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Fine tuning breath-hold-based cerebrovascular reactivity analysis models.

van Niftrik CH, Piccirelli M, Bozinov O, Pangalu A, Valavanis A, Regli L, Fierstra J - Brain Behav (2016)

Bottom Line: All models showed significant differences in CVR and coherence between the affected-hemodynamic impaired-and unaffected hemisphere.Voxel-wise phase determination significantly increases CVR (0.60 ± 0.18 vs. 0.82 ± 0.27; P < 0.05).Our CVR analysis demonstrates an improved CVR and coherence after implementation of voxel-wise phase and frequency adjustment.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery University Hospital Zurich University of Zurich Clinical Neuroscience Center Frauenklinikstrasse 10 8091 Zurich Switzerland.

ABSTRACT

Introduction: We elaborate on existing analysis methods for breath-hold (BH)-derived cerebrovascular reactivity (CVR) measurements and describe novel insights and models toward more exact CVR interpretation.

Methods: Five blood-oxygen-level-dependent (BOLD) fMRI datasets of neurovascular patients with unilateral hemispheric hemodynamic impairment were used to test various BH CVR analysis methods. Temporal lag (phase), percent BOLD signal change (CVR), and explained variance (coherence) maps were calculated using three different sine models and two novel "Optimal Signal" model-free methods based on the unaffected hemisphere and the sagittal sinus fMRI signal time series, respectively.

Results: All models showed significant differences in CVR and coherence between the affected-hemodynamic impaired-and unaffected hemisphere. Voxel-wise phase determination significantly increases CVR (0.60 ± 0.18 vs. 0.82 ± 0.27; P < 0.05). Incorporating different durations of breath hold and resting period in one sine model (two-task) did increase coherence in the unaffected hemisphere, as well as eliminating negative phase commonly obtained by one-task frequency models. The novel model-free "optimal signal" methods both explained the BOLD MR data similar to the two task sine model.

Conclusions: Our CVR analysis demonstrates an improved CVR and coherence after implementation of voxel-wise phase and frequency adjustment. The novel "optimal signal" methods provide a robust and feasible alternative to the sine models, as both are model-free and independent of compliance. Here, the sagittal sinus model may be advantageous, as it is independent of hemispheric CVR impairment.

No MeSH data available.


Related in: MedlinePlus

Breath‐hold paradigm and BOLD time series. (A) Breath‐hold paradigm presented as a taskbar. The gray blocks indicate the three breath hold periods of 22 TR (44 sec). The white blocks, amidst, represent the resting periods of 44 TR each, except for the first one: 22 sec. Total duration of this protocol is 7:20 min. (B) Illustrative whole brain combined gray and white matter BOLD time series of one subject. The time series is displayed over the period of 220 repetition times (TR) (440 sec). (C) Hemispheric mean BOLD time series of gray and white matter. The time courses of the unaffected hemisphere are illustrated with a bold line, whereas the affected hemisphere time courses are displayed with a dotted line. The dark lines indicate gray matter, whereas gray lines indicate the white matter. As expected, the unaffected hemisphere reacts to a greater extent to the given stimulus than the affected hemisphere, as does the gray matter compared to the white matter. The time to reach signal maximum is also faster in the unaffected hemisphere, which results in different phase between hemispheres.
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brb3426-fig-0001: Breath‐hold paradigm and BOLD time series. (A) Breath‐hold paradigm presented as a taskbar. The gray blocks indicate the three breath hold periods of 22 TR (44 sec). The white blocks, amidst, represent the resting periods of 44 TR each, except for the first one: 22 sec. Total duration of this protocol is 7:20 min. (B) Illustrative whole brain combined gray and white matter BOLD time series of one subject. The time series is displayed over the period of 220 repetition times (TR) (440 sec). (C) Hemispheric mean BOLD time series of gray and white matter. The time courses of the unaffected hemisphere are illustrated with a bold line, whereas the affected hemisphere time courses are displayed with a dotted line. The dark lines indicate gray matter, whereas gray lines indicate the white matter. As expected, the unaffected hemisphere reacts to a greater extent to the given stimulus than the affected hemisphere, as does the gray matter compared to the white matter. The time to reach signal maximum is also faster in the unaffected hemisphere, which results in different phase between hemispheres.

Mentions: The BH paradigm consisted of a 44 second preparation period of ventilator controlled breathing after which apnea was induced for 44 sec by turning off the ventilator. After the BH period, the ventilator controlled breathing was resumed. To simulate post‐BH hyperventilation, we applied a series of six manual ventilations with an AMBI bag to facilitate apt return to baseline CO2. In total, three repetitive cycles with a BH block of 44 sec and following resting baseline block of 88 sec were performed (Fig. 1A).


