Simultaneous SPECT and CT with shutter controlled radionuclide line sources and parallel collimator geometry

Summary form only given. A computer-controlled shutter device with four narrow collimated radionuclide line-sources for combined SPECT (single photon emission computed tomography) and CT (computed tomography) using a rotating gamma camera has been designed. Accurate attenuation of information is limited to four sections of the object but the activity of the sources, and thus the number of events through these sections, can be increased without overloading the camera. With ⁹⁹ Tc^m, SPECT data are acquired with the shutter closed and CT data with the shutter open. In this case, correction for disturbing emission data in the transmission data is necessary and the examination time is prolonged by 30-50%. With four 1 GBq ⁹⁹Tc ^m line-sources, the image noise was about 8% (SD) in each of the four sections at a transmission acquisition time of 3 s/angle and 128 angles. The reliability of the transmission data and its noise propagation have been further analyzed by simulation and by phantom and patient-measurements for various radionuclides and different methods of attenuation correction