QUANTIFICATION OF PERFUSION CHANGES DURING A MOTOR TASK USING ASL.

P. VILELA (1), M. PIMENTEL (2), I. SOUSA(3), P. FIGUEIREDO(3)

1 – NEURORADIOLOGY - IMAGING DEPARTMENT, HOSPITAL DA LUZ, LISBON, PORTUGAL; 2 - FACULDADE DE CIÊNCIAS E TECNOLOGIA, UNIVERSIDADE NOVA, LISBON, PORTUGAL;

3 - INSTITUTO SUPERIOR TÉCNICO, TECHNICAL UNIVERSITY, LISBON, PORTUGAL.

pvilela@hospitaldaluz.pt

Objectives:

Quantification of the CBF variation induced by the neural activity during a common motor task (finger tapping).

rest CBF; activation CBF; Δ CBF; % Δ CBF

CMRO2

Subjects: 15 healthy volunteers (6F/9M, mean age 25.6)

Stimulus: finger tapping by sequential thumb-digit opposition of the right hand

Acquisition: 3.0T MRI system (Siemens Magnetom Verio)

Paradigm Protocol:

#1

ASL: 1 cycles rest/task (total acquisition time 3min51secX2).

#2

BOLD-ASL: 5 cycles rest/task, 25 sec blocks (total acquisition time 4min12.5sec).

Material & Methods

25 sec

3.51 min 3.51 min

Material & MethodsSubjects: 15 healthy volunteers (6F/9M, mean age 25.6)

Stimulus: finger tapping by sequential thumb-digit opposition of the right hand

Acquisition: 3.0T MRI system (Siemens Magnetom Verio)

ASL imaging:

TR/TE = 2500ms/25ms 9 contiguous slices; 8mm

slice thickness; 91x2 volumes, matrix 64x64;

voxel size 3x3x8 mm3 (pulsed ASL sequence:

PICORE Q2TIPS TI1 = 700 ms, TI1s = 1600 ms

and TI2 = 1800 ms )

EPI BOLD-ASL imaging:

TR/TE = 2500ms/11ms 9 contiguous slices; 8mm

slice thickness; 101 volumes, matrix 64x64; voxel

size 3x3x6 mm3 (pulsed ASL sequence: PICORE

Q2TIPS TI1/TI2=700ms/1800ms)

Material & Methods-Analysis:- Standard General Linear Model (GLM) approach using FEAT from FSL [http://www.fmrib.ox.ac.uk/fsl]- -Pre-processing: motion correction, spatial smoothing FWHM = 5 mm, high-pass temporal filtering (f = 100ms)Protocol #1-Concatenation of the rest and activation scans in one single time-series data with the elimination of the first volume of each time-series, creating a single time-series dataset with 180 volumes (first 90 volumes – rest state and the other 90 volumes - activation state).

-Analysis:

Cluster of activation:

Z map Threshold: Z > 2.5

Cluster significance threshold: p < 0.05

Material & Methods

Clusters of activation: CBF Quantification (ml / 100g / min)•CBF rest; CBF activation•Δ CBF = CBFact – CBFrest• % Δ CBF = 100 x (CBFact – CBFrest) / CBFrest

The respective CBF activation clusters given by statistical analysis were used to mask the respective quantitative maps, and the mean value within the cluster was calculated.

Material & Methods

The respective CBF activation clusters given by statistical analysis were used to mask the respective quantitative maps, and the mean value within the cluster was calculated.

Clusters of activation: CMRO2 Quantification

fractional BOLD signal change: ∆S/S0

(Davis et al. 1998).

α = 0.38 (Grubb et al.1974; Mandeville et al. 1998).

