Originally published 1/6/2014
It’s hard to believe more than eight years have passed since we posted the blog below. At the time of its writing, conventional ultrasound could not differentiate healthy prostate tissue from prostate cancer. It has been likened to playing darts blindfolded. With the advent of multiparametric MRI (mpMRI) and its excellent tissue characterization that can depict clinically significant prostate cancer, ultrasound could not compete. However, advances in ultrasound are gaining ground.
Two noteworthy ultrasound improvements are a) real-time tissue elastography (RTE) which differentiates prostate cancer from normal tissue according to elasticity, and b) micro-ultrasound (micro-u/s) which better reveals prostate tumors because it has 300 times the resolution of conventional ultrasound. In fact, a side-by-side study of mpMRI and micro-u/s found only slight differences between the two methods of detecting clinically significant prostate cancer.[i] This has special appeal for urologists, since the technology is “inexpensive, accessible and convenient.”[ii] However, more large scale, randomized studies are needed.
That said, ultrasound will continue to lag behind mpMRI, particularly due to the marriage of MRI and Artificial Intelligence. The unparalleled information provided by each MR imaging sequence, or parameter, is complemented by the objective diagnostic accuracy of the latest features of AI, thanks to machine learning and deep learning. Patients who want the most accurate information in order to maximize their treatment decision will opt for 3T mpMRI in the hands of an expert team, such as the Sperling Prostate Center offers.
Some patients cannot tolerate IV gadolinium contrast due to impaired kidney function or other conditions. In these patients, Dr. Sperling utilizes Power Doppler Sonography (Ultrasound) of the prostate, a non-invasive way to evaluate for prostate tumors with their abnormal blood vessels without contrast. Dr. Sperling will then fuse these ultrasound images onto the non-contrast MRI study.
As imaging improves, so does prostate cancer detection. Beginning with the use of gray-scale ultrasound (black-and-white images) in the late 1980s, doctors had the ability to guide biopsy needles into the prostate gland, thus raising the rate of cancer-positive detection. It again increased during the last decade with the introduction of Color Doppler ultrasound, since brightly colored areas can indicate the increased blood flow (hypervascularity) of suspected tumors. This allows for more selective biopsies. I see where many contributors to prostate cancer patient blogs are skeptical about Color Doppler ultrasound (CDUS). They citestudies such as this one from Italy at http://prostatecancerinfolink.net/2011/08/01/color-doppler-ultrasound-in-the-biopsy-based-diagnosisof-prostate-cancer/ or this one from Germany at http://prostatecancerinfolink.net/2010/07/09/colordoppler-ultrasound-and-prostate-cancer-biopsy/ that reflect only a small advantage, if any, in the use of CDUS over gray-scale US. While I know there are highly experienced CDUS ultrasonographers in the U.S. with great diagnostic proficiency, I can only be satisfied with the most consistently reliable, top quality imaging. I rely on state-of-the-art MRI which I find superior to CDUS.
As far back as 2003, a team of radiologists from the Kyoto Prefectural University of Medicine (Kyoto, Japan) set out to compare the accuracy and sensitivity of contrast-enhanced MRI vs. CDUS in terms of detecting cancer-related hypervascularity (increased blood supply). Prior to biopsy, 111 men with elevated PSA values and/or abnormal DRE results underwent both imaging types prior to having a systematic octant biopsy (8 needles) guided by transrectal gray-scale ultrasound.
The CDUS evaluations were performed by a team of two experienced urologists who reached consensus on the findings for each patient. A team of two experienced radiologists did the contrast-enhanced MRI imaging, again reporting a consensus of results. Neither the urologists nor the radiologists were aware of the findings of the other team.
The biopsies were done after the imaging evaluations were performed. Cancer-positive tissue samples were found in 31 patients. The biopsy results for these 31 men were compared with the CDUS and MRI findings. The authors concluded that while both CDUS and contrast-enhanced MRI can be used to detect the hypervascularity that accompanies prostate cancer, the MRI was significantly more sensitive than CDUS in the peripheral (outer) zones of the prostate, where 70% of cancers cancers begin. While the CDUS proved marginally better than MRI regarding the innermost gland zones, the authors suggested ways to improve MRI utlization for better detection in that area.
MRI has three advantages. First, it reveals the area where biopsy will be most productive, thus reducing the number of needles. Second, for men with elevated PSA and a history of repeat negative biopsies, it ends the sequence of these costly, unproductive biopsies by identifying cancer previously missed. Third, it confirms which patients are candidates for a focal ablation treatment. If they choose a focal treatment, thanks to MRI guidance I am confident in my ability to accurately destroy the tumor.
For me, there is literally no comparison between MRI and CDUS. I am committed to bringing the best possible prostate cancer detection and treatments to patients through the best possible imaging.
NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.
[i] Klotz, L. Can high resolution micro-ultrasound replace MRI in the diagnosis of prostate cancer? Eur Urol Focus. 2020 Mar 15;6(2):419-423.