Geometric Uncertainties

Geometric Uncertainties in Daily Online IGRT – updated report

Geometric Uncertainties in Radiotherapy: This document provides useful tools to aid radiotherapy professionals analyse sources of geometric uncertainty and will be of interest to anyone working within radiotherapy and oncology. It is an update to the ever popular BIR working party report, Geometric Uncertainties in Radiotherapy: Defining the Planning Target Volume, 2003.  See the BIR bookshop 

Lung Sabr outlineThe 2003 report gave oncologists, physicists and radiographers the tools to estimate geometric uncertainties in their own centre and showed how these uncertainties could be minimized and accommodated by appropriate protocols.

Much of the 2003 report remains relevant and is required reading for radiotherapy professionals who wish to fully understand the technical steps associated with generating a CTV–PTV margin, however this new guidance, published by the BIR in 2020 includes new areas relevant to modern practice.




The working party members for the update are: G. Samuel J. Tudor (Chair), David Bernstein, Stephen Riley, Yvonne Rimmer, Simon J. Thomas, Marcel van Herk and Amanda Webster.

              Prostate_base                        Prostate_central



The original 2003 report is available for purchase from this site. 


Top:  Delineation study showing the variation of fifteen outlines from different observers for a lung SABR case

Bottom left: A central axial slice through a prostate with manual contours (yellow and turquoise) and a ruler (red) showing the measured range across relevant contours.

Bottom right: An axial slice near the base of the prostate showing large differences between the contours which have arisen as a result of out of plane changes in the shape of the prostate.



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