title: Accuracy and reproducibility of a novel semi-automatic segmentation technique for MR volumetry of the pituitary gland.
abstract: BACKGROUND
  Although several reports about volumetric determination of the pituitary gland exist, volumetries have been solely performed by indirect measurements or manual tracing on the gland's boundaries. The purpose of this study was to evaluate the accuracy and reproducibility of a novel semi-automatic MR-based segmentation technique.
  
  
  METHODS
  In an initial technical investigation, T1-weighted 3D native magnetised prepared rapid gradient echo sequences (1.5 T) with 1 mm isotropic voxel size achieved high reliability and were utilised in different in vitro and in vivo studies. The computer-assisted segmentation technique was based on an interactive watershed transform after resampling and gradient computation. Volumetry was performed by three observers with different software and neuroradiologic experiences, evaluating phantoms of known volume (0.3, 0.9 and 1.62 ml) and healthy subjects (26 to 38 years; overall 135 volumetries).
  
  
  RESULTS
  High accuracy of the volumetry was shown by phantom analysis; measurement errors were <4% with a mean error of 2.2%. In vitro, reproducibility was also promising with intra-observer variability of 0.7% for observer 1 and 0.3% for observers 2 and 3; mean inter-observer variability was in vitro 1.2%. In vivo, scan-rescan, intra-observer and inter-observer variability showed mean values of 3.2%, 1.8% and 3.3%, respectively. Unifactorial analysis of variance demonstrated no significant differences between pituitary volumes for various MR scans or software calculations in the healthy study groups (p > 0.05).
  
  
  CONCLUSIONS
  The analysed semi-automatic MR volumetry of the pituitary gland is a valid, reliable and fast technique. Possible clinical applications are hyperplasia or atrophy of the gland in pathological circumstances either by a single assessment or by monitoring in follow-up studies.
authors.affiliation: Department of Radiology, Charité University Medicine Berlin, Campus Virchow Clinic, Augustenburger Platz 1, 13353, Berlin, Germany. diane.renz@charite.de
authors.forename: Diane M
authors.initials: DM
authors.lastname: Renz
authors.forename: Horst K
authors.initials: HK
authors.lastname: Hahn
authors.forename: Peter
authors.initials: P
authors.lastname: Schmidt
authors.forename: Jan
authors.initials: J
authors.lastname: Rexilius
authors.forename: Markus
authors.initials: M
authors.lastname: Lentschig
authors.forename: Alexander
authors.initials: A
authors.lastname: Pfeil
authors.forename: Dieter
authors.initials: D
authors.lastname: Sauner
authors.forename: Clemens
authors.initials: C
authors.lastname: Fitzek
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Mentzel
authors.forename: Werner A
authors.initials: WA
authors.lastname: Kaiser
authors.forename: Jürgen R
authors.initials: JR
authors.lastname: Reichenbach
authors.forename: Joachim
authors.initials: J
authors.lastname: Böttcher
mesh_terms: D000328:Adult; D000465:Algorithms; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009929:Organ Size; D010902:Pituitary Gland / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012984:Software