SPECT reconstruction

More documents

Recommendations

Info

The principle of the iterative algorithms is to find a solution (that is - to reconstruct an image of a tomographic slice from projections) by successive estimates. The projections corresponding to the current estimate are compared with the measured projections. The result of the comparison is used to modify the current estimate, thereby creating a new estimate. The algorithms differ in the way the measured and estimated projections are compared and the kind of correction applied to the current estimate. The process is initiated by arbitrarily creating a first estimate - for example, a uniform image (all pixels equal zero, one, or a mean pixel value,…). Corrections are carried out either as addition of differences or multiplication by quotients between measured and estimated projections.
algorithm (a recipe) (1) make the first arbitrary estimate of the slice (homogeneous image), (2) project the estimated slice into projections analogous to those measured by the camera (important: in this step, physical corrections can be introduced - for attenuation, scatter, and depth-dependent collimator resolution), (3) compare the projections of the estimate with measured projections (subtract or divide the corresponding projections in order to obtain correction factors - in the form of differences or quotients), (4) stop or continue: if the correction factors are approaching zero, if they do not change in subsequent iterations, or if the maximum number of iterations was achieved, then finish; otherwise (5) apply corrections to the estimate (add the differences to individual pixels or multiply pixel values by correction quotients) - thus make the new estimate of the slice, (6) go to step (2).
Page 1 and 2: Regional Training Workshop Advanced
Page 3 and 4: anterior view lateral view courtesy
Page 5 and 6: Groch MW, Erwin WD. J Nucl Med Tech
Page 7 and 8: 2nd step in tomography = reconstruc
Page 9 and 10: Recording projections of a slice
Page 11 and 12: Filtered back-projection (FBP)
Page 14 and 15: 1 2 3 4
Page 16 and 17: 1 2 3 3 4 7 1 5 4 2 5 4 6 3
Page 18 and 19: 3 3 3 7 7 7 1 5 4 2 5 4 6 3
Page 20 and 21: 12 11 3 14 18 7 1 5 4 2 5 4 6 3
Page 22 and 23: 3 (divide each entry by 3) 3 6 4 9
Page 26 and 27: ack projection (BP) = summation of
Page 28 and 29: Sequence of summing original and fi
Page 30 and 31: Reconstruction of a slice from proj
Page 34 and 35: measured projections first estimate
Page 36 and 37: 1 2 3 2.5 2.5 5 3 4 7 2.5 2.5 5 4 6
Page 38 and 39: 1 2 3 1 2.5 5 3 4 7 2.5 2.5 5 4 6 5
Page 40 and 41: 1 2 3 1 2 5 3 4 7 3 2.5 5 4 6 5 5 c
Page 42 and 43: Iterative reconstruction - multipli
Page 44 and 45: Iterative reconstruction - multipli
Page 46 and 47: Filtered back-projection • very f
Page 48 and 49: References: Groch MW, Erwin WD. SPE

SPECT reconstruction

Create successful ePaper yourself

Delete template?

Save as template?