CONTACT: TOM MOORE
Joint Office for Planning, Marketing and Communications
8788 John Pappajohn Pavilion
Iowa City IA 52242
Release:Oct. 4, 2002
NOTE TO EDITORS: Ryken will participate in a news conference about this subject
from 10:30 to 11:30 a.m. (Pacific Time) Thursday, Oct. 8 in the ACS press
conference room in the North Hall registration area of the Moscone Convention
Center in San Francisco.
UI neurosurgeons to present findings at national meeting
University of Iowa Health Care neurosurgeons will discuss research findings
from their study of an advanced technology that may enhance outcomes for patients
with brain tumors during the upcoming American College of Surgeons Clinical
San Francisco Oct. 6-10.
The commercially available computerized image-guided neurosurgery system
links sonograms with magnetic resonance imaging (MRI) scans to produce a highly
detailed roadmap of a patient's brain. As a result, the surgeons are able
to track the actual movement of surgical instruments as they operate on brain
tissue, thus increasing their assurance that they have completely excised
"We don't have to wait for a postoperative image to know if we removed
all of a tumor. We can be more confident when we walk out of the operating
room that we have accomplished what we set out to do," said Timothy C.
Ryken, M.D., UI associate professor of neurosurgery.
The image-guided surgery system takes advantage of the immediacy of ultrasound
and the precision of MRI. Ultrasound is an inexpensive way of obtaining imaging
information during surgery. Surgeons can pass an ultrasound probe directly
over the surgical field and obtain real-time images of a patient's anatomy,
but the resolution of ultrasound images is poor. Because of the grainy quality
of sonograms, surgeons often cannot distinguish between normal and abnormal
"Some tumors are not very discrete or easily recognized by ultrasound
alone," Ryken explained.
MRI performed with intravenous contrast media is highly definitive. Contrast
material (a chemical that is taken up by, and alters the appearance of, abnormal
structures in the body) travels to and enhances the sites of brain tumors
so they appear as white masses on MRI scans. However, having a dedicated MR
scanner to identify brain tumors in patients during surgery is extremely expensive.
Furthermore, MR imaging during surgery requires surgeons to use special,
non-metallic instruments. Therefore, surgeons commonly have to rely on slices
of static MR images that were obtained preoperatively to identify tumors.
With the computerized image-guided neurosurgery system that marries ultrasound
and MRI, Ryken and his colleagues can view both intra-operative sonograms
and preoperative MRI data at the same time on the same operating room computer
workstation. The system's software reconstructs the information from the MRI
that corresponds to the spot where the surgeon is holding the ultrasound probe.
The system also compensates for the inevitable shift of tissue that occurs
during brain surgery, which interferes with the interpretation of preoperative
MRI scans and intra-operative findings.
"When we have a patient in the MRI scanner, the brain is fixed and solid
within the cranium. During surgery, we have to remove a part of the skull
to reach the brain. Depending on the position of the craniotomy, the degree
of atmospheric pressure and the severity of the patient's condition, brain
tissue may bulge out or sink away. The tumor may now be two to four centimeters
away from where we would have predicted it to be, based on the preoperative
MRI scan," Ryken said.
Imaging information from the system also altered the surgical approach to
treatment in some patients, Ryken added.
"There were times when I thought I was finished resecting a tumor but
then went back and took some more tissue out because of what the ultrasound
and MR images showed," he said.
Ryken and his colleagues have performed approximately 200 intra-cranial
procedures using the intra-operative image-guided system.
"The preoperative MRI and intra-operative ultrasound aren't linked
perfectly, so the system doesn't replace the surgeons judgment. It is
still a tool," Ryken emphasized. He also noted that researchers still
need to determine how the system will translate into improved long-term outcomes
Manali Barua, M.D., and John Haller, Ph.D., were also involved in the study
of patients with metastatic brain tumors.
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the University of Iowa Roy J. and Lucille A. Carver College of Medicine and
UI Hospitals and Clinics and the patient care, medical education and research
programs and services they provide. Visit UI Health Care online at www.uihealthcare.com.