It is absolutely imperative in the clinical field to maintain proper function and performance of medical equipment that meets certain standards while also providing best - quality images and securing safeties for operators. In order to implement these goals, equipment manufacturers and users are required to execute tight quality control of the equipment on each side. Manufacturers have been carrying out QA (quality assurance) and QC (quality control) programs for their products based on their own quality standards for long time, whereas only a portion of users have been conducting their own tests so far. However, recently a broad users' QA & QC movement has started to evolve following activities of the QC group of the JSRT (Japanese Society of Radiological Technology) and the publication of QC programs. I present the analysis of causes of malfunction of CT for the purpose of safety and also describe about QA & QC methods from the user's viewpoint.
