A quantitative comparison of attenuation-weighted backprojection with multiplicative and iterative postprocessing attenuation compensation in SPECT

Comparisons are made between different analytic attenuation compensation methods used in SPECT imaging. The methods include a multiplicative technique and a single-iterative technique, both applied after filtered backprojection, and two different implementations of an attenuation-weighted filtered backprojection technique (A-W FBP). The methods are compared using simple phantoms of line sources and water-filled circular and elliptical cylinders. both simulated data (without scatter) and experimental data (with scatter) are reconstructed. None of the methods is truly quantitative, even without the presence of scatter, but are potentially useful and improve quantitation. All techniques provide good peak compensation for line sources in attenuating media. The weighted backprojection methods eliminate nearly all deformation due to nonisotropic attenuation for a line source centered in an ellipse. However, the measured noise is amplified by A-W FBP, unless the method is further modified to reduce the amplification.