By: Dan Sperling, MD
Many urologists now routinely order a prostate MRI before performing a standard 10-12 core transrectal ultrasound-guided (TRUS) biopsy. In a recent Journal of Urology article, authors Peter Albertsen and Leonard Marks acknowledge the promise of MRI, especially 3T multiparametric MRI, but express some reserve before it might be embraced wholesale within urology.[i] One of the concerns they raise is lack of consistent standards and quality.
This issue was addressed in a course offered at the 2014 annual meeting of the American Urological Association (Orlando, FL), “Integration of Multiparametric MRI into the Urologic Management of Prostate Cancer.” Presenter Peter L. Choyke, MD[ii] outlined three factors that influence MRI quality:
- Patient preparation
- Scan performance
- Communication of results
Timing is important. It is preferable to conduct the MRI session prior to a biopsy. According to Dr. Choyke, if the patient has already had a prostate biopsy, a period of 10-12 weeks should elapse for the healing of any residual blood artifacts from the needle punctures. (Author’s note: at our Center, we often shorten this period due to our advanced technology and authoritative experience in reading prostate mpMRI results.)
Patients do not need a bowel prep. However, claustrophobic patients may need appropriate premedication as it is important to remain motionless during imaging. It is vital to screen patients before hand for any metallic implants, including pacemakers and bilateral hip prostheses.
According to Dr. Choyke, “Image quality is directly related to signal to noise rations. As such it is axiomatic that 3T Scanners produce higher quality images than 1.5T…” Dr. Choyke favors use of an endorectal coil (ERC), explaining that patients tolerate this well after the initial discomfort of placement. On the other hand, he points out, “Many radiologists believe that 3T scans without ERC are sufficient or that 1.5T scans with an endorectal coil produce very high quality images.” (Author’s note: At our Center, we do not utilize ERC for 3T mpMRI, as we are confident that our high quality imaging would be diminished by any distortion of the prostate that may occur due to the pressure of the coil.)
Communication of results
Thanks to new scoring systems, particularly PI-RADS, interpreting prostate MRI images has more consistency among radiologic readers who generate the reports (see our blog entries explaining PI-RADS at https://sperlingprostatecenter.com/pi-rads-score/ and https://sperlingprostatecenter.com/testing-pi-rads-accuracy/). The scoring system compiles the functional parameters (T2 weighted, Diffusion weighted imaging, and Dynamic Contrast Enhancement.) Because many urologists are not yet conversant with reading prostate MRI’s, it is suggested that the results be depicted on a “map” so the location is easily understood by the referring physician who receives the results. The report should be clear that these are areas or regions of “suspicion,” or likelihood of prostate cancer, rather than “prostate cancer.” Dr. Choyke points out, “If the mpMRI results suggest the need for a biopsy, the lesion should be carefully identified and a segmentation of the MRI should be performed to fuse with the transrectal ultrasound.”
As the specialty medical field of urology increasingly incorporates 3T mpMRI results into the detection and diagnosis of prostate cancer, patients will be better served thanks to avoiding unnecessary biopsies, better targeting of suspicious areas when a biopsy is needed, and more accurate diagnosis of disease aggression due to targeted biopsies. The fact that highly respected institutions such as the National Cancer Institute and New York University/Langone Medical Center are taking leadership in urology/radiology collaborations reveals how well-recognized the incorporation of 3T mpMRI prostate imaging represents the future of urologic care.