calibration wg

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