MRI/Ultrasound Fusion: Not Ready for Prime Time

When an authoritative person weighs in on a topic, we sit up and take notice. Dr. Ardeshir (Art) Rastinehead is an Interventional Urologic Oncologist and he is impressively credentialed. His experience includes fellowship training at the National Cancer Institute (NIH) with. Peter A. Pinto and Bradford J. Wood, pioneers in the research and development of new minimally invasive diagnostic and therapeutic interventions for the treatment of prostate cancer. He has published on such topics as image-guided biopsy and multiparametric MRI. Most recently, he issued a commentary article addressing the need for a 12-core repeat biopsy for patients with a previous negative biopsy but whose rising PSA or abnormal digital rectal exam continue the concern that prostate cancer (PCa) still lurks undetected.[i]

His commentary is based on a study of MRI/ultrasound fusion guided biopsy, or simply fusion guided biopsy. To learn about the difference between the real-time MRI guided biopsy, as we offer at our Center, and a fusion guided biopsy, see my article at https://sperlingprostatecenter.com/mri-guided-biopsy-vs-fusion-whats-difference/.

Interested readers can follow the link in the footnote to read Dr. Rastinehead’s brief article in its entirety. I want to address a few points he makes.

  1. “We evaluated the use of mpMRI to help select men at risk of prostate cancer and also utilized this information to overcome the inherent limitations associated with the standard ultrasound technology.” At our Center, we recognize that standard ultrasound is an imperfect guidance technology for prostate biopsy because it cannot discriminate cancerous tissue from benign (harmless) tissue. Thus, a transrectal ultrasound (TRUS) guided biopsy has shortcomings.  Don’t let the word “systematic” fool you because it is blind and basically random.
  2. “We also compared the difference in diagnostic accuracy of a fusion-guided biopsy to the standard prostate biopsy.” It is not surprising that merging MRI images of suspicious areas with real-time ultrasound would give better results than randomly sampling a gland. Patients whose initial biopsy has false negative results (it didn’t find the cancer that’s there) are more than 50% likely to have another false negative biopsy because TRUS biopsies tend to miss the same places, even when repeated. So if the MRI highlights an abnormality, a doctor stands a good chance of deliberately sampling that area either with ultrasound alone (now that he knows what he’s looking for) or with fusion.
  3. “It is extremely important to understand that this technology [MRI/ultrasound fusion] is in its early stages of implementation.” Dr. Rastinehead states that urologists who are developing their skills with fusion have contacted him to say they don’t get the same results as he has reported in the literature. This is not surprising. In addition to the distortions that can occur with fusion, there is a learning curve with the device and the software.
  4. “Patients and physicians need to understand that high quality mpMRI of the prostate with an experienced reader are paramount to obtaining these results.” Published research that compares less experienced readers with more experienced readers supports this statement. In addition, those who read the MRI scans are radiologists whose training has been devoted to this, whereas urologists are trained as surgeons, meaning they are used to looking at the inside of bodies with their own eyes, instead of reading images. As more urologists recognize the value of multiparametric MRI, it’s expectable that they will improve their own ability to understand what the image is showing them. At this time, however, such urologists are still in the minority.
  5. “The prostate mpMRI is not a substitute for a biopsy.” We agree. We recognize that some potentially deadly cancers exist without stimulating a rise in PSA; and some indolent cancers that may never become deadly can still lead to an elevated PSA. It’s important to a) get the cells under a microscope, and pending those results, b) get a genetic analysis of the cell line.

To sum up, the Sperling Prostate Center has been a pioneer in 3T mpMRI and MRI-guided targeted biopsies. We believe we offer patients the most accurate detection and diagnosis of prostate cancer that is possible today. We stay abreast of international research and new technologic developments, so that we can always provide state-of-the-art services to our patients. We agree with Dr. Rastinehead’s positive but cautious assessment of fusion technology as promising, knowing that MRI is the foundation of it. But we still know that there is no substitute for real time multiparametric MRI.


[i] Rastinehead, A. Is 12-core biopsy still necessary, in addition to a targeted biopsy, in patients with a previous negative biopsy and a suspicious lesion on MRI? “Beyond the Abstract.” April 2, 2015. http://www.urotoday.com/index.php?option=com_content&view=article&id=79526:is-a-12-core-biopsy-still-necessary-in-addition-to-a-targeted-biopsy-in-patients-with-a-previous-negative-prostate-biopsy-and-a-suspicious-lesion-on-mri-beyond-the-abstract-by-art-r-rastinehad-do&catid=1134:prostate-cancer&Itemid=782&utm_source=newsletter_2568&utm_medium=email&utm_campaign=uroalerts-prostate-cancer-weekly

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