Transverse section imaging of mean clearance time

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Abstract
Transverse sections representing the magnitude of clearance rates or the mean transit time of radionuclide flow through known volumes of interest were computed from angular projections. The integrated counts for all time intervals at each projection bin for each angle were computed. These modified projection sums were convolved with a filter and backprojected to form an integrated event image. A 2nd image was formed by backprojecting the sum over time of the projected values for each angle weighted by time. The ratio of the 2nd image to the 1st image gave a mean clearance time image with high signal to noise and accuracy after thresholding to remove noise in zero-flow regions. The algorithm was verified by computer simulations and had a major benefit in the savings of computational time by a factor of 10 for anticipated clinical studies of human brain and kidney blood flow and lung ventilation and perfusion.