Table 2.

MR scanner magnetic field strength, vasoactive stimulus and CVR calculation method.^a

Study	Field strength	Vasoactive stimulus	Effect of stimulus	Imaging parameters	Method of calculating CVR
Gauthier et al.15	3 T	Prospective end-tidal CO2 targeting (Respiract™) – alternating periods of 2 min at each EtCO2 concentration. Total CVR imaging time 10 min	EtCO2 manipulated between 40 and 45 mm Hg	Dual-echo pseudocontinuous arterial spin labelling (used to obtain simultaneous CBF and BOLD measurements); TR/TE1/TE2 = 3000/10/30 ms; FA = 90°; parallel imaging acceleration factor = 2; 4 x 4 mm in-plane resolution with 7/8 partial Fourier sampling; 11 x 7 mm slices with 1 mm gap	Linear regression with CVR expressed as %BOLD signal change per mm Hg change in EtCO2
Richiardi et al.16	3 T	7% CO2 in air via nasal cannula in 2 min spells alternating with air. Total CVR imaging time 9 min	No monitoring of EtCO2	Multi-echo EPI; TR/TE = 2970/29.5 ms; in-plane resolution 3.44 x 3.44 mm; 34 x 3.5 mm slices	Convolved the CO2 on–off timing vector with a filter to create a regressor that allowed description of ‘CVR velocity’
Conijn et al.17	7 T to assess microbleeds and CVR 1.5 T for WMH	Breath holding – 5 periods, 4 of which were 21 s long, 5th period as long as possible, total CVR imaging time 4 min 15 s plus time of last breath hold	No monitoring of EtCO2	Single-shot EPI; TR/TE = 3000/20 ms; parallel imaging acceleration factor = 3.5; in-plane resolution 1.5 x 1.5 mm; 45 x 1.5 mm slices with no gap	Multiple linear regression to select activated voxels and then expressed CVR as either mean % of voxels with significant signal change or mean % whole brain signal change
Yezhuvath et al.18	3 T	5% CO2 in air in 1 min spells alternating with air. Total CVR imaging time 7 min	Mean increase in EtCO2 of 11.9 mm Hg in patients and 12.2 mm Hg in controls	Single-shot EPI; TR/TE = 3000/30 ms; FA = 90°; in-plane resolution = 1.7 x 1.7 mm; 25 x 6 mm axial slices	General linear model with EtCO2 as the regressor and expressed CVR as % BOLD signal change per mm Hg change in EtCO2
Hund-Georgiadis et al.19	3 T	Hyperventilation for 2 min alternating with 4 min periods of normal breathing	At least 10 mm Hg decrease in EtCO2	Single-shot EPI; TR/TE = 2000/75 ms; FA = 90°; in-plane resolution = 3 x 3 mm; 16 x 5 mm axial slices with 1 mm gap	Calculated the contrast between different conditions using the t statistic, with t values subsequently being transformed into z scores. CVR was then defined as voxels with a z score of at least −5 with ventilation

^aDescription of MR scanner magnetic field strength, vasoactive stimulus, imaging parameters and CVR calculation method for each included study.