KINETIC PARAMETER-ESTIMATION FROM SPECT CONE-BEAM PROJECTION MEASUREMENTS

Kinetic parameters are commonly estimated from dynamically acquired nu clear medicine data, by first reconstructing a dynamic sequence of ima ges and subsequently fitting the parameters to time-activity curves ge nerated from regions of interest overlaid upon the image sequence. Bia sed estimates can result from images reconstructed using inconsistent projections of a time-varying distribution of radiopharmaceutical acqu ired by a rotating SPECT system. If the SPECT data are acquired using cone-beam collimators wherein the gantry rotates so that the focal poi nt of the collimators always remains in a plane, additional biases can arise from images reconstructed using insufficient, as well as trunca ted, projection samples. To overcome these problems we have investigat ed the estimation of kinetic parameters directly from SPECT cone-beam projection data by modelling the data acquisition process. To accompli sh this it was necessary to parametrize the spatial and temporal distr ibution of the radiopharmaceutical within the SPECT field of view. In a simulated chest image volume, kinetic parameters were estimated for simple one-compartment models for four myocardial regions of interest. Myocardial uptake and washout parameters estimated by conventional an alysis of noiseless simulated cone-beam data had biases ranging betwee n 3-26% and 0-28%, respectively. Parameters estimated directly from th e noiseless projection data were unbiased as expected, since the model used for fitting was faithful to the simulation. Statistical uncertai nties of parameter estimates for 10 000 000 events ranged between 0.2- 9% for the uptake parameters and between 0.3-6% for the washout parame ters.