Calculation of lung-heart ratios for single-photon emission computed tomography

The effectiveness of simple iterative reconstruction techniques in calculating lung-heart activity ratios (LHRs) was investigated. The LHR was shown to be an effective indicator of the severity of coronary artery disease in cardiac SPECT. A study was conducted with a mathematical cardiac torso phantom that modelled uptake of 201Tl in the heart and lung regions. The projection data included only the effects of nonuniform photon attenuation. The data were first reconstructed with zeroth-order Chang and a variant of the Bellini method, both of which utilize information from the nonuniforms attenuation map. These recommendations were then used as initial estimates in the iterative Chang, variable step-size Chang, and Morozumi methods, for one and five iterations. Using the same reconstruction procedure, the sample mean LHR and standard deviation from 21 noisy 3D reconstructions were also calculated.