| 摘要 |
<p>A nuclear camera system, e.g. for medical diagnostic imaging, comprises a plurality of radiation detector heads (10a, 10b, 10c) mounted on a rotatable portion (16) of a gantry (18). A transmission radiation source and collimator assembly (40, 42) is mounted on the rotatable gantry portion opposite one of the detector heads. The radiation source (60) of the assembly is mounted in a lead shield (62) with an opening (64) pointing toward an examination region (12). A shutter (66) is rotatable between a closed position in which a lead arc segment (70) blocks the opening (64), a calibration orientation in which tin (72) covers opening (64), and an open position in which an opening (74) is aligned with the opening (64). A safety interlock means (80) locks the shutter in the closed position and against rotation when the radiation source and collimator assembly is removed from the rotatable gantry portion. The collimator (42) has lead side walls (200) and tin or tin alloy septa (202). When the radiation from the radiation source strikes the lead side walls, they emit characteristic lead x-rays of about 88 keV whereas the tin radiates x-rays of only about 30 keV. A filter (210) includes an inner layer (212) of tin for attenuating any remaining 88 keV lead x-rays coming from the transmission line source assembly and converting them to about 30 keV radiation. The filter has an outer layer (214) for attenuating the radiation around 30 keV. <IMAGE></p> |
