title: Validation of an arterial tortuosity measure with application to hypertension collection of clinical hypertensive patients.
abstract: BACKGROUND
  Hypertension may increase tortuosity or twistedness of arteries. We applied a centerline extraction algorithm and tortuosity metric to magnetic resonance angiography (MRA) brain images to quantitatively measure the tortuosity of arterial vessel centerlines. The most commonly used arterial tortuosity measure is the distance factor metric (DFM). This study tested a DFM based measurement's ability to detect increases in arterial tortuosity of hypertensives using existing images. Existing images presented challenges such as different resolutions which may affect the tortuosity measurement, different depths of the area imaged, and different artifacts of imaging that require filtering.
  
  
  METHODS
  The stability and accuracy of alternative centerline algorithms was validated in numerically generated models and test brain MRA data. Existing images were gathered from previous studies and clinical medical systems by manually reading electronic medical records to identify hypertensives and negatives. Images of different resolutions were interpolated to similar resolutions. Arterial tortuosity in MRA images was measured from a DFM curve and tested on numerically generated models as well as MRA images from two hypertensive and three negative control populations. Comparisons were made between different resolutions, different filters, hypertensives versus negatives, and different negative controls.
  
  
  RESULTS
  In tests using numerical models of a simple helix, the measured tortuosity increased as expected with more tightly coiled helices. Interpolation reduced resolution-dependent differences in measured tortuosity. The Korean hypertensive population had significantly higher arterial tortuosity than its corresponding negative control population across multiple arteries. In addition one negative control population of different ethnicity had significantly less arterial tortuosity than the other two.
  
  
  CONCLUSIONS
  Tortuosity can be compared between images of different resolutions by interpolating from lower to higher resolutions. Use of a universal negative control was not possible in this study. The method described here detected elevated arterial tortuosity in a hypertensive population compared to the negative control population and can be used to study this relation in other populations.
authors.affiliation: Utah Center for Advanced Imaging Research, Department of Radiology, University of Utah, 729 Arapeen Drive, Salt Lake City, UT 84108, USA. Karl.Diedrich@utah.edu
authors.forename: Karl T
authors.initials: KT
authors.lastname: Diedrich
authors.forename: John A
authors.initials: JA
authors.lastname: Roberts
authors.forename: Richard H
authors.initials: RH
authors.lastname: Schmidt
authors.forename: Chang-Ki
authors.initials: CK
authors.lastname: Kang
authors.forename: Zang-Hee
authors.initials: ZH
authors.lastname: Cho
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Parker
mesh_terms: D000465:Algorithms; D001158:Arteries / Q000473:pathology*; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000208:ethnology / Q000473:pathology*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies