Lectio

Quality ImprovementsQuality Improvementsfor Multi-Modal Neuroimagingfor Multi-Modal Neuroimaging

Mika SeppäMika Seppä

Brain Research Unit / LTLBrain Research Unit / LTL

AMI-CentreAMI-Centre

Helsinki University of TechnologyHelsinki University of Technology

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1. Registration1. Registration

2. Resampling2. Resampling

3. Visualization3. Visualization

3 central stages:3 central stages:

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Match metricMatch metric Single-modal registrationSingle-modal registration

– sum of squared differencessum of squared differences

Multi-modal registrationMulti-modal registration– mutual informationmutual information

1. Registration1. Registration

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MI artifactsMI artifacts

Images alignedImages aligned Same pixel/voxel Same pixel/voxel

sizessizes

Registration biasRegistration bias Local maximaLocal maxima

Continuous samplingContinuous sampling– higher-order methodhigher-order method

offset (pixels) offset (pixels)

MI

MI

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2. Resampling2. Resampling

Very common operationVery common operation– geom. correction, motion correction, group geom. correction, motion correction, group

average etc.average etc.

15 x15 xSNR = 10*log10(s2/e2)SNR = 10*log10(s2/e2)

......

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Two-stage resamplingTwo-stage resamplingSN

R (

dB

)SN

R (

dB

)

Time (ms)Time (ms)

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3. Visualization3. Visualization

0.1-5 fps0.1-5 fps

800 fps800 fps

120 fps120 fps

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Seppä (2007). On continuous sampling and sub-Seppä (2007). On continuous sampling and sub-sample accuracy in mutual-information registration. sample accuracy in mutual-information registration.

TKK ReportTKK Report, TKK-KYL-017., TKK-KYL-017.

Seppä (2007). High-quality two-stage resampling for 3-Seppä (2007). High-quality two-stage resampling for 3-D volumes in medical imaging. D volumes in medical imaging. Medical Image Medical Image

AnalysisAnalysis, 11:346-360., 11:346-360.

Seppä, Hämäläinen (2005). Visualizing human brain Seppä, Hämäläinen (2005). Visualizing human brain surface from T1-weighted MR images using texture-surface from T1-weighted MR images using texture-

mapped triangle meshes. mapped triangle meshes. NeuroImageNeuroImage, 26:1-12., 26:1-12.

Hiltunen, Suortti, Arvela, Seppä, Joensuu, Hari (2005). Hiltunen, Suortti, Arvela, Seppä, Joensuu, Hari (2005). Diffusion tensor imaging and tractography of distal Diffusion tensor imaging and tractography of distal peripheral nerves at 3 T. peripheral nerves at 3 T. Clinical NeurophysiologyClinical Neurophysiology, ,

116:2315-2323.116:2315-2323.

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