Multi-Echo and Single-Echo EPI sequences for task-fMRI: A comparative study
Poster No:
1047
Submission Type:
Abstract Submission
Authors:
Alice Giubergia1, Giulio Ferrazzi2, Marco Castellaro3, Sara Mascheretti4, Valentina Lampis5, Florian Montano1, Alessandra Bertoldo3, Denis Peruzzo1
Institutions:
1Scientific Institute IRCCS Eugenio Medea, Bosisio Parini (LC), Italy, 2Philips Healthcare, Milan, Italy, 3University of Padova, Padova, Italy, 4University of Pavia, Pavia, Italy, 5 Scientific Institute IRCCS Eugenio Medea, Bosisio Parini (LC), Italy
First Author:
Co-Author(s):
Introduction:
Multi-Echo (ME) fMRI has been proposed to improve the fidelity of fMRI signals (Kundu et al.,2017;Lombardo et al.,2016). The perks of ME-fMRI have been presented by a few studies (Gilmore et al.,2022;Heunis et al.,2021), but a comparison with an Optimized Single-Echo (OSE) acquisition (i.e. not with data derived from ME itself, which is suboptimal as this leads to artificial OSE data but with longer TRs) remains uncovered. The current analysis aimed to address the benefits of ME against an optimized OSE protocol in a task-fMRI paradigm eliciting the reading system.
Methods:
Twelve healthy Italian native speakers (male=4,age=28±5 yo) volunteered for a manipulated (rotation; mirroring; spacing) word reading task experiment.
Data was acquired on a 3T Philips Achieva d-Stream scanner with a 32-channel head coil. The MRI acquisition protocol included T1w and FLAIR, and OSE- and ME- fMRI data acquired with T2*w GE planar sequences (OSE: TR/TE=1100/23ms, flip angle=50°, voxel size=2.5mm iso; ME: TR/TEs=1650/14-40-66ms, flip angle=74°, voxel size=3x3x3.3mm). Two repetitions were acquired for each sequence.
Single-echo data followed a standard fMRI processing pipeline. The same procedure was applied to both OSE and the second collected echo (Echo-2) from the ME data to best match the TE to the T2* value of GM (Heunis et al., 2021).
In the processing of ME data, motion parameters were estimated from the Echo-2 time series, and slice timing and motion correction with the estimated parameters were performed on each echo. Data from the three echoes were optimally combined and denoised using tedana and corrected for B0 distortions. Combined data were coregistered to anatomical, intensity normalized, and spatially smoothed.
OSE, Echo-2 and ME were analyzed in SPM12 using a GLM modeling the effects related to unpracticed reading and including six motion parameters as confound. Statistical thresholds were set to p<0.001 at voxel level and p<0.05 FWE corrected at cluster level.
We characterized the different datasets (i.e., OSE, ME, Echo-2) with a multi-level approach.
Time-series level. Preprocessed images were compared computing the tSNR in the cortical GM (Parrish et al.,2000).
Subject-level. Contrast maps were derived to compute (i)activation extent, (ii)activation magnitude, (iii)sensitivity metrics.
Group-level. We performed population voxelwise analysis concatenating the two runs to verify wether the considered task elicited the recruitment of the dorsal pathway.
fMRI reliability. We assessed contrasts via Intra-Class Correlation coefficients (ICC (3,1)) (Noble et al.,2021) to address the reliability of ratings (i.e. contrast maps t-values).
Data was acquired on a 3T Philips Achieva d-Stream scanner with a 32-channel head coil. The MRI acquisition protocol included T1w and FLAIR, and OSE- and ME- fMRI data acquired with T2*w GE planar sequences (OSE: TR/TE=1100/23ms, flip angle=50°, voxel size=2.5mm iso; ME: TR/TEs=1650/14-40-66ms, flip angle=74°, voxel size=3x3x3.3mm). Two repetitions were acquired for each sequence.
Single-echo data followed a standard fMRI processing pipeline. The same procedure was applied to both OSE and the second collected echo (Echo-2) from the ME data to best match the TE to the T2* value of GM (Heunis et al., 2021).
In the processing of ME data, motion parameters were estimated from the Echo-2 time series, and slice timing and motion correction with the estimated parameters were performed on each echo. Data from the three echoes were optimally combined and denoised using tedana and corrected for B0 distortions. Combined data were coregistered to anatomical, intensity normalized, and spatially smoothed.
OSE, Echo-2 and ME were analyzed in SPM12 using a GLM modeling the effects related to unpracticed reading and including six motion parameters as confound. Statistical thresholds were set to p<0.001 at voxel level and p<0.05 FWE corrected at cluster level.
We characterized the different datasets (i.e., OSE, ME, Echo-2) with a multi-level approach.
Time-series level. Preprocessed images were compared computing the tSNR in the cortical GM (Parrish et al.,2000).
Subject-level. Contrast maps were derived to compute (i)activation extent, (ii)activation magnitude, (iii)sensitivity metrics.
Group-level. We performed population voxelwise analysis concatenating the two runs to verify wether the considered task elicited the recruitment of the dorsal pathway.
fMRI reliability. We assessed contrasts via Intra-Class Correlation coefficients (ICC (3,1)) (Noble et al.,2021) to address the reliability of ratings (i.e. contrast maps t-values).
Results:
Time-series level. Both OSE and ME data showed a significantly larger tSNR compared to echo-2, with OSE also showing a significantly greater tSNR than ME.
Subject-level. ME showed a larger activation compared to OSE, while OSE is characterized by the largest activation magnitude in GM. OSE and ME data outperformed echo-2 in the analysed metrics.
Group-level. Contrasts revealed similar activation patterns in both acquisition protocols (i.e., ME and OSE) as Fig. 1 reports.
fMRI reliability. ICCs showed consistent spatial distributions in the comparison at the voxel level. Higher ICC values are located in the visual system, independently of the contrast. The ICC analysis produced a range of findings, with ME being more reliable in certain contrasts while failing in others (Fig. 2).
Subject-level. ME showed a larger activation compared to OSE, while OSE is characterized by the largest activation magnitude in GM. OSE and ME data outperformed echo-2 in the analysed metrics.
Group-level. Contrasts revealed similar activation patterns in both acquisition protocols (i.e., ME and OSE) as Fig. 1 reports.
fMRI reliability. ICCs showed consistent spatial distributions in the comparison at the voxel level. Higher ICC values are located in the visual system, independently of the contrast. The ICC analysis produced a range of findings, with ME being more reliable in certain contrasts while failing in others (Fig. 2).
Conclusions:
We compared single-echo with ME acquisition techniques. ME confirmed earlier findings (Gilmore et al.,2022; Gonzalez-Castillo et al.,2016) by outperforming the single echo extracted from ME data (i.e. Echo-2). However, the superior performance of ME is not confirmed, yielding results similar to those of OSE.
To compare different acquisition techniques, it is essential to acquire each independently at its optimal performance, rather than deriving one from the other.
To compare different acquisition techniques, it is essential to acquire each independently at its optimal performance, rather than deriving one from the other.
Language:
Reading and Writing
Modeling and Analysis Methods:
Activation (eg. BOLD task-fMRI) 1
Novel Imaging Acquisition Methods:
BOLD fMRI 2
Keywords:
Data analysis
FUNCTIONAL MRI
Language
1|2Indicates the priority used for review
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