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Improved Techniques for

Fast Sliding Thin-Slab

Volume VisualizationJanice Z Turlington*, William E. Higgins*** Electrical Engineering, **The BioEngineering Program,

and *Computer Science and EngineeringThe Pennsylvania State University, University Park, PA 16802

SPIE Medical Imaging 2000, San Diego CA, 13 February

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Motivation Locate small structures in 3D CT volume

ObjectivesShow “true” information

Confident results for professional use

Fast techniques for real-time use

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Existing Visualization Techniques

projection imaging1

curved-section reformatting3

volume/surface rendering4multi-planar reconstruction2

virtual endoscopic rendering5

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Existing Limitationsdependence on a priori knowledge

voxel intensity decisions

partial-volume artifacts

voxel boundaries1{Hohne87,Napel92}

2{Robb1988,Remy96,McGuinness97}3{Robb1988,Hara96,Ramaswamy99}

4{Ney90,Drebin88,Tiede90} 5{Vining94,Ramaswamy99}

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Sliding Thin-Slab Visualization

improve understanding of lung changes

more precise characterization of distribution changes{Remy-Jardin et al. 96}

{Napel 92}(STS-MIP)

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Our New STS Techniques

fast general-purpose algorithms

dynamic sequence visualization

accurate 3D impression

slab change volume evolution

Depth-Weighted Maximum (DWmax)(DWmax)Extreme Gradient (EG)

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volume window column point slab

Sliding Thin-Slab Movement

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Fast STS Algorithmstemporal coherence1

adjacent views change little

only 2 slices differ

slabi window calculations apply to slab i+1

1{Ramaswamy1999}

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Depth-Weighted Maximum (DWmax)

wi = (depth of view – distancei from base)

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Depth-Weighting: 1D process

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sub-

volume

DWmax Algorithmsvolume

column

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STS-MIP

DWmax

{Turlington 2000}{Napel 1992}

CT image slice

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DWmax: Transverse Sequence Viewss=28

s=43 s=49

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DWmax: coronal detail

coronal sequence viewssingle sliceprojection image

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DWmax: sagittal detail

base slice

base slice

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Extreme Gradient (EG)Mapping of max tissue-density changes in slab

s(x,y) = max x,y{ } – max x,y{ }

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sub-

volume

volume

column

EG Algorithms

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small change

large change

moderate change

Extreme Gradient

EG not windowed

• image extremes• structure size• slab size

Function of:

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Endoluminal Border Detection

merging DWmax and EG

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Computation Gains of New Techniques

inversely proportionally to slab-size (ds)

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Current Reconstruction Techniques

cross-sectional imaging is CT gold standard

axial images alone enable remarkably accurate assessment

true paradigm shift requires comparison to traditional methods

{Naidich et al. 97}

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lymph node

detection

S=39

currently under development

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lymph node?

EG: soft tissue

EG: high density

DWmax

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Conclusion: New Techniquesfast, real-time

small structures visible

depth perception

true information

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My thanks to:Dr. William E. Higgins

The Whitaker FoundationDr. K. Kirk ShungDr. Cheng Dong

My Father

“For nothing is hidden, except to be revealed;nor has been secret, but that it should come to light.”

Mark 4:22

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2:40 pm Today…California Room

A. J. Sherbondy

Virtual Bronchoscopic ApproachCombining 3D CT and Endoscopic Video

Physiology and Functions from Multidimensional ImagesConference 3978

5:30 to 7:30 pm Today…California Room

G. McLennan

The Place of Virtual Bronchoscopy in Clinical Practice: Barriers and

SolutionsPhysiology and Functions from Multidimensional Images

Conference 3978

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DWmax errorNOT visible

Occurs in less than 2%of pointsmust occur simultaneously:1. closer to base than voxel of previous slab’s max2. depth-weighted voxel must differ:

< 5.5% of 16-bit previous-slab point (=0.7% 8-bit)

if error occurs: errror < 5 HU (16-bit) or 0 HU (8-bit)