7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

1/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Analysis of the Multiexponential Relaxation

Curve in MRI for Myelin Water Imaging

Eric Y. Zhao

Department of Cellular & Physiological Sciences, The University of BritishColumbia

PHYS 542 Presentation

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

2/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

The time course of relaxation.

A theoretical homogeneous T2 relaxation curve.

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

3/16

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

4/16

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

5/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

The physical basis for multiexponential relaxation.

Magnetization exchange and diffusion

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

6/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

The physical basis for multiexponential relaxation.

Multiexponential relaxation arises from various water

compartments

C T T S

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

7/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Multiexponential decay analysis

Non-negative least squares

y(ti) = yi =

ba

s(T)eti/TdT, i = 1, 2, . . . , N. (1)

y = As, (2)

Misfit: D= |As y|2 (3)

=

Ni=1(y

py yi)

2

2i

, (4)

= 2 (5)

Aim is to minimize the least squares misfit, which is equal to 2,

which characterizes the variability of the data. 2 N indicates

a good fit.

A Cl L k t T R l ti A l i f T R l ti M li W t I i S

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

8/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Multiexponential decay analysis

Identification of component contributions

A Closer Look at T Relaxation Analysis of T Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

9/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Multiexponential decay analysis

Example of a myelin map obtained by NNLS of a T2

GRASE image

A Closer Look at T Relaxation Analysis of T Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

10/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Myelin imaging by echo time linear combination filtering

Suppression of tissue and CSF by linear combination

filtering

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

11/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Myelin imaging by echo time linear combination filtering

Myelin map generated by linear combination filter

approach

A less robust but much faster approach.

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

12/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Study of myelin using MRI

Difference in MWF between white matter and grey

matter structures

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

13/16

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

Study of myelin using MRI

Correlation with histopathology

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

14/16

2 y 2 y g g y

MWF in the study of MS

Demyelinating lesions visualized by MWF

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

15/16

2 y 2 y g g y

MWF in the study of MS

Demyelination of normal appearing white matter

structures

A Closer Look at T2 Relaxation Analysis of T2 Relaxation Myelin Water Imaging Summary

7/27/2019 Physics 540 Presentation: T2 Relaxation Analysis Techniques

16/16

Summary

Summary

THERE ARE THINGS THAT YOU CAN DO TODAY THAT, YEARS

AGO, THERE WAS NOTHING. The community today needs to

know that with MRI and the current medications the view is

good.- Teri Garr

Multiecho analysis of T2 opens possibilities for new and

physiologically relevant contrasts in MRI.

Myelin water imaging has been validated ex vivo, andmay give new insight in the study of demyelinating

diseases such as MS.