Abstract
Abstract Ultrasound compounding techniques offer the possibility to enlarge the otherwise limited field of view of ultrasound. However, existing works mainly rely on larger ultrasound sensors. In this work, we attach electromagnetic (EM) tracking sensors to small tubular echo probes, namely an intracardiac echocardiographic (ICE) probe and a transesophageal echocardiographic (TEE) transducer. The EM tracking allows, when synchronized to the ultrasound, localization of the probes in either 5 DOF (Degrees of Freedom) or 6 DOF without line-of-sight requirement. For computation of the references between the two systems, we developed a novel customized 3D-printable phantom, which is especially convenient for tubular probes that acquire images laterally. Calibration with the phantom and 3D volume reconstruction was conducted in the Plus Toolkit. The volume reconstructor uses the captured position and orientation information to fuse 2D ultrasound slices into a compounded volume. Mean calibration error is below 2.5 mm for ICE and TEE. An accuracy evaluation of the 3D reconstruction using an object of known geometry revealed that tracking with 5 DOF provides unsatisfactory results, while the combination of 6 DOF and TEE achieved a mean absolute difference of 3.08 mm. Our calibration phantom fCal-Echo1.0 is openly available at http://perk-software.cs.queensu.ca/plus/doc/nightly/modelcatalog/.
Highlights
Echocardiography is a fast, flexible, and inexpensive medical imaging modality
Different examinations range from transesophageal echocardiography (TEE), over transthoracic echocardiography (TTE) to intracardiac echocardiography (ICE), which all require different probes
In TTE, the ultrasound (US) transducer is placed on the chest to allow for a noninvasive examination of cardiac structures
Summary
Echocardiography is a fast, flexible, and inexpensive medical imaging modality. It is an invaluable tool in preoperative diagnosis, intraoperative guidance, and postoperative monitoring of patients with cardiovascular diseases. In case of TEE, a small probe is inserted in the esophagus and 2D/3D images are captured in different positions. In case of ICE, a small ultrasound probe is integrated at the tip of a catheter, which allows imaging from inside the heart. Image compounding methods are an attractive solution to increase the field-of-view. This is interesting for ICE approaches, which are often hampered by a loss of orientation during maneuvering of the catheter. The contribution of our work is threefold: (1) We integrate a novel openly available calibration phantom into an existing open-source calibration procedure to link and synchronize EM tracking with ICE and TEE probes. (3) Using the volume reconstruction plugin of the Plus toolkit, we perform a 3D-volume reconstruction of the captured 2D-slices on an object of known geometry and report the reconstruction error
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