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BS IEC 62945 pdf free download

BS IEC 62945 pdf free download.Radiation protection instrumentation – Measuring the imaging performance of X-ray computed tomography (CT) security-screening systems.
System components and adjustments should be as for the standard commercial product in normal security screening operation mode; any deviations shall be noted by the evaluators in the manually recorded data. If the system is approved to operate under more than one configuration, the user may want to request the test be carried out at all appropriate settings. Evaluation is to be based on images or other data normally used in standard mode of operation. The exposure time and level shall be chosen as that used when the CT system is operated for the intended use in the security screening application. A calibration of the CT system shall be carried out prior to any testing. Any recalibration of the CT system shall be allowed according to the standard operation of the system. In order to ensure that the system is using a configuration approved by the appropriate regulatory agency, the user may wish to request that the vendor provide the specific settings used during the evaluation such as: tube voltage(s),amperage, voxel size, belt speed, etc. Changes in CT image reconstruction software should be followed by gathering a new baseline measurement set. Alternatively, new baseline results may be recomputed offline if the data are available.The test articles (see 4.2) shall be presented to the system in a controlled position and orientation. The main axis of each test article should be parallel to the conveyor belt motion direction and the front of the article shall enter the system first (front designated via labeling). The test method described in 6.3 determines the angle of rotation and side to side offset of the test articles relative to the centerline of the system conveyor. Results for rotations more than 2 degrees off parallel from conveyor centerline shall be rejected. This document requires that the test articles be measured at the center of the belt, directly on the belt, within 土2 cm of the conveyor centerline. If the user decides to also run the test articles off centerline, the parallel requirement shall still be met, and the data shall be segregated and treated separately. For reference, Figure 1 shows the coordinate system that shall be used for all procedure descriptions. The z axis is aligned along the direction of the conveyor motion. The y axis is in the vertical direction and the X axis is across the belt. The positive/negative direction of the axis system is immaterial as used in this document. Not all the methods stated are applicable to all CT systems. Each method shall identify whether it is applicable to all CT types or only a subset. Each of the test methods specified in this document can include required procedures and examples of optional techniques for achieving the required results. This is necessary because of the range of implementations used in security CT equipment. Each test method identifies where latitude for deviation from the analysis techniques exists. Any deviation from provided example techniques shall be documented including rationale for deviating from the suggested standard method of analysis. Such documentation shall be provided to the end user of the image quality evaluation.
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