Error Analysis of a Quantitative Cerebral Blood Flow Measurement Using H₂¹⁵O Autoradiography and Positron Emission Tomography, with Respect to the Dispersion of the Input Function

Abstract

The effect of the inaccuracy of the input function on CBF measured by the H2(15)O autoradiographic method was investigated. In H2(15)O autoradiography the measured input function usually includes a larger dispersion than the true input function, as well as the absolute time axis having been already lost. The time constant of the external dispersion that occurred in our continuous sampling system was evaluated as 10-12 s when the dispersion function was approximated by a monoexponential function. The internal dispersion occurring in arterial lines in a human body was evaluated as 4-6 s. Such dispersion, indispensable in a patient study, was found to produce large errors in calculating CBF, e.g., 5(10) s of the dispersion caused +15(33) and +10(20)% systematic overestimations for the 40- and 60-s accumulation time respectively. An analytical correction employing an inverse Laplace transform was applied to clinical CBF studies, and the results were compared with those from the C15O2 steady-state inhalation method. Correction by 10 s in time constant, corresponding to the external dispersion, reduced the overestimation significantly from 70-100% to approximately 20%. Further correction by 5 s, corresponding to the internal dispersion, resulted in a negligible difference (less than a few percent) from the steady-state method.

The C15O2 Build-up Technique to Measure Regional Cerebral Blood Flow and Volume of Distribution of Water

“…The value of dispersion coefficient within the radial artery and/or cannula estimated by each study duration to those for the total study period of 10 min are shown. Iida et al (1986) is of the same order of magnitude as the values obtained in the present study. A major advantage of the build-up technique is therefore the capability to measure this dispersion.…”

“…Dispersion within the radial artery and/or cannula might also explain the discrepancy between rCBF values obtained from autoradiographic and steady state techniques (Kanno et al, 1984) as indicated by Iida et al (1986). The value of dispersion coefficient within the radial artery and/or cannula estimated by each study duration to those for the total study period of 10 min are shown.…”

Rapid Quantitative Measurement of CMRO2 and CBF by Dual Administration of 15O-Labeled Oxygen and Water During a Single PET Scan—a Validation Study and Error Analysis in Anesthetized Monkeys

“…Values for CBF, OEF, and CMRO 2 were calculated based on three-step ARG and DARG. To shift the dispersion time constants, the true arterial TAC was convoluted or deconvoluted with a simple exponential (Iida et al, 1986;Kanno et al, 1987). For simulating the error in the values of p and V B , the value of p was varied from 0.7 to 0.9 mL/g, and that of V B from 0.02 to 0.06 mL/g; in each situation, tissue TACs were created and CBF, OEF, and CMRO 2 values were calculated using these TACs, assuming P ¼ 0.8 mL/g and V B ¼ 0.04 mL/g.…”

Quantitative Evaluation of Cerebral Hemodynamics in Patients with Moyamoya Disease by Dynamic Susceptibility Contrast Magnetic Resonance Imaging—Comparison with Positron Emission Tomography

“…The regional CBF and OEF were measured during continuous and consecutive 9-min inhalations of C 15 O 2 and 15 O 2 with continuous arterial blood sampling, employing a table-lookup technique (Senda et al, 1988). The regional CBF and OEF were obtained by calculating the values with lookup tables created from the arterial whole blood and plasma radioactivity curves, and then correcting them for delay and dispersion (Iida et al, 1986). The CBV was measured by a 3-min inhalation of C 15 O with blood sampling (Grubb et al, 1978).…”