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Table 1 Comparison of two analysis pipelines used to estimate metabolic rate of 18F-FDG to assess pulmonary inflammation

From: Reproducibility of compartmental modelling of 18F-FDG PET/CT to evaluate lung inflammation

ParameterPipeline APipeline B: initialPipeline B: final
Blood ROI sizeCircular, 5 pixel diameter, aortic arch to variableCircular, 8 pixel diameter, 25 slices beginning aortic archAs pipeline A
Lung ROI closing and erosion operation5 pixel diameter disc3 pixel diameter discAs pipeline B initial
Input function modelExponential basis functionsTri- or biexponential fitsAs pipeline A
Time delay estimationInside compartmental model optimisationOutside compartmental model optimisationAs pipeline A
Time delay fittingDelays spanning −50 to 50 s using 1-compartmental model fitted for first 5 min—lowest residual sum of squaresAdditional parameter within estimation of rate constantsAs pipeline A
OptimisationLocal optimumGlobal optimumAs pipeline A
Start point of optimisationK1 = 0.5, k2 = 0.2, k3 = 0.3, Vb = 0.1Multiple start points generated finds best guess (lowest objective function value)As pipeline A
  1. The columns “Pipeline B: initial” and “Pipeline B: final” describes the parameters which were used in the initial evaluation and the final settings used following adjustments to pipeline B respectively. The table highlights the key differences between the implementations of the compartmental model. Parameters not included below were identical between the analysis pipelines. WL = whole lung, DA = descending aorta, ROI = region of interest