This study measures the "tortuosity" or twistedness of brain arteries to determine if increased tortuosity is predictive of intracranial aneurysm development. Researchers will compare the tortuosity of 500 high-risk patients to normal-risk patients and establish a tortuosity risk indicator. Tortuosity will be measured using a "distance factor metric" that divides the actual path length of the artery by the straight line distance between endpoints.

1. Artery Tortuosity measurement
Karl Diedrich
John Roberts
Dennis Parker

2. Summary
• Intracranial aneurysms are balloon
like bulges in the artery walls in the
brain
• Ruptures cause strokes usually
resulting in severe disability or death
• This study measures the twistedness
or tortuosity of brain arteries to test
if increased tortuosity predicts
intracranial aneurysm development
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3. Tortuosity & Risk
• Compare tortuosity of 500 patients
from known high risk pedigrees with
normal risk patients [Farnham, 2004]
• Establish tortuosity risk indicator
– High aneurysm risk Low aneurysm risk
–
– Expect high tortuosity Expect low tortuosity
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4. Visual Tortuosity Comparison
Looking up from below
Side view
Low internal carotid tortuosity
High internal carotid tortuosity
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5. Tortuosity Measure
• Distance Factor Metric = L/d
– Divide the distance L along
the centerline by the straight
end to end distance d.
– Use a bifurcation as a starting L/d
point and calculate L/d ratio
for every voxel along the
artery.
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6. Maximum Intensity Projection (MIP)
• Rays through
image stack
• Keep maximum
intensity pixel
• Goal: extract
blood vessel
from rest of
image in 3-D
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7. MIP Z-Buffer
• Intensity is
position in image
slice stack of
maximum pixel
intensity; dark is
closer, brighter is
farther
• Contiguous blood
vessels are
smooth
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8. 3-D Region Growing
• Check if pixels
neighboring 26
voxels are above
seed histogram
threshold and add
non-maximal 3-D
pixels
• MIP of 3-D region
grown image
stack
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9. Finding Centerlines
Highest
Neighborhood
modified
Distance From Edge (DFE) Modified DFE (MDFE)
Goal
Inverse Lowest
higher cost
MDFE paths to
is lower every voxel
Path Cost
cost Voxel weights/cost
Start from farthest voxel
from goal and work back
to goal or an earlier path
Centerline 9

10. Artery Centerline
Artery MIP Least cost Paths MIP Centerline MIP,
Bifurcations in green
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11. Centerlines on MIP
DFE threshold
0.3 mm reduces
Centerlines of
noise
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