ESTRO 2024 - Abstract Book

S5540

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

Figure 1. Population random and systematic errors

Compared with the previous studies, both systematic and random errors are reduced in the AP direction and show little difference in the LR direction compared with 2019. In the SI direction, the random error is comparable to that in 2019 but the systematic error has increased. This could be due to the fact that PRR could not be corrected at the time of treatment due to lack of 6 degrees of freedom couch capability on our Linear Accelerators. If this was available at the time, the SI direction may have been improved if PRR could be applied. Staff improvement in matching capabilities has also increased since 2019 with the move to daily CBCT and therefore matching may have become more accurate over time. With the addition specific match points, matching is now more focused rather than using a ‘best fit’ match which may give a better representation of patient position.

Conclusion:

We demonstrated a reduction of systematic and random errors in the ant/post direction with the use of separate thermoplastic shoulder and head immobilisation devices. However, further work is necessary to reduce systematic errors in the sup/inf direction. Current RCR guidelines require soft tissue matching for patients receiving highly