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. 2024 Mar 26;14(1):7134.
doi: 10.1038/s41598-024-57644-4.

Evaluation of the deliverability of dynamic conformal arc therapy (DCAT) by gantry wobble and its influence on dose

Changhwan Kim  1 , Hojae Kim  2 , Dongmin Jung  2 , Heesoo Kim  2 , Yeonok Park  3 , Min Cheol Han  1 , Chae-Seon Hong  1 , Hojin Kim  1 , Ho Lee  1 , Jinsil Sung  1 , Dong Wook Kim  4 , Jin Sung Kim  5
Affiliations

Evaluation of the deliverability of dynamic conformal arc therapy (DCAT) by gantry wobble and its influence on dose

Changhwan Kim et al. Sci Rep. .

Abstract

We aimed to investigate the deliverability of dynamic conformal arc therapy (DCAT) by gantry wobble owing to the intrinsic inter-segment break of the Elekta linear accelerator (LINAC) and its adverse influence on the dose to the patient. The deliverability of DCAT was evaluated according to the plan parameters, which affect the gantry rotation speed and resultant positional inaccuracies; the deliverability according to the number of control points and dose rates was investigated by using treatment machine log files and dosimetry devices, respectively. A non-negligible degradation in DCAT deliverability due to gantry wobble was observed in both the treatment machine log files and dosimetry devices. The resulting dose-delivery error occurred below a certain number of control points or above a certain dose rate. Dose simulations in the patient domain showed a similar impact on deteriorated deliverability. For targets located primarily in the isocenter, the dose differences were negligible, whereas for organs at risk located mainly off-isocenter, the dose differences were significant up to - 8.77%. To ensure safe and accurate radiotherapy, optimal plan parameters should be selected, and gantry angle-specific validations should be conducted before treatment.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
ArcCHECK measurements of 6 MV-FFF DCAT plans with different numbers of control points. (a) 25, (b) 49, (c) 73, (d) 91, (e) 145, and (f) 241.
Figure 2
Figure 2
ArcCHECK measurements of 10 MV-FFF DCAT plans with different numbers of control points. (a) 25, (b) 49, (c) 73, (d) 91, (e) 145, and (f) 241.
Figure 3
Figure 3
Maximum absolute dose error at inter-segment breakpoints according to the number of control points measured by ArcCHECK, and linear fitted line with R-squared values. (a) 6 MV-FFF, (b) 10 MV-FFF.
Figure 4
Figure 4
ArcCHECK measurements of DCAT plans with different dose rate. (a) 600 MU/min (6 MV), (b) 1400 MU/min (6 MV-FFF), (c) 1400 MU/min (6 MV-FFF), and (d) 1800 MU/min (10 MV-FFF), respectively. (a,b) are based on the plan of Case 1, and (c,d) are based on the plan of Case 2. The number of control points for all plans was fixed as 25.
Figure 5
Figure 5
Maximum absolute dose error at inter-segment breakpoints according to the dose rate measured by ArcCHECK, and a linear fitted line with R-squared value.
Figure 6
Figure 6
Two-dimensional distributions of computed dose and measured dose by Octavius 1000 SRS and gamma indices for Case 1 (6 MV-FFF), according to different numbers of control points (3%/3 mm local gamma criterion (10% low-dose threshold)). (a) 25, (b) 49, (c) 73, (d) 91, (e) 145, and (f) 241.
Figure 7
Figure 7
Two-dimensional distributions of computed dose and measured dose by Octavius 1000 SRS and gamma indices for Case 2 (10 MV-FFF), according to different numbers of control points (3%/3 mm local gamma criterion (10% low-dose threshold)). (a) 25, (b) 49, (c) 73, (d) 91, (e) 145, and (f) 241.
Figure 8
Figure 8
Two-dimensional distributions of computed dose and measured dose by Octavius 1000 SRS and gamma indices according to different dose rates (a) 600 MU/min (6 MV), (b) 1,400 MU/min (6 MV-FFF), (c) 1400 MU/min (6 MV-FFF), and (d) 1800 MU/min (10 MV-FFF), respectively. (a,b) are based on the plan of Case 1; (c,d) are from Case 2. (3%/3 mm local gamma criterion (10% low-dose threshold)).
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