Radionuclide plethysmography for noninvasive evaluation of peripheral arterial blood flow.

We validated a noninvasive radionuclide plethysmography technique to evaluate peripheral arterial blood flow during reactive hyperemia. This method, based on the measurement of blood volume variations during repetitive venous occlusions, was compared with strain-gauge venous impedance plethysmography. The technique uses 99mTc-labeled autologous red blood cells scintigraphy to determine the rate of change of forearm scintigraphic counts during venous occlusion. Thirteen subjects were simultaneously evaluated with radionuclide and impedance plethysmography. Six baseline flow measurements were performed to evaluate the reproducibility of each method. Twenty-seven serial measurements were then made to evaluate flow variation during forearm reactive hyperemia. After 30 min of recovery, resting forearm blood flows were again evaluated. Impedance and radionuclide methods showed excellent reproducibility with intraclass correlation coefficients of 0.96 and 0.93, respectively. There was also good correlation of flows between both methods during reactive hyperemia (r = 0.87). Resting flows at 30 min after reactive hyperemia were slightly lower than at baseline with both methods. We conclude that radionuclide plethysmography could be used for the noninvasive evaluation of forearm blood flow and its dynamic variations during reactive hyperemia.

An 82Rb infusion system for quantitative perfusion imaging with 3D PET.

A (82)Rb infusion system is described with two important features for imaging with 3D positron emission tomography. First, a generator bypass line is added to flush the patient infusion line at the end of an elution. Second, feedback control is implemented to permit 'slow-bolus' constant-activity elutions. A model for the activity eluted from a (82)Sr/(82)Rb generator based on a volume-activity empirical relationship, is used as the basis for performing simulations to demonstrate the efficacy of varying the flow rate through the generator to achieve desired eluted (82)Rb activity rate profiles. A (82)Rb infusion system was constructed to verify the accuracy of the simulations. The system can deliver accurate constant-activity elutions from 10% to 70% of the total generator activity.