WASHINGTON, D.C.—An imaging technique that combines MRI and transrectal ultrasound (MRI-TRUS) is feasible for performing targeted prostate biopsies. This approach may have some advantages over traditional biopsy methods, researchers said here at the Society of Interventional Radiology annual meeting.
The approach uses electromagnetic tracking and combines ultrasound images with 3D reconstructions that are then registered with pre-acquired T2-weighted or dynamic-enhanced MRI images. With this approach, suspected tumor locations visible on MRI are overlaid on live TRUS images while the ultrasound automatically corrects the overlay for motion and deformation of the prostate. The researchers used custom software that allowed for real time navigation and feedback.
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This technique was used successfully in all 53 patients—33 for feasibility and twenty for a prospective comparison of targeted biopsies and conventional techniques. The 20-patient group consisted of patients with either previously diagnosed prostate cancer or a high clinical suspicion for cancer based on elevated PSA levels and abnormal digital rectal examination.
Successful fusion imaging of MR to real time TRUS was achieved in all patients. In 1 of 20 patients prospectively studied with both targeted biopsy and conventional technique, the use of US/MRI fusion was able to diagnose prostate cancer that was not diagnosed with conventional sampling.
EM-guided biopsies allowed for the use of pre-procedural MRI to perform targeted biopsies without requiring the use of an MRI suite.
“No single imaging modality is adequate for prostate imaging guidance,” said Aradhana Venkatesan, MD, assistant clinical investigator in the division of diagnostic radiology at the National Institutes of Health Clinical Center in Bethesda, Md. Dr. Venkatesan collaborated with Peter Pinto, MD, senior investigator, in the Urologic Oncology Branch of the National Cancer Institute and Bradford J. Wood, MD, chief of Interventional Radiology Research at the NIH Clinical Center.
“Until recently we have not been able to have real-time MRI guidance for most interventions; even now, use of an MRI suite to perform interventions with MR guidance is time-consuming and expensive. Ultrasound’s limitations include its relative lack of spatial resolution. Fusing pre-acquired MRI with real-time TRUS brings valuable information to image-guided biopsy with minimal impact on standard workflow.”
This technology could be applied to patients with equivocal biopsies or added to standard screening, Dr. Venkatesan said.
“Further study by our multidisciplinary group is underway to further clarify the clinical merits of this technology. It is important that there be input and validation of this technique from multiple disciplines, including urology and radiology. With preliminary use of electromagnetic tracking and image fusion, a subset of our patients have been able to get a positive diagnosis and a Gleason scoring of their cancer, which assists with treatment planning.”
