title: Volume measurement of the intracranial aneurysm: a discussion and comparison of the alternatives to manual segmentation.
abstract: OBJECTIVE
  Several modalities are available for volumetric measurement of the intracranial aneurysm. We discuss the challenges involved in manual segmentation, and analyze the application of alternative methods using automatic segmentation and geometric formulae in measurement of aneurysm volumes and coil packing density.
  
  
  METHODS
  The volumes and morphology of 38 aneurysms treated with endovascular coiling at a single center were measured using three-dimensional rotational angiography (3DRA) reconstruction software using automatic segmentation. Aneurysm volumes were also calculated from their height, width, depth, size of neck, and assumed shape in 3DRA images using simple geometric formulae. The aneurysm volumes were dichotomized as "small" or "large" using the median volume of the studied population (54 mm(3)) measured by automatic segmentation as the cut-off value for further statistical analysis.
  
  
  RESULTS
  A greater proportion of aneurysms were categorized as being "small" when geometric formulae were applied. The median aneurysm volumes obtained were 54.5 mm(3) by 3DRA software, and 30.6 mm(3) using mathematical equations. An underestimation of aneurysm volume with a resultant overestimation in the calculated coil packing density (p = 0.002) was observed.
  
  
  CONCLUSIONS
  Caution must be exercised in the application of simple geometric formulae in the management of intracranial aneurysms as volumes may potentially be underestimated and packing densities falsely elevated. Future research should focus on validation of automatic segmentation in volumetric measurement and improving its accuracy to enhance its application in clinical practice.
authors.affiliation: Department of Radiology, Queen Mary Hospital, Hong Kong S.A.R, China.
authors.forename: Siang-Hua Victor
authors.initials: SH
authors.lastname: Chan
authors.affiliation: Department of Neurosurgery, Kwong Wah Hospital, Hong Kong S.A.R, China.
authors.forename: Kai-Sing Alain
authors.initials: KS
authors.lastname: Wong
authors.affiliation: Department of Neurosurgery, Kwong Wah Hospital, Hong Kong S.A.R, China.
authors.forename: Yat-Ming Peter
authors.initials: YM
authors.lastname: Woo
authors.affiliation: Department of Neurosurgery, Kwong Wah Hospital, Hong Kong S.A.R, China.
authors.forename: Kwong-Yau
authors.initials: KY
authors.lastname: Chan
authors.affiliation: Department of Neurosurgery, Kwong Wah Hospital, Hong Kong S.A.R, China.
authors.forename: Kar-Ming
authors.initials: KM
authors.lastname: Leung
keywords: Automatic segmentation; Coil packing density; Geometric formulae; Intracranial aneurysm volume; Three-dimensional rotational angiography