Using simultaneous transmission and scatter SPECT imaging from external sources for the determination of thoracic μ-map

The authors describe a new technique for determination of segmented attenuation μ-map which is necessary for proper attenuation correction and quantification of radiopharmaceutical uptake in cardiac SPECT. For transmission imaging a line source and a fan-beam collimator on one head of a triple-head SPECT system are used. For scatter imaging two external ring sources and parallel collimators on the two other heads are used. Fan-beam transmission data are truncated, while parallel-beam data are not. The technique uses both sets of tomographic data to complement each other and to obtain a composite image. Three regions with distinct μ-values are determined from the composite image. This final μ-map can then be used as the basis for one of the known attenuation correction methods (Chang´s, iterative, etc.)