calibration wg
DESCRIPTION
Calibration WG. Overall goals:. 1. Develop and maintain scanner QA methods. Procedures on web site Paper in press: Friedman & Glover, JMRI. Develop and implement means for reducing intersite variations in fMRI sensitivity. Bonus Aim. Calibration WG. - PowerPoint PPT PresentationTRANSCRIPT
Calibration WG
Overall goals:
2.Develop and implement means for reducing intersite variations in fMRI sensitivity
- Procedures on web site- Paper in press: Friedman & Glover, JMRI
1. Develop and maintain scanner QA methods
Calibration WG
Proposed intersite calibration aims:
1. Further develop BH methods (GHG)
2.Develop ASL methods (Tom Liu)
3. Examine smoothing equalization (Friedman et al., in review)
4. Develop new method based on SFNR (Lee Friedman)
Bonus Aim
Update on BH
• Theory and measurements developedPaper on BH kids/adults
(Thomason, NI 2005)Paper on BH calib (Thomason, HBM in
press)
• Next steps
ChildrenWorking Memory Adults
Spatial
Verbal
M. Thomason
low
high
medium
low
high
medium
BH-induced BOLD signal
Vascular res. HR CBF hypoxia
Basal metab. O2, CO2, NO, H+ vasodilation rCBF
Thomason, et. al, NI 2005
Vascular BOLD Uniformity
Thomason, et. al, NI 2005
BH Task: Children vs. Adults
Thomason, et. al, NI 2005
BH Task: Children vs. Adults
Thomason, et. al, NI 2005
BOLD Signal
Davis, PNAS (1998)Buxton, 2003
rCBF[HbO2]
OEF
[Hb]
CMRO2 = OEF x rCBF x [HbO2]
€
ΔR2*∝ rCBVa[Hb]aβ − rCBV0[Hb]0
β
BOLD∝−TE ⋅ΔR2*
rCBV ∝ rCBF α
BOLDa = S0[ fα (m
f)β −1]
m ≡CMRO2a /CMRO20f = rCBFa /rCBF0
€
BOLDa = BOLDBH
[ faα (m
fa)β −1]
[ fBHα −β −1]€
BOLDBH = S0[ fBHα −β −1]
M. Thomason
et al., HBM 2006
BOLD Signal
Kastrup (1999)
Hoge (1999)
BH
task
F = fBH/fa
M. Thomason
et al., HBM 2006
• Use BH task (non-neuronal, no change in CMRO2) to normalize cognitive task
• Reduces signal change related to vasoreactivity
• Should reduce inter-subject variance
BH Calibration Method
• Adult subjects performed - SWM task (Sternberg)- BH task
• Compared intersubject variability in WMeffect with/without BH calibration
WM/BH Study
M. Thomason et al., HBM 2006
Raw
Calib
Calibration: WM
M. Thomason et al., HBM 2006
Calibration: WM
Raw
pixel-wise
ROI
wholebrain
1 Slice for all subjects
M. Thomason et al., HBM 2006
Calibration: WM
Raw
pixel-wise
1 Slice for 3 subjectsM. Thomason et al., HBM
2006
No calib
BH Calibration: Individual Subs
Calib
5 ≤ t ≤ 20M. Thomason et al., HBM 2006
Calibration: SWM
0
500
1000
1500
2000
2500
SWM SWM calib
Activation volume
sd: p = 0.05 *vol: ns
5 subjects, parietal
M. Thomason et al., HBM 2006
No cal Calib
3.5 ≤ t ≤ 10
vol = 1.24 @ p .001 vol = 1.0
BH Calibration: Group Activation
M. Thomason et al., HBM 2006
Activation Response
M. Thomason et al., HBM 2006
t-score average = 7.82 t-score average = 14.58
No cal Calib
Update on BH
• Theory and measurements developed
Paper published on BH kids/adults
Paper in press BH calib
• Next steps
Update on BH
• Theory and measurements developed
Paper published on BH kids/adults
Paper in press BH calib
• Next steps
• Variations in inspiration may modulate blood oxygenation
Vascular Responsivity: BH
slices 11-20
y = 0.0034x + 1.425
R2 = 0.9737
2.00
2.50
3.00
3.50
4.00
4.50
200 300 400 500 600 700 800 900
inspiration level, mv
BOLD signal, %
Sl 10, aud
Behavioral Effect Mitigation Approaches
• Model breathing variations using GLMSignal = a * Resp + b * HR
Vascular Responsivity: BH
GHG111603
Behavioral Effect Mitigation Approaches
• Model breathing variations using GLMSignal = a * Resp + b * HR
• Provide respiration feedback to maintain inspiration level constant
BH Status
• Program available to make calibrated timeseries- input = timeseries, BH scan, params
• Developing feedback devicepiezo electric resp monitor from ADILED meter, analog electronics. Est. cost $500