The methods described in the BIR report on Geometric Uncertainties in Daily Online IGRT will be applied to two clinical cases. The first case will be radiotherapy to the prostate and seminal vesicles (calculating separate margins around the prostate and SV). The second case will be a 5-fraction lung SABR plan. In each site, we will look at typical values for delineation error, target deformation, rotational errors, intrafraction motion, surrogate error, matching error, technical delivery accuracy, penumbral width, and the value of β to use in the in the van Herk margin formula.

The margin formula will be used to combine these values to calculate margin values

Educational aim:

- To illustrate the various parameters required to calculate a CTV-PTV margin for use with daily online IGRT

- To recognise the key clinical and imaging characteristics of thyroglossal duct and branchial cleft cysts

- To describe the role of further imaging and tissue sampling when acquired pathology mimics benign congenital disease 

0.5 CPD credit.

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Duration:23 mins