. Author manuscript; available in PMC: 2013 Apr 8.

Published in final edited form as: Brain Imaging Behav. 2011 Dec;5(4):295–306. doi: 10.1007/s11682-011-9133-4

Table 2.

Balloon model parameters for SCA patients and Control Patients

Parameter	Group Average Model		Individual Models
	Control	SCA	Control	SCA
V₀	0.04	0.06	0.04 (0.021, 0.051)	0.06 (0.045, 0.070)
rHb	1.00	0.76	1.00 (0.86, 1.13)	0.76 (0.56, 0.89)
ΔE/E₀	0.36	0.26	0.35 (0.21, 0.52)	0.25 (0.14, 0.34)
Δf	0.85	0.62	0.85 (0.51, 1.50)	0.60 (0.39, 0.83)
α	0.40	0.48	0.40 (0.1, 0.5)	0.48 (0, 0.65)
τ	2	3	2 (1.0, 4.0)	3 (2.0, 4.2)
τ₊	10	8	10 (3, 25)	9 (3.5, 30)
τ₋	20	12	20 (10, 40)	17 (1, 40)

Notes: V₀: fractional blood volume; rHgb: relative blood hemoglobin concentration; E0: baseline oxygen extraction fraction, ΔE: oxygen extraction fraction change during activation; Δf: fractional CBF change during activation; α: Flow-volume relationship; τ: mean transit time; τ+: vascular balloon inflation time-constant; τ−: vascular balloon deflation time-constant (see supplementary online material for details of the modeling).