Atlas Assisted Tomography

1
Atlas Assisted Tomography

• THE PROBLEM
• A rotating C-arm can provide input images for
  tomographic cone-beam reconstruction.
• Cone-beam reconstruction requires the C-arm
  trajectory to cover 180 (cone_angle / 2).
• In many cases, completing this trajectory is
  infeasible.

(a)
(b)
Figure 1 (a) Full sweep cone-beam trajectory
180 (cone_angle/2). (b) Partial sweep
trajectory (green) with trajectory of atlas
projections (red)

• THE SOLUTION
• Use C-arm for partial-sweep trajectory imaging.
• Register 2D C-arm images with a 3D deformable
  statistical atlas.
• Use atlas projections to compensate for missing
  C-arm angles in the reconstruction.

Figure 2 Flowchart for atlas assisted
reconstruction

• RESULTS AND STATUS
• 2D-3D deformable registration and atlas-assisted
  reconstruction for a hemipelvis model.
• Atlas-assisted reconstruction for a full-pelvis
  model.
• Model constructed from one CT dataset

• THE FUTURE
• Create a statistical model of the full pelvis and
  use it for deformable registration.
• Incorporate soft-tissue models into the
  reconstruction process.
• Perform quantitative analysis of reconstruction
  accuracy to compare the hybrid reconstruction to
  conventional reconstruction.

• THE IMPACT
• Significant increase of reconstruction quality
  with limited-angle C-arm tomography.
• Obtain approximation of fine-detailed structures
  in presence of noise, occlusions, or
  abnormalities
• surgical tools
• osteophytes
• fractures

Figure 3 Results from different cone-beam
tomographic reconstruction methods.

• PEOPLE INVOLVED
• Graduate Students Krishnakumar Ramamurthi (JHU,
  Dept. of ECE), Ofri Sadowsky (JHU, Dept. of CS)
• Engineering Faculty Dr. Jerry L. Prince (JHU),
  Dr. Russell H. Taylor (JHU)

• PUBLICATIONS
• Sadowsky, O, Kumar, K, et al. An Atlas-Assisted
  Method for Limited-Angle Cone-Beam Tomography. In
  Digital Biology The Emerging Paradigm
  Symposium Proceedings, NIH, 2003

• SUPPORTED BY
• NSF Engineering Research Center grant EEC9731478
• NIH R21 (Jerry Prince P.I.)

Engineering Research Center for Computer
Integrated Surgical Systems and Technology