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
Guide wires are commonly used to assist surgeons during vascular surgery. Guide wires are usually the first to be placed, eventually allowing easy exchange of surgical tools to the target site. The surgeon has to manually control and manipulate the guide wire to the target region. This process is complicated by the tortuous nature of the vasculature and is made worse as the surgeon has limited vision (constant need to switch between overlay angiographs) and control over the guide wire tip (controlling the distal tip from the proximal end). For the first time towards minimally invasive Arteriovenous Fistula Angioplasty Procedures, we aim to improve the controllability of the in vivo guide wire via the attachment of a magnetic tip to the distal end of the guide wire, which under the control of external magnetic field generators can deflect the magnetic tip. This controlled deflection translates to the selection of entrance angle for the guide wire tip, affording distal control.
This is especially useful for navigating around stenosis which is common for patients with Arteriovenous(AV) Fistula. The repeated use of the fistula during dialysis has been claimed as a cause for the high occurrence of stenosis (due to tissue scaring from access). Fistulas and their grafts are however still preferred over other renal access in most situation due to its lower risk of infections. Our proposed system here can improve the controllability, safety and speed of current procedures and can enable AV-Fistula Angioplasty Procedures to be shifted to out-patient clinics.
Student: Bok Seng Yeow
Research fellow: Jinji Sun
Project Investigators: Hongliang Ren, Jackie Ho
Yeow, B. S.; Sun, J.; Ho, J. & Ren, H. Towards Magnetically Actuated Guide-wire Steering in Arteriovenous Fistula Angioplasty Procedures IEEE Conference on Real-time Computing and Robotics (RCAR), IEEE, 2016, best student paper.