Johns Hopkins DTI ProjectsJonathan Farrell

Bennett Landman, Hao Huang,

Thomas Ng Man Cheuk, Susumu Mori

2 Progress Report Slides

To Do List from 2005

• High SNR DTI Calibration Dataset @ 1.5T– Several studies wrap up & publish

– Original and coregistered data post

– Useful software post

• DTI Database of 61 Healthy Controls @ 1.5T– Original data post

– Coregistered and processed data post

• Image Distortion Correction for DTI– Study wrap up & publish

• Tractography Reproducibility– Study wrap up & publish

Progress Report in 2006

• High SNR DTI Calibration Dataset @ 1.5T– Several studies 2 papers submitted

– Original and coregistered data Posted

– Useful software 2 posted + 1 soon

• DTI Database of 61 Healthy Controls 1.5T– Original data Posted

– Coregistered and processed data soon

• Image Distortion Correction for DTI– Study under revision (round 2)

• Tractography Reproducibility– Study under revision (round 2)

Summary of Each Project

GoalResults

Endpoints

DTI Calibration Study: SNR

QUESTION: How does SNR affect DTI contrasts in vivo ?

TAKE HOME POINT: Provide methods to calibrate SNR across sites

ENDPOINT: Paper submitted September 2006

DTI Calibration Study: DW Scheme

QUESTION: Which diffusion weighting scheme should you use and why?

TAKE HOME POINT: Use a scheme with many directions ( ~ 30) to get uniform precision and accuracy at all

fiber orientations. BUT…Effect size is small (less than intra and inter scan variability)

ENDPOINT: Paper submitted October 2006

Multi-Site DTI Calibration Study

GOAL: Measure accuracy and precision of DTI contrasts at several imaging sites and scanners.

DATA COLLECTION SITES: Johns Hopkins Duke MGH University of Texas South Western

DETIALS: Will make DTI-contrast vs SNR curves Hopefully, the sites show similar behavior

Software: CATNAP

GOAL: To simplify and accelerate DTI &

anatomical data processing

HOW IT WORKS: Coregistration with FSL FLIRT Computes DTI gradient table Computes diffusion tensor and

DTI contrasts

DETIALS: Runs in MATLAB Philips data only (so far)

http://www.nbirn.net/downloads/

Software: DTI_gradient_table_creator

GOAL: Figure out the gradient

table for Philips DTI data

HOW IT WORKS: Takes scanner / imaging

options & parameters into account

Rules can be tricky !

DETIALS: MATLAB function JAVA applet (online)

http://www.nbirn.net/downloads/

Software: PARtoNRRD_Philips

GOAL: Create NRRD headers files for Philips DTI data .nhdr files contain all relevant DTI parameters

Resolution, FOV, Slices Gradient directions, b-value, coordinate space

Compatible with Slicer

HOW IT WORKS: Uses .par file (Philips text file) Uses DTI_gradient_table_creator_Philips_RelX

WHAT YOU NEED : .nhdr file and .rec (data file) Will be posted soon

http://www.nbirn.net/downloads/

GOAL: Distribute DTI data for 61 healthy controls

DTI Database of Healthy Controls

ISSUES: Data management, defacing and de-identification

ENDPOINT: Original data (posted), coregistered data (TBD), meta-data (TBD)

http://www.nbirn.net/downloads/

Tractography Reproducibility

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Intra-rater

Inter-raterAlmost perfect

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Moderate

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GOAL: Test reproducibility of tractography Performed multi-site inter-rater tests for 11 major WM tracts.

RESULTS: Substantial reproducibility

was observed for the protocol developed under this project

ENDPOINT: Paper submitted and under

revision

Image Distortion Correction for DTI

a) Non distorted T1w image, b) DTI with distortion

c) Landmark-based LDDMM correction

d) Intensity –based SPM e) segmentation-based SPM.

f) The LDDMM method undistorts the image smoothly g) Guantifies the distortion by Jacobian. Although the segmentation-based SPM could correct the distortion (e), the transformation contains severe discontinuity (h), which may cause DTI calculation errors.

Paper is in preparation.Working on implementing other techniques (Song, others)