Fine tuning breath-hold-based cerebrovascular reactivity analysis models.

van Niftrik CH, Piccirelli M, Bozinov O, Pangalu A, Valavanis A, Regli L, Fierstra J - Brain Behav (2016)

Breath‐hold paradigm and BOLD time series. (A) Breath‐hold paradigm presented as a taskbar. The gray blocks indicate the three breath hold periods of 22 TR (44 sec). The white blocks, amidst, represent the resting periods of 44 TR each, except for the first one: 22 sec. Total duration of this protocol is 7:20 min. (B) Illustrative whole brain combined gray and white matter BOLD time series of one subject. The time series is displayed over the period of 220 repetition times (TR) (440 sec). (C) Hemispheric mean BOLD time series of gray and white matter. The time courses of the unaffected hemisphere are illustrated with a bold line, whereas the affected hemisphere time courses are displayed with a dotted line. The dark lines indicate gray matter, whereas gray lines indicate the white matter. As expected, the unaffected hemisphere reacts to a greater extent to the given stimulus than the affected hemisphere, as does the gray matter compared to the white matter. The time to reach signal maximum is also faster in the unaffected hemisphere, which results in different phase between hemispheres.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834934&req=5

brb3426-fig-0001: Breath‐hold paradigm and BOLD time series. (A) Breath‐hold paradigm presented as a taskbar. The gray blocks indicate the three breath hold periods of 22 TR (44 sec). The white blocks, amidst, represent the resting periods of 44 TR each, except for the first one: 22 sec. Total duration of this protocol is 7:20 min. (B) Illustrative whole brain combined gray and white matter BOLD time series of one subject. The time series is displayed over the period of 220 repetition times (TR) (440 sec). (C) Hemispheric mean BOLD time series of gray and white matter. The time courses of the unaffected hemisphere are illustrated with a bold line, whereas the affected hemisphere time courses are displayed with a dotted line. The dark lines indicate gray matter, whereas gray lines indicate the white matter. As expected, the unaffected hemisphere reacts to a greater extent to the given stimulus than the affected hemisphere, as does the gray matter compared to the white matter. The time to reach signal maximum is also faster in the unaffected hemisphere, which results in different phase between hemispheres.
Mentions: The BH paradigm consisted of a 44 second preparation period of ventilator controlled breathing after which apnea was induced for 44 sec by turning off the ventilator. After the BH period, the ventilator controlled breathing was resumed. To simulate post‐BH hyperventilation, we applied a series of six manual ventilations with an AMBI bag to facilitate apt return to baseline CO2. In total, three repetitive cycles with a BH block of 44 sec and following resting baseline block of 88 sec were performed (Fig. 1A).

Bottom Line: All models showed significant differences in CVR and coherence between the affected-hemodynamic impaired-and unaffected hemisphere.Voxel-wise phase determination significantly increases CVR (0.60 ± 0.18 vs. 0.82 ± 0.27; P < 0.05).Our CVR analysis demonstrates an improved CVR and coherence after implementation of voxel-wise phase and frequency adjustment.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurosurgery University Hospital Zurich University of Zurich Clinical Neuroscience Center Frauenklinikstrasse 10 8091 Zurich Switzerland.

ABSTRACT

Introduction: We elaborate on existing analysis methods for breath-hold (BH)-derived cerebrovascular reactivity (CVR) measurements and describe novel insights and models toward more exact CVR interpretation.

Methods: Five blood-oxygen-level-dependent (BOLD) fMRI datasets of neurovascular patients with unilateral hemispheric hemodynamic impairment were used to test various BH CVR analysis methods. Temporal lag (phase), percent BOLD signal change (CVR), and explained variance (coherence) maps were calculated using three different sine models and two novel "Optimal Signal" model-free methods based on the unaffected hemisphere and the sagittal sinus fMRI signal time series, respectively.

Results: All models showed significant differences in CVR and coherence between the affected-hemodynamic impaired-and unaffected hemisphere. Voxel-wise phase determination significantly increases CVR (0.60 ± 0.18 vs. 0.82 ± 0.27; P < 0.05). Incorporating different durations of breath hold and resting period in one sine model (two-task) did increase coherence in the unaffected hemisphere, as well as eliminating negative phase commonly obtained by one-task frequency models. The novel model-free "optimal signal" methods both explained the BOLD MR data similar to the two task sine model.

Conclusions: Our CVR analysis demonstrates an improved CVR and coherence after implementation of voxel-wise phase and frequency adjustment. The novel "optimal signal" methods provide a robust and feasible alternative to the sine models, as both are model-free and independent of compliance. Here, the sagittal sinus model may be advantageous, as it is independent of hemispheric CVR impairment.

No MeSH data available.


Related in: MedlinePlus