The Reproducibility of Cerebrovascular Reactivity Across MRI Scanners

Abstract

Cerebrovascular reactivity (CVR) is defined as the ratio of the cerebral blood flow (CBF) response to an increase in a vasoactive stimulus. We used changes in blood oxygenation level-dependent (BOLD) MRI as surrogates for changes of CBF, and standardized quantitative changes in arterial partial pressure of carbon dioxide as the stimulus. Despite uniform stimulus and test conditions, differences in voxel-wise BOLD changes between testing sites may remain, attributable to physiologic and machine variability. We generated a reference atlas of normal CVR metrics (voxel-wise mean and SD) for each of two sites. We hypothesized that there would be no significant differences in CVR between the two atlases enabling each atlas to be used at any site. A total of 69 healthy subjects were tested to create site-specific atlases, with 20 of those individuals tested at both sites. 38 subjects were scanned at Site 1 (17F, 37.5 ± 16.8 y) and 51 subjects were tested at Site 2 (22F, 40.9 ± 17.4 y). MRI platforms were: Site 1, 3T Magnetom Skyra Siemens scanner with 20-channel head and neck coil; and Site 2, 3T HDx Signa GE scanner with 8-channel head coil. To construct the atlases, test results of individual subjects were co-registered into a standard space and voxel-wise mean and SD CVR metrics were calculated. Map comparisons of z scores found no significant differences between white matter or gray matter in the 20 subjects scanned at both sites when analyzed with either atlas. We conclude that individual CVR testing, and atlas generation are compatible across sites provided that standardized respiratory stimuli and BOLD MRI scan parameters are used. This enables the use of a single atlas to score the normality of CVR metrics across multiple sites.

Assessment of cerebrovascular function in patients with sickle cell disease using transfer function analysis

“…Atlas creation involved co‐registering the maps into a standard space and calculating a voxel‐by‐voxel mean and standard deviation for each metric for each corresponding atlas. Atlas creation is discussed in further detail elsewhere (Poublanc et al, 2015 ; Sobczyk et al, 2015 ; McKetton et al, 2018a ; Sobczyk et al, 2021 ). Results from a 35‐person SCD patient group cohort was compared to the healthy 24‐person HC atlas.…”

Increased Risk of Recurrent Stroke in Symptomatic Large Vessel Disease With Impaired BOLD Cerebrovascular Reactivity

“…The standardized application of the CO 2 -based vasoactive stimulus during BOLD acquisition allows for a voxelwise CVR quantification with a high intersubject and intrasubject agreement, 11,12 even across different medical centers. 30 Such standardization of BOLD-CVR across subjects enables the development of a healthy subject CVR reference atlas, which can be used to calculate the normal range in terms of mean±SD for each voxel. This approach facilitates the calculation of the BOLD-CVR cutoff point of 0.1% BOLD signal change per mm Hg CO 2 based on 2 SD from the mean.…”

Transcranial Doppler Ultrasonography as a Diagnostic Tool for Cerebrovascular Disorders

“…Cerebrovascular reactivity is attributed to the difference in CBF or CBFV in response to vasoactive stimuli, such as CO 2 , hyper/hypoventilation, acetazolamide (AZ), or breath-holding (Sobczyk et al, 2021). Changes in cerebral perfusion pressure do not affect CBF because cerebral arterioles can control the vascular resistance, which is an important part of autoregulation (Krishnamurthy et al, 2021).…”