Table 3. Summary of comparison of CVR and its z-maps.

	CVR	z-map
Sensitivity	Low: mainly identifies presence/absence of steal	Higher sensitivity by detecting graded reductions in CVR short of steal.
Specificity	High: steal is accepted sign of abnormal vasculature.	Lower specificity mitigated by (1) normalization of CVR to normal range for region highlights abnormal CVR and (2) confluence of reduced z-scores is statistically unlikely in tissue with normal CVR
Anatomic location specificity	No: CVR maps score absolute values of CVR	Yes: z-score normalizes CVR for anatomic location
Identification of abnormality distribution	Identifies only the distribution where steal occurs as abnormal	Identifies the distributions of various grades of reduced CVR beyond that of steal
Platform specificity	CVR can be performed on any magnet, however, CVR is specific for that magnet	Probably: each platform may require its own unique atlas
Comparison across platforms	Possibly: requires, at a minimum, standardized MR sequence parameters and uniform stimulus across platforms	Yes: requires only consistency of sequences and stimulus between atlas and patient within each platform: z-values should then be comparable across platforms

CVR, cerebrovascular reactivity; MR, magnetic resonance.