ter haar romeny, fev mit ai lab automatic polyp detection
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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
ter Haar Romeny, FEV
Current visualization
Normal doseSmooth surface
Low doseBlobs appear
Normal doseRough surface
ter Haar Romeny, FEV
Proposed solutions
Bilateral filtering blobs
Gradient smoothing rough surface
ter Haar Romeny, FEV
Results: normal dose
ter Haar Romeny, FEV
Results: all dose levels
1.6 mAs 6.25 mAs 64 mAs
ter Haar Romeny, FEV
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
ter Haar Romeny, FEV
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
ter Haar Romeny, FEV
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
ter Haar Romeny, FEV
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
ter Haar Romeny, FEV
Scale integration
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Closest Vessel Projection
ter Haar Romeny, FEV
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”
ter Haar Romeny, FEV
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
ter Haar Romeny, FEV
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
ter Haar Romeny, FEV
Dominant orientations
Orientations preferentially along anatomical axis
Histogram of 3D directions: