Restriction Spectrum MRI Technique Improves Diagnosis of Prostate Cancer

The group of scientists and physicians, from the University of California (UC), San Diego School of Medicine (USA), with colleagues at University of California, Los Angeles (UCLA; USA), published their findings in the January 6, 2015, issue of the journal Prostate Cancer and Prostatic Disease. “This new approach is a more reliable imaging technique for localizing tumors. It provides a better target for biopsies, especially for smaller tumors,” said Rebecca Rakow-Penner, MD, PhD, a research resident in the department of radiology and the study’s first author.

The technique is also beneficial in surgical planning and image staging, according to David S. Karow, MD, PhD, assistant professor of radiology at UC San Diego, and the study’s corresponding author. “Doctors at UC San Diego and UCLA now have a noninvasive imaging method to more accurately assess the local extent of the tumor and possibly predict the grade of the tumor, which can help them more precisely and effectively determine appropriate treatment.”

The current standard of care for detecting and diagnosing prostate cancer is contrast-enhanced magnetic resonance imaging (MRI), which involves intravenously injecting patients with a contrast agent to highlight blood flow. Greater blood flow is often a requirement of growing cancer cells. When compared to surrounding healthy tissues, it is hoped that contrast-enhanced MRI scans will reveal the shape and composition of any tumors present.

But many tumors do not significantly differ from surrounding healthy tissues with contrast enhanced MRI and so evade easy detection. An imaging technique called diffusion MRI measures the diffusion of water and has been a standard imaging technique in the brain and an emerging technique in the prostate. Cancer tissues are denser than healthy tissues and typically limit the amount and mobility of water within them. However, diffusion MRI suffers from magnetic field artifacts that can distort the actual location of tumors by as much as 1.2 cm—a substantial distance when surgeons are trying, for instance, to evaluate whether a tumor extends beyond the prostate and into adjacent nerve bundles.

The new imaging strategy in the study is called restriction spectrum imaging-MRI (RSI-MRI). It corrects for magnetic field distortions and focuses upon water diffusion within tumor cells. By doing both, the ability of imaging to accurately plot a tumor’s location is increased and there is a more refined sense of the tumor’s extent, according to Nathan White, PhD, assistant project scientist at UC San Diego, study coauthor, and co-inventor of the RSI-MRI technique.

In a related study to be published in the journal Frontiers in Oncology, the same researchers reported that RSI-MRI appears to predict tumor grade. Higher grade tumors correlate with higher restricted water volume in the cancer cells’ large nuclei. “Prostate cancer can often be an indolent disease, where a patient may only require surveillance rather than aggressive surgery,” noted coauthor Christopher J. Kane, MD, professor of urology at UC San Diego.

“If by imaging we could predict the tumor grade,” added Robert Reiter, MD, professor of urology at UCLA, “we may be able to spare some patients from prostate resection and monitor their cancer with imaging.”

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University of California, San Diego
University of California, Los Angeles