Adams R
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The purpose of the NEMA Standards is to "eliminate misunderstandings between the manufacturer and the purchaser and to assist the purchaser in selecting the proper product for its particular need" (NEMA Bylaw Art. V, Sec. 1). The sections on count-rate performance, however, have caused considerable misunderstanding of NEMA specifications by salespersons and users, many of whom fail to distinguish between input and observed count rates and between intrinsic and system (extrinsic) performance. The "maximum count rate" is shown to be an unreliable index of camera performance at useful count rates, and is misconstrued by some users to mean the maximum clinically useful count rate. The sections on count-rate performance can be made more meaningful to users by substituting "observed count rate" for "input count rate," by deleting the section on "maximum count rate," and by adding a section on system count-rate performance.
美国国家电气制造商协会（NEMA）标准的目的是“消除制造商与购买者之间的误解，并帮助购买者选择适合其特定需求的产品”（NEMA章程第五条第1款）。然而，关于计数率性能的章节却导致销售人员和用户对NEMA规范产生了相当大的误解，其中许多人未能区分输入计数率和观察到的计数率，以及固有性能和系统（外在）性能。“最大计数率”被证明在有用计数率下是相机性能的不可靠指标，并且一些用户将其误解为最大临床有用计数率。通过用“观察到的计数率”代替“输入计数率”、删除“最大计数率”部分并添加系统计数率性能部分，可以使关于计数率性能的章节对用户更有意义。
