FINSIG 05

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FINSIG 2005Kuopio, FinlandReduction of parameters In some cases we are interested in the total activity of someRegions of Interest (usually certain organs) rather than theactivities of each pixel separately. By constructing a matrix Rwhose i’th column is the index set of the pixels that belong to i’thROI, we can compute the total activity of each ROI by equationφ = R T θ If we assume that the activity distribution is approximatelyconstant within each ROI, we can estimate the mean activity ofthe ROI’s directly by modifying the observation model. In this case the number of unknown parameters is reduced to thenumber of ROI’s (compare to the N 2 unknowns in pixel-basedcase.)Mikko Kervinen, Department of Applied Physics, University of Kuopio Slide 19
FINSIG 2005Kuopio, Finland When prior information about the ROI’s is used, the model isoverdetermined In this case also the LS-estimates can be computed sequentiallycorresponding to each measurementKalman SmootherLeast SquaresNormalized activity concentration10.80.60.40.2ROI #1ROI #2ROI #3ROI #4ROI #5Normalized activity concentration10.80.60.40.2ROI #1ROI #2ROI #3ROI #4ROI #500 50 100 150t (s)00 50 100 150t (s)Mikko Kervinen, Department of Applied Physics, University of Kuopio Slide 20
Page 1 and 2: Mikko Kervinen † , Marko Vauhkone
Page 3 and 4: FINSIG 2005Kuopio, FinlandIntroduct
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Page 9 and 10: FINSIG 2005Kuopio, FinlandTomograph
Page 11 and 12: FINSIG 2005Kuopio, FinlandNotations
Page 13 and 14: FINSIG 2005Kuopio, Finland In SPECT
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Page 17 and 18: FINSIG 2005Kuopio, Finland In case
Page 19 and 20: FINSIG 2005Kuopio, Finland In SPECT
Page 21 and 22: FINSIG 2005Kuopio, FinlandResults P
Page 23: FINSIG 2005Kuopio, FinlandNormalize
Page 27: FINSIG 2005Kuopio, FinlandConclusio

FINSIG 05

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