Introduction
To evaluate the dosimetry of a six-channel high-dose-rate (HDR) applicator for treatment of esophageal cancer with respect to lateral directionality and heterogeneous media.

Material and methods
A computed tomography (CT)- and magnetic resonance imaging (MRI)-compatible esophageal applicator consisting of 2 inflatable portions (anchor and therapeutic balloons) with 6 longitudinal treatment catheters equally spaced circumferentially was constructed. Treatment plans were prepared using Oncentra 4.5 for various catheter loadings and target locations and sizes. Calculated dose distributions were compared to measured distributions obtained using film and a water phantom. Balloon inflations with water and with air were tested.

Results
TG-43 dose calculations matched measurements well when inflation balloons were filled with water. When air was used to inflate, model-based dose calculations (TG-186) improved the comparison with measurement. Several cases with simulated ring targets demonstrated better dose conformity to non-uniform targets compared to a single central catheter. Additionally, the use of this applicator compared to a single catheter, gave rise to considerable improvement in sparing non-target tissue.

Conclusions
Lateral dose modulