Simultaneous quantitative assessment of cerebral physiology using respiratory-calibrated MRI and near-infrared spectroscopy in healthy adults

The dynamics of cerebrovascular reactivity shown with transfer function analysis

“…First, that a linear CBF response to CO 2 was present over the PaCO 2 range of our study (Battisti-Charbonney et al, 2011), and BOLD increases in our study were b 10% so that the Davis [dHb] dilution model (Davis et al, 1998) would predict a linear BOLD-CBF relation. In support of this assumption we note that experimental evidence from simultaneous measures of brain oxygenation using near infra-red spectroscopy and BOLD during hypercapnia has shown that the they were strongly correlated (Alderliesten et al, 2014). We also assumed that the possible contribution of CBV changes to BOLD with hypercapnia was small compared to that of the changes in CBF, because in normal subjects, the fractional change in CBV relative to baseline can be approximated by the fractional change in CBF relative to baseline raised to the power of 0.2 (Chen and Pike, 2010;Mark et al, 2012).…”

T2-prepared velocity selective labelling: A novel idea for full-brain mapping of oxygen saturation

“…As CMRO 2 remains relatively stable during hypercapnia (HC), cerebral oxygen saturation should follow an increase in CBF induced by HC (Chen and Pike, 2010;Tachtsidis et al, 2006). Hypercapnia was induced by using a computerized end-tidal gas targeting system (RespirAct™, Thornhill Research Inc, Toronto, Canada) (Slessarev et al, 2007) as described before (Alderliesten et al, 2013). Before each experiment the subjects" individual baseline respiratory parameters (end-tidal CO 2 [P ETCO2 ], end-tidal O 2 [P ETO2 ], respiratory rate and gas breathing volume) were determined and subsequently used to tailor the settings of the RespirAct™.…”

“…NIRS data was obtained continuously throughout the whole MRI session as described before (Alderliesten et al, 2013). In summary, an Oxymon Mk III continuous wave NIRS system (Artinis Medical Systems, Elst, The Netherlands) was used to determine regional oxygen saturation (SO 2 in %) and absolute changes (in µM) in oxygenated (O 2 Hb), deoxygenated (HHb) and total haemoglobin (tHb = O 2 Hb + HHb) concentration with respect to an arbitrary baseline.…”

“…One approach is the respiratory calibration of the BOLD signal (Alderliesten et al, 2013;Bulte et al, 2012). Although calibrated BOLD approaches can provide invaluable information, the experimental setup is complex, the framework relies on several assumptions (e.g.…”

“…The CBF has been shown to have an association with, S v O 2 and SO 2-NIRS (Alderliesten et al, 2013;Xu et al, 2009) . Thereby we hypothesized that CBF has a positive association with (mixed compartment) SO 2 .…”