| 摘要 |
A nuclear gamma camera employs a virtual contouring technique in order to maximize the portion of transmission radiation fan beams (32a, 32b) which pass through a subject (12). A plurality of radiation detector heads (20a-20c) having radiation receiving faces and a plurality of radiation sources (30a, 30b) are mounted to a gantry (16). An orbit memory (42) stores clearance offset orbit (45) around the subject and a subject support (10). A tangent calculator (46) calculates virtual lines (48a, 48b) between the radiation sources (30a, 30b) and the corresponding radiation detector heads (20a, 20b). The virtual lines (48a, 48b) correspond to edge rays of the transmission radiation fans (32a, 32b). A shift calculator (50) calculates and sends shift commands to a motor orbit controller (52) which controls rotational and translational drives attached to the detector heads (20a-20c). The detector heads are translated such that the virtual lines (48a, 48b) remain tangent to a predefined contour of the subject throughout rotation of the detector heads about the subject receiving aperture (18). The detected transmission radiation (32a, 32b) is reconstructed (64t) into an attenuation volumetric image representation and used to correct (68) detected emission radiation data. The corrected emission data is then reconstructed (64e) into a volumetric image representation. The virtual contouring minimizes lost rays (40) of transmission radiation and facilitates an artifact-free attenuat
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