The ¹⁵O Steady-State Method: Correction for Variation in Arterial Concentration

Abstract

One of the factors limiting the accuracy of the 15O steady-state method for the measurement of regional cerebral blood flow and oxygen metabolism is the requirement that a constant arterial blood concentration be maintained over long periods. A new method has been developed to correct for the variation of the arterial concentration in the C15O2 and 15O2 steady-state inhalation technique. The time course of the arterial activity is obtained by multiple sampling over the study period. The same 15O model as is used in the steady-state method is employed but is solved without assuming equilibrium. Look-up tables are generated to relate flow and oxygen extraction fraction to tissue activity, and from them the regional parameters are estimated. Theory and simulation studies suggest that substantial improvement in accuracy can be obtained with no increase in statistical error. The validity of the method was checked experimentally by making repeated measurements in the same subject after perturbing the gas delivery. The conventional steady-state method showed significantly larger deviations in repeat measurement than did the new method. Thus, it is concluded that the proposed method is superior.

Evaluation of the 11CO2 Positron Emission Tomographic Method for Measuring Brain pH. II. Quantitative pH Mapping in Patients with Ischemic Cerebrovascular Diseases

“…Each blood sample was collected for 25 s to reduce the effects of respiratory fluc tuations, and the activity concentrations of whole blood and plasma were measured with a well counter. The im ages were reconstructed and calibrated in the same way as the pH study, and quantitative CBF, OEF, and CMR02 maps were generated using a technique devel oped in our laboratory (Senda et al, 1988), which cor rects for variation of arterial concentration. Activity in the blood pool was corrected assuming a uniform blood volume fraction (4%) in the entire brain.…”

Noninvasive Evaluation of CBF and Perfusion Delay of Moyamoya Disease Using Arterial Spin-Labeling MRI with Multiple Postlabeling Delays: Comparison with15O-Gas PET and DSC-MRI

“…CBF was measured by continuous and consecutive 9-minute inhalations of C 15 O 2 with continuous arterial blood sampling, using a table-lookup technique. 35,36 The regional CBF value was 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.…”

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

“…Briefly, the PET study was performed using a Headtome-V scanner (Shimadzu Corporation, Kyoto, Japan). 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).…”