A standard approach to measurement uncertainties for scientists and engineers in medicine

Abstract

The critical nature of health care demands high performance levels from medical equipment. To ensure these performance levels are maintained, medical physicists and biomedical engineers conduct a range of measurements on equipment during acceptance testing and on-going quality assurance programs. Wherever there are measurements, there are measurement uncertainties with potential conflicts between the measurements made by installers, owners and occasionally regulators. Prior to 1993, various methods were used to calculate and report measurement uncertainties. In 1993, the International Organization for Standardization published the Guide to the Expression of Uncertainty in Measurement (GUM). The document was jointly published with six international organizations principally involved in measurements and standards. The GUM is regarded as an international benchmark on how measurement uncertainty should be calculated and reported. Despite the critical nature of these measurements, there has not been widespread use of the GUM by medical physicists and biomedical engineers. This may be due to the complexity of the GUM. Some organisations have published guidance on the GUM tailored to specific measurement disciplines. This paper presents the philosophy behind the GUM, and demonstrates, with a medical physics measurement example, how the GUM recommends uncertainties be calculated and reported.

Enhancement of natural background gamma-radiation dose around uranium microparticles in the human body

“…+1%), giving a statistical uncertainty in the calculation of the enhancement factors of +2 per cent for the solid large particles, +3 per cent for the large particles with cavities and +4 per cent for the small particles, equivalent to +3 per cent on average for the different particle types. Assuming that the sources of the uncertainties are independent of each other, the final overall uncertainty in the estimated enhancement factors is the square-root of the sum of the various contributing uncertainties squared (Gregory et al 2005)-in this case +9 per cent. Compared with the natural variability of the shape of the spectrum of the natural background gamma-radiation, which for the five spectra used in this study is +33 per cent about the average curve, the estimates of the enhancement factors obtained in this study are reasonable, having uncertainties less than the variability of the natural background gamma-radiation spectrum.…”

ISO-GUM and Supplements are Utilized for QA of BCA Data

“…If also gives the same answers as Monte Carlo analysis does when information is abundant. If it is an abnormal distribution, a setup will became difficult about a trueness value, and the reference value by ISO-GUM is then calculated for QA [10] Fig. 1.…”

“…It has published by Joint Committee guide Measurement (JCGM). JCGM document number is JCGM 100-107.And ISO14253 [10] was publish as ISO standard.…”

“…The first item has role important for security of reaction and the analysis of an outlier. (9) to (10). An affinity state is shown on the reaction curve at time.…”

Integration Versus Apartheid in Post-Roman Britain: A Response to Thomas et al. (2008)

“…Methods for estimating uncertainties in deterministic models are well established (e.g., see Gregory et al 2005). My model was based on estimates of an actual varying population, with varying numbers of surviving children in each successive generation who in turn had children, this approach is more realistic than the simple exponential population model used by Weale et al, or than randomly sampling the total number of individuals per generation moving from one ethnic group to another from a binomial distribution, as done by Thomas et al (2006).…”