimation of the speed-of-sound at the target site of surgery is impractical as it varies among individual patients, leading to significant calibration errors during surgery.
In order to resolve this issue, we propose an un-precedented method of `in-situ' ultrasound calibration, utilizing the tracked surgical tool, which is scanned by the bi-plane ultrasound while the tool is introduced into the left ventricle of the heart. In this method the ultrasound probe is calibrated based on the high-quality 2D bi-plane images, and the ultrasound reflection of the tool is being automatically segmented. In addition, we propose an `online 3D' ultrasound calibration, which is derived from the bi-plane calibration followed by the fixed relationship between the TEE bi-plane and the 3D coordinate systems. The intrinsic transform is inferred based on the internal parameters of the imaging system. Note that calibration of the bi-plane and 3D ultrasound imaging modes are essential throughout the surgical procedure for the targeting and positioning tasks. Our approach achieved sub-millimeter accuracy in a simulated surgical environment and compensated for the correct speed-of-sound of the target medium. This was obtained within the limited range of movement available for manipulating the tool and the TEE probe during the process.
Faraz, Azharhosein, "In-situ Ultrasound Calibration" (2016). Electronic Thesis and Dissertation Repository. 3851.