Project Report 3D Lung Model

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Project Report3D Lung Model CT Simulator

• Under Supervision of
• Prof.Benjamin B. Kimia
• By
• Rahul Gautam

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How this began

• The NIH Proposal 2003
• Model-based Tomographic Reconstruction of
  Vessel Networks

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Aims of the Proposal

• Develop algorithms for the direct tomographic
  reconstruction of pulmonary vessel networks based
  on a 3-d representation of vessels and junctions
• Demonstrate the accuracy of the reconstructed
  network for
• x-ray CT using manual segmentation as
  ground truth.

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Preparing the way

• A search for good 3D Lung model...
• Options?
• ....Many
• Chose
• One of the best available

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Our Choice

• A three-dimensional model of the human airway
  tree
• By Prof. Hiroko Kitaoka, Ryuji
  Takaki, and Béla Suki

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The Reason

• This algorithm generates geometric data of a
  three-dimensional human airway tree whose
  morphometric characteristics are in good
  agreement with those reported in the literature

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The basic Principle

• generation of the dimensions and directionality
  of two daughter branches is governed by the
  properties of the parent branch and the region
  the parent supplies
• The terminal branches of the tree are
  homogeneously arranged within the organ

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The Rules

• The algorithm is composed of nine basic rules and
  four complementary rules.

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Rules

• Branching is dichotomous.
• The parent branch and its two daughter branches
  lie in the same plane, called the branching
  plane.
• The volumetric flow rate through the parent
  branch is conserved after branching that is, the
  sum of the flows in the daughter branches is
  equal to the flow in the parent branch.

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RulesContinued

• The region supplied by a parent branch is
  divided into two daughter regions by a plane
  called the "space-dividing plane." The
  space-dividing plane is perpendicular to the
  branching plane and extends out to the border of
  the parent region
• The flow-dividing ratio is set to be equal to
  the volume-dividing ratio, defined as the ratio
  of the volume of the smaller daughter region to
  that of its parent.

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Rules few more

• The length of each daughter branch is assigned a
  value that is three times its diameter
• If branching continues in a given direction, the
  daughter branch becomes the new parent branch,
  and the associated branching plane is set
  perpendicular to the branching plane of the old
  parent

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Just a few more

• The branching process in a given direction stops
  whenever the flow rate becomes less than a
  specified threshold or the branch extends beyond
  its own region.
• THATS IT

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So the first step

• Applied the algorithm to generate 3D Lung data

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The Result
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OopsA Problem

• Rough edges , abrupt at branching points.
• Unrealistic if used to model a lung

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The Solution

• Generate a Volumetric model,

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• apply Gaussian Smoothing to it,
• Use Marching cubes to extract surface..

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The Outcome
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Breaking News

• Brown Eyes now has 3D Lung Model Generator

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Mission 3D Lung Model

• Accomplished

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The Next Step

• ...Mission CT
• To obtain a CT Simulator
• that performs CT scan on virtual 3D models and
  generate projection data

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CT????
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CT Computed Tomography
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CT is

• the general process of transmitting X-rays and
  creating cross-sectional or tomographic images
  from projections of the object at multiple angles
  and using a computer for image reconstruction

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Projection measurement
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Exponential attenuation of X-rays
Ni
No
m
Ni input intensity of X-ray No output intensity
of X-ray m linear X-ray attenuation
?x
Ni
No
??
??
??
x
Attenuatedmore
X-rays
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Ray-Sum of X-ray Attenuation
Ni
No
?k
?x
Ray-sum
Line integral
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Projection Sinogram
SinogramAll projections
ProjectionAll ray-sums in a direction
?
y
P(??t)
t
p
?
x
f(x,y)
t
X-rays
Sinogram
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Scanning modes
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First Generation
One detector Translation-rotation Parallel-beam
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Second Generation
Multiple detectors Translation-rotation Small
fan-beam
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Third Generation
Multiple detectors Translation-rotation Large
fan-beam
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Fourth Generation
Detector ring Source-rotation Large fan-beam
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Spiral/Helical Scanning

• Simultaneous
• Source rotation
• Table translation
• Data acquisition

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Cone-Beam Geometry
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Back to the Problem

• ..Mission CT

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Our Requirements...

• Cone Beam CT
• Should scan 3D phantom objects
• Close to a real CT scanner

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Here we go again
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Event

• .. Birth of CTSim
• Specifications
• Resolution .Variable
• Magnification .Variable
• Spot size detector. As desired
• Spot size source..point
• No beam hardening
• No Quantum noise

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The Outcome.
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The Result

• Too good to be Real

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Keeping it Real.

• Accounting for factors like
• Photon statistics/quantum noise
• Spot size
• Beam Hardening

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Quantum noise
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The Outcome

• Background Noise Comparison

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Spot SizeSource
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Outcome
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Sinograms
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Finally what we have

• CTSim has found its new home in Brown eyes

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CTSim In action
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The Road ahead

• Making CTSim more realistic by including
  effects like beam hardening.

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Special thanks to these great guys

• Amir
• Vishal
• Ming
• Ozge

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Last but not the least

• Prof. Benjamin B. Kimia for guiding me all the
  way.

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Easy questions Plz
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Thank You