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									Project Report

3D Lung Model
      &
 CT Simulator


Under Supervision of~
Prof.Benjamin B. Kimia


         By:
    Rahul Gautam
             How this began…

• The NIH Proposal 2003~
 Model-based Tomographic Reconstruction of Vessel Networks
    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.
     Preparing the way~
• A search for good 3D Lung model...

Options?
           ....Many

Chose…
         One of the best available…
              Our Choice…

‘A three-dimensional model of the human airway tree’

      By~ Prof. Hiroko Kitaoka, Ryuji Takaki, and Béla Suki
        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
     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
          The Rules


• The algorithm is composed of nine
  basic rules and four complementary
  rules.
                 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.
        Rules…Continued
• ~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.
       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
     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.

         THAT’S IT
    So the first step…


• Applied the algorithm to generate
  3D Lung data
The Result…
       Oops…A Problem
• Rough edges , abrupt at branching
  points….
    Unrealistic if used to model a lung
  The Solution…
Generate a Volumetric model,
…apply Gaussian Smoothing to it,



Use Marching cubes to extract
 surface..
The Outcome…
      Breaking News…
• Brown Eyes now has… 3D Lung Model
  Generator…
Mission 3D Lung Model…




    …Accomplished
      The Next Step…

             ...Mission CT
• To obtain a CT Simulator…

that performs CT scan on virtual 3D
  models and generate projection data
CT…????
CT~ Computed Tomography




 (From Siemens)
                  (From Picker)
           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
Projection measurement…
Exponential attenuation of X-rays
                                             x
       Ni            No
                               N o  Ni e
                              Ni: input intensity of X-ray
                               No: output intensity of X-ray
                               : linear X-ray attenuation
                x
  Ni                      No
                                                 ( 1  2  3 ) x
                   
                                    N o  Ni e
                                x

                                             Attenuated
  X-rays                                        more
Ray-Sum of X-ray Attenuation
 Ni                                     No
                     k

      x


Ray-sum                             Line integral

                          
                Ni                         Ni
    k x  ln             ( x)dx  ln
  k             No        
                                           No
              Projection &
               Sinogram
Projection:                    Sinogram:
All ray-sums in a direction    All
              y                projections
                                    
     P(t)
                      t
                                    p
                          x

     f(x,y)
                      X-rays                 t
                               Sinogram
Scanning modes
First Generation


         One detector
         Translation-rotation
         Parallel-beam
Second Generation


         Multiple detectors
         Translation-rotation
         Small fan-beam
Third Generation


         Multiple detectors
         Translation-rotation
         Large fan-beam
Fourth Generation



           Detector ring
           Source-rotation
           Large fan-beam
Spiral/Helical Scanning


               Simultaneous
               •Source rotation
               •Table translation
               •Data acquisition
Cone-Beam Geometry

          Z




                Y




      X
Back to the Problem…



     ..Mission CT
    Our Requirements...

• Cone Beam CT

• Should scan 3D phantom objects

• Close to a real CT scanner
Here we go again…
   Event:
          .. Birth of CTSim

• Specifications
      Resolution ….Variable
      Magnification ….Variable
      Spot size detector…. As desired
      Spot size source…..point
       No beam hardening
       No Quantum noise
The Outcome….
 The Result…



Too good to be Real
     Keeping it Real….

Accounting for factors like…

~Photon statistics/quantum noise
~Spot size
~Beam Hardening
Quantum noise
        The Outcome…
• Background Noise Comparison…
Spot Size…Source
Outcome…
Sinograms…
  Finally what we have…
• CTSim has found its new home in Brown eyes
CTSim In action…
   The Road ahead…

Making CTSim more realistic by
including effects like beam
hardening.
Special thanks to these
     great guys…
   Amir



   Vishal



   Ming



   Ozge
Last but not the least…


Prof. Benjamin B. Kimia for guiding me
  all the way.
Easy questions Plz…
Thank You

								
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