Multiparametric magnetic resonance imaging (mpMRI) is the current state-of-the-art imaging modality in the assessment of patients with suspected or confirmed prostate cancer (PC). In mpMRI morphological T2-weighted images (T2-WI) are supplemented with diffusion-weighted imaging (DWI) and dynamic contrast-enhanced imaging (DCE). High-grade PC can be detected on mpMRI with high accuracy as it typically appears as a low signal intensity lesion on T2-WI (Figure 1), with restricted diffusion (Figure 2) and strong contrast enhancement. With the technical improvement of the available DWI sequences in recent years, the added value of performing DCE in all patients is currently being questioned.
To standardize the scanning protocol and the interpretation of mpMRI, the European Society of Urogenital Radiology (ESUR) introduced the Prostate Imaging and Reporting and Database System (PI-RADS) in 2011, which was adopted by the American College of Radiology (ACR) in 2015 (PI-RADS version 2). The PI-RADS scoring system reflects the likelihood of the presence of a clinically significant PC on a 5-point scale. In 2019, some refinements and clarifications were made, which resulted in an updated version, PI-RADS v2.1.
In patients with elevated PSA, traditionally a systematic (i.e. 10–12 cores taken randomly throughout the prostate) transrectal ultrasound (TRUS) guided prostate biopsy is performed to detect PC, but in up to 30% of cases the tumor or the most aggressive components of the tumor are missed. Recently published level A evidence and the 2019 updated guidelines of the European Association of Urology have shown that it is advantageous to perform mpMRI of the prostate before a biopsy. When mpMRI is normal, the risk of a clinically significant tumor is low and the biopsy may be postponed, provided that the patient is closely clinically followed up. When a suspicious lesion is detected on mpMRI, a targeted biopsy can be performed. There are three methods to perform a MRI targeted biopsy: cognitive, US-MRI fusion and in-bore MRI-guided biopsy. With a cognitive approach, the clinician keeps the MRI images in mind when performing a random TRUS biopsy with some additional cores in the region where the suspicious lesion is about located. This method is most frequently used in clinical practice because it is fast and cheap. For large PC this method is sufficient, but for very small or anteriorly located lesions it is less accurate. With TRUS-MRI fusion, dedicated software is used to fuse the MRI images virtually with the live TRUS images. A random biopsy is performed with some additional cores to the region where the suspicious lesion is highlighted by the software. An in-bore MRI guided prostate biopsy (Figure 3) is performed while the patient is in the MRI scanner and the position of the biopsy needle is followed with repetitive scans. This is the most accurate method to take a biopsy of target lesions that are very small or are at a difficult location in the prostate.
The authors have no competing interests to declare.