Ultrasound contrast agents for prostate imaging and biopsy

Transrectal gray scale ultrasound (TRUS)–directed prostate biopsy is the standard technique used to diagnose prostate cancer. While prostate cancer can often be detected as a hypoechoic lesion, the ability to differentiate malignant foci based on TRUS imaging lacks sufficient sensitivity and specificity to use the ultrasound image alone to direct the biopsy. To compensate for these limitations, increasing the numbers of prostate biopsies from the standard six to 10–12 or more has been advocated. Enhanced TRUS techniques such as color Doppler have also been investigated but are not particularly useful in most patients. The use of ultrasound contrast agents is a new approach to identify malignant lesions in the prostate. These agents contain microbubbles that are administered intravenously and can enhance standard gray scale and Doppler images of the prostate. Altered vascular anatomy around malignant lesions is thought to be the reason that these contrast agents enhance the detection of cancer. Ultrasound contrast agents offer the potential to allow more targeted biopsy of the prostate and improve accuracy in the diagnosis of cancer.