Innovative applications of visualized thermosensitive color-changing personalized boluses in post-mastectomy radiotherapy: a dosimetric analysis.

Abstract

Background and purpose: To explore the feasibility and advantages of the visualized thermosensitive color-changing personalized bolus in post-mastectomy radiotherapy (PMRT).

Materials and methods: Forty PMRT patients (June 2023-June 2024) were randomized into two groups. Group A (experimental group, 20 patients) underwent two CT scans: A₁ (without compensator) and A₂ (with the visualized thermosensitive color-changing personalized bolus), followed by treatment with the thermosensitive color-changing personalized bolus. Group B (control group, 20 patients) also underwent two CT scans: B₁ (without bolus) and B₂ (with a conventional commercial bolus), followed by treatment with the commercial bolus. Treatment plans were generated for virtual bolus (A₁-Plan, B₁-Plan) and real bolus (A₂-Plan, B₂-Plan). A₃-Plan (A₁-Plan applied to thermosensitive bolus treatment) and B₂-Plan (B₁-Plan applied to commercial bolus treatment) were compared to evaluate dosimetric differences in target volumes, organs at risk (OARs), and skin toxicity.

Results: In Group A, A₁-Plan and A₂-Plan showed no significant differences in OAR doses (e.g., ipsilateral lung, heart, contralateral breast, skin D_max/D_mean) or target metrics (V_50Gy, D_max, homogeneity index (HI), conformity index (CI), monitor units (MU)). A₃-Plan compared to A₁-Plan had minor differences in target coverage (94.05% vs. 95.14%), HI (0.148 vs. 0.147), and CI (0.83 vs. 0.84). In Group B, B₂-Plan had significantly reduced target coverage (89.9% vs. 95%), homogeneity (0.153 vs. 0.136), and conformity (0.817 vs. 0.810) compared to B₁-Plan, attributed to air gaps from the commercial bolus. The thermosensitive color-changing personalized bolus had better skin adherence, significantly reduced air cavity volumes (3833 mm³ vs. 21498 mm³), and maintained equivalent dosimetric performance to virtual boluses. Skin toxicity was Grade I in all patients without differences between groups.

Conclusions: The visualized thermosensitive color-changing personalized bolus demonstrated superior skin adherence, smaller air gaps, and better positional reproducibility compared to commercial boluses. Its dosimetric performance was consistent with virtual bolus plans, ensuring target coverage and OAR protection without increased skin toxicity. These findings support its clinical application in PMRT.