Attenuation correction in SPECT using active surfaces

To compensate for the photon attenuation in SPECT, we propose to determine the boundary of the uniform attenuation map by detecting the surface of the patient body from the emission data. We use an active surface model which is a three dimensional generalisation of the active contour model known as snakes. The model is an elastic surface that is deformed under the action of internal and external forces. The internal forces model the smoothness constraints while the external forces model the image constraints. In our case, the image constraints are three-dimensional detected edges obtained using the Zucker and Hummel operator applied on the emission volume. The finite difference method is used to solve the energy-minimisation problem for a surface. The segmentation of the patient body from the emission tomography reconstruction is compared to the segmentation from the transmission tomography reconstruction. Moreover, tomography reconstruction corrected for the non-uniform attenuation is compared to the tomography reconstruction corrected for the uniform attenuation. Uniform attenuation correction is performed using the boundary detected from the emission data