similarly backprojected into the reconstruction matrix. This type of back-
projection results in superimposition of data in each projection, thereby
forming the final transverse image with areas of increased or decreased
activity (Fig. 12.3C).
Similarly, backprojecting data from the other three rows of the 4 × 4
matrix of all views, four transverse cross-sectional images (slices) can be
produced. Therefore, using 64 ×64 matrices for both acquisition and recon-
struction, 64 transverse slices can be generated. From transverse slices,
appropriate pixels are sorted out along the horizontal and vertical long axes,
and used to form sagittal and coronal images, respectively. It is a common
practice to lump several slices together to increase the count density in the
individual slices to reduce statistical fluctuations.
158 12. Single Photon Emission Computed Tomography
Fig. 12.4. An illustration of the backprojection technique using the data from an
acquisition matrix into a reconstruction matrix.