The first version of the PI-RADS scoring system was described in 2012, followed closely by version 2 in 2016. PI-RADS v2 standardized the lexicon, revised the scoring system, and standardized the schema for deriving an overall assessment category. Today, the state of the art technique for performing prostate MRI includes (i) use of a 1.5 or 3.0 tesla magnet, (ii) a surface coil with or without an endorectal coil, and (iii) three phases (for multi-parametric MRI): multiplanar T2-WI, DWI/ADC map and DCE T1-WI. T2-WI provides detailed anatomic information for staging and is the dominant parameter for transitional zone lesions. DWI/ADC provides tissue microarchitecture and cellularity, is the dominant modality for peripheral zone lesions, and the ADC map is an inverse correlation with Gleason score. DCE assesses tissue vascularity, since prostate cancer has poorly formed vessels with increased permeability. However, DCE has a limited role in lesion detection and characterization. Dr. Purysko notes that the delineation between PI-RADS score 4 and 5 is that PI-RADS 5 is >1.5 cm and/or involves extraprostatic extension.
Dr. Purysko notes several important points for implementing a prostate MRI program, revolving around the key personnel involved: (i) the referring physician (urologist, medical oncologist, radiation oncologist), (ii) hospital administration/leadership, (iii) IT department, and (iv) radiologists/technologists. According to Dr. Purysko, the role of the local champion is to collaborate with urologists/referring physicians on institutional policies for imaging utilization and in the acquisition and deployment of related technologies. The technologist is responsible for ensuring consistent and adequate imaging quality, as well as developing imaging protocols ensuring they meet or exceed the parameters standardized by PI-RADS v2. The radiologist is responsible for development and use of report templates and assisting in improvement of consistency and accuracy of reports. Continued improvement is vital according to Dr. Purysko, including informal review and formal case discussion in conferences, tumor boards, and periodic radiologic-pathologic correlation. Furthermore, it is important to have a feedback mechanism in place that enables evaluation and interpretative skills that impact technological development.
PI-RADS v2.1 is currently under development and will incorporate several aspects: (i) biopsy recommendations, (ii) inclusion of quantitative assessment – requiring further standardization of technical parameters and radiomics, and (iii) inclusion of imaging criteria for other applications such as staging, criteria for active surveillance, and evaluation of recurrence. In summary, Dr. Purysko highlighted several take-home points:
1) Advances in hardware and software over the last few decades have helped establish MRI as a fairly accurate method for detecting prostate cancer
2) The development of technical standards for imaging acquisition and reporting have facilitated the utilization of prostate MRI in clinical practice
3) Numerous resources are available to assist in the implementation and optimization of prostate MRI
An excellent website for educational aspects of prostate MRI is available at: www.learnprostatemri.com
Speaker: Andrei S. Purysko, Cleveland Clinic Foundation, Cleveland, OH, USA
Written by: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre,Twitter: @zklaassen_md, at the AUA Quality Improvement Summit - October 21, 2017- Linthicum, Maryland