核医学射线测量仪器.ppt

体外样品测量（2） 活度相对比较，如RIA 井型闪烁探测器+脉冲幅度分析器+...（ +自动换样机构） 探测效率高 晶体、核素 注意事项 样品体积和位置 样品活度（？） 3、体内测量（in vivo） 活度相对比较 准直器+固体闪烁探测器+脉冲幅度分析器... 注意事项 准直器选用、安装 射线衰减的影响 射线散射的影响 计数率特性 铅 铅 探测器 全敏感区 半影区 体内测量例1：甲状腺摄131I功能试验 患者空腹口服131I溶液2~10μCi，服后继续禁食1小时；于口服131I溶液后4、6、24小时用γ射线探测仪测定甲状腺部位放射性计数。同时需取与病人等量的131I配制标准源，并测定室内放射性本底计数。按以下公式计算摄131I率，描绘吸碘功能曲线 体内测量例2：放射性肾图 谢谢！ * Single and Two-Stage Amplifier Circuits The Figures shows how a two-stage amplifier increases the signal-to-noise ratio. ?The ?radiation ?detector ?is ?located ?some ?distance ?from ?the ?readout. ??A ?shielded ?coaxial cable transmits the detector output to the amplifier. ?The output signal of the detector may be as low as 0.01 volts. ?A total gain of 1000 is needed to increase this signal to 10 volts, which ?is ?a ?usable output ?pulse ?voltage. ??There ?is ?always ?a ?pickup of ?noise ?in ?the ?long cable run; this noise can amount to 0.001 volts. If all amplification were done at the remote amplifier, the 0.01-volt pulse signal would be 10 volts, and the 0.001 noise signal would be 1 volt. ??This is a signal-to-noise ratio of 10 and could be significantly reduced by dividing the total gain between two stages of amplification. ??A preamplifier located near the detector and a remote amplifier could be ?used. ???The ?preamplifier ?virtually ?eliminates ?cable ?noise ?because ?of ?the ?short ?cable length. ??If, for a total gain of 1000, the preamplifier has a gain of 100 and the amplifier has a gain of 10, the output signal from the preamplifier is 1 volt. ?The signal transmitted via the long cable run still picks up the 0.001-volt noise. ?The amplifier amplifies the 1.0- volt pulse signal and the 0.001-volt noise signal by a factor of 10. ?The result is a 10-volt pulse signal and a 0.01-volt noise signal. ??This gives a signal-to-noise ratio of 1000. * 提示滤波和成形的等效性 同学有兴趣的话，可板书（阻-容网络）微分电路和积分电路的作用。 可结合同学对“本底”的演讲内容，讲一下对本底的处理。 * 注意：图中输出的并不是恒定幅度的脉冲信号。 * 能量窗的范围有较多的称呼： 上阈、下阈 基线、窗宽 等 * Gamma spectroscopy is a radiochemistry meas