ESTRO meets Asia 2024 - Abstract Book

S391

RTT – Treatment planning, OAR and target definitions

ESTRO meets Asia 2024

We selected 4 patients with hip prostheses (3 unilateral and 1 bilateral) and created 4 plans with different planning strategies:

- Plan_1: No restriction.

- Plan_2: "No entry+exit" optimization.

- Plan_3: "No entry" optimization.

- Plan_4: Exclusion segments.

Figure 1. Patients

Results:

We observed a considerable decrease in PTV coverage in Plan_2 for all patients due to its highly restrictive condition. However, in Plan_3, we achieved good PTV coverage and dose conformity without affecting the organs at risk.

All patients received 2 full arcs except for Patient 1, who received two partial arcs. Therefore, Plan_4 was discarded for this patient since there were not enough arcs to obtain optimal results.

Plan_4 was tested for Patients 2 and 3 using segments of 35º-90º and 63º-138.7º in both clockwise (CW) and counterclockwise (CCW) directions. Meanwhile, for Patient 4, the segments were 247º-305º CW and 99º-31º CCW.

Table 1. Measures

In cases where angles coincide with both the prosthesis and partial PTV, it is better to use Plan_3 because it continues to irradiate other areas of the PTV without entering the prosthesis, unlike Plan_4.

Conclusion: