ter Haar Romeny, FEV

MIT AI Lab

AutomaticPolypDetection

ter Haar Romeny, FEV

Enhancement byGaussian curvature

PMS

CT slice with tagged residual sticking to the wall

Same slice after electronic cleansing

Philips MS

Electronic colon cleansing

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Current visualization

Normal doseSmooth surface

Low doseBlobs appear

Normal doseRough surface

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Proposed solutions

Bilateral filtering blobs

Gradient smoothing rough surface

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Results: normal dose

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Results: all dose levels

1.6 mAs 6.25 mAs 64 mAs

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Extract vasculature with ‘vesselness’

From T1w MRI with contrast

Frangi’s vesselness measure [Frangi et al., 1998]

Enhance tubular structures while reducing other morphologies

E. Brunenberg, MSc project

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Vesselness measure

Based on eigenvalue analysis

of Hessian:

two low eigenvalues

one high eigenvalue

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Vesselness - 1

Eigenvalue analysis of Hessian:

extract directions of principal curvature

Hessian:

where

and

xx xy xz

yx yy yz

zx zy zz

I I I

H I I I

I I I

G

I2

2 ,I

xx x

G e

2

223

2

1,

2

x

x

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Vesselness - 2Eigenvalues ordered as |λ1| ≤ |λ2| ≤ |λ3|

Bright vessel region: λ1 small, ideally zero; λ2 and λ3 large

but negative.

Ratio for blobness:

Ratio for plate-like:

Image structure:

BR1

2 3

,1 forblob-like

AR2

3

,0 for line-like

S 2 2 21 2 3 ,1 formuch contrast

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Vesselness - 3

Total vesselness function:

Parameters:

α = β = 0.5

c = 0.5 * maximum Hessian norm

Multiscale approach:

22 2

22 2

2 3

22 2

0 if 0 or 0

,1 1 otherwise

BARR S

cV

e e e

x

min max

max ,V V

x x

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Vessel enhancement filtering

Better delineation of small vessels

Preprocessing before MIP

Preprocessing for segmentation procedure

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Abdominal MRA

Maximum intensity projection

No 3D information

Overlapping organs

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2D Example: DSA

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Scale integration

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Closest Vessel Projection

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Trabecular Bone

Bone appears in two forms

Cortical Bone

Trabecular Bone

Trabecular Bone

connected network of rods & plates

loading dependent architecture Wiro Niessen, PhD

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Stress routes

Wolff’s Law

“The internal structure and external shape of a

bone develop in response to the change in function

and forces acting upon it”

Culman Meyer

“Trabecular pattern is oriented with routes of

stress”

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Clinical Relevance

Trabecular Architecture important parameter in bone strength

(clinically proven)

Applications for in vivo analysis

determine fracture risk

monitoring structure in aging

monitor degree and development of osteoporosis

(treatment available)

monitoring malgrowth near epiphyses

placing implants and evaluating receipt

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ter Haar Romeny, FEV

Stress Routes in Ankle

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MR Ankle, FFE, short TE (300m)

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CT dry femur (250m)

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Structural Information

2D 3D Orientation PatternHigh High High High High noisy no preferred orientationHigh Low High High Low tubular structure

High Low Low platelike structureLow Low Low Low Low smooth region

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3D orientaties

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Dominant orientations

Orientations preferentially along anatomical axis

Histogram of 3D directions: