Cohen`s Kappa should not be considered a gold standard for an agreement on time and movement studies. In biological research, where nothing can be considered absolute and accurate, as in physics, the accuracy of a new measurement method is considered assured when the measurement principle is sound and a number of measures do not deviate from a pre-defined standard or a series of measurements carried out using a recognized reference method. The acceptable deviation limit must be set arbitrarily from the outset. Accuracy is generally calculated and discussed with respect to standard deviations and coefficients of variation (CV), compliance percentages, standard measurement errors, and Bland-Altman parcels with appropriate compliance limits . In their systematic review of the study of agreements published between 2007 and 2009, Zaki and colleagues concluded that the Bland-Altman approach is by far the most used (178 studies (85%), followed by the Pearson correlation coefficient (27%), and the comparison of averages (18%)  Although Bland-Altman plots have been proposed to compare two measurement methods [8-10], they have also been valuable when comparing two observers (inter-observer variability assessment) or repeated measurements of the same observer (assessment of intra-observer variability). However, the Bland-Altman approach was not designed to assess the variability of the inter-observer, with more than two observers, nor to study the different sources of variation in the data. Based on the concept of variance component analysis (VCA), we assessed deviations due to errors, which were caused by separate elements of a PET scan (tracer, scanner, time, patient, observer, etc.) to express the composite uncertainty of repeated measurements and obtain relevant repeatability coefficients (RCs) that have a unique reference with Bland Altman plots in simple retest test parameters : RC is the limit below which 95% of the differences are. , where different sources of variation are fixed. The two clinical studies that provided data for this trial were approved by the Regional Committees of Scientific Ethics in Southern Denmark (Project ID: S-20120100 and S-20120137).