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142Chapter8REGISTRATIONAND VISUALIZATIONTodisplaythehologramsinthecorrectanatomicalorientationwhenlookingthroughtheHoloLensanaccurateregistrationofthehologramswiththeabdomenofthepatientisrequiredA3D–printedsterilizablestainlesssteelpointerwithalaserengravedsecondquickresponsemarkerwasdesignedinhouse Withthispointer,theuserindicatesthefiveabdominalnevionthepatientthathadradiopaque skinmarkers on them during the acquisition of the computedtomographicangiograph(Figure3)TheHoloLensregistersthe3DlocationsofthenevibytrackingthesecondquickresponsemarkeronthepointerByusingaProcrustesalgorithmtheHoloLenscalculateshowtheimported3Dmodelsfromthecomputedtomographicangiographshouldfitoverthepatientintheroom(Figure 4) With voicecommandsoraholographicmenu theusercanswitchbetweenthevisualizationofdifferentanatomicalstructuresBecausethepatient’spositionistrackedbytheHoloLensusingthequickresponsemarkerabovethenavelitispossibletoinspecttheanatomyhologramfromdifferentpositionsevenwhenthepatientortheHoloLensuserismovingNowtheusercanusethehologramtomarktheperforatorlocationsinpreparationforaDIEPflapharvestorusetheHoloLenstovisualizethecourseoftheepigastricarteriesduringsurgeryIntheoperatingroomdissectioncanbeginwhilethehologramremainsinplacebecauseitisregistered toasterilizedquickresponsecodeoutside thesurgicalareaanddoesnotneedthenevianymoreFigure3 Tomake theHoloLensregister theanatomyhologram to thequickresponsecodeabove thenavelabdominalneviareindicatedwithastainless-steelpointerthatisrecognizedbytheHoloLens