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In recent years, technological advances in the area of medical equipments have allowed the use of these devices for different types of illness diagnosis and treatment of patients. Thereby, nowadays a lot of quantities and parameters related to the health state of the patient can be measured and used by clinicians to take a decision about the correct conduct to be adopted during the treatment. However, despite the huge advances in the area, a question always must be arisen related to the use of medical equipments: the measurements are reliable? According to Lira (2002) and Parvis & Vallan (2002), such reliability is fundamental and a wrong evaluated value by the medical equipment can affect any decision and even compromise the condition of a patient at all. Therefore, the use of medical equipments requires periodical calibration and evaluation of measurement uncertainty. All measuring instruments must be calibrated, to be considered adequate for use (Ferreira et al. 2010). VIM (2008) defines calibration as an operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties and in second step, uses this information to establish a relation for obtaining a measurement result from an indication. This fact drew the attention of metrology and health organisms all around the world that have written a number of guides and technical recommendation for instrument calibration and determination of uncertainty for medical instrumentation before use in order to ensure high quality of the measurements. The Guide (GUM, 2003) is the result of a joint international committee whose aim was to publish a guide for uncertainty evaluation to be used as conventional guidelines in several different countries. That is the case of Brazil whose local NMI (National Measurement Institute), the INMETRO (Brazilian National Institute of Metrology, Standardization and Industrial Quality) has adopted the Guide to rule device calibration and its measurement uncertainty evaluation in the country. In the Guide, the idea that the result of a measurement is only complete if the measured quantity value and the measured uncertainty are evaluated is reinforced. The Guide also |
