Introduction
Although multiparametric MRI (mpMRI) is the most accurate tool in the detection of clinically significant Prostate Cancer (CsPCa), some limitations have reduced its use as a triage test. Recent improvement in trans rectal ultrasound (TRUS) such as Color Doppler and micro-ultrasound have been introduced with the aim to ease the diagnostic workup of patients with suspicion of PCa, improving the detection of CsPCa with promising results. ExactVu is a real-time micro-ultrasound system capable of providing 300% higher resolution (down to 70 μm) compared to conventional TRUS. The aim of our study was to evaluate the performance of ExactVu in the detection of CsPCa.
Matherial and Methods
Patients with a fusion biopsy proven PCa were imaged with ExactVu. CsPCa was defined as any Gleason Score ≥ 3+4. ExactVu examination was considered as positive when PRI-MUS score was ≥ 3. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and area under the receiver operator characteristic curve (AUC) were calculated.
Results 
57 patients out of 68 (84%) had a CsPCa. Overall, ExactVue micro ultrasound had sensitivity and Positive Predictive Value (PPV) of 72% and 94%, respectively. Considering exclusively CsPCa, sensitivity, specificity, PPV, and NPV was 68%, 73%, 93%, and 31% respectively, with AUC 0.7 (95% CI 0.5-0-8, p=0.035). Accounting only for CsPCa located in the peripheral zone sensitivity, specificity, PPV, and NPV raised up to 74%, 75%, 94%, 33% respectively, with AUC 0.75 (95% CI 0.5-0-9; p=0.028). When CsPCa was in the transition/anterior zone, sensitivity, specificity, PPV, and NPV were 45%, 66%, 83%, 25%, respectively with AUC 0.5 (95% CI 0.2-0-9; p=0.75). Among the 57 CsPCa, PRI-MUS score was correctly assessed (PRI-MUS ≥3) in 39 cases (57%, p=0.01). 
Conclusions
Despite poor accuracy in the detection of CsPCa in the transition/anterior zone, ExactVu provides high resolution of the prostatic peripheral zone and it represents a step forward in the detection of posterior CsPCa, compared to conventional TRUS. Moreover, PRI-MUS score could help to characterize prostatic lesions, to standardize the imaging methodology increasing its reproducibility and to provide a scoring system which differentiates the risk of CsPCa in each zone of the prostate. However, further studies are needed to confirm these promising results.

Diagnostic Accuracy of a Novel 29 MHz Micro-Ultrasound for the detection of Clinically Significant Prostate Cancer on prostate biopsy specimen: a prospective single institutional study.