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Physicians Update

 
Fall 2011

Ultrasound/MRI Biopsy Enhance Treatment for Prostate Tumors

10/19/2011

Prostate Treatment Unlike most other cancers, prostate tumors are often not lethal and may never require treatment. With active surveillance, patients who have non-aggressive tumors can be spared the pain, risks and side effects of surgery or radiation therapy. The problem has been finding reliable ways of predicting which patients need treatment and which ones can simply be monitored.

A UCLA team of urologists, radiologists, pathologists and biomedical engineers is now advancing a new approach that could dramatically improve the prostate biopsy and thus lead to better-informed treatment decisions.

As part of a $1.7 million grant from the National Cancer Institute, the UCLA team is testing a new technology that fuses MRI and ultrasound, enabling urologists to be guided in their real-time ultrasound prostate biopsy by the superior visual insights obtained through MRI.

“This is bringing sophisticated MRI imaging to the patient’s bedside,” says urologist Leonard S. Marks, M.D. “We want the serious cancers to get picked up and treated, and the ones that are not serious not to get treated. If we can see the tumor, we have a better idea of how to take care of it.”

 Prostate cancer was always difficult to visualize in the early stages through imaging because of the limited contrast between normal and malignant tissues within the prostate. That began to change with the emergence of MRI. For more than a decade, radiologists have used MRI to evaluate prostate cancer. However, several barriers have stood in the way of MRI’s use in prostate biopsies: the size of the instrument; the length of time it takes to acquire the information, particularly since it has typically been used in conjunction with MR spectroscopic imaging; and discomfort to the patient, given the need for a coil to be placed through the rectum next to the prostate.

Prostate MRIBut two recent MRI techniques have enhanced the ability of expert radiologists to identify and evaluate areas of the prostate that are suspicious for a tumor in a way that’s far less cumbersome, says diagnostic radiologist Daniel Margolis, M.D. With dynamic contrast imaging, contrast is injected through an IV line just like any contrast-enhanced MRI scan, but multiple sequential 3D images are generated to track its arrival and washout, which are abnormal in tumors. With diffusion-weighted imaging, MRI is used to examine water motion restriction: In normal prostate tissue there is little restriction, whereas prostate-cancer cells are smaller and more densely packed, restricting water motion.

 “Combined, these two techniques are about as sensitive as spectroscopic imaging,” says Dr. Margolis. “For biopsy planning, we can use these techniques that are much faster and don’t require the use of an endorectal coil.”

Drs. Margolis and Marks have developed a protocol for quantifying the level of suspicion of different prostate areas. Diffusion-weighted imaging is given the most weight, followed by dynamic-contrast and tissue-contrast images. “Dr. Marks can be given a map of the patient’s prostate and can use ultrasound guidance to target the biopsy to the suspicious area,” Dr. Margolis explains. “Our hope is that by looking at the quantitative data and our qualitative evaluation, we will eventually be able to determine which patients don’t need a biopsy at all.”

The reason Dr. Marks is now able to visualize the tumor while performing the ultrasound-guided biopsy has to do with the work of the team’s biomedical engineers and the new technology that fuses MRI and ultrasound, known as Artemis. UCLA biomedical engineers are using the MR images to create a virtual 3D model of the prostate. That model is then fed from a CD into the Artemis device, where it is fused with the ultrasound to virtually map the target areas onto the ultrasound image.

“We never had the ability to see prostate cancer under real-time ultrasound,” says Dr. Marks. “This allows us to identify the area of concern and aim for it.” In addition, the technology enables urologists to return to the same location to resample over time.

Prostate BiopsyThe Artemis device has been approved by the FDA but needs to be refined before it is more widely used, Dr. Marks says. The UCLA group is working with the manufacturer, Eigen Corp., to optimize the software. Meanwhile, referrals are coming from across the country, particularly for patients who have an abnormal PSA test with biopsies showing no cancer or only a small, non-aggressive cancer.

“With these patients there may be a high level of suspicion that cancer is being missed with systematic biopsies,” explains Dr. Margolis. “We have shown that this device can give us much more accurate biopsies. What we have to show now is that this improves patient management.”

“The hope is that in some patients we will be able to safely defer definitive management, and in others we can give them a better sense of which of the therapies would be most beneficial,” says Dr. Marks. “This has the potential to help us avoid surgeries that provide no benefit to the patient.”





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