Feature Emphasis and Contextual Cutaways for Multimodal Medical Visualization

Michael BurnsMartin Haidacher

Eduard Gröller

Ivan ViolaWolfgang Wein

CT scan with embedded Ultrasound data

Michael Burns - Contextual Medical Visualization

Poking needlesLiver biopsyRadio frequency

ablation

Procedure:Patient has CT scanNeedle path is plannedUses ultrasound probe to help guide needleDoctor views CT scan at time of procedure


CT Scan Data Ultrasound Data


Ultrasound embedded in dense volume


Ultrasound embedded in sparse volume


Ultrasound with contextual cutaway


Volumetric dataTissue types differentiated and ranked

○ Important materials most visible○ Unimportant materials provide context

Ultrasound imageCaptured with 3D position and orientation of

probeRegistration between coordinate frames

[Wein05]


Volumetric Data(e.g. CT Scan)


Importance in the Transfer Function


Viewpoint InformationViewpoint Information Object of Interest(e.g. Ultrasound Plane)

Object of Interest(e.g. Ultrasound Plane)

Contextual Cutaway Views

Contextual Cutaway ViewsImportance-Driven

Shading

Importance-Driven Shading

Integrating Occlusion with Importance



Rank materials by relevance

1. Definition in volumetric spaceUses auxiliary volumeRequires preprocessing per dataset

2. Definition in transfer function spaceExtra value in transfer functionShared among datasets


Material boundaries

F(x, y, z)

|F(

x, y

, z)|










Shading





Visual distinction between materialsEmphasis of important materials

Material propertiesColorOpacity

Lighting propertiesShading conveys detail


Full Shading No Shading


Full Shading Importance Shading


Importance Shading

Emphasis: E

Shaded color: Cshaded

Subdued color:Csubdued = E * Cunshaded +

(1 – E) * Cshaded

Final color:Cfinal = I * Cshaded +

(1 – I) * Csubdued










Shading





Object of interest obscured by volumeHigh importance

○ Should be visible○ May obscure object

Low importance○ Not necessarily visible○ May not obscure object

View-dependent cutaway structure


v

Base

Clear

Object of Interest


Small Large


v

1

2

Base

Transition

Clear

Overlay

d


Base Transition


Base, Transition Overlay


Base, Transition, Overlay Base










Shading





v = 1

= 0

1

0.75

0.5

0.25

0


Fade material based on occlusion value between two occlusion thresholdsThresholds based on importance

Modify opacity:τu = I

τl = max(2 * I – 1, 0)

α’ = α * (1 – ramp(τu, τl, Ω))


Base

Trans

ition

Clear

Overla

y

Liver (0.5)Liver (0.5) Vessels (0.99)Vessels (0.99)

Occlusion value (Ω)

α sc

ale

fact

or

0 10.5

Flesh (0.01)Flesh (0.01)0

1

τu = Iτl = max(2 * I – 1, 0)


No cutaway(over draw)


Simple cutaway


Simple cutawaywith interior


Interior becomes overlay region


Transition area added


VisualizationMaterial importance defined within transfer functionImportant materials emphasized through shadingView-dependent cutaway structure determines

occlusion of object-of-interestMaterials removed in occluding areas, according to

their importance

ApplicationVisualize ultrasound data within CT scan for needle

driven operationsInitial feedback has been positiveCurrently being evaluated for clinical use


Gianluca PaladiniSiemens Corporate Research

Adam FinkelsteinPrinceton University

Paper reviewers EuroVis 2007 hosts


Feature Emphasis and Contextual Cutaways for Multimodal Medical Visualization

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