[Enlargement of effective field of view in gamma-ray transmission CT using a fan-beam geometry].

Quantitative SPECT images require to correct attenuation of the gamma rays in the body, therefore, it is desired to obtain a true attenuation map measured by gamma-ray transmission CT. Many methods and geometries of the gamma-ray transmission data acquisition system have been proposed, however, there is a limitation in the size of the scintillator and this causes a serious artifact in reconstructed images of thorax. In this paper, we formulated the relation between the detector length and the effective field of view for following data acquisition geometries in gamma-ray transmission CT; a detector with a symmetric fan-beam collimator which has long focal length, two detectors with a symmetric fan-beam collimator, and a detector with an asymmetric fan-beam collimator.