Transforming Static CT in Gated PET/CT Studies

to

Multiple Respiratory Phases

M Dawood, F Büther, N Lang, X Jiang, KP Schäfers

Department of Nuclear Medicine, University Hospital Münster, Germany

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

PET/CTPositron Emission Tomography / Computed Tomography

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

PETPositron Emission Tomography

β+-decay of 18F:

18F → 18O + e+ + νe

Pair annihilation: e+ + e- → 2 γ

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

LOR

φ

s

Detector 2

Detector 1

s

φ

LOR

Sinogram

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Reconstruction

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Attenuation

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Problem

Spatial non-correspondance between PET and CT due to motion

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Solution

Divide the PET data into respiratory phases, and transform the static CT to corresponding phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Gating

…

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Gating: Acquiring the respiratory signal

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Optical Flow

A method to estimate deformation between image frames

Independent of the form and type of movement between the frames

Non-rigid and pixel-based

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Combined Local/Global

Minimize fLG

dxdydzdtVVIIVkf TTLG )(*

2

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Discontinuity Preserving Non-Quadratic

Non-Quadratic approach allows better approximation than least squares

Discontinuity preservation allows better estimation across organ boundaries

Minimize fD

2

222

21

12

i

ii

ss

dxdydzdtSmoothingDataf D

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Lukas/Kanade Horn/Schunck Bruhn

Non-Linear Discontinuity Preserving Result

Demonstration

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Results: Gated data

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Results: Attenuation Without Motion Correction

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Results: Transformed Attenuation Map

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Transforming static CT to multiple phases

M. Dawood et al. Motion correction in 3d PET/CT with advanced optical flow algorithms. Submitted to ieee transactions on medical imaging.

Results: Attenuation With Transformed Map