1011-116 Myocardial Rb Extraction Fraction: Determination in Humans

Abstract

Ouantitation of myocardial blood flow (MBF) with diffusion-limited radiotracers as 82 Rb and positron emission tomography (PET) requires knowledge of flow dependence of myocardial 82 Rb extraction fraction. To determine this dependence we evaluated 7 patients (mean age (61.0 ± 9.7) years, 4 males, 3 females) who had undergone coronary angiography with exclusion of relevant coronary stenoses and normal left ventricular function. 82 Rb-PET clearance was simultaneously assessed with global MBF by the argon (Ar) inert gas method. 82 Rb clearance was dynamically measured by a CTI-Siemens ECAT 931-08-12 scanner after i.v. injection of 1–1.2 GBq 82 Rb. Ar gas desaturation was obtained by simultaneous arterial and coronary sinus blood sampling. Measurements were performed at rest and during vasodilatation induced by i.v. dipyridamole (0.7 mg/kg/4 min). Mean 82 Rb clearance and Ar flow values were (0.39 ± 0,03) ml/g/min and (0.69 ± 0.14) ml/g/min at rest, respectively, and (0.47 ± 0.09) ml/g/min and (1.48 ± 0.49) ml/g/min during hyperemia. A fit with a two compartment model yielded E = PS/(PS + MBF) with PS = (0.82 ± 0.09) ml/g/min (PS: permeability surface area product). These data (figure) provide for the best of our knowledge the first measured 82 Rb extraction fraction in humans and may form the basis for more accurate quantitation of myocardial blood flow with 82 Rb-PET.