1	Automatic interpretation of stroke images by means of an anatomical atlas Wieslaw L. Nowinski^1,2, Ihar Volkau¹, Bhanu Prakash KN¹, A Ananthasubramaniam¹, Nick Ivanov¹, Norman Beauchamp² ¹Biomedical Imaging Lab Agency for Science, Technology and Research, Singapore ²Department of Radiology, University of Washington Medical Center, Seattle, WA
2	Outline Introduction Material Method Atlas-assisted tool Discussion Future work
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4	Definition of stroke Stroke (or cerebrovascular accident) is a sudden onset of neurological injury vascular in origin. Stroke often results in the impairment of movement, sensation, and/or function.
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6	Stroke then…. Hippocrates provided the first clear description of stroke Greatness is no protection: Yalta Conference: Roosevelt, Churchill, and Stalin, all had CVD Roosevelt later died of a fatal stroke
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8	Stroke epidemiology in US (2003) 745,700 diagnosed with acute stroke 599,000 were ischemic strokes 146,700 were hemorrhagic strokes 37% of hemorrhagic attacks resulted in death 10% of ischemic attacks resulted in death 68% of all deaths due to ischemic strokes
9	Epidemiology in US (2003) 5% to 30% of stroke survivors are permanently disabled; 20% require institutional care at 3 months after the attack; Ichemic stroke survivors over the age of 65 (6 months after the stroke): aphasia (19%); dependence in daily living activities (26%); depressive symptoms (35%); hemiparesis (50%); inability to walk unassisted (30%); institutionalization in a care facility (26%).
10	Cost The cost for inpatient care, rehabilitation, and necessary follow-up care for mild ischemic stroke totals approximately $13,019 within 1 month of the attack. The cost of a severe ischemic stroke totals approximately $20,346, resulting in an average lifetime cost for ischemic stroke of $140,048. In 2003, the estimated direct and indirect costs for stroke in the U.S. exceeded $50 billion.
11	Stroke epidemiology trends in US 167% increase in the incidence among men; 140% increase in the incidence among women; Surpass 1 million in 2050.
12	Stroke service organization
13	Clinical goals Advances in neuroimaging redefining the treatment algorithms for neurovascular disease less invasive greater diagnostic yield redefining the treatment window in acute stroke through image guidance Risk factor identification neuroimaging for patient selection and outcome measure in epidemiological studies
14	Prevention via safer evaluation Cut point for surgical intervention incorporates in the surgical arm “risk of evaluation” Strokes referable to carotid often in patients with stenosis less than this cut point-60-70% decreasing risk of evaluation can lower the cut point at which surgery, or stenting, is advantageous better characterization of carotid disease may enable identification of a higher risk cohort
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16	Material: scans and maps MR diffusion scans MR perfusion maps Cerebral blood flow (CBF) Cerebral blood volume (CBV) Mean transit time (MTT) Time to peak (TTP) Peak height (PKHT)
17	Diffusion and perfusion images
18	"METHOD" METHOD
19	Rationale – figures USA, 2003: 7.0 million stroke-related diagnostic imaging procedures $ 266.4 million in generated sales $1,813.0 million in MRI sales
20	Rationale – objectives Facilitate image interpretation Reduce cost Reduce time
21	Method Electronic brain atlas is constructed Fast atlas-to-data mapping is devised Tool for atlas-assisted interpretation of stroke images is developed
22	Brain atlas construction Talairach-Tournoux print atlas is digitized Atlas is fully segmented and extended Brodmann’s areas and gyri are segmented Atlas is fully labeled
23	Electronic brain atlas Original atlas Electronic atlas Atlas with labels
24	Atlas to data mapping Identification of the midsagittal plane (MSP) Identification of the superior axial plane of the cerebrum Identification of the inferior axial plane of the cerebrum Determination of the cerebrum shape Fitting the atlas MSP and cerebrum shape to those of the data
25	MSP calculation The MSP is calculated by using cross entropy (Kullback and Leibler's measure) The calculation is fully automatic and takes a fraction of second The method handles DWI and all perfusion maps
26	Midsagittal plane - examples
27	Bounding box calculation A box bounding of the brain at each slice is calculated by: determining the largest connected component projecting it horizontally and vertically with respect to the MSP calculating the extent of the projections The calculation is fully automatic and takes a fraction of second
28	Bounding box - examples
29	"RESULTS" RESULTS
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31	Perfusion maps (CBV, MTT) labeled
32	"TOOL" TOOL
33	Atlas-assisted tool A system is developed in Java facilitating atlas-assisted interpretation of MR stroke images. It performs the following functions: Load scan Warp and overlay atlas Browse scan/atlas Read anatomical labels - Blend diffusion-perfusion-atlas
34	Workflow Load an MR diffusion scan Warp and overlay the atlas Browse and label the scan and read the underlying anatomy Load perfusion maps Select a map to be overlaid on DWI Browse, label, and blend diffusion-perfusion-atlas
35	"DISCUSSION" DISCUSSION
36	Advantages Underlying anatomy provided Increased confidence Facilitated presentation Reduced time
37	Advantages - anatomy Anatomy without morphological scan acquisition Anatomy without registration of morphology with diffusion/perfusion Anatomy provided within a few seconds
38	"FUTURE WORK" FUTURE WORK
39	Potential More information/images can be added: More modalities Atlases Textual information Archive of previous cases
40	Atlas-related potential More atlases can be added including: Blood supply territories atlas Probabilistic atlas of blood supply territories Probabilistic atlas of cerebrovascular lesions Atlas of cerebrovascular variants
41	Example - combined atlas: anatomy + blood supply territories
42	Summary Atlas-assisted interpretation of MR stroke images can potentially: Provide underlying anatomy and vasculature Provide variability Increase confidence Facilitate presentation Reduce time Lower cost Enable aggregation of knowledge
43	Thank you If you want to try this tool, please visit our stand alone electronic Scientific Exhibit #32 : Nowinski et al: A reference atlas of cerebral vasculature.