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Purpose: To assess the accuracy of the movement of a brachytherapy source using a high‐speed camera for evaluating source position, dwell time, and transit dose. Methods: A high‐speed camera was used to record the source position of an Ir‐192 source relative to a ruler within a custom positioning jig in a remote afterloading system. The analyzed frames can be used to assess dwell positions and times. Treatment plans had multiple dwell times equal to 0.1, 0.5, 1.0, and 2.0 s in 2.5‐ and 5‐mm step sizes. Images were acquired at a rate of 146 frames/s. Acquired images were processed to automatically track the actual source using the correlation between a template image and each frame. The brachytherapy dose calculation formalism (AAPM TG43‐U1) was applied to each frame to evaluate the transit dose contribution to the total dose. Results: The differences in measured source positions from the nominal for dwell times equal to 0.1, 0.5, 1.0, and 2.0 s in treatment plans were approximately ≤1 mm. The corresponding differences in measured dwell times from the nominal values at 5 mm steps were −15, −9, −5, and 5 ms, respectively. The source velocities at 5 mm steps were approximately 393 mm/s. The dose differences at 5 mm from the source movement with and without the transit dose for these dwell times were 38%, 7%, 3%, and 2%, respectively. Conclusions: Recording a brachytherapy source using a high‐speed camera allowed the evaluation of positional and dwell time accuracies as well as dosimetry assessments, such as the transit dose, based on the application of AAPM TG‐43U1. [ABSTRACT FROM AUTHOR]

This study compared the applicator position relative to the tracheal wall and dosimetric parameters between conventional and novel applicators among patients receiving endobronchial brachytherapy (EBBT) for intratracheal tumors. Data from 7 patients who received EBBT for intratracheal tumors were retrospectively analyzed; 4 and 3 patients were treated with conventional (2-wing) or novel (5-wing) applicators, respectively. Applicator centrality was evaluated using the distance between the center of the trachea and main bronchus (TMB) lumen and path of source (L). Dosimetric parameters, including plans normalized to D 2cc of the TMB = 45 Gy (normalized plan), were compared between the applicators. The mean and maximum values of L in cases of the 2-wing applicator group were approximately 5.0 mm and 10.0 mm, respectively. In the novel applicator group, the corresponding values were approximately 3.0 and 6.0 mm, respectively. In the normalized plan of the 2-wing applicator group, the ranges of median V 90% of clinical target volume (CTV) and D 0.1cc of the TMB in all cases were 23.0–91.9% and 66.3–153.1 Gy, respectively. In the 5-wing applicator group, the corresponding values were 69.2–83.8% and 60.4–84.5 Gy, respectively. In the 5-wing applicator group, the range was narrow in all dose–volume parameters except for D 2cc of the TMB. Compared to the conventional applicator, the 5-wing applicator can give a stable dose to the CTV and can reduce the maximum dose of the TMB. This suggests that stable EBBT can be given to any patient using the 5-wing applicator. [ABSTRACT FROM AUTHOR]