Physics and Radiobiology of Nuclear Medicine

Single Photon Emission Computed Tomography 167

Estimated

image

Calculated

projections

of estimated

image

Compare A & B projections Measured

Reconstructed

image

Correct for

differences

Create new

estimated image

Initial

guess

Unfold

projections

A B

Maximum

agreement

Discrepancy

Fig. 12.12. Conceptual scheme of iterative reconstruction.

C

qi

j

Fig. 12.13. A projection qiin the estimated image is the sum of counts in all pixels
Cjand is compared with the measured projection pi.