Which measurement method should be used for prostate volume for PI-RADS? A comparison of ellipsoid and segmentation methods

Published:September 20, 2021DOI:


      • Traditional ellipsoid measurements overestimate prostate volume versus segmentation.
      • Both methods derived PSA density have similar performance for Gleason >/=7 disease.
      • Segmentation method for PSA density outperforms ellipsoid for high grade cancer.



      Prostate volume and PSA density (PSAd) are important in the risk stratification of suspected prostate cancer (Pca). PI-RADS v2.1 allows for determining volume via segmentation or ellipsoid calculation. The purpose of our study was to compare ellipsoid and segmentation volume calculation methods and evaluate if PSAd diagnostic performance is altered.


      We retrospectively assessed 397 patients (mean age/standard deviation: 63.7/7.4 years) who underwent MRI and prostate biopsy or prostatectomy, with Pca classified by Gleason ≥3 + 4 and ≥4 + 4 disease. Prostate total volumes were determined with ellipsoid calculations (TVe) and with semi-automated segmentation (TVs), along with inter-rater reliability with intraclass correlation coefficient (ICC). PSAd was calculated for TVe and TVs and ROC curves were created to compare performance for Gleason ≥3 + 4 and ≥4 + 4 disease.


      TVe was significantly higher than TVs (p < 0.0001), with mean TVe = 55.4 mL and TVs = 51.0 mL. ROC area under the curve for PSAd derived with TVe (0.63, 95%CI:0.59–0.68) and TVs (0.64, 95%CI:0.59–0.68) showed no significant difference for Gleason ≥3 + 4 disease (p = 0.45), but PSAd derived with TVs (0.63, 95%CI: 0.58–0.68) significantly outperformed TVe (0.61, 95%CI: 0.57–0.67) for Gleason ≥4 + 4 disease (p = 0.02). Both methods demonstrated excellent inter-rater reliability with TVe with ICC of 0.93(95%CI: 0.92–0.94) and TVs with ICC of 0.98(95%CI: 0.98–0.99).


