An Analytical Formalism for the Assessment of Dosimetric Uncertainties Due to Positioning Uncertainties

The assessment of the type-B uncertainty due to detector positioning in small photon fields. This uncertainty can be caused by uncertainties in the determination of the position of the maximum dose, the step width of the scanning phantom and uncertainties in collimator (re- )positioning when changing the field size. While positioning makes up an important contribution to the overall dosimetric uncertainty of small fields, there is limited consensus how to assess this uncertainty and published uncertainty estimates for similar experimental conditions can vary by up to an order of magnitude.