Estimation of arterial input by a noninvasive image derived method in brain H₂¹⁵O PET study: confirmation of arterial...

A noninvasive method to estimate input function directly from H₂¹⁵O brain PET data for measurement of cerebral blood flow (CBF) was proposed in this study. The image derived input function (IDIF) method extracted the time-activity curves (TAC) of the major cerebral arteries at the skull base from the dynamic PET data. The extracted primordial IDIF showed almost the same radioactivity as the arterial input function (AIF) from sampled blood at the plateau part in the later phase, but significantly lower radioactivity in the initial arterial phase compared with that of AIF-TAC. To correct the initial part of the IDIF, a dispersion function was applied and two constants for the correction were determined by fitting with the individual AIF in 15 patients with unilateral arterial stenoocclusive lesions. The area under the curves (AUC) from the two input functions showed good agreement with the mean AUC_IDIF/AUC_AIF ratio of 0.92  ±  0.09. The final products of CBF and arterial-to-capillary vascular volume (V ₀) obtained from the IDIF and AIF showed no difference, and had with high correlation coefficients.