What is  ISO 15708‑4 about?  
ISO 15708-4 is the fourth part of a series of documents applicable to the radiation methods for computed tomography.
ISO 15708-4 presents an outline of the operation of a computed tomography (CT) system and the interpretation of results with the aim of providing the operator with technical information to enable the selection of suitable parameters.
Note: ISO 15708-4 is applicable to industrial imaging (i.e., non-medical applications) and gives a consistent set of CT performance parameter definitions, including how those performance parameters relate to CT system specifications.
Who is  ISO 15708‑4 for? 
 ISO 15708‑4 on the radiation methods for computed tomography is useful for: 
- Medical practitioners
- Radiographers and radiology technologists
- CT systems equipment manufacturers
- Suppliers and purchasers of CT systems 
Why should you use ISO 15708‑4?  
 Computed tomography is used in the industry both for defect testing and dimensional testing and measurement. Since computed tomography does not directly provide a measurement of desired quantities such as, for example, pore size or wall thickness, these quantities must be derived from the X-ray linear attenuation data represented by the CT grey values. The detectability of features and the degree of accuracy required to depend on the inspection task, the specification of the available test equipment, and the analysis and evaluation methods used. When the determination of such quantities is required, a special task-specific qualification test specified in ISO 15708‑4 of the computed tomography system is required. The qualification should be carried out by trained personnel. The trained personnel shall be able to prove they have undergone training and qualification in digital industrial radiography or radioscopy as described in ISO 15708‑4.
ISO 15708‑4 deals with computed axial tomography and excludes other types of tomography such as translational tomography and tomosynthesis.
Under test qualifications in ISO 15708‑4, the suitability of the computed tomography inspection technique for measuring a quantity to the required precision should be verified. The following steps described are typical of those for the successful verification of the suitability of computed tomography for industrial applications.
