Asymmetric cone-beam transmission tomography

Transmission scans are an important part of the process of obtaining patient attenuation maps for accurate SPECT (single photon emission computed tomography) imaging. In order to avoid truncation of the projection data, asymmetric cone-beam imaging geometries were investigated. By using the Beacon^TM SPECT system, it was shown that in the acquisition process transmission and emission imaging geometries can be different. Utilizing this new system, cone-beam transmission scans can be performed while the parallel collimators are attached for emission data acquisition. Patient and phantom studies were performed and compared with X-ray CT. A whole-body helical scan to obtain a whole-body attenuation map is also proposed. For helical asymmetric cone-beam geometries, at least two detectors are required in order to provide sufficient cone-beam data. If two detectors are used, they must have opposite geometries. Computer simulations were performed to demonstrate the feasibility of the proposed asymmetric helical cone-beam scanning geometry