In this study, we propose using a MEGA semi-LASER sequence with non-water suppressed metabolite-cycling as a 2D MRSI data acquisition method at 3T for high-resolution GABA, Glutamate, and T2*detection throughout a whole axial slice. Simultaneous measurement T2* with neurotransmitter maps will provide useful information on functional hemodynamic changes due to physiological interventions. GABA spectroscopy edited GABA 1H MEGA-PRESS spectra GABA-edited

1. SIMULTANEOUS MAPPING
OF T2
* AND MAJOR
NEUROTRANSMITTERS
USING MRSI AT 3T
FATIMAH ALMOMEN1 , PINGYU XIA1 , XIAOPENG ZHOU1 , MARK CHIEW2, ADAM STEEL3 , ALBERT THOMAS4, ULRIKE DYDAK1, UZAY E EMIR1
1PURDUE UNIVERSITY, WEST LAFAYETTE, IN, 2OXFORD UNIVERSITY, OXFORD, OXFORD, 3DARTMOUTH COLLEGE, HANOVER, NH, 4DAVID GEFFEN SCHOOL OF MEDICINE AT UCLA, LOS ANGELES, CA
EMAIL: UEMIR@PURDUE.EDU

2. NEUROTRANSMITTERS
AND NEUROVASCULAR
COUPLING
• Gamma-aminobutyric acid (GABA)
and glutamate (Glu) are the brain's
primary inhibitory (I) and
excitatory (E) neurotransmitters.
• They are both strongly implicated
in functional changes in neural
circuitry
• Neurotransmitters: Glutamate and
GABA cause neurons and
astrocytes to activate a chain of
intracellular events, involving the
control of constriction and dilation
of the blood vessels BOLD
response

3. BOLD EFFECT , T2
* CHANGE
AND NEUROCHEMICALS
• Percent signal changes during activation
compared to baseline due to the BOLD signal
changes at 3 T (Δ%T2
* = 5.4 ± 1.4)
• At longer echo time (TE = 68 ms, GABA
sensitive echo time), change in T2*
exacerbates and results in signal alterations
of neurotransmitters due to the BOLD effect.
Zhu, X.-H. and Chen, W. (2001),
Monitoring T2
* while measuring
neurochemicals/neurotransmitters is
essential.
Difference Difference

4. • SIMULTANEOUS MEASUREMENT T2
*
WITH NEUROTRANSMITTER MAPS
MIGHT PROVIDE USEFUL
INFORMATION ON FUNCTIONAL
HEMODYNAMIC CHANGES DUE
PHYSIOLOGICAL INTERVENTIONS.
• We propose using a MEGA-semi-LASER sequence
with non-water suppressed metabolite-cycling as
2D MRSI data acquisition method at 3T for high-
resolution GABA, Glutamate and T2
*detection
throughout a whole axial slice.

5. METHODS
• Four healthy volunteers (28.8 ±3.4 years) participated.
• MRSI scans were performed on Siemens Prisma 3T whole body MRI
scanner with
• MEGA semi-LASER localization (TR = 1 s, TE = 68 ms, number of
averages, Navg = 2, 512 s)
• The 2D polar k‐space data results in a nominal voxel of 7.5 x 7.5 x 20
mm3 (1.125 mL) Chiew, NMR in Biomed, 2017.
• MRSI spectra and Metabolite maps were stored in
NIFTI format
• FSL/FSLeyes(FMRIB, Oxford University) to
visualize/process metabolite maps
• LCModel with internal water reference.
• Unsuppressed water signals were used to generate
T2* maps using TEDANA tool, TE-dependent
analysis of multi-echo functional magnetic
resonance imaging,
The use of FSL and NIFTI for MRSI
spectra and metabolite maps

6. PHANTOM MEASUREMENT (NOMINAL VOXEL OF
7.5 X 7.5 X 15 mm3)
Two spheres with GABA concentrations of 1 umol/g and 2 umol/g
1
1.5
2
2.5
3
2 umol/g
1 umol/g
MEGA semi-LASER localization (TR = 1 s, TE = 68 ms,
number of averages, Navg = 2, 512 s)
GABA GABA GABA
Chiew, NMR in Biomed, 2018

7. MEGA-SLASER WITH METABOLITE
CYCLING TO MEASURE
NEUROTRANSMITTERS AND T2
*
RELAXATION
• Voxel-vise frequency, phase
and eddy current correction
• Significantly reduces
sideband artifact
• Rigid body Motion Correction
• Multi-echo information can
be used T2
* mapping
Chiew, NMR in Biomed, 2017

8. ECHO TIME-DEPENDENT ANALYSIS OF MULTI-ECHO
MAGNETIC RESONANCE SPECTROSCOPIC IMAGING
20ms 100ms
T2
* [ms]
0 0.2 0.4 0.6 0.8 1
Gray/(Gray_White)
40
50
60
70
80
90
100
110
120
T2*
[ms]
R Value = 0.59
0 0.2 0.4 0.6 0.8 1
Gray/(Gray+White)
60
70
80
90
100
110
120
T2*[ms]
R Value = 0.59
0 0.2 0.4 0.6 0.8 1
Gray/(Gray+White)
40
50
60
70
80
90
100
110
120
T2*
[ms]
R Value = 0.65
0 0.2 0.4 0.6 0.8 1
Gray/(Gray+White)
50
60
70
80
90
100
110
120
T2*[ms]
R Value = 0.40
100 150 200 250 300 350 400 450 500
[s]
54
56
58
60
62
64
66
T2*
[ms]
100 150 200 250 300 350 400 450 500
[s]
60
62
64
66
68
70
72
74
76
78
T2*
[ms]
100 150 200 250 300 350 400 450 500
[s]
56
58
60
62
64
66
68
70
T2*
[ms]
100 150 200 250 300 350 400 450 500
[s]
62
64
66
68
70
72
74
76
78
80
T2*[ms]
Gray Matter White Matter

9. GABA AND
GLUTAMATE
Chiew, NMR in Biomed, 2017

10. GABA, GLUTAMATE AND T2*
45 50 55 60 65 70 75 80
T2* [ms]
0
5
10
15
20
25
30
Glutamate
[umol/g]
45 50 55 60 65 70 75 80
T2* [ms]
0
1
2
3
4
5
6
GABA
[umol/g]
R value = 0.17
R value = 0.26

11. CONCLUSION
• A sequence that generates simultaneously
• GABA+
• Glutamate+Glutamine
• T2
* within a clinically feasible acquisition time of 8.5 min with a nominal voxel
dimension of 7.5 x 7.5 x 20 mm3 at 3T.
• Simultaneous measurement T2
* maps with neurochemicals is a powerful tool to
provide useful information on PHYSIOLOGICAL INTERVENTIONS which aim TO
MANIPULATE EXCITITORY-INHIBITORY BALANCE

12. THANK YOU SO MUCH
Uzay E Emir, uemir@purdue.edu