1.1 本指南涵盖了将应用要求转换为计算机断层扫描（CT）系统要求/规范的指南，并建立了一个通用术语，用于指导买方和供应商选择CT系统。本指南适用于CT系统和扫描服务的购买者。计算机断层扫描系统是一种复杂的仪器，由许多组件组成，这些组件必须正确交互，才能生成重复再现满意检查结果的图像。计算机断层扫描系统购买者通常关心应用要求。计算机断层扫描系统供应商通常关心系统组件的选择，以满足买方的性能要求。 本指南的目的不是限制或限制，而是解决应用要求和性能规范之间的关系，必须理解和考虑这些关系，以便正确选择CT系统。 1.2 计算机断层扫描（CT）可用于新的应用，或代替射线照相或放射检查，前提是能够披露构成验收/拒收标准的物理特征或指示，并有充分的文件记录和可供审查。一般来说，CT的空间分辨率低于胶片射线照相，除非使用放大倍率，否则与数字射线照相或射线照相具有相当的空间分辨率。 放大可以用于CT或射线照相/射线照相，以提高空间分辨率，但同时会损失视野。 1.3 计算机断层扫描（CT）系统使用沿从多个不同方向投影通过物体的一组路径进行的一组传输测量。这些视图中的每个透射测量值都被数字化并存储在计算机中，随后在计算机中对其进行调节（例如，归一化和校正）并重建，通常通过各种技术之一将其重建为垂直于投影路径集的对象切片。如果重建多个切片，则获得对象的三维表示。 指南中对CT原理进行了深入讨论 E1441 . 1.4 与传统的射线照相和放射检查一样，计算机断层扫描（CT）广泛适用于穿透辐射束可能通过和检测的任何材料或物体，包括金属、塑料、陶瓷、金属/非金属复合材料和组件。CT的主要优点是，它有可能提供穿过物体的薄横截面的密度测量（即辐射密度和几何形状）图像。在许多较新的系统中，横截面现在被合并到三维数据体中，以进行额外的解释。由于没有结构叠加，图像可能比常规放射学图像更容易解释。 新购买者可以快速学习读取CT数据，因为与传统投影放射学相比，图像更符合人类思维可视化3D结构的方式。此外，由于CT图像是数字的，因此与其他无损评估模式的数字数据相比，可以增强、分析、压缩、归档图像，将其作为数据输入性能计算，或者将其传输到其他位置进行远程查看。三维数据集可以通过计算机图形渲染为实体模型。实体模型可以切片或分割，以显示三维内部信息或输出为CAD文件。虽然许多细节在本质上是通用的，但本指南隐含地假设使用穿透辐射，特别是X射线和γ射线。 1.5 单位- 以国际单位制表示的数值应视为标准值。括号中给出的值是英寸-磅单位的数学转换，仅供参考，不被视为标准值。 1.6 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。 1.7 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====== 5.1 本指南将帮助买方制定CT系统规范。本指南涵盖了将买方要求转换为系统组件的过程，这些组件是编制有用的CT系统规范所必需的。 5.2 其他信息可通过与潜在供应商或独立顾问的讨论获得。 5.3 本指南适用于寻求扫描服务的购买者。 5.4 本指南适用于需要为特定检查应用采购CT系统的购买者。

1.1 This guide covers guidelines for translating application requirements into computed tomography (CT) system requirements/specifications and establishes a common terminology to guide both purchaser and supplier in the CT system selection process. This guide is applicable to the purchaser of both CT systems and scan services. Computed tomography systems are complex instruments, consisting of many components that must correctly interact in order to yield images that repeatedly reproduce satisfactory examination results. Computed tomography system purchasers are generally concerned with application requirements. Computed tomography system suppliers are generally concerned with the system component selection to meet the purchaser's performance requirements. This guide is not intended to be limiting or restrictive, but rather to address the relationships between application requirements and performance specifications that must be understood and considered for proper CT system selection. 1.2 Computed tomography (CT) may be used for new applications or in place of radiography or radioscopy, provided that the capability to disclose physical features or indications that form the acceptance/rejection criteria is fully documented and available for review. In general, CT has lower spatial resolution than film radiography and is of comparable spatial resolution with digital radiography or radioscopy unless magnification is used. Magnification can be used in CT or radiography/radioscopy to increase spatial resolution but concurrently with loss of field of view. 1.3 Computed tomography (CT) systems use a set of transmission measurements made along a set of paths projected through the object from many different directions. Each of the transmission measurements within these views is digitized and stored in a computer, where they are subsequently conditioned (for example, normalized and corrected) and reconstructed, typically into slices of the object normal to the set of projection paths by one of a variety of techniques. If many slices are reconstructed, a three dimensional representation of the object is obtained. An in-depth treatment of CT principles is given in Guide E1441 . 1.4 Computed tomography (CT), as with conventional radiography and radioscopic examinations, is broadly applicable to any material or object through which a beam of penetrating radiation may be passed and detected, including metals, plastics, ceramics, metallic/nonmetallic composite material and assemblies. The principal advantage of CT is that it has the potential to provide densitometric (that is, radiological density and geometry) images of thin cross sections through an object. In many newer systems the cross-sections are now combined into 3D data volumes for additional interpretation. Because of the absence of structural superposition, images may be much easier to interpret than conventional radiological images. The new purchaser can quickly learn to read CT data because images correspond more closely to the way the human mind visualizes 3D structures than conventional projection radiology. Further, because CT images are digital, the images may be enhanced, analyzed, compressed, archived, input as data into performance calculations, compared with digital data from other nondestructive evaluation modalities, or transmitted to other locations for remote viewing. 3D data sets can be rendered by computer graphics into solid models. The solid models can be sliced or segmented to reveal 3D internal information or output as CAD files. While many of the details are generic in nature, this guide implicitly assumes the use of penetrating radiation, specifically X rays and gamma rays. 1.5 Units— The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard. 1.6 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. 1.7 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 ====== 5.1 This guide will aid the purchaser in generating a CT system specification. This guide covers the conversion of purchaser's requirements to system components that must occur for a useful CT system specification to be prepared. 5.2 Additional information can be gained in discussions with potential suppliers or with independent consultants. 5.3 This guide is applicable to purchasers seeking scan services. 5.4 This guide is applicable to purchasers needing to procure a CT system for a specific examination application.