Reproducibility of a Ramping Protocol to Measure Cerebral Vascular Reactivity Using Functional Magnetic Resonance Imaging
Year: 2018
Type: conference-abstract
Abstract: PURPOSE: Though individual differences in arterial carbon dioxide and oxygen levels inherently exist, the degree of their influence on cerebral vascular reactivity (CVR) is less clear at the micro-vessel level. The introduction of a partial re-breathing method that independently controls end-tidal carbon dioxide (PetCO2) and end-tidal oxygen (PetO2) has enabled examination of hypercapnic effects on blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal changes. The purpose of this study was to examine the within- and between-visit reproducibility of BOLD signal changes to an iso-oxic ramping protocol in PetCO2. METHODS: To stimulate changes in CVR, PetCO2 was altered while PetO2 was held constant using a computer controlled prospective gas-blending device. Two fMRI scans, each including a linear change in PetCO2, were performed on the same visit using a 3-Tesla (3T) scanner. This ramp sequence consisted of decreasing PetCO2 to 30 mmHg and then increasing PetCO2 linearly to 50 mmHg over a 7 min period. The protocol was repeated on a separate visit with minimum of 3 days between scanning sessions. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) were calculated to quantify reproducibility. RESULTS: Eleven subjects (6 females; mean age 26.5±5.7 years) completed the full testing protocol. Very good reproducibility was observed for the within-visit ramp wave (Visit 1: ICC = 0.82, CV = 6.5%; Visit 2: ICC = 0.74, CV = 6.36%). Similarly, ramp waves were reproducible between scanning sessions (Scan 1: ICC = 0.74, CV = 6.5%; Scan 2: ICC = 0.66, CV = 6.13%). CONCLUSION: This study demonstrates BOLD signal changes in response to ramp alterations in PetCO2 are reproducible both within- and between-visit MRI scans. Establishment of reproducible methodologies for measuring BOLD signal changes while altering PetCO2 using a ramp protocol will allow researchers to study CVR functionality. Finally, adding a ramping protocol to CVR studies could provide information about linear changes in CVR over a broad range of PetCO2.
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2807154412