Global brain physiology does not impact regional BOLD activations Yufen Jennie Chen Xue Wang Todd B. Parrish 1 53rd ASNR meeting 2015, Chicago IL Poster

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Global brain physiology does not impact regional BOLD activations

Yufen Jennie Chen

Xue Wang

Todd B. Parrish

53rd ASNR meeting 2015, Chicago IL Poster #:EP-20

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Disclosure

The authors have no relevant financial interest or relationship to disclose with regard to the subject matter of this presentation.



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Purpose Blood-oxygenation level dependent (BOLD) fMRI is a

complex interplay between multiple physiological processes including cerebral blood flow, cerebral blood volume, oxygen consumption and neural activity. Intersubject variability in baseline local CBF accounts for

variability in BOLD response to tasks1

Recently developed MRI techniques can quantitatively measure global cerebral metabolic rate of oxygen (CMRO2)2

The purpose of this study is to investigate whether global CMRO2 will affect the amplitude of task-related BOLD response


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Materials & MethodsSubjects

Group 1: 9 subjects (4F, 36 ± 9 years old)Group 2: 8 subjects (4F, 29 ± 4 years old)

TasksSynonyms task (group 1): alternating 30s epochs

of word pairs and letter strings, repeated 8 times (scan time: 8’06”)

Story comprehension (group 2): alternating 24s epochs of stories and scrambled words, repeated 8 times (scan time: 6’30”)


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Materials & MethodsImaging

3.0T Siemens TIM Trio & 32 channel head coilBOLD fMRI: gradient-echo echo planar imaging

(EPI) Group 1: 1.7x1.7x3mm3, TE=20ms, TR=2s, 35 slices Group 2: 1.7x1.7x3mm3, TE=20ms, TR=2.4s, 42 slices

Venous oxygenation: postsat-TRUST3

1.4x1.4x5mm3, TE=18ms, TR=4s, TEeff=0/40/80/160 ms, 1 slice through sagittal sinus


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Materials & MethodsImaging (Cont.)

Global blood flow: retro-gated phased contrast MRI (PC-MRI) 0.5x0.5x5mm3, Venc=80cm/s, 20 phases, TE=3.81ms,

TR=66.3ms, 1 slice positioned perpendicular to carotids and vertebrals based on non-contrast time-of-flight scan

Multiple scans were run to ensure perpendicular cross-section for all major arteries

Sample position planning of scan for carotids


7Materials & MethodsBOLD analysis

Preprocessing: coregistration, motion correction, smoothing (6mm), non-linear spatial normalization to MNI152_T1 template

First-level GLM analysis for each subject Preprocessing and first-level analysis performed

via online pipeline4 Second-level GLM analysis on the contrast

images of the group % signal change extracted from two ROIs using

MarsBar5

Location of ROIs

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8Materials & MethodsData analysis for TRUST

Coregistration between TEeff data and motion-correction within TEeff

datapairwise subtraction between control

& tag imagesExtract mean signal of 6 highest

signal voxels in sagittal sinusFit for blood T2 and Yv3

Example of data & fit


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Materials & MethodsData analysis for PC-MRI

Calculate total CBF by summation of flow in bilateral carotids and vertebral arteries, average over cardiac cycle

Estimate brain volume from tissue segmentation of high resolution anatomical T1

Calculate normalized CBF per tissue mass


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Materials & MethodsCMRO2 calculation

CMRO2 = CBF * (Ya-Yv) * Ca

Ya = arterial oxygenation ~ 100% Yv = venous oxygenation (calculated from TRUST)Ca = amount of oxygen/volume of blood = 8.337 mol O2/ml of blood


11Results: Correlations with physiology

Total flow is positively correlated with both venous oxygenation (Yv) and cerebral metabolic rate of oxygen (CMRO2)


12Results: Correlations with %BOLD

ROI1 ROI2

r p r p

Group 1

CBF (ml/100g/min)

0.33 0.38 0.14 0.71

Yv (%) 0.35 0.36 0.22 0.57

CMRO2 (mol/100g/min)

0.26 0.50 0.10 0.79

Group 2

CBF (ml/100g/min)

0.03 0.94 0.15 0.72

Yv (%) 0.02 0.97 0.28 0.51

CMRO2 (mol/100g/min)

0.14 0.74 -0.37 0.36


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ConclusionGlobal CBF is positively correlated with venous oxygenation and oxygen consumption

None of the physiological metrics correlated with %BOLDGlobal physiology is preserved in spite of local

disturbances such as functional activationCurrent CMRO2 technique is a static measure, which

may not be sensitive to local dynamic changes queried by BOLD

Balance in global physiology may be disrupted with aging and disease of the neurovascular system


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Future WorkImplement technique for local physiological metrics to better understand their effects on functional activity

Extend findings in older healthy controls and chronic stroke patients


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References1. Liau J., Liu TT. Inter-subject variability in hypercapnic normalization

of the BOLD fMRI response. Neuroimage 45 (2009) 420–430

2. Xu F., Ge Y., Lu H. Noninvasive Quantification of Whole-Brain Cerebral Metabolic Rate of Oxygen (CMRO2) by MRI. Magn Reson Med 62 (2009) 141–148

3. Xu F., Uh J., Liu P., Lu H. On Improving the Speed and Reliability of T2-Relaxation-Under-Spin-Tagging (TRUST) MRI. Magn Reson Med 68 (2012) 198–204

4. Song X., et al. Robust web-based parallel-optimized minimal preprocessing and analysis pipeline for fMRI big data. OHBM 2015, Honolulu, Hawaii

5. Brett M., et al. Region of interest analysis using an SPM toolbox. OHBM 2002, Sendai, Japan

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Global brain physiology does not impact regional BOLD activations Yufen Jennie Chen Xue Wang Todd B. Parrish 1 53rd ASNR meeting 2015, Chicago IL Poster