Image Reconstruction and Motion Correction using

STIR

MIC 2009 STIR Workshop

Nikolaos DikaiosSupervisor: Tim Fryer

CAMBRIDGE

UNIVERSITY OF

Why STIR?

ν Well evaluated reconstruction algorithms

ν User friendly

ν Useful utilities

ν Easy to develop

Image ReconstructionNCAT (GE Advance)

OSEM (8 iterations, 12 subsets)Sinogram

Motion Correction using STIR

ν Calculate motion parameters from registration (ITK library)

ν Motion correction methods

– post-reconstruction registration

– motion compensated 4D image

reconstruction

Target Image

Source Image

RegistrationDeformation

Field

Motion Parameters

Source Image Target Image Deformation Field

Evaluate Registration

Target - RegisteredTarget - Source

SSD CC NMI

Before registration 64.4 0.962 1.439

After registration 34.9 0.989 1.645

Motion Correction (I)

Post-Reconstruction Registration (PRR)

N

fWf

f

N

n

nn∑=

→

+

=2

11 ~~

~

Reconstruct gated

projection data

separately

Register

reconstructed

images – produce

DOFs

Deform reconstructed

images & calculate the

average

Motion Correction (II)

Motion Compensated 4D Image Reconstruction (MCIR)

1

1PWP

n

n

→

=

∑∑ =

=

=

N

n n

nT

nN

n

T

n

fP

gP

P

ff

1

1

~

where

Features

• Unlike PRR all acquired data are taken into account when updating the estimate

• Computationally expensive

LOR

n

bvp

pbv1

Evaluation Using NCAT

Target Frame

No Motion Correction

PRR

MCIR

Lesion Quantification

−⋅=

etT

etTframesAllbiasPercentage

arg

arg100

-35

-30

-25

-20

-15

-10

-5

0

Liver Lesion Left Lung Lesion Right Lung Lesion

No motion correction

PRR

MCI

Add Poisson Noise

Target Frame

No Motion Correction

PRR

MCIR

Lesion Quantification

−⋅=

etT

etTframesAllbiasPercentage

arg

arg100

-35

-30

-25

-20

-15

-10

-5

0

Liver Lesion Left Lung Lesion Right Lung Lesion

No motion correction

PRR

MCI

PET+MR: Cambridge Scanner

Image ReconstructionMOBY (Focus 120)

OSEM (8 iterations, 12 subsets)

Summary

ν We have implemented motion correction in STIR– PRR

– MCIR

ν Motion correction improved lesion quantification in NCAT

ν STIR-based motion correction has also been applied to real MR/pseudo-PET (poster M05-253)