Fig 1.
The optimization function interface for VMAT plan in the Eclipse TPS.
The settings include dose-volume objectives, normal tissue objectives, and MU objective, where MU objective are used to control the total MU of the VMAT plan.
Table 1.
Dose comparisons of target PGTV and PGTVnd for plan S50, S80, S100 vs base plan (n = 21).
Table 2.
Dose comparisons of target PCTV1 and PCTV2 for plan S50, S80, S100 vs base plan (n = 21).
Fig 2.
The relative difference between the target dose of plan S50 and base plan (n
= 21). Among the 21 patients in plan S50, only one showed a decrease in target dose exceeding 2% but remaining below 2.5% compared to the base plan. For the PGTV, dose deviations were within 1% of the base plan.
Fig 3.
The relative difference between the target dose of plan S80 and base plan (n
= 21). Among the 21 patients in Plan S80, only one case showed a deviation of D95% exceeding 1.5% but remaining below 2% compared to the base plan. For PGTV, all cases D95% deviations were within 1% of the base plan.
Fig 4.
The relative difference between the target dose of plan S100 and base plan (n
= 21). In Plan S100, the PCTV2 showed a notable dose reduction compared to the base plan. Among the cases, four patients demonstrated a decrease in D95% exceeding 3%, while another four patients had a D98% reduction surpassing 4%. However, for the PGTV, all dose deviations from the base plan were within 2%.
Fig 5.
Cross-sectional dose distribution of one patient, with the top left, top right, bottom left, and bottom right indicating planned base, S50, S80, and S100, respectively.
The 7000 cGy isodose lines (yellow) in all four plans demonstrated adequate coverage of the target PGTV (red). However, in Plan S100, the 7000 cGy isodose line showed inward retraction and failed to completely cover the PGTV. Compared with the base plan, Plan S50, S80 and S100 exhibited progressively expanding low-dose isodose lines (4500 cGy and 4000 cGy), resulting in deteriorated dose conformity.
Fig 6.
DVH of each structure of four plans for one patient, where “-solid line” represents base plan, “-- long dashed line” represents plan S50, “-. dotted dash line” represents plan S80, and “: dotted line” represents plan S100.
For the target, plan S100 showed significant deviations in the DVH compared to the base plan. Regarding OARs, plan S100 also exhibited notable DVH variations for the parotid glands and spinal cord. In contrast, plan S50 demonstrated nearly identical DVH curves to the base plan for both target and OARs.
Table 3.
Dose comparison of brainstem, lens, chiasma, optic nerve, pituitary gland and spinal cord for plan S50, S80, S100 vs base plan (n = 21).
Table 4.
Dose comparison of parotid gland, temporal lobe, temporomandibular joint, thyroid gland and submandibular gland for plan S50, S80, S100 vs base plan (n = 21).
Table 5.
MUs and beam on time for plan S50, S80, S100 vs base plan (n = 21).s.
Table 6.
Gamma pass rates of the four plans under different evaluation conditions.