Evaluating Diffusion Metrics for Quantitative ADC Analysis in Prostate MRI

Overview

This bicentric study investigated the use of diffusion levels (DLs) derived from apparent diffusion coefficient (ADC) values in prostate MRI to improve the assessment of clinically significant prostate cancer (csPCa). The study aimed to standardize ADC interpretation in peripheral zone lesions and evaluate DLs as a diagnostic tool alone or combined with PI-RADS v2.1.

Background

Diffusion-weighted imaging (DWI) is a key component of prostate MRI, especially for lesions in the peripheral zone, influencing biopsy decisions. Although ADC values have potential as biomarkers for prostate cancer diagnosis and risk stratification, variability in measurements limits their clinical utility. The ADC ratio has been explored but suffers from reproducibility issues. Inspired by breast MRI, where diffusion levels (DLs) based on ADC ranges improve diagnostic accuracy, this study explores applying a similar DL approach to prostate MRI to complement PI-RADS and refine biopsy strategies.

Data Highlights

The study included men aged ≥18 years undergoing prostate MRI followed by biopsy due to PI-RADS ≥3 lesions or high clinical risk. MRI was performed on 3.0-T scanners with dual DWI sequences to generate ADC maps. Biopsy included systematic 12-core plus targeted cores on suspicious lesions. Clinically significant prostate cancer was defined as ISUP grade group ≥2. ADC measurements were performed by expert radiologists blinded to biopsy results. The study period spanned March 2020 to April 2023 across two centers.

Key Findings

• DLs based on ADC values were successfully derived from a bicentric real-world prostate MRI dataset focusing on peripheral zone lesions.
• DLs showed potential to standardize ADC interpretation and corresponded to different risks of clinically significant prostate cancer.
• Using DLs as a stand-alone tool or combined with PI-RADS v2.1 improved diagnostic performance for csPCa detection.
• ADC ratio methods were limited by reproducibility issues due to variability in reference tissue selection.
• The dual DWI sequence approach enabled consistent ADC map generation across different MRI systems and centers.

Clinical Implications

Implementing ADC-based diffusion levels in prostate MRI interpretation may enhance the objectivity and reproducibility of lesion assessment, particularly in the peripheral zone. This approach could complement PI-RADS scoring, aiding clinicians in biopsy decision-making and potentially reducing unnecessary biopsies. Standardizing ADC interpretation across centers and MRI platforms may improve risk stratification and patient management.

Conclusion

This proof-of-concept bicentric study demonstrates that diffusion levels derived from ADC values can standardize prostate MRI interpretation and improve detection of clinically significant prostate cancer. Further validation may establish DLs as a valuable adjunct to PI-RADS in clinical practice.

References

1. PI-RADS Steering Committee 2019 -- PI-RADS v2.1: Prostate Imaging Reporting and Data System
2. European Society of Breast Imaging (EUSOBI) 2020 -- DWI Working Group Consensus on Breast MRI
3. Bickel et al. 2021 -- ADC Diffusion Levels in Breast MRI