title: Development and Evaluation of a Semi-automated Segmentation Tool and a Modified Ellipsoid Formula for Volumetric Analysis of the Kidney in Non-contrast T2-Weighted MR Images.
abstract: Volumetric analysis of the kidney parenchyma provides additional information for the detection and monitoring of various renal diseases. Therefore the purposes of the study were to develop and evaluate a semi-automated segmentation tool and a modified ellipsoid formula for volumetric analysis of the kidney in non-contrast T2-weighted magnetic resonance (MR)-images. Three readers performed semi-automated segmentation of the total kidney volume (TKV) in axial, non-contrast-enhanced T2-weighted MR-images of 24 healthy volunteers (48 kidneys) twice. A semi-automated threshold-based segmentation tool was developed to segment the kidney parenchyma. Furthermore, the three readers measured renal dimensions (length, width, depth) and applied different formulas to calculate the TKV. Manual segmentation served as a reference volume. Volumes of the different methods were compared and time required was recorded. There was no significant difference between the semi-automatically and manually segmented TKV (p = 0.31). The difference in mean volumes was 0.3 ml (95% confidence interval (CI), -10.1 to 10.7 ml). Semi-automated segmentation was significantly faster than manual segmentation, with a mean difference = 188 s (220 vs. 408 s); p < 0.05. Volumes did not differ significantly comparing the results of different readers. Calculation of TKV with a modified ellipsoid formula (ellipsoid volume × 0.85) did not differ significantly from the reference volume; however, the mean error was three times higher (difference of mean volumes -0.1 ml; CI -31.1 to 30.9 ml; p = 0.95). Applying the modified ellipsoid formula was the fastest way to get an estimation of the renal volume (41 s). Semi-automated segmentation and volumetric analysis of the kidney in native T2-weighted MR data delivers accurate and reproducible results and was significantly faster than manual segmentation. Applying a modified ellipsoid formula quickly provides an accurate kidney volume.
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Hannes
authors.initials: H
authors.lastname: Seuss
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Janka
authors.affiliation: Chimaera GmbH, Am Weichselgarten 7, 91058, Erlangen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Prümmer
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Cavallaro
authors.affiliation: Department of Neurology, Klinikum Nuremberg, Breslauer Str. 201, 90471, Nuremberg, Germany.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hammon
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Ragnar
authors.initials: R
authors.lastname: Theis
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Sandmair
authors.affiliation: Department of Nephropathology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Krankenhausstr. 8-10, 91054, Erlangen, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Amann
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Bäuerle
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Uder
authors.affiliation: Department of Radiology, University Hospital Erlangen, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg, Maximiliansplatz 1, 91054, Erlangen, Germany. matthias.hammon@uk-erlangen.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Hammon
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging*; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D015203:Reproducibility of Results
keywords: Clinical application; Ellipsoid; Evaluation research; Image analysis; Kidney; Magnetic resonance imaging; Radiology workflow; Segmentation; Semi-automated