EAU 2017: European Society of Urogenital Radiology (ESUR) lecture PI-RADS in clinical practice including differential diagnoses in prostate imaging
PIRADS is based on information received from the mpMRI, which can be divided to morphological and functional information. The mpMRI includes standard anatomical T1 and T2- weighted imaging used to ascertain lesion size and location, and the functional sequences including dynamic contrast-enhanced (DCE) MRI and diffusion-weighted imaging (DWI), which includes the calculation of apparent diffusion co-efficient (ADC) maps. DWI with ADC give an indication of tumor aggressiveness. The lower the ADC, the higher the Gleason score.
The mpMRI should preferably be performed on a 3 Tesla without endorectal coil. Before the test an antiperistaltic drug should be given and an enema administered by the patient. The patient should evacuate his rectum just before the mpMRI. When considering performing a mpMRI after biopsy, a period of at least six weeks should pass before the undergoing mpMRI, in order to reduce the chance of postbiopsy changes influencing interpretation.
The anatomy of the prostate is divided to 39 sectors (36 within the prostate, 2 seminal vesicles and one external urethral sphincter). PIRADS uses a 5 point scale based on mpMRI results to assess the probability of the presence of clinically significant prostate cancer. The scale goes from P1 – highly unlikely to have clinically significant cancer to P5 – very likely. PIRADS 5 is defined as a suspicious lesion greater than 1.5 cm, or seminal vesicle invasion, or presence of extra-prostatic extension. All lesions should be identified on the mpMRI and the index lesion, which is either the largest lesion, or the lesion with the highest PIRADS category, or the one causing extra-prostatic extension, must be identified. All lesions should be measured on the axial plane and if it is in the peripheral zone (PZ) this should be done on DWI+ADC, while if it is in the transition zone (TZ), this should be done on T2. The DCE-MRI has a minor role primarily for qualitative analysis.
The report given at the end of the mpMRI should be detailed with clinical information of the patient, description of the technique that was used for the MRI, findings of the mpMRI including prostate volume, description of PZ and all its lesions and description of the TZ and all its lesions. All Lesions found should described elaborately detailing size, exact location, borders, T2 signal intensity, DWI-MRI signal intensities, DCE-MRI (presence or absence of focal enhancement), assignment of PIRADS score for each lesion up to 4, presence of extra-capsular extension and seminal vesicle involvement. Finally the report should conclude with presence of enlarged/suspicious lymph nodes, bone marrow abnormalities and any additional findings.
Differential diagnosis include benign prostatic hyperplasia (BPH) which usually arises in the TZ but can sometime be found in the PZ as well. BPH is a mixture of stromal and glandular hyperplasia and might impede diffusion on DWI-MRI and cause focal enhancement. Therefore, correlation with T2 is important. Differential diagnosis includes prostatitis as well, which can cause decreased signal intensity in the PZ on T2 with impeded diffusion (low ADC)
Dr. Theony concludes her presentation stating PIRADS ver. 2 improves detection of significant prostate cancer and decreases inter-reader variability, and most importantly improves communication between the urologist and radiologist.
Speaker(s): Harriet Thoeny, Berne
Written By: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto
Twitter: @GoldbergHanan
at the #EAU17 - March 24-28, 2017- London, England