Contrast Enhanced Ultrasound Flash Replenishment Method for Directed Prostate Biopsies

Abstract

We evaluated prostate cancer detection with contrast enhanced ultrasound of the prostate using MicroFlow Imaging (Toshiba America Medical Systems, Tustin, California) compared to systematic biopsy. A total of 60 patients referred for prostate biopsy were evaluated with pre-contrast and contrast enhanced MicroFlow Imaging transrectal ultrasound. MicroFlow Imaging is a flash replenishment technique that uses high power flash pulses to destroy contrast microbubbles, followed by low power pulses to demonstrate contrast replenishment. A composite image depicting the vascular architecture is constructed through maximum intensity capture of temporal data in consecutive low power images. Using MicroFlow Imaging up to 5 directed biopsy cores were obtained from areas of abnormal vascular enhancement or morphology, followed by a systematic 10-core biopsy protocol. A biopsy positive for cancer was found in 79 of the 825 cores (10%) from 18 of the 60 subjects (30%). Positive biopsies were obtained in 50 of 600 systematic core biopsies (8.3%) and in 29 of 225 directed cores (13%) (OR 2.02, p = 0.034). Five of the 18 patients diagnosed with cancer were identified only by systematic biopsy, 2 were identified only by directed biopsy with MicroFlow Imaging and 11 were identified by the 2 techniques (p >0.25). Twice the number of patients was detected per core with directed vs systematic biopsy (0.058 vs 0.027). The vascular detail provided by MicroFlow Imaging allowed directed biopsy of these areas with increased detection of prostate cancer. Although a minority of cancers were not detected with MicroFlow Imaging directed biopsy, this technique detected twice as many patients with prostate cancer per biopsy core.