β = 1.3(Bulte et al. 2009)

M value= 4.3(Chiarelli et al. 2007)

Results: Rest CBF Analysis

- Protocol #1 mean rest CBF: 61.0 ml/100g/min

-Protocol #2 mean rest CBF: 69.4 ml/100g/min

Mean valueValues

Results: Activation CBF Analysis

- Protocol #1 mean activation CBF: 104.8 ml /100g/min

- Protocol #2 mean activation CBF: 109.9 ml/100g/min

Mean valueValues

Results: Δ CBF Analysis

- Protocol #1 Δ CBF: 43.7 ml/100g/min

- Protocol #2 Δ CBF: 40.5 ml/100g/min

Mean valueValues

Results: %Δ CBF Analysis

-Protocol #1 %Δ CBF: 73±6 %

- Protocol #2 %Δ CBF: 62±7 %

Mean valueValues

Results: summary

Protocol #1 Protocol #2

mean rest CBF mL/100g/min 61 69.4

mean activation CBF mL/100g/min 104.8 109.9

Δ CBF mL/100g/min 43.7 40.5

%Δ CBF 73.6% 62.7%

Results: summary• ∆CBF = rCBFact – rCBFrest•Tissue type: p < 0.001; Correction: p = 0.031; Segmentation method: p < 0.001

GM

WM

-Cerebral metabolic rate of oxygen (CMRO2).

-EvaluationProtocol #29 volunteers

-Mean %GM: 49%

-Mean %CBF: 62.49% (SE:8.52%)

-Mean BOLD SC: 0.71(SE:006%)

-Mean %CMRO2:22.56% (SE:5.48%)

Results: CMRO2

fractional BOLD signal change: ∆S/S0

(Davis et al. 1998).

α = 0.38 (Grubb et al.1974; Mandeville et al. 1998).β = 1.3 (Bulte et al. 2009) M value= 4.3 (Chiarelli et al. 2007)

Aerobic (oxidative) metabolism

-Cerebral metabolic rate of oxygen (CMRO2).

-EvaluationProtocol #29 volunteers

-Mean %GM: 49%

-Mean %CBF: 62.49% (SE:8.52%)

-Mean BOLD SC: 0.71(SE:006%)

-Mean %CMRO2:22.56% (SE:5.48%)

-CMRO2 / CBF: 0.33 (normal range 0.25-0.5)

Results: CMRO2

Perfusion /CMRO2 Coupling

CBF

CMRO2

Conclusions

These results show that both activation vs rest (protocol #1) and block design (protocol #2) functional protocols were capable to detect consistent variations in perfusion associated with a simple motor task.

The block design has the advantages of requiring shorter acquisitions and allowing the acquisition of simultaneous BOLD contrast information, being the preferable approach for the evaluation of perfusion changes to endogenous stimuli.

Conclusions

Perfusion ASL is a reliable method for the quantification (CBF) of the hemodynamic brain response to brain activation, and by combining the BOLD and CBF is able to estimate the cerebral metabolic rate of oxygen (CMRO2).

This combined information (CBF & CMRO2) widens the scope of the ASL-fMRI applications as a non-invasive and reliable imaging approach to the study of the brain hemodynamic responses and metabolism activity.

Acknowledgments

Technologists:Ana Cristina SantosCidália MartinsFernando GonçalvesRuben Teixeira

Authors:Marco PimentelInês SousaPatrícia Figueiredo

pvilela@hospitaldaluz.pt

QUANTIFICATION OF PERFUSION CHANGES DURING A MOTOR TASK USING ASL.

P. VILELA (1), M. PIMENTEL (2), I. SOUSA(3), P. FIGUEIREDO(3)

1 – NEURORADIOLOGY - IMAGING DEPARTMENT, HOSPITAL DA LUZ, LISBON, PORTUGAL; 2 - FACULDADE DE CIÊNCIAS E TECNOLOGIA, UNIVERSIDADE NOVA, LISBON, PORTUGAL;

3 - INSTITUTO SUPERIOR TÉCNICO, TECHNICAL UNIVERSITY, LISBON, PORTUGAL.

pvilela@hospitaldaluz.pt