Fig. 4

Emami paper [5] examples from expert opinion and Burman [6] models. Arrows depict how the 5% risk levels were interpolated from the Burman [6] model for the Emami [5] table of dose tolerance. Dots on the graph depict the TD 5/5 and TD 50/5 tolerance doses, which correspond to the values in the table. Kidney is a parallel structure so it is intuitive that the 5% risk level for 1/3 and 3/3 volumes were very different, whereas brachial plexus is predominantly a serial structure, so the 5% risk levels were fairly similar for conventional fractionation regardless of volume. However, Table 3 of the Karolinska study [2] shows a 50% reduction in tolerance of brachial plexus D3cc as compared to the maximum point dose (Dmax), therefore volume effects may be more important for SBRT. In the Emami paper [5], for both kidney and brachial plexus the TD5/5 and TD50/5 limits were in close agreement with the models. However, for other structures such as Bladder there was more reliance on expert opinion, as can be observed by the location of the TD 5/5 and TD 50/5 dots in the Burman paper [6], in relation to the modeled curves