Flat panel X-ray detector based SPECT/CT

415 Objectives We designed a small-footprint variable angle SPECT camera with volumetric CT imaging functionality matched to Nuclear Medicine requirements. Methods We developed a SPECT/CT system with a rotating-anode X-ray tube and a deployable Flat Panel CsI X-ray Detector added to a Gamma-ray camera gantry. An off-center geometry was used to produce a field-of-view of 47 cm transaxial and 14 cm axial in each 360° rotation. A dedicated Anti-Scatter Grid and advanced scatter correction are employed to compensate for the increased scatter inherent in Cone Beam CT. This allows us to exploit the half-cone-beam geometry to minimize the gantry size and retain full SPECT positioning functionality. A weighted FDK reconstruction is implemented with a GPU to provide CT reconstructions of 140 slices, 1 mm thick, in 60 seconds. Co-Planar imaging combined with scan time flexibility – 12 second breath hold, 24 or 60 second free breathing – improve co-registration between modalities. Isotropic voxels (0.33, 0.5, 1 and 2 mm) provide high contrast resolution and flexibility in reorienting data. Results Imaging a Catphan CT phantom, >15 lp/cm @ 10% MTF are consistently achieved as well as low contrast detectability of a 7mm lesion @ 1.0% contrast and 5mm slice thickness. The system was evaluated with both phantom and patient studies.Phantom and clinical images were reoriented in oblique angles without artifacts caused by non-isotropic voxels. Conclusions A SPECT/CT system that fits into the same floor space as a SPECT system has been designed. High-contrast CT resolution is similar to multi-slice CT image quality. Flexible CT acquisition times allow acquisition in a breath hold or during tidal respiration.