Abstract
The identification and classification of the risks associated with the use of electromedical equipment is a critical part of its design, requiring the application of precise methods to analyse such risks. The result of this analysis leads to the preparation of documents assessing all possible risks associated with the manufacture of electromedical devices, from design to production and final use, including installation and maintenance activities, and after-sales surveillance. This process translates into a guarantee of device reliability. The more that is done to make the device design safe, the greater its reliability will be and the lower the frequency of failures. Failure Mode, Effects, and Criticality Analysis (FMECA) is one of the many risk analysis techniques proposed by the ISO 14971 standard. This method makes it possible to identify and evaluate the consequences of the failure of each component in a complex system and to quantify the extent of each failure using numerical indices. This paper describes the application of this methodology to a small Computer Tomography (CT) prototype device designed to investigate the extremities of the human body. This prototype uses Cone Beam CT (CBCT) technology, employing a divergent, cone shaped X-ray beam rather than the classic fan-shaped beam. A special bed is used in conjunction with the CT scanner to support the patient. This bed is not merely an added accessory but is part of a complex system.
Highlights
Computed Tomography (CT) was developed in the 1970s with the aim of overcoming the limits of traditional radiography, which only provided a single projection of the district of interest with low contrast resolution [1], [2]
The malfunction of power supplies connected to more than one load or to components required for scanning has a higher Risk Priority Number (RPN) than those that supply secondary components, such as lasers
Regarding the flat panel shifter motor, the possibility that this could lead to slippage of the detector off its rails was considered: this failure mode is prevented by the presence of mechanical limit stops
Summary
Computed Tomography (CT) was developed in the 1970s with the aim of overcoming the limits of traditional radiography, which only provided a single projection of the district of interest with low contrast resolution [1], [2]. In a CT scanner, the source and detector rotate around the patient, acquiring a series of images from different angles obtaining computer generated projections. The final images are representative of the distribution of the μ(x,y) attenuation coefficient of the object in a predefined section. A CT exam generates a series of matrices (slices) that are approximately 0.5-10 mm thick. These slices are aligned perpendicularly to the axis of the scanned section, which represents a ‘‘slice’’ of the patient’s body, in which the varation of μ between different tissues can be observed [3]. Four generations of tomography have been developed, which differ in the reciprocal rotation of source and detector and in the geometry of the radiated
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