New Guidance System Could Improve Minimally Invasive Surgery
Mar 27, 2014 - 1:11:52 PM



"Imaging in the operating room opens new possibilities for patient safety and high-precision surgical guidance," says Jeffrey Siewerdsen, Ph.D., a professor of biomedical engineering in the Johns Hopkins University School of Medicine. "In this work, we devised an imaging method that could overcome traditional barriers in precision and workflow. Rather than adding complicated tracking systems and special markers to the already busy surgical scene, we realized a method in which the imaging system is the tracker and the patient is the marker."

Siewerdsen explains that current state-of-the-art surgical navigation involves an often cumbersome process in which someone - usually a surgical technician, resident or fellow - manually matches points on the patient's body to those in a preoperative CT image. This process, called registration, enables a computer to orient the image of the patient within the geometry of the operating room. "The registration process can be error-prone, require multiple manual attempts to achieve high accuracy and tends to degrade over the course of the operation," Siewerdsen says.



"The breakthrough came when we discovered how much geometric information could be extracted from just one or two X-ray images of the patient," says Ali Uneri, a graduate student in the Department of Computer Science in the Johns Hopkins University Whiting School of Engineering. "From just a single frame, we achieved better than 3 millimeters of accuracy, and with two frames acquired with a small angular separation, we could provide surgical navigation more accurately than a conventional tracker."


An additional advantage of the system, Uneri says, is that the two X-ray images can be acquired at extremely low dose of radiation - far below what is needed for a visually clear image, but enough for the algorithm to extract accurate geometric information.


A. Jay Khanna, M.D., an associate professor of orthopaedic surgery and biomedical engineering at the Johns Hopkins University School of Medicine, evaluated the system in its first application to spine surgery. "Accurate surgical navigation is essential to high-quality minimally invasive surgery," he says. "But conventional navigation systems can present a major cost barrier and a bottleneck to workflow. This system could provide accurate navigation with simple systems that are already in the OR and with a sophisticated registration algorithm under the hood."

Ziya Gokaslan, M.D., a professor of neurosurgery at the Johns Hopkins University School of Medicine, is leading the translational research team. "We are already seeing how intraoperative imaging can be used to enhance workflow and improve patient safety," he says. "Extending those methods to the task of surgical navigation is very promising, and it could open the availability of high-precision guidance to a broader spectrum of surgeries than previously available."



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