1.1 本试验方法涵盖铱-192、钴-60和硒-75射线源尺寸的测定。该测定基于源组件投影射线照片中源图像的测量，并与同一射线照片或源导管中参考样品图像的测量进行比较。 1.2 单位- 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值不一定是精确的等价物；因此，为确保符合本标准，每个系统应独立使用，且两个系统的值不得组合。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 影响射线照相图像质量的因素之一是几何不清晰度。 几何不清晰度的程度取决于光源的大小、光源与待射线照相物体之间的距离，以及待射线照相物体与胶片或数字探测器之间的距离。该测试方法允许用户确定光源的大小，并使用该结果确定光源到物体以及物体到胶片或探测器的距离，以保持所需的几何不清晰度。 注1: 欧洲标准CEN EN 12579描述了测量Ir-192、Co-60和Se-75源尺寸的简化程序。Ir-192的最终光源尺寸与本试验方法获得的结果相当。

1.1 This test method covers the determination of the size of Iridium-192, Cobalt-60, and Selenium-75 radiographic sources. The determination is based upon measurement of the image of the source in a projection radiograph of the source assembly and comparison to the measurement of the image of a reference sample in the same radiograph or the source guide tube. 1.2 Units— The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 One of the factors affecting the quality of a radiographic image is geometric unsharpness. The degree of geometric unsharpness is dependent upon the size of the source, the distance between the source and the object to be radiographed, and the distance between the object to be radiographed and the film or digital detector. This test method allows the user to determine the size of the source and to use this result to establish source to object and object to film or detector distances appropriate for maintaining the desired degree of geometric unsharpness. Note 1: The European standard CEN EN 12579 describes a simplified procedure for measurement of source sizes of Ir-192, Co-60, and Se-75. The resulting source size of Ir-192 is comparable to the results obtained by this test method.