An update on the prostate imaging reporting and data system (PI-RADS) and use of multi-parametric magnetic resonance imaging in non-invasive assessment of prostate cancer

Abstract

Learning Objectives: The learning objectives for the following exhibit are to outline the use of the PI-RADS Version 2 guidelines in using multi-parametric magnetic resonance imaging (mpMRI) in improving the detection, localization, characterization and risk stratification in patients with suspected prostate cancer. Demonstration of this PI-RADS v2 guidelines will then be applied using a case study exemplar. Background: The use of magnetic resonance imaging (MRI) in noninvasive assessment of the prostate gland dates back to the 1980s and initially included morphologic assessment using T1-weighted (T1W) and T2-weighted (T2W) pulse sequences for locoregional staging of biopsy proven prostate cancer. Subsequent advancements in MRI technology led to the development of multi-parametric MRI which combined T2W sequences with diffusion-weighted imaging (DWI), apparent-diffusion coefficient (ADC) maps and dynamic contrast- enhanced (DCE) MRI. These advancements led to improved detection of clinically significant cancer and improved the accuracy of diagnosing benign disease and clinically insignificant malignancies which do not require treatment. Combining these different modalities into a comprehensive and authoritative guideline led to the development of the PI-RADS guidelines and is ultimately aimed at standardizing the reporting of mpMRI examinations. Findings on mpMRI are assessed according to the PI-RADS v2 five-point category scale from 1 (very low risk of cancer) to 5 (very high risk of clinically significant cancer) with separate assessment of peripheral and transition zone lesions. Imaging Findings: Application of the PI-RADS v2 guidelines demonstrated a PI-RADS 5 lesion, with imaging findings including a 32.1 mm × 15.6 mm oval region of decreased T2 signal involving the left antero-lateral aspect of the transitional zone and peripheral zone in the basal third of the prostate. Restricted diffusion noted with an ADC value of 679. Early enhancement noted on the dynamic post contrast imaging. TRUS biopsy demonstrated a Gleason 3 + 3 = 6 prostatic adenocarcinoma. Conclusion: The PI-RADS v2 resulted from collaborative efforts to develop a comprehensive guideline for interpretation of multiparametric MRI imaging of the prostate. Knowledge of the PI-RADS guidelines is essential for the radiology trainee in interpreting mpMRI findings relating to potential malignant prostatic lesions. This second iteration of the PI-RADS system improves the accuracy of mpMRI and aids in triaging of patients to appropriate management through initial detection and staging and in some cases avoiding unnecessary TRUS biopsies.L618976911 <br />