Technology Fuses MRI, Ultrasound for Targeted Biopsy of Prostate Cancer

Targeted biopsy, an important development in prostate cancer diagnostics, fuses magnetic resonance imaging (MRI) with real-time three-dimensional (3D) ultrasound, providing a precise method to obtain biopsy specimens from suspicious areas in the prostate.

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 the University of California, Los Angeles (UCLA; USA) Professor of urology Dr. Leonard S. Marks, a study author.

Four UCLA departments--urology, radiology, pathology, and biomedical engineering--collaborated with the medical device company Eigen, Inc. (Grass Valley, CA, USA) to develop and evaluate the technology. The team's preliminary experiences are reported in the online May/June 2011 issue of the journal Urologic Oncology.

"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 Dr. 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. We are hopeful that new imaging methods like MRI-ultrasound fusion may soon change that."

Dr. Marks noted that the new technology might 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 aggressive.

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 codirector of prostate imaging at the David Geffen School of Medicine at UCLA. "We hope the multiparameter 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, Dr. Margolis individually graded each component and provided an overall score to gauge cancer risk. He noted that the additional MRI information might 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 phase, UCLA biomedical engineer Dr. Shyam Natarajan took the data and scores from the MRI prostate scans and, using software created at UCLA, generated a 3D 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 3D prostate biopsy system that allows the stored MRI images to be electronically transferred and fused with the real-time ultrasound, providing a 3D 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 Dr. 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 3D 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 nontargeted, systematic biopsy. Re-biopsy of a suspicious site was found to be accurate within a few millimeters. 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 fusion scans.

"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 identifying cancer."

Eigen manufacturers the Artemis device. The device was approved by the US Food and Drug Administration in May 2008, but widespread distribution of it has been postponed until further usability development, similar to that underway at UCLA, has been achieved.

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