Image guidance during minimally invasive cardiovascular interventions is primarily achieved based on X-ray fluoroscopy, which has several limitations including limited 3D imaging, significant doses of radiation to operators, and lack of contact force measurement between the cardiovascular anatomy and interventional tools. Ultrasound imaging may complement or possibly replace 2D fluoroscopy for intravascular interventions due to its portability, safety, and the ability of providing depth information. However, it is a challenging work to perfectly visualize catheters and guidewires in the ultrasound images. In this paper, we developed a novel method to locate the position and orientation of the catheter tip in 2D ultrasound images in real time by detecting and tracking a passive marker attached to the catheter tip. Moreover, the contact force can also be measured due to the length variation of the marker in real time. An active geometrical structure model based method was proposed to detect the initial position of the marker, and a KLT (Kanade-Lucas-Tomasi) based algorithm was developed to track the position, orientation, and the length of the marker. The ex vivo experimental results indicate that the proposed method is able to automatically locate the catheter tip in the ultrasound images and sense the contact force, so as to facilitate the operators’ work during intravascular interventions.
Research Fellow: Jin Guo
Project Investigator: Hongliang Ren
Magnetic microbubbles which can be controlled by an external magnetic field have been explored as a method for precise and efficient drug delivery. In this paper, a technique for the fabrication of microbubble encapsulated magnetic spheres is presented. The resultant magnetic spheres were subsequently imaged using ultrasound and the encapsulated microbubbles proved to appear as bright spots and resulted in enhanced ultrasound image contrast, as compared to the solid magnetic spheres which appeared dull. A tracking algorithm was then developed for the tracking of the magnetic microbubbles based on optical flow tracking. Further development of the magnetic microbubbles and tracking algorithm can lead to future use of the tracking algorithm in the case of in vivo injection of the magnetic microbubbles.
1. Loh Kai Ting, Ren Hongliang and Li Jun, Tracking Magnetic Particles under Ultrasound Imaging using Contrast-Enhancing Microbubbles, The 11th Asian Conference on Computer Aided Surgery, 2015.
Poster in BME Showcase 2015
We consider the use of wireless sensor networks to automatically track “perceptive pallets” of materials in ware-houses for the purpose of monitoring volumetric and spatial constraints. A combination of radio frequency and ultrasound chirping produces position estimates that are noisy and prone to error. To address this, we measure and characterize the ultrasound response from standard “Cricket” wireless sensor motes and beacons. We develop a non-parametric particle filtering approach to estimate trajectories of moving motes and introduce two asymmetric observation models that incorporate measured cardioid-shaped response patterns of ultrasound.
Collaborator: Automation Lab of Professor Ken Goldberg, EECS UC Berkeley