EFFECTS OF LUNG MOTION AND TRACER KINETICS CORRECTIONS ON PET IMAGINGOF PULMONARY-FUNCTION

A method to assess the three-dimensional distribution of alveolar vent ilation-perfusion ratio ((V) over A/(Q) over dot) by imaging the lungs with positron emission tomography (PET) during a constant-rate intrav enous infusion of (NN)-N-13-labeled saline solution was developed by C . G. Rhodes, S. O. Valind, L. H. Brudin, P. E. Wollmer, T. Jones, P. D . Buckingham, and J. M. B. Hughes (J. Appl. Physiol. 66: 1896-1904 and 1905-1913, 1989). We have modified this methodology to obtain high-re solution, low-noise PET images of local (V) over dot A/(Q) over dot wh ere lung motion artifact was eliminated by respiratory gating of image collection. In addition, we have refined and implemented the methods to assess local alveolar ventilation by imaging the washout of equilib rated (NN)-N-13 and local perfusion by imaging the distribution of an intravenous bolus of (NN)-N-13-labeled saline solution during apnea. T his paper experimentally evaluates the effect of the implemented modif ications in mechanically ventilated and anesthetized dogs. We found th at the lack of gating had no significant effect on the average recover ed (V) over dot A/(Q) over dot, but the spatial heterogeneity [pixel-b y-pixel coefficient of variation squared (CV2) = SD2/mean(2)] was unde restimated by 14%. The lack of gating during the washout underestimate d the average specific ventilation by 11% and decreased the correspond ing CV2 by 50%.