Ellipsoid volume & PSA density

PI-RADS v2.1USMRI

Volume = L × W × H × π/6 (≈0.52). Used for prostate, thyroid lobes, bladder and lesions. For prostate MRI, measure maximum AP and length on mid-sagittal T2W and maximum transverse on axial T2W.

Volume

Length (cm) Width (cm) Height / AP (cm) PSA (ng/mL, optional)

Volume–mLPSAD–

PSA density ≥0.15 ng/mL/cc is a commonly used threshold favoring biopsy, especially with PI-RADS 3 lesions.

Sources

Turkbey B, Rosenkrantz AB, Haider MA, et al. Prostate Imaging Reporting and Data System version 2.1. Eur Urol. 2019;76:340–351.PubMed ↗

Radessential summarizes published classification systems for practicing radiologists. Summaries are condensed; confirm details against the cited source before relying on them for patient care.