Cerebrovascular Reactivity Assessment During Carbon Dioxide Inhalation Using SPECT

Background: Perfusion single-photon emission computed tomography (SPECT) using an acetazolamide is an important clinical tool
used to assess cerebrovascular reactivity (CVR) in patients, but its use has
been limited to clinical diagnostics. This study aimed to preliminarily
evaluate the feasibility of perfusion SPECT using carbon dioxide (CO2).
Methods: Ten healthy subjects
participated in two consecutive SPECT scans using CO2 inhalation. To
evaluate brain perfusion after preprocessing, the voxel-by-voxel CVR values
were averaged in 13 subgroup regions of interest (ROIs) based on a template.
Subsequently, averaged CVR values of each ROI were analyzed based on both
cerebellar hemispheres. Results:
CVR values in the eight subgroup ROIs, which included vermis, both
insula/cingulate, and frontal cortices, showed significant changes (p < 0.05). CVR values were higher in
vermis and right insula/cingulate by [KO2] 3.34% and 3.15%, respectively. Conclusions: This study showed that quantitative SPECT with CO2
inhalation could be used to evaluate the voxel-based CVR in healthy subjects,
which could be beneficial for elucidating induced hypercapnic states and for
longitudinally investigating the healthy aging in brain vessels. Furthermore,
the cerebrovascular hemodynamic parameters induced by CO2 could play
an important role as a biomarker to evaluate treatment progress in patients with
cerebrovascular disease.