Methods of calculating uterine blood flow from the wash-out curves of intra-arterial and local injections of 133Xenon.

The wash-out curve from the human non-pregnant uterus of intra-arterially and locally injected 133Xenon can be broken down into two, sometimes three components. It has not been shown that these components are physiologically meaningful. However, if it is assumed that the uterus is composed of two or three compartments perfused in parallel, it is possible to calculate total blood flow per unit weight using relative weights of the compartments and compartment blood flows. Relative weights may be determined from the amount of isotope present in each compartment at the start of the washout. The possibly false assumption of a certain number of compartments has in this study been avoided by evaluating curves after intra-arterial injections according to the stochastic method of Zierler analysis, disregarding any elimination of isotope left after 20 minutes. After local injections initial slope analysis has been used. The equation for values according to Zierler as a function of compartment values is y=0.9772x-0.5921, for modified Zierler analysis values y=1.2582x-2.3993 and for initial slope values y=0.8679x-1.3412. The conclusion is that compartment analysis may be a good alternative for calculation of mean blood flow, even if it has not been shown that individual compartment values are physiologically meaningful.