Engineering Expertise Aids Radiofrequency Probe Project
 Filip Banovac, M.D. Georgetown University |
 Kevin Cleary, Ph.D. Georgetown University |
Combining his biomedical engineering background with an RSNA Research & Education (R&E) Grant, Georgetown University researcher Filip Banovac, M.D., developed a novel system that uses real-time electromagnetic position sensing of the needle tip to aid with precision guidance into a liver tumor.
Data from that research led to Dr. Banovac's current project developing physician-assist systems that incorporate visualization and instrument tracking to aid the physician in minimally invasive interventions.
"The RSNA study channeled very nicely into further research in this field," said Dr. Banovac, an associate professor of radiology and chief of vascular interventional radiology and clinical director for the Computer Aided Interventions and Medical Robotics Division of the Imaging Science and Information Systems (ISIS) Center at Georgetown University in Washington, D.C.
Dr. Banovac's 2001 study, "Development and Validation of New Magnetic Position Sensing Technology Used to Assist in Precise Placement of Radiofrequency Probes during Hepatic Tumor Ablation," was funded by a $30,000 RSNA Research Resident Seed Grant.
At the time, radiofrequency ablation of primary and metastatic liver tumors was becoming an accepted alternative to surgical resection, said Dr. Banovac. Despite promising applications in liver cancer treatment, radiofrequency ablation had shortcomings including probe positioning and real-time treatment monitoring.
Tumors larger than 4–5 cm required multiple probe repositioning to achieve adequate tumor margins. However, probe repositioning using ultrasound—the most common guidance and monitoring modality—can be technically difficult, he said.
Although conventional contrast-enhanced CT provided excellent pre-procedural visualization of the tumor and relative anatomic relationships to other structures, it was not a real-time modality and required multiple "blind" repositionings with repeated re-scanning for confirmation of the probe location, Dr. Banovac said.
System Uses Magnetic Position Sensing
Drawing on his background in biomedical engineering, Dr. Banovac proposed a system that used real-time magnetic position sensing of the needle tip.
The system consisted of a magnetic field generator, a compatible custom-made needle/stylette combination that could be tracked using the position sensing system, as well as software used to register, plan the path to the tumor and provide that real-time visual assistance.
The research was not without challenges.
Researchers compared the accuracy of needle placement into silicone liver tumors within a liver phantom that simulated respiration. Residents and faculty placed the needle into multiple silicone tumors using both conventional CT guidance and the new magnetic position sensing system and researchers compared the difference. Finally, researchers performed swine studies comparing the same task in an anesthetized animal.
There was no statistical difference in the planning time, procedure time or accuracy between experienced and inexperienced operators, according to the study. But researchers encountered overall errors in system accuracy, altering the second goal of the study, Dr. Banovac said.
Because software modifications could not rectify the error, researchers opted not to compare magnetic tracking to CT placement. CT placement may require multiple repositioning of the needle, but ultimately the target would be reached and comparison in accuracy would be meaningless, said Dr. Banovac.
"At that time, the magnetic system did not function well in a CT environment," he continued. "Electromagnetic fields created in the CT suite interfered with the signal of our electromagnetic device. However, the magnetic system has since improved and we have now started a CT-based clinical trial."
Nevertheless, the research yielded advancements, said Dr. Banovac. "We still evaluated the ability of the system to aid experienced and inexperienced radiologists in needle placement and compare the two groups."
Research Continues on Medical Robotics
Preliminary data from that research are the basis for Dr. Banovac's current Computer Aided Interventions and Medical Robotics Project focusing on developing physician-assist systems for precision placement and manipulation of surgical instruments.
Goals of the project headed by Kevin Cleary, Ph.D., director and associate professor at ISIS, are the use of medical robotics for precision needle placement in perispinal nerve and facet blocks and magnetic tracking of instruments. The research is funded by the U.S. Army and the National Institutes of Health.
"One long-term goal is to define what precision is needed for these procedures and to develop methods for characterizing the precision attainable with this new technology," Dr. Banovac said. "In a related effort, we are investigating the problem of respiratory motion. The characterization of respiratory motion and compensation for its effects is another long-term goal."
Researchers recently received conditional approval for an FDA investigational device exemption to use a joystick-controlled robot in a randomized clinical trial for needle placement in perispinal nerve and facet blocks. Additionally, animal studies are planned on a liver respiratory motion simulator.
"We hope our systems will help physicians complete these procedures in a more accurate manner," Dr. Cleary said.
Although less invasive procedures are beneficial to patients, they require a great deal of skill for physicians, said Dr. Cleary, also the principal investigator for the Image-Guided Surgery Toolkit, a high-level, component-based framework that provides a common functionality for image-guided surgery applications.
Because he bridges the medical and engineering worlds, researchers like Dr. Banovac are vital to this line of research because, Dr. Cleary said.
"Dr. Banovac's engineering background has positioned him well," said Dr. Cleary, who also trained as a mechanical engineer with a background in systems engineering and robotics.
Grant Provided Vital Start
The initial data from the RSNA-funded research was necessary to securing funding for their current research, according to Drs. Cleary and Banovac.
"The R&E Foundation grants provide a vital start at a time when it is difficult to secure larger grants without preliminary data," said Dr. Cleary.
Dr. Banovac agreed, pointing out the springboard effect the grants provided. "It's seed money that really enables young scientists who wouldn't otherwise have the funds to obtain preliminary data and go for bigger grants."
"The initial RSNA grant also clarified for me that I wanted an academic career," added Dr. Banovac.
Subsequently, Dr. Banovac served as the scientific advisor to Amy White, M.D., whose RSNA grant-funded research, "Uterine Artery Embolization: The Role of Postembolization Abdominal Aortography and Associated Patient Radiation Exposure," was published in the July 2007 edition of Radiology.
"Mentoring continues the pipeline of education and research," said Dr. Banovac.
2010 RSNA Research & Education Foundation Board of Trustees Announced
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In 2010, the RSNA Research & Education Foundation will advance its mission through funding radiologic research and education. In its 25 years, the Foundation has awarded 760 grants, totaling nearly $30 million. Members of the 2010 Board of Trustees: (top row, left to right) Jack E. Price, chair, Hedvig Hricak, M.D., Ph.D., Dr. h.c., Burton P. Drayer, M.D., James P. Borgstede, M.D., Valerie P. Jackson, M.D., G. Scott Gazelle, M.D., Ph.D., Sarah S. Donaldson, M.D. (bottom row, left to right) R. Gilbert Jost, M.D., treasurer, Theresa C. McLoud, M.D., chair-elect, Vijay M. Rao, M.D., E. Russell Ritenour, Ph.D., secretary; (not present, right) Richard L. Ehman, M.D. |
