Dosimetry and treatment efficiency of SBRT using TaiChiB radiotherapy system for two-lung lesions with one overlapping organs at risk.

Purpose: This study aims to assess the dosimetry and treatment efficiency of TaiChiB-based Stereotactic Body Radiotherapy (SBRT) plans applying to treat two-lung lesions with one overlapping organs at risk. Methods: For four retrospective patients diagnosed with two-lung lesions each patient, four treatment plans were designed including Plan _Edge, TaiChiB linac-based, RGS-based, and a linac-RGS hybrid (Plan _TCLinac, Plan _TCRGS, and Plan _TCHybrid). Dosimetric metrics and beam-on time were employed to evaluate and compare the TaiChiB-based plans against Plan _Edge. Results: For Conformity Index (CI), Plan _TCRGS outperformed all other plans with an average CI of 1.06, as opposed to Plan _Edge′s 1.33. Similarly, for R_{50 %}, Plan _TCRGS was superior with an average R_{50 %} of 3.79, better than Plan _Edge′s 4.28. In terms of D_2cm, Plan _TCRGS also led with an average of 48.48%, compared to Plan _Edge′s 56.25%. For organ at risk (OAR) sparing, Plan _TCRGS often displayed the lowest dosimetric values, notably for the spinal cord (D_max 5.92 Gy) and lungs (D_1500cc 1.00 Gy, D_1000cc 2.61 Gy, V_10Gy 15.14%). However, its high D_max values for the heart and great vessels sometimes exceeded safety thresholds. Plan _TCHybrid presented a balanced approach, showing doses comparable to or better than Plan _Edge without crossing safety limits. In terms of beam-on time, Plan _TCLinac emerged as the most efficient treatment option in three out of four cases, followed closely by Plan _Edge in one case. Plan _TCRGS, despite its dosimetric advantages, was the least efficient, recording notably longer beam-on times, with a peak at 33.28 minutes in Case 2. Conclusion: For patients with two-lung lesions treated by SBRT whose one lesion overlaps with OARs, the Plan _TCHybrid delivered by TaiChiB digital radiotherapy system can be recommended as a clinical option. [ABSTRACT FROM AUTHOR]