This International Standard applies to: - CT SCANNERS that are able to display and report CTDIVOL in accordance with IEC 60601-2-44 and - RADIATION Dose Index Monitoring Software (RDIMS) for the purpose of displaying and recording the SIZE SPECIFIC DOSE ESTIMATE (SSDE) and its associated components. Specifically, the objective of this standard is to provide standardized methods and requirements for calculating, displaying, or recording of SSDE, SSDE(z), WATER EQUIVALENT DIAMETER (DW), and DW(z), where z represents a specific longitudinal position of the scanned object. This standard provides a method of determining a reference water equivalent diameter, DW,REF(z), using CT scans of two cylindrical water PHANTOMS and an anthropomorphic PHANTOM(S), which conform to the specifications defined in this standard. The method of calculating the water equivalent diameter that is implemented by the MANUFACTURER, DW,IMP(z), shall be tested and validated against DW,REF(z) using the TEST OBJECTS and methods defined within this standard. This standard also describes the methods for calculating SSDE and DW, which represent the average values of SSDE(z) and DW(z) over the RECONSTRUCTION LENGTH. This standardization is important to ensure that comparisons between reported SSDEs are valid.