© Schattauer 2013 Methods Inf Med 6/2013 467 Original Articles A Statistical Cerebroarterial Atlas Derived from 700 MRA Datasets N. D. Forkert 1 ; J. Fiehler 1 ; S. Suniaga 2 ; H. Wersching 3 ; S. Knecht 4 ; A. Kemmling 1,5 1 Department of Diagnostic and Interventional Neuroradiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; 2 Department of Computational Neuroscience, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; 3 Department of Epidemiology and Social Medicine, University of Münster, Münster, Germany; 4 Department of Neurology, University of Münster, Münster, Germany; 5 Department of Clinical Radiology, University of Münster, Münster, Germany Keywords Magnetic resonance imaging, angiography, arteries, statistical atlas, computer-assisted image processing Summary Objectives: The cerebroarterial system is a complex network of arteries that supply the brain cells with vitally important nutrients and oxygen. The inter-individual differences of the cerebral arteries, especially at a finer level, are still not understood sufficiently. The aim of this work is to present a statistical cerebroarterial atlas that can be used to overcome this problem. Methods: Overall, 700 Time-of-Flight (TOF) magnetic resonance angiography (MRA) datasets of healthy subjects were used for atlas generation. Therefore, the cerebral ar- teries were automatically segmented in each dataset and used for a quantification of the vessel diameters. After this, each TOF MRA dataset as well as the corresponding vessel segmentation and vessel diameter dataset were registered to the MNI brain atlas. Fi- nally, the registered datasets were used to calculate a statistical cerebroarterial atlas that incorporates information about the aver- age TOF intensity, probability for a vessel oc- currence and mean vessel diameter for each voxel. Results: Visual analysis revealed that ar- teries with a diameter as small as 0.5 mm are well represented in the atlas with quanti- tative values that are within range of ana- tomical reference values. Moreover, a highly significant strong positive correlation be- tween the vessel diameter and occurrence probability was found. Furthermore, it was shown that an intensity-based automatic segmentation of cerebral vessels can be con- siderable improved by incorporating the atlas information leading to results within the range of the inter-observer agreement. Conclusion: The presented cerebroarterial atlas seems useful for improving the under- standing about normal variations of cerebral arteries, initialization of cerebrovascular seg- mentation methods and may even lay the foundation for a reliable quantification of subtle morphological vascular changes. Correspondence to: Nils Daniel Forkert Department of Diagnostic and Interventional Neuroradiology University Medical Center Hamburg-Eppendorf Bldg. W36 Martinistraße 52 20246 Hamburg Germany E-mail: n.forkert@uke.uni-hamburg.de Methods Inf Med 2013; 52: 467–474 doi: 10.3414/ME13-02-0001 received: February 1, 2013 accepted: April 30, 2013 prepublished: November 5, 2013 1. Introduction The cerebrovascular system is a very com- plex network of blood vessels that cross through the whole brain and supply the cells of the brain tissue with vitally impor- tant nutrients and oxygen. Although the coarse structure and spatial relationship of the main cerebrovascular arteries are well known, inter-individual differences of the cerebral arteries at a finer level are still not understood sufficiently. More precisely, not much is known about the variability of shape, size and position of the small vessels but it may be assumed that the variabil- ity of the cerebral arteries increases with each bifurcation towards the periphery (▶Figure 1). Morphological changes of the cerebro- vascular system have been associated with age-related alterations of the human brain [1] as well as to several diseases such as- hypertension [2] and Alzheimer’s disease [3]. However, the differentiation between significant morphological changes and normal variations of cerebral arteries may not be eye-catching and difficult. Thus, an improved understanding of normal inter- individual variations is most important to identify significant structural pathological changes. Several deterministic atlases of the cerebrovascular system have been gener- ated and are currently available. However, these deterministic cerebrovascular atlases focus mostly on the symbolic description of the cerebrovascular system, which was derived from only one subject in most cases (e.g. [4]). Thus, these atlases are not capable of representing variations of cer- ebral vessels between different individuals but have rather an educational purpose in For personal or educational use only. No other uses without permission. All rights reserved. Downloaded from www.methods-online.com on 2017-12-30 | IP: 54.70.40.11