title: Magnetic resonance imaging diffusion tensor tractography: evaluation of anatomic accuracy of different fiber tracking software packages.
abstract: BACKGROUND
  Diffusion tensor imaging (DTI)-based tractography has become an integral part of preoperative diagnostic imaging in many neurosurgical centers, and other nonsurgical specialties depend increasingly on DTI tractography as a diagnostic tool. The aim of this study was to analyze the anatomic accuracy of visualized white matter fiber pathways using different, readily available DTI tractography software programs.
  
  
  METHODS
  Magnetic resonance imaging scans of the head of 20 healthy volunteers were acquired using a Siemens Symphony TIM 1.5T scanner and a 12-channel head array coil. The standard settings of the scans in this study were 12 diffusion directions and 5-mm slices. The fornices were chosen as an anatomic structure for the comparative fiber tracking. Identical data sets were loaded into nine different fiber tracking packages that used different algorithms. The nine software packages and algorithms used were NeuroQLab (modified tensor deflection [TEND] algorithm), Sörensen DTI task card (modified streamline tracking technique algorithm), Siemens DTI module (modified fourth-order Runge-Kutta algorithm), six different software packages from Trackvis (interpolated streamline algorithm, modified FACT algorithm, second-order Runge-Kutta algorithm, Q-ball [FACT algorithm], tensorline algorithm, Q-ball [second-order Runge-Kutta algorithm]), DTI Query (modified streamline tracking technique algorithm), Medinria (modified TEND algorithm), Brainvoyager (modified TEND algorithm), DTI Studio modified FACT algorithm, and the BrainLab DTI module based on the modified Runge-Kutta algorithm. Three examiners (a neuroradiologist, a magnetic resonance imaging physicist, and a neurosurgeon) served as examiners. They were double-blinded with respect to the test subject and the fiber tracking software used in the presented images. Each examiner evaluated 301 images. The examiners were instructed to evaluate screenshots from the different programs based on two main criteria: (i) anatomic accuracy of the course of the displayed fibers and (ii) number of fibers displayed outside the anatomic boundaries.
  
  
  RESULTS
  The mean overall grade for anatomic accuracy was 2.2 (range, 1.1-3.6) with a standard deviation (SD) of 0.9. The mean overall grade for incorrectly displayed fibers was 2.5 (range, 1.6-3.5) with a SD of 0.6. The mean grade of the overall program ranking was 2.3 with a SD of 0.6. The overall mean grade of the program ranked number one (NeuroQLab) was 1.7 (range, 1.5-2.8). The mean overall grade of the program ranked last (BrainLab iPlan Cranial 2.6 DTI Module) was 3.3 (range, 1.7-4). The difference between the mean grades of these two programs was statistically highly significant (P < 0.0001). There was no statistically significant difference between the programs ranked 1-3: NeuroQLab, Sörensen DTI Task Card, and Siemens DTI module.
  
  
  CONCLUSIONS
  The results of this study show that there is a statistically significant difference in the anatomic accuracy of the tested DTI fiber tracking programs. Although incorrectly displayed fibers could lead to wrong conclusions in the neurosciences field, which relies heavily on this noninvasive imaging technique, incorrectly displayed fibers in neurosurgery could lead to surgical decisions potentially harmful for the patient if used without intraoperative cortical stimulation. DTI fiber tracking presents a valuable noninvasive preoperative imaging tool, which requires further validation after important standardization of the acquisition and processing techniques currently available.
authors.affiliation: Department of Neurosurgery, University Hospital Regensburg, Regensburg, Germany. Electronic address: guenther.feigl@web.de.
authors.forename: Guenther C
authors.initials: GC
authors.lastname: Feigl
authors.affiliation: Department of Neurosurgery, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hiergeist
authors.affiliation: Institute of Radiology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Fellner
authors.affiliation: Department of Neurosurgery, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Karl-Michael M
authors.initials: KM
authors.lastname: Schebesch
authors.affiliation: Department of Neurosurgery, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Doenitz
authors.affiliation: Institute of Radiology, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Finkenzeller
authors.affiliation: Department of Neurosurgery, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Brawanski
authors.affiliation: Department of Neurosurgery, University Hospital Regensburg, Regensburg, Germany.
authors.forename: Juergen
authors.initials: J
authors.lastname: Schlaier
mesh_terms: D000328:Adult; D000465:Algorithms; D016880:Anisotropy; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009434:Neural Pathways; D009493:Neurosurgery; D011871:Radiology; D015203:Reproducibility of Results; D012984:Software; D055815:Young Adult
keywords: Anatomic accuracy; Brain mapping; DTI; Navigation; Surgery