Microflow imaging may boost prostate biopsy yield

Dec 20, 2006

A targeted biopsy approach employing contrast-enhanced ultrasound microflow imaging (MFI) may increase the number of positive biopsies compared with systematic sextant biopsy, according to research from Thomas Jefferson University in Philadelphia.

"Targeted biopsy cores with MFI images are twice as likely to be positive compared with systematic cores," said Dr. Ethan Halpern. He presented the research during a scientific session at the 2006 RSNA meeting in Chicago.

Introduced in 1989, systematic sextant biopsy was the standard of care for about a decade, but the technique misses approximately 30% of cancers, according to Halpern. As a result, newer biopsy strategies that involve obtaining 10-12 cores or "saturation" biopsy approaches have been employed. However, these approaches lead to increased pathology costs and morbidity, he said.

MFI may be of help in this setting. With this flash-replenishment technique, high-power flash pulses destroy the contrast microbubbles while low-power pulses demonstrate replenishment, Halpern said. In a composite image, the vascular architecture is constructed through maximum intensity capture of temporal data in consecutive low-power images, he said.

The study team sought to evaluate the technique's prostate cancer detection capabilities with a targeted biopsy approach based upon continuous harmonic imaging (CHI) and MFI, and also compare the results with systematic biopsy.

Sixty patients with an elevated prostate-specific antigen (PSA) level (≥ 4 ng/mL) or an abnormal digital rectal examination were included in the study. All patients received two vials' worth of Definity (Bristol-Myers Squibb Medical Imaging, North Billerica, MA) in 50 mL of saline via intravenous infusion, followed by CHI and MFI imaging. Scanning was performed on an Aplio scanner (Toshiba America Medical Systems, Tustin, CA) with a 6.5-MHz end-fire transrectal transducer.

Up to five targeted cores based on MFI results were obtained, followed by 10 systematic biopsy cores. Statistical analysis was then performed to compare the two methods.

Cancer was found in 18 of the 60 (30%) patients. Of the targeted cores, 29 of the 225 (12.9%) yielded cancer, compared with 50 out of the 600 (8.3%) sextant cores.

Targeted cores were more likely to detect cancer (p = 0.034), according to Halpern. In cancer detection rates by patient, both targeted and systematic biopsies were negative in 40 patients.

Targeted biopsy was negative and systematic biopsy was positive in five patients, while targeted was positive and systematic negative in two cases. Both targeted and systematic approaches were positive in 11 patients.

For cancer detection rate by patient per biopsy core, 13 cancer patients were detected with 225 cores. This represents a detection rate of 58 patients per 1,000 cores, Halpern said. Systematic biopsy resulted in 16 patients detected with 600 cores, for a detection rate of 27 patients per 1,000 cores.

Microflow imaging reveals increased definition of vessels in the prostate. Image courtesy of Dr. Ethan Halpern.

Contrast-enhanced MFI clearly depicts vascular patterns within the prostate, Halpern concluded. No significant difference was seen in the number of patients detected with five targeted cores compared with 10 systematic cores.

"The number of patients detected per core is twice as high for targeted biopsy cores (with MFI)," Halpern said. "What we're hoping to work toward is a system where you can just do targeted biopsies, and thereby decrease the total number of cores that are taken, and improve patient morbidity and decrease the pathology costs."

By Erik L. Ridley
AuntMinnie.com staff writer
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