Michael Burns Martin Haidacher Eduard Gröller Ivan ViolaWolfgang Wein

Feature Emphasis and Contextual Cutaways

for Multimodal Medical Visualization

Michael BurnsMartin Haidacher

Eduard Gröller

Ivan ViolaWolfgang Wein

Michael Burns - Contextual Medical Visualization

Preface

CT scan with embedded Ultrasound data


Visualization Scenario Poking needles

Liver biopsyRadio frequency

ablation

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


Visualization Scenario

CT Scan Data Ultrasound Data



Ultrasound embedded in dense volume



Ultrasound embedded in sparse volume



Ultrasound with contextual cutaway


Key Requirements

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]


Visualization PipelineVolumetric Data(e.g. CT Scan)

Importance in the Transfer Function

Viewpoint InformationObject of Interest

(e.g. Ultrasound Plane)

Contextual Cutaway ViewsImportance-Driven

Shading

Integrating Occlusion with Importance







Shading



Defining 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


Defining Importance

Material boundaries

Component 1

Component 2

c2, α2, I2

c1, α1, I1

F(x, y, z)

|F(x

, y, z

)|







Shading



Feature Emphasis

Visual distinction between materialsEmphasis of important materials

Material propertiesColorOpacity

Lighting propertiesShading conveys detail


Feature Emphasis

Full Shading No Shading


Feature Emphasis

Full Shading Importance Shading


Feature Emphasis

Importance Shading

Emphasis: E

Shaded color: Cshaded

Subdued color:Csubdued = E * Cunshaded +

(1 – E) * Cshaded

Final color:Cfinal = I * Cshaded +

(1 – I) * Csubdued


Feature Emphasis







Shading



Contextual Cutaways

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


Traditional Cutaways

v

Base

Clear

Object of Interest


Traditional Cutaways

Small Large


Contextual Cutaways

v

1

2

Base

Transition

Clear

Overlay

d


Layered Visualization

Base Transition



Base, Transition Overlay



Base, Transition, Overlay Base







Shading



Occlusion

v = 1

= 0

1

0.75

0.5

0.25

0


Occlusion Compensation 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))


Occlusion Compensation

Base

Tran

sition

Clear

Overla

y

Liver (0.5) Vessels (0.99)

Occlusion value (Ω)

α sc

ale

fact

or

0 10.5

Flesh (0.01)0

1

τu = Iτl = max(2 * I – 1, 0)


Results

No cutaway(over draw)


Results

Simple cutaway


Results

Simple cutawaywith interior


Results

Interior becomes overlay region


Results

Transition area added


Results


Conclusions Visualization

Material importance defined within transfer function Important 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 operations Initial feedback has been positiveCurrently being evaluated for clinical use


Acknowledgments

Gianluca PaladiniSiemens Corporate Research

Adam FinkelsteinPrinceton University

Paper reviewers EuroVis 2007 hosts

Documents

Michael Burns Martin Haidacher Eduard Gröller Ivan ViolaWolfgang Wein