ESTRO 2024 - Abstract Book

S5606

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

ESTRO 2024

superior with the open-face mask. Therefore, overall translation pre-positioning was not significantly superior with either method of patient positioning.

Intra-fractional motion analysis for open and closed masks using pre- and post-treatment kV imaging showed no significant difference in mask stability between the two mask types (Mean vertical deviation 0.34 [SD 0.63] vs. 0.34 [SD 0.46], p=0.27; Mean longitudinal deviation 0.56 [SD 0.45] vs. 0.44 [SD 0.37], p=0.06; Mean lateral deviation 0.30 [SD 0.22] vs. 0.28 [SD 0.22], p=0.21; Mean pitch deviation 0.30 [SD 0.32] vs. 0.24 [SD 0.23], p=0.21; Mean roll deviation 0.21 [SD 0.19] vs. 0.17 [SD 0.16], p=0.09; Mean rotational deviation 0.27 [SD 0.23] vs. 0.23 [SD 0.20], p=0.14). For open face masks, assessment of intra-fractional motion using pre- and post-treatment kV and SGRT data was performed. Reporting of intra-fractional motion between kV imaging and SGRT was comparable (Table 1).

Vertical [mm]

Longitudinal [mm]

Lateral [mm]

Pitch [°]

Roll [°]

Rotation [°]

Open mask – AlignRT (n=72) Open mask - kV (n=72)

0.13 ± 0.16

0.29 ± 0.30

0.20 ± 0.54

0.20 ± 0.21

0.17 ± 0.49

0.16 ± 0.19

0.35 ± 0.70

0.50 ± 0.46

0.30 ± 0.23

0.24 ± 0.22

0.19 ± 0.18

0.27 ± 0.23

Table 1 . Mask stability. Mean absolute position deviations comparing before and after treatment measured with kV imaging (top row) and SGRT (bottom row) for open-face masks

Conclusion:

Patient pre-positioning accuracy was similar between the two mask types. Open-face and closed masks are equally stable. SGRT and kV reporting of intra-fraction motion are comparable. In light of these results, open-face masks could be considered as the preferred method of immobilization for fractionated cranial radiotherapy in combination with SGRT and kV imaging.