Table 2. Error in δCMRO2 and n as calculated by the classic and optimized Davis models for the standard subject as defined in Table 1.
While the optimized Davis model is best for all couplings of δCBF and δCMRO2, the classic Davis model with the true value of M also produces reasonable estimates of δCMRO2 around n=2.5 and n=5.0. Calculations using the classic Davis model parameters with a biased M (as might be determined from a hypercapnia calibration) are also given, and at n=2.5 this model is also quite accurate. However, the classic Davis model with the biased M is not accurate for n=5.0 or n=−0.8. Even the classic model with the true M is not accurate for n=−0.8.
| Classic α and β | Optimized α and β | Classic α and β Biased M (rHC=0.9) |
|
|---|---|---|---|
| Typical functional activation (MRI): (n=2.5) δCBF = +50% δCMRO2 = +20% |
δCMRO2 = 18.0% ξ = −9.8% n = 2.8 |
δCMRO2 = 19.7% ξ = −1.3% n = 2.5 |
δCMRO2 = 21.0% ξ = 5.1% n = 2.4 |
| Typical functional activation (PET): (n=5.0) δCBF = +50% δCMRO2 = +10% |
δCMRO2 = 9.3% ξ = −6.9% n = 5.4 |
δCMRO2 = 9.8% ξ = −2.5% n = 5.1 |
δCMRO2 = 13.9% ξ = 38.9% n = 3.6 |
| Typical response to caffeine: (n=−0.8) δCBF = −25% δCMRO2 = +30% |
δCMRO2 = 18.6% ξ = −38.0% n = −1.3 |
δCMRO2 = 29.6% ξ = −1.2% n = −0.8 |
δCMRO2 = 12.7% ξ = −57.7% n = −2.0 |