      Traditional ellipsoid measurements tend to overestimate total prostate volume compared to segmentation, but both methods demonstrate similar diagnostic performance of derived PSA density for PI-RADS clinically significant disease. For higher grade disease, PSAd derived from segmentation volumes demonstrates statistically significant superior performance. Both methods are viable, but segmentation volume is potentially better.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Clinical Imaging
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Nordström T.
        • Akre O.
        • Aly M.
        • Grönberg H.
        • Eklund M.
        Prostate-specific antigen (PSA) density in the diagnostic algorithm of prostate cancer.
        Prostate Cancer Prostatic Dis. 2018 Apr; 21: 57-63
        • Al-Qaisieh B.
        • Brearley E.
        • St Clair S.
        • Flynn A.
        A study of a pretreatment method to predict the number of I-125 seeds required for prostate brachytherapy.
        Int J Radiat Oncol Biol Phys. 2006 May 1; 65: 304-307
        • McConnell J.D.
        • Bruskewitz R.
        • Walsh P.
        • et al.
        The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment among men with benign prostatic hyperplasia. Finasteride long-term efficacy and safety study group.
        N Engl J Med. 1998 Feb 26; 338: 557-563
        • Choi Y.J.
        • Kim J.K.
        • Kim H.J.
        • Cho K.S.
        Interobserver variability of transrectal ultrasound for prostate volume measurement according to volume and observer experience.
        AJR Am J Roentgenol. 2009 Feb; 192: 444-449
        • Park K.J.
        • Kim M.H.
        • Kim J.K.
        • Cho K.S.
        Characterization and PI-RADS version 2 assessment of prostate cancers missed by prebiopsy 3-T multiparametric MRI: correlation with whole-mount thin-section histopathology.
        Clin Imaging. 2019 May-Jun; 55: 174-180
        • Wang W.
        • Wang G.
        • Wu X.
        • Ding X.
        • Cao X.
        • Wang L.
        • Zhang J.
        • Wang P.
        Automatic segmentation of prostate magnetic resonance imaging using generative adversarial networks.
        Clin Imaging. 2021 Feb; 70: 1-9
        • Tosun M.
        • Uslu H.
        Prebiopsy multiparametric MRI and PI-RADS version 2.0 for differentiating histologically benign prostate disease from prostate cancer in biopsies: a retrospective single-center comparison.
        Clin Imaging. 2021 Mar 20; 78: 98-103
        • Turkbey B.
        • Rosenkrantz A.B.
        • Haider M.A.
        • Padhani A.R.
        • Villeirs G.
        • Macura K.J.
        • Tempany C.M.
        • Choyke P.L.
        • Cornud F.
        • Margolis D.J.
        • Thoeny H.C.
        • Verma S.
        • Barentsz J.
        • Weinreb J.C.
        Prostate imaging reporting and data system version 2.1: 2019 update of prostate imaging reporting and data system version 2.
        Eur Urol. 2019 Sep; 76: 340-351
        • Razek A.A.K.A.
        • El-Diasty T.
        • Elhendy A.
        • Fahmy D.
        • El-Adalany M.A.
        Prostate Imaging Reporting and Data System (PI-RADS): what the radiologists need to know?.
        Clin Imaging. 2021 May 31; 79: 183-200
        • Trent G.P.
        • Ye N.
        • Chopra J.
        • Chen R.
        • Wong-You-Cheong J.
        • Naslund M.
        • Siddiqui M.M.
        • Wnorowski A.
        Performance of PI-RADS v2 assessment categories assigned prior to MR-US fusion biopsy in a new fusion biopsy program.
        Clin Imaging. 2020 Aug; 64: 29-34
        • Wang G.
        • Yu G.
        • Chen J.
        • Yang G.
        • Xu H.
        • Chen Z.
        • Wang G.
        • Bai Z.
        Can high b-value 3.0 T biparametric MRI with the Simplified Prostate Image Reporting and Data System (S-PI-RADS) be used in biopsy-naïve men?.
        Clin Imaging. 2021 Jun 29;
        • Epstein J.I.
        • Egevad L.
        • Amin M.B.
        • Delahunt B.
        • Srigley J.R.
        • Humphrey P.A.
        • Grading Committee
        The 2014 International Society of Urological Pathology (ISUP) consensus conference on gleason grading of prostatic carcinoma: definition of grading patterns and proposal for a new grading system.
        Am. J. Surg. Pathol. 2016 Feb; 40: 244-252
        • Wasserman N.F.
        • Niendorf E.
        • Spilseth B.
        Measurement of prostate volume with MRI (A guide for the Perplexed): biproximate method with analysis of precision and accuracy.
        Sci Rep. 2020 Jan 17; 10: 575 PMID: 31953425; PMCID: PMC6969030
        • Akoglu H.
        User's guide to correlation coefficients.
        Turk J Emerg Med. 2018; 18: 91-93
        • Bezinque A.
        • Moriarity A.
        • Farrell C.
        • Peabody H.
        • Noyes S.L.
        • Lane B.R.
        Determination of prostate volume: a comparison of contemporary methods.
        Acad Radiol. 2018 Dec; 25: 1582-1587
        • Ghafoor S.
        • Becker A.S.
        • Woo S.
        • Causa Andrieu P.I.
        • Stocker D.
        • Gangai N.
        • Hricak H.
        • Vargas H.A.
        Comparison of PI-RADS versions 2.0 and 2.1 for MRI-based calculation of the prostate volume.
        Acad Radiol. 2020 Aug 17;
        • Gündoğdu E.
        • Emekli E.
        Evaluation of prostate volume in mpMRI: comparison of the recommendations of PI-RADS v2 and PI-RADS v2.1.
        Diagn Interv Radiol. 2021 Jan; 27: 15-19
        • Stanzione A.
        • Ponsiglione A.
        • Di Fiore G.A.
        • Picchi S.G.
        • Di Stasi M.
        • Verde F.
        • Petretta M.
        • Imbriaco M.
        • Cuocolo R.
        Prostate volume estimation on MRI: accuracy and effects of ellipsoid and bullet-shaped measurements on PSA density.
        Acad Radiol. 2020 Jun 14;
        • National Comprehensive Cancer Network
        Prostate cancer (version 2.2021).
        • Distler F.A.
        • Radtke J.P.
        • Bonekamp D.
        • Kesch C.
        • Schlemmer H.P.
        • Wieczorek K.
        • Kirchner M.
        • Pahernik S.
        • Hohenfellner M.
        • Hadaschik B.A.
        The value of PSA density in combination with PI-RADS™ for the accuracy of prostate cancer prediction.
        J Urol. 2017 Sep; 198: 575-582
        • Stevens E.
        • Truong M.
        • Bullen J.A.
        • Ward R.D.
        • Purysko A.S.
        • Klein E.A.
        Clinical utility of PSAD combined with PI-RADS category for the detection of clinically significant prostate cancer.
        Urol Oncol. 2020 Nov; 38: 846.e9-846.e16
        • Haas M.
        • Günzel K.
        • Miller K.
        • Hamm B.
        • Cash H.
        • Asbach P.
        Is the ellipsoid formula the new standard for 3-T MRI prostate volume calculation without endorectal coil?.
        Urol Int. 2017; 98: 49-53
        • Paterson N.R.
        • Lavallée L.T.
        • Nguyen L.N.
        • Witiuk K.
        • Ross J.
        • Mallick R.
        • Shabana W.
        • MacDonald B.
        • Scheida N.
        • Fergusson D.
        • Momoli F.
        • Cnossen S.
        • Morash C.
        • Cagiannos I.
        • Breau R.H.
        Prostate volume estimations using magnetic resonance imaging and transrectal ultrasound compared to radical prostatectomy specimens.
        Can Urol Assoc J. 2016 Aug; 10: 264-268
        • Mazaheri Y.
        • Goldman D.A.
        • Di Paolo P.L.
        • Akin O.
        • Hricak H.
        Comparison of prostate volume measured by endorectal coil MRI to prostate specimen volume and mass after radical prostatectomy.
        Acad Radiol. 2015 May; 22: 556-562
        • Lee J.S.
        • Chung B.H.
        Transrectal ultrasound versus magnetic resonance imaging in the estimation of prostate volume as compared with radical prostatectomy specimens.
        Urol Int. 2007; 78: 323-327