Simultaneous Segmentation and Anatomical Labeling of the Cerebral Vasculature

We present a novel algorithm for the simultaneous segmentation and anatomical labeling of the cerebral vasculature. The method first constructs an over-complete graph capturing the vasculature. It then selects and labels the subset of edges that most likely represents the true vasculature. Unlike existing approaches that first attempt to obtain a good segmentation and then perform labeling, we jointly optimize for both by simultaneously taking into account the image evidence and the prior knowledge about the geometry and connectivity of the vasculature. This results in an Integer Program (IP), which we solve optimally using a branch-and-cut algorithm. We evaluate our approach on a public dataset of 50 cerebral MRA images, and demonstrate that it compares favorably against state-of-the-art methods

Anatomical labeling of the Circle of Willis using Maximum A Posteriori graph matching

A new method for anatomically labeling the vasculature is presented and applied to the Circle of Willis. Our method converts the segmented vasculature into a graph that is matched with an annotated graph atlas in a maximum a posteriori (MAP) way. The MAP matching is formulated as a quadratic binary programming problem which can be solved efficiently. Unlike previous methods, our approach can handle non tree-like vasculature and large topological differences. The method is evaluated in a leave-one-out test on MRA of 30 subjects where it achieves a sensitivity of 93% and a specificity of 85% with an average error of 1.5 mm on matching bifurcations in the vascular graph.Robben D., Sunaert S., Thijs V., Wilms G., Maes F., Suetens P., ''Anatomical labeling of the Circle of Willis using Maximum A Posteriori graph matching'', Lecture notes in computer science, vol. 8149, part I, pp. 566-573, 2013 (16th international conference on medical image computing and computer assisted intervention - MICCAI 2013, September 22-26, 2013, Nagoya, Japan).status: publishe

Circle of Willis variants and cerebrovascular health: Representations, prevalences, functions and related consequences. Incomplete anatomy and changes to flow appear to induce more unfavourable health outcomes

Background: The Circle of Willis (CoW) is a circular structure of arteries in which most of the blood flowing to our brains pass through. The structure has primarily been regarded as important for its ability to redistribute blood flow in case of acute arterial occlusion, but may also have a role in dampening the pressure gradient in cerebral blood flow. The CoW anatomy also varies considerably, where its segments can be missing or thinner than normal, and therefore appears as a risk factor for cerebrovascular health. Objectives: To describe and report (I) the observed CoW variants and anatomy, and also examine the incomplete CoW variants’ associations to (II) white matter hyperintensities (WMH) and (III) saccular intracranial aneurysms (IA) compared to the complete CoW variant. Methods: Participants were invited from The Seventh Tromsø Study of which 1878 underwent magnetic resonance imaging. From the scans, CoW variants were semiautomatically classified. Likewise, WMH was automatically segmented and IAs were manually ascertained by radiologists. Results: The complete CoW is not very prevalent in participants older than 40 years old, and our findings suggest that the CoW becomes more incomplete with older age. Furthermore, incomplete CoW variants were not associated with increased WMH volume compared to the complete CoW variant. Incomplete CoW variants were associated increased odds of IA presence compared to the complete CoW variant. Conclusion: The results indicate that a complete CoW variant is not common in adults and elderly, which may have unfortunate consequences when incomplete CoW variants are associated with increased prevalence of IAs. Fortunately, not all results imply unfavourable outcomes, but further study of the CoW changes and possible effects of the variants over time are required.Bakgrunn: Willis Sirkel (CoW) er en sirkulær struktur av arterier i bunnen av hjernen som det meste av blodet går igjennom på tur til hjernen. Strukturen har vært antatt viktig for dens evner til å omdisponere blod i tilfellet arterier går tett, men i nyere tid har det også blitt foreslått at strukturen kan være viktig for å dempe pulstrykket i hjernen fra hjertet. Anatomien til CoW varierer mye, der segmenter mangler eller er tynnere enn normalt, og framstår dermed som et mulig risikomoment for hjernehelsen. Mål: Å beskrive (I) CoW varianter og anatomi. Analysere ufullstendige CoW varianters assosiasjoner til (II) vevsskader i hjernens indre som kalles hvit materie hyperintensiteter (WMH) og (III) sakkulære intrakranielle aneurismer (IA) sammenliknet med den fullstendige CoW varianten. Metoder: Deltakere ble invitert fra den Syvende Tromsøundersøkelsen hvorav 1878 ble tatt hjernebilder av med magnetresonans. Fra disse bildene ble CoW anatomi klassifisert. Likeså ble WMH automatisk segmentert og IA påvist av radiologer. Resultater: Den fullstendige CoW var ikke vanlig blant deltakerne eldre enn 40 år, og vi observerte også at CoW anatomien ble mer og mer ufullstendig hos eldre. Videre var ufullstendige CoW varianter ikke assosiert med høyere forekomst av WMH sammenliknet med den fullstendige CoW. Videre var ufullstendige CoW varianter assosiert med forhøyet odds for å ha IA sammenliknet med den fullstendige CoW. Konklusjon: Resultatene antyder at en fullstendig CoW ikke er spesielt vanlig hos voksne og eldre, noe som kan få uheldige følger når ufullstendige CoW er assosiert med økt forekomst av IA. Heldigvis antyder ikke alle resultatene negative følger, men mer forskning på CoW endringer og mulige effekter av anatomien over tid behøves for å stadfeste resultatene