MRI with real-time 3D ultrasound enables targeted biopsy of prostate
26 May 2011
A team at University of California Los Angeles has fused two
imaging types, MRI with real-time 3D ultrasound, to provide an
exacting method to obtain biopsy specimens from the prostate for testing
for cancer. (Also see video below)
The unique fusion method
provides a major improvement in the way prostate biopsy is performed
since the current biopsy methods were developed in the mid-1980s,
according to UCLA professor of urology Dr. Leonard S. Marks, one of the
authors of the study published in
Four UCLA departments — urology, radiology, pathology and
biomedical engineering — collaborated with the medical device
company Eigen Inc. to develop and test the technology.
"It's difficult to identify and target suspicious areas using
two-dimensional, conventional ultrasound, so urologists currently
take samples systematically from the entire prostate," said Marks.
"The advent of MRI–ultrasound fusion has led to a promising advance
in prostate imaging and biopsy targeting.
"Despite the technology revolution of the past several decades,
we are still performing prostate biopsies just the same as in the
mid-1980s," he said. "We are hopeful that new imaging methods like
MRI–ultrasound fusion may soon change that."
Many small prostate cancers are not serious health threats, and
in those cases, surveillance programs can help men avoid radical
treatments like surgery. Many smaller cancers grow so slowly that
they may never require treatment at all. The new imaging technology
could help doctors differentiate the serious cancers from the
Marks noted that the new technology may be most beneficial for
patients who fall into one of two categories: those who had prior
negative biopsies but have persistently elevated prostate-specific
antigen (PSA) levels, and "active surveillance" patients — those
with low-risk prostate cancers who are being carefully monitored
over time to see if their cancer progresses or becomes more
The study, conducted between 2009 and 2010, involved 218 men
between the ages of 35 and 87, all of whom received prostate
biopsies. Of the 218, 47 men who fell into one of the two categories
mentioned above received prostate biopsies using MRI images fused
with real-time ultrasound. These patients first received MRI scans
of the prostate that assessed three components in detecting cancer:
suspicious contrasts in tissue, abnormal cellular density and
unusual blood flow within the prostate.
"While other major cancers can be imaged within the organ of
origin, the small, compact prostate has proven elusive for a number
of reasons, such as the similarity of cancer and benign tissue and
the lack of tissue uniformity," said study author Dr. Daniel
Margolis, an assistant professor of radiology in abdominal imaging
and co-director of prostate imaging at the David Geffen School of
Medicine at UCLA. "We hope the multi-parameter MRI information, used
with the new system, will help us better distinguish problem areas
and provide the most accurate information possible."
After reviewing the MRI prostate scans, Margolis individually
graded each component and provided an overall score to gauge cancer
risk. He notes that the additional MRI information may help improve
targeting and possibly eliminate the need for taking multiple biopsy
samples. Currently, 12 areas from the entire prostate are
systematically biopsied, whether they are suspicious areas or not.
For the next step, UCLA biomedical engineer Shyam Natarajan took
the data and scores from the MRI prostate scans and, using software
created at UCLA, generated a 3-D image of the 47 patients'
prostates, which clearly showed the location of any suspicious
areas. The information was transferred to a CD that was ready for
use in the clinic during a real-time ultrasound prostate biopsy.
During the prostate biopsy, the CD was loaded into Artemis, a 3-D
prostate biopsy system that allows the stored MRI images to be
electronically transferred and fused with the real-time ultrasound,
providing a 3-D image similar to a roadmap to help guide the tiny
biopsy needle into targeted areas.
"The application of such three-dimensional imaging or modeling is
used in other fields, like animation and gaming, and is also being
used more frequently in developing medical diagnostics," said
Natarajan, an author of the study and a researcher at both the UCLA
Henry Samueli School of Engineering and Applied Science and the UCLA
Center for Advanced Surgical and Interventional Technology.
The other 171 men in the study did not undergo MRI but received
prostate biopsies in which the Artemis tracking system was attached
to the ultrasound probe, allowing their prostates to be scanned
using 3-D imaging, which may be beneficial in providing more even
distribution of the biopsy sites when using conventional ultrasound
technology, according to the study authors.
The UCLA team found that targeted biopsy was about five times
more likely to find cancer than non-targeted, systematic biopsy.
Re-biopsy of a suspicious site was found to be accurate within a few
millimeters. "These early results are promising, but more study
needs to be completed before we can conclusively show the benefit of
tracking and targeting biopsy with this new method," said Marks.
The team is also helping track the accuracy of MRI–ultrasound
fusion by studying cancerous prostates that have been removed from
study patients. The researchers can then compare the location of the
diseased tissue on the actual prostate with the MRI and ultrasound
"Using the actual prostate tissue allows us to pinpoint the exact
location of the cancer, as well as assess the cancer's nature, such
as determining if it will spread," said study author Dr. Jiaoti
Huang, a professor and director of urologic pathology in the
department of pathology at the Geffen School of Medicine. "We can
also gauge the accuracy of the MRI and ultrasound fusion scans in