Purpose: This study evaluates the feasibility of utilizing robotic-assisted bronchoscopy with cone beam computed tomography (RB-CBCT) platform to perform low-dose-rate brachytherapy implants (LDR-BT) in a mechanically ventilated human cadaveric model. Post-implant dosimetry was compared to standard stereotactic body radiation therapy plans (SBRT).
Materials and methods: The RB-CBCT platform was used to place inert LDR-BT seeds into mechanically ventilated human cadavers with percutaneously injected pseudotumors. LDR-BT dosimetry plans were created a priori with a prescription dose of 100 Gy to the pseudotumor plus a 3mm margin to define a planning target volume (PTV). Implant quality was assessed by post-implant dosimetry and seed placement accuracy. Brachytherapy dosimetry was compared to standard SBRT treatment plans for the same cadaveric tumor volumes.
Results: Eight pseudotumors were planned with a total of 41 LDR-BT seeds, with a median of 5 seeds to achieve appropriate target coverage. All 41 LDR-BT seeds were successfully implanted in the 8 pseudotumors using RB-CBCT. On post-implant analysis, the average (± standard deviation) dosimetry to the pseudotumor was a V95% of 99.4 ± 3.3% and D90% of 128 ± 23Gy. The average distance between the planned and delivered seed location was 3.8 ± 1.1 mm. In comparison to SBRT plans, LDR-BT dose conformity was superior for the ratio of the V50% to the volume of the PTV (2.3 to 4.0, p < 0.001) and V25% (5.0 vs 17.5, p < 0.001).
Conclusions: RB-CBCT may be a feasible technology for implantation of LDR-BT seeds in peripheral lung tumors and can achieve pre-planned dosimetry goals with better dose conformity compared to SBRT. Further clinical studies are indicated to demonstrate safety and efficacy of LDR-BT delivered by RB-CBCT for treating early-stage lung cancer.
Keywords: Brachytherapy; low-dose rate brachytherapy; lung cancer; robotic bronchoscopy with cone beam computed tomography guidance.
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