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Keywords:

  • PIRADS-score;
  • mpMRI;
  • prostate;
  • biopsy;
  • hybrid imaging

Objectives

  • To evaluate the Prostate Imaging Reporting and Data System (PIRADS) in multiparametric magnetic resonance imaging (mpMRI) based on single cores and single-core histology.
  • To calculate positive (PPV) and negative predictive values (NPV) of different modalities of mpMRI.

Patients and Methods

  • We performed MRI-targeted transrectal ultrasound-guided perineal prostate biopsies on 50 patients (mean age 66 years, mean PSA level of 9.9 ng/mL) with suspicion of prostate cancer. The biopsy trajectories of every core taken were documented in three dimensions (3D) in a 3D-prostate model.
  • Every core was evaluated separately for prostate cancer and the performed biopsy trajectories were projected on mpMRI images.
  • PIRADS scores of 1177 cores were then assessed by a histology ‘blinded’ uro-radiologist in T2-weighted (T2W), dynamic contrast-enhanced (DCE), diffusion-weighted imaging (DWI) and magnetic resonance spectroscopy (MRS).

Results

  • The PIRADS score was significantly higher in cores positive for cancer than in negative cores.
  • There was a significant correlation between the PIRADS score and histopathology for every modality.
  • Receiver operating characteristic (ROC) analysis showed excellent specificity for T2W (90% peripheral zone/97% transition zone) and DWI (98%/97%) images regardless of the prostate region observed. These numbers decreased for DCE (80%/93%) and MRS (76%/83%).
  • All modalities had NPVs of 99%, if a PIRADS score threshold of 2 (for T2W, DCE, and MRS) or 3 (for DWI) was used. However, PPVs were low.

Conclusions

  • Our results show that PIRADS scoring is feasible for clinical routine and allows standardised reporting.
  • PIRADS can be used as a decision-support system for targeting of suspicious lesions.
  • mpMRI has a high NPV for prostate cancer and, thus, might be a valuable tool in the initial diagnostic evaluation.