Limits...
Resting state BOLD functional connectivity at 3T: spin echo versus gradient echo EPI.

Chiacchiaretta P, Ferretti A - PLoS ONE (2015)

Bottom Line: Main results showed that, within subject, the GE sensitivity is overall larger with respect to that of SE, but to a less extent than previously reported for activation studies.Noteworthy, the reduced sensitivity of SE was counterbalanced by a reduced inter-subject variability, resulting in comparable group statistical connectivity maps for the two sequences.Future studies should clarify if these features of the SE BOLD signal can be beneficial to distinguish subtle variations of functional connectivity across different populations and/or treatments when vascular confounds or regions affected by signal dropout can be a critical issue.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti, Chieti, Italy; Institute for Advanced Biomedical Technologies (ITAB), University "G. d'Annunzio" of Chieti, Chieti, Italy; Bioengineering Unit, IRCCS Neuromed, Pozzilli (IS), Italy.

ABSTRACT
Previous evidence showed that, due to refocusing of static dephasing effects around large vessels, spin-echo (SE) BOLD signals offer an increased linearity and promptness with respect to gradient-echo (GE) acquisition, even at low field. These characteristics suggest that, despite the reduced sensitivity, SE fMRI might also provide a potential benefit when investigating spontaneous fluctuations of brain activity. However, there are no reports on the application of spin-echo fMRI for connectivity studies at low field. In this study we compared resting state functional connectivity as measured with GE and SE EPI sequences at 3T. Main results showed that, within subject, the GE sensitivity is overall larger with respect to that of SE, but to a less extent than previously reported for activation studies. Noteworthy, the reduced sensitivity of SE was counterbalanced by a reduced inter-subject variability, resulting in comparable group statistical connectivity maps for the two sequences. Furthermore, the SE method performed better in the ventral portion of the default mode network, a region affected by signal dropout in standard GE acquisition. Future studies should clarify if these features of the SE BOLD signal can be beneficial to distinguish subtle variations of functional connectivity across different populations and/or treatments when vascular confounds or regions affected by signal dropout can be a critical issue.

Show MeSH

Related in: MedlinePlus

GE and SE group connectivity maps for the default mode network in the inferior brain regions.The map is superimposed on the Talairach transformed EPI images of one subject. The signal void is clearly visible in the GE images, with the corresponding loss of functional contrast in the ventromedial prefrontal node. Both raw signal and functional contrast are instead recovered in SE images.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4352074&req=5

pone.0120398.g004: GE and SE group connectivity maps for the default mode network in the inferior brain regions.The map is superimposed on the Talairach transformed EPI images of one subject. The signal void is clearly visible in the GE images, with the corresponding loss of functional contrast in the ventromedial prefrontal node. Both raw signal and functional contrast are instead recovered in SE images.

Mentions: A remarkable exception was the ventromedial prefrontal node of DMN, that showed larger t-values and r-values for SE. In this region, the GE-EPI functional images showed the well known signal voiding artifact, whereas no susceptibility-induced signal voiding was found in the SE-EPI images (Fig. 4).


Resting state BOLD functional connectivity at 3T: spin echo versus gradient echo EPI.

Chiacchiaretta P, Ferretti A - PLoS ONE (2015)

GE and SE group connectivity maps for the default mode network in the inferior brain regions.The map is superimposed on the Talairach transformed EPI images of one subject. The signal void is clearly visible in the GE images, with the corresponding loss of functional contrast in the ventromedial prefrontal node. Both raw signal and functional contrast are instead recovered in SE images.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4352074&req=5

pone.0120398.g004: GE and SE group connectivity maps for the default mode network in the inferior brain regions.The map is superimposed on the Talairach transformed EPI images of one subject. The signal void is clearly visible in the GE images, with the corresponding loss of functional contrast in the ventromedial prefrontal node. Both raw signal and functional contrast are instead recovered in SE images.
Mentions: A remarkable exception was the ventromedial prefrontal node of DMN, that showed larger t-values and r-values for SE. In this region, the GE-EPI functional images showed the well known signal voiding artifact, whereas no susceptibility-induced signal voiding was found in the SE-EPI images (Fig. 4).

Bottom Line: Main results showed that, within subject, the GE sensitivity is overall larger with respect to that of SE, but to a less extent than previously reported for activation studies.Noteworthy, the reduced sensitivity of SE was counterbalanced by a reduced inter-subject variability, resulting in comparable group statistical connectivity maps for the two sequences.Future studies should clarify if these features of the SE BOLD signal can be beneficial to distinguish subtle variations of functional connectivity across different populations and/or treatments when vascular confounds or regions affected by signal dropout can be a critical issue.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio" of Chieti, Chieti, Italy; Institute for Advanced Biomedical Technologies (ITAB), University "G. d'Annunzio" of Chieti, Chieti, Italy; Bioengineering Unit, IRCCS Neuromed, Pozzilli (IS), Italy.

ABSTRACT
Previous evidence showed that, due to refocusing of static dephasing effects around large vessels, spin-echo (SE) BOLD signals offer an increased linearity and promptness with respect to gradient-echo (GE) acquisition, even at low field. These characteristics suggest that, despite the reduced sensitivity, SE fMRI might also provide a potential benefit when investigating spontaneous fluctuations of brain activity. However, there are no reports on the application of spin-echo fMRI for connectivity studies at low field. In this study we compared resting state functional connectivity as measured with GE and SE EPI sequences at 3T. Main results showed that, within subject, the GE sensitivity is overall larger with respect to that of SE, but to a less extent than previously reported for activation studies. Noteworthy, the reduced sensitivity of SE was counterbalanced by a reduced inter-subject variability, resulting in comparable group statistical connectivity maps for the two sequences. Furthermore, the SE method performed better in the ventral portion of the default mode network, a region affected by signal dropout in standard GE acquisition. Future studies should clarify if these features of the SE BOLD signal can be beneficial to distinguish subtle variations of functional connectivity across different populations and/or treatments when vascular confounds or regions affected by signal dropout can be a critical issue.

Show MeSH
Related in: MedlinePlus