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Volume measurement of the intracranial aneurysm: a discussion and comparison of the alternatives to manual segmentation.

Chan SH, Wong KS, Woo YM, Chan KY, Leung KM - J Cerebrovasc Endovasc Neurosurg (2014)

Bottom Line: Several modalities are available for volumetric measurement of the intracranial aneurysm.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Queen Mary Hospital, Hong Kong S.A.R, China.

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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus

The aneurysm is identified and isolated with its parent vessels.
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Figure 2: The aneurysm is identified and isolated with its parent vessels.

Mentions: Neck size, height, width, and depth were measured using three-dimensional rotational angiography (3DRA). 3DRA images were acquired using an angiographic unit (Integris Allura Neuro; Philips Healthcare, Best, The Netherlands) and injection of a non-ionic contrast agent into an internal carotid artery or a vertebral artery. On a dedicated 3DRA workstation, the relevant cerebral vasculature was reconstructed and a three-dimensional "road-map" was acquired with a 2563 matrix. The aneurysm, with its parent vessels was first identified (Fig. 1) and outlined individually by a neurosurgeon who specialized in angiographic neuro-intervention, as well as by the primary author, a radiologist, for the purposes of segmentation. The histogram was standardized to default settings to eliminate inter-observer variability of aneurysm size. Next, using a "cut" tool provided by the workstation, the aneurysm was isolated from the parent vessels and related vasculature (Fig. 2). To ensure accuracy, the reconstructed and isolated aneurysm image would be viewed from different three-dimensional angles, before placing the automatic segmentation cursor over the perceived epicenter of the aneurysm. The computer workstation then proceeded with the interactive contouring based on isointensity surface extraction (ISE) and subsequent measurement of the aneurysm volume (Fig. 3). The isointensity surface is defined3) as the interface between the regions of the image I: I ≥ c (the inside), and I < c (the outside), where c is a constant intensity value, the surface is obtained by marching cubes method, where the points of the voxel cube are obtained by linear interpolation, producing a mesh with subvoxel accuracy, displayed with a measured aneurysm volume on the workstation. ISE and other forms of automatic segmentation have been previously reviewed and are known to have differed from the gold standard of manual segmentation within acceptable limits.3)


Volume measurement of the intracranial aneurysm: a discussion and comparison of the alternatives to manual segmentation.

Chan SH, Wong KS, Woo YM, Chan KY, Leung KM - J Cerebrovasc Endovasc Neurosurg (2014)

The aneurysm is identified and isolated with its parent vessels.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4296048&req=5

Figure 2: The aneurysm is identified and isolated with its parent vessels.
Mentions: Neck size, height, width, and depth were measured using three-dimensional rotational angiography (3DRA). 3DRA images were acquired using an angiographic unit (Integris Allura Neuro; Philips Healthcare, Best, The Netherlands) and injection of a non-ionic contrast agent into an internal carotid artery or a vertebral artery. On a dedicated 3DRA workstation, the relevant cerebral vasculature was reconstructed and a three-dimensional "road-map" was acquired with a 2563 matrix. The aneurysm, with its parent vessels was first identified (Fig. 1) and outlined individually by a neurosurgeon who specialized in angiographic neuro-intervention, as well as by the primary author, a radiologist, for the purposes of segmentation. The histogram was standardized to default settings to eliminate inter-observer variability of aneurysm size. Next, using a "cut" tool provided by the workstation, the aneurysm was isolated from the parent vessels and related vasculature (Fig. 2). To ensure accuracy, the reconstructed and isolated aneurysm image would be viewed from different three-dimensional angles, before placing the automatic segmentation cursor over the perceived epicenter of the aneurysm. The computer workstation then proceeded with the interactive contouring based on isointensity surface extraction (ISE) and subsequent measurement of the aneurysm volume (Fig. 3). The isointensity surface is defined3) as the interface between the regions of the image I: I ≥ c (the inside), and I < c (the outside), where c is a constant intensity value, the surface is obtained by marching cubes method, where the points of the voxel cube are obtained by linear interpolation, producing a mesh with subvoxel accuracy, displayed with a measured aneurysm volume on the workstation. ISE and other forms of automatic segmentation have been previously reviewed and are known to have differed from the gold standard of manual segmentation within acceptable limits.3)

Bottom Line: Several modalities are available for volumetric measurement of the intracranial aneurysm.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology, Queen Mary Hospital, Hong Kong S.A.R, China.

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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus