Fig 1.
Image of immobilization and set-up.
Thermoplast masks were used for immobilization.
Fig 2.
Body volume was measured using cone beam computed tomography.
The measurement range was 7.5 cm in the superior and inferior directions from the centre of the CBCT.
Fig 3.
Schema of treatment procedure and calculation of body indices and set-up error.
Table 1.
Patient characteristics.
Fig 4.
Correlations between body weight variations and body volume variations.
Table 2.
Descriptive statistics of inter- and intra-fractional variations.
Table 3.
Correlations between body weight or body volume variations and inter-fractional variations.
Table 4.
Correlations between body weight or body volume variations and intra-fractional variations.
Table 5.
Correlations between body weight or body volume variations and absolute value of inter-fractional variations.
Table 6.
Correlations between body weight or body volume variations and absolute value of intra-fractional variations.
Fig 5.
(A) Receiver operating characteristic curve of intra-fractional variations (≥2 mm) of anterior-posterior and decrease of body weight or volume. (B) Receiver operating characteristic curve of intra-fractional variations (≥2 mm) of three-dimensional vector and decrease of body weight or volume. (C) Receiver operating characteristic curve of intra-fractional variations (≥2 mm) of any directions and decrease of body weight or volume.
Table 7.
Results of receiver operating characteristic analysis between decrease of body weight or volume and inter- (≥3 mm) or intra-fractional (≥ 2 mm) variations.
Fig 6.
(A) Box plot of intra-fractional variation of anterior-posterior direction per body weight variation group of 1 kg. (B) Box plot of intra-fractional variation of pitch per body weight variation group of 1 kg. (C) Box plot of intra-fractional variation of three-dimensional vector per body weight variation group of 1 kg.
Table 8.
Optimal margins for PTV considering both inter- and intra-fractional variations.
Fig 7.
(A) Intra-fractional error of patient number eight. Simulation had to be repeated in this patient after the 15th fraction. The average and standard deviation of three-dimensional intra-fractional variations before and after repeated simulation were 1.37±0.84 mm and 1.19±0.51 mm, respectively. (B) Intra-fractional error of patient number 11. Simulation had to be repeated in this patient after the 17th fraction. The average and standard deviation of three-dimensional intra-fractional variations before and after repeated simulation were 1.73 ± 1.02 mm and 1.46 ± 0.68 mm, respectively.
Table 9.
Comparisons of calculated margins for planning target volumes with those of previous studies considering inter-fractional variations.
Table 10.
Comparisons of calculated margins for planning target volumes with those of previous studies considering both inter- and intra-fractional variations.