title: Threshold selection criteria for quantification of lumbosacral cerebrospinal fluid and root volumes from MRI.
abstract: OBJECTIVE
  The high variability of CSF volumes partly explains the inconsistency of anesthetic effects, but may also be due to image analysis itself. In this study, criteria for threshold selection are anatomically defined.
  
  
  METHODS
  T2 MR images (n = 7 cases) were analyzed using 3-dimentional software. Maximal-minimal thresholds were selected in standardized blocks of 50 slices of the dural sac ending caudally at the L5-S1 intervertebral space (caudal blocks) and middle L3 (rostral blocks). Maximal CSF thresholds: threshold value was increased until at least one voxel in a CSF area appeared unlabeled and decreased until that voxel was labeled again: this final threshold was selected. Minimal root thresholds: thresholds values that selected cauda equina root area but not adjacent gray voxels in the CSF-root interface were chosen.
  
  
  RESULTS
  Significant differences were found between caudal and rostral thresholds. No significant differences were found between expert and nonexpert observers. Average max/min thresholds were around 1.30 but max/min CSF volumes were around 1.15. Great interindividual CSF volume variability was detected (max/min volumes 1.6-2.7).
  
  
  CONCLUSIONS
  The estimation of a close range of CSF volumes which probably contains the real CSF volume value can be standardized and calculated prior to certain intrathecal procedures.
authors: Laboratory of Neuroanatomy, Human Anatomy and Embryology Unit. Faculty of Medicine, Universitat de Barcelona, Barcelona, Spain; CAP Antãn Borja, Consorci Sanitari de Terrassa, Rubí, Barcelona, Spain.
authors: Anna
authors: A
authors: Puigdellívol-Sánchez
authors: Miguel Angel
authors: MA
authors: Reina
authors: Juan
authors: J
authors: San-Molina
authors: José Manuel
authors: JM
authors: Escobar
authors: Julio
authors: J
authors: Castedo
authors: Alberto
authors: A
authors: Prats-Galino
mesh_terms: D000465:Algorithms; D002555:Cerebrospinal Fluid / Q000166:cytology*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D017116:Low Back Pain / Q000473:pathology*; D008161:Lumbosacral Region / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013116:Spinal Cord / Q000473:pathology*; D013126:Spinal Nerve Roots / Q000473:pathology*
keywords: MRI; Threshold; cerebrospinal fluid; lumbosacral region