Quantitative assessment of cerebral hemodynamics using single photon emission computed tomography with venous blood sampling

Objective: Quantitative cerebral blood flow (CBF) measured by single photon emission computed tomography (SPECT) with arterial blood sampling is one of the most reliable methods to assess the hemodynamics in individual patients. SPECT with venous blood sampling is less invasive. The present study compared the measurement of CBF using N-isopropyl-p-(iodine-123)-iodoamphetamine SPECT with venous blood sampling and with arterial blood sampling in patients with major cerebral artery occlusive disease. Methods: Two normal subjects and 14 patients with major cerebral artery occlusive disease underwent SPECT with arterial and venous blood sampling. The microsphere method was used for quantitative SPECT imaging. Whole brain radioactivity was corrected when the detectors rotated in the forward direction (F₁-F₇). Venous sampling was performed 30 min after radiotracer injection. Arterial blood radioactivity was estimated by multiple regression analysis from these parameters. The cerebrovascular reactivity to acetazolamide was also measured. Results: Multiple regression analysis established the following formula:Ca₁₀=-1. 099F₁+1.629F₂-2.143F₃-2.766F ₄-1.208F₅+2.113F₆+3.259F₇+1. 241Cv₃₀+94.958(where Ca₁₀ is the arterial blood radioactivity at 10 min, F₁-F₇ are the whole brain radioactivity in the forward direction, Cv₃₀ is the venous blood radioactivity at 30 min). Mean CBF values were 32.2 ± 6.6 ml/100 g/min for measured arterial radioactivity and 42.2 ± 7.8 ml/100 g/min for calculated arterial radioactivity based on venous radioactivity. Conclusions: The present modified method of calculating quantitative CBF from whole brain and venous blood radioactivities correlated well with values determined with arterial blood radioactivity.