Investigation of the quantitative capabilities of a positron emission mammography system

A method for performing a quantitative calibration on a PEM system has been found. Following dead-time characterization and correction, the quantitative calibration factor was measured as a function of object thickness. The calibration allows generation of quantitative PEM imagesets over the clinical range of activity concentration. Methods: Three (8.5 x 9.0 x 3.5) cm tissue culture flasks were filled from a common source with F-18 FDG. A series of ten 10-minute scans, using 1-3 flasks, was acquired over an 8-hour span. A system dead-time model was derived from the three lowest activity scans for each flask configuration. ROI analysis was performed on images reconstructed with BP and ML-EM to determine uniformity and the quantitative calibration factors. No corrections for attenuation or scatter were applied. Results: The model for dead-time was found for each flask configuration and parameterized by a linear fit of the model parameters, allowing generation of dead-time correction based on object thickness and true plus scatter coincidence count rate. A second-order polynomial fit to the ROI analysis results allowed characterization of the quantitative calibration factors as a function of object thickness. Conclusions: A dead-time model and quantitative calibration method has been found for the PEM system used in this study. Quantitative calibration factors have been derived from parameters available as part of standard data acquisition.