Table 2.
Mean (± standard deviation) blood-to-brain influx constant (Ki; × 10−3 mL/g/min) of areas with blood–brain barrier opening as determined by two different methods of calculation and sources of data, MRI and radiotracer-quantitative auto-radiography (QAR), from the same experiment
| Method of calculation | Source of data |
Arterial input function (AIF) |
Ki per brain structure (n) | ||
|---|---|---|---|---|---|
| PoA (13) | Str (10) | PCx (2) | |||
| Single-time equation | MRI | AIF-I | 3.5 ± 0.6 | 2.9 ± 0.9 | 4.4 ± 3.1 |
| MRI | AIF-II | 3.2 ± 1.0 | 2.6 ± 1.0 | 3.9 ± 3.7 | |
| QAR | AIF* | 3.0 ± 1.0 | 2.7 ± 1.0 | 4.2 ± 1.7 | |
| Patlak plot | MRI | AIF-I | 2.9 ± 0.6 | 2.6 ± 0.9 | 3.7 ± 3.1 |
| MRI | AIF-II | 2.6 ± 0.7 | 2.4 ± 0.7 | 3.2 ± 2.0 | |
n, sample size; PCx, parietal cortex; PoA, preoptic area of anterior hypothalamus; Str, striatum.
The sample size is given in parentheses. The differences between the Ki values of the two methods were not significant for PoA and Str (two-tailed, paired t-test). Calculations showed that Ki values approximated the permeability–surface area product in these experiments, and therefore the latter are not reported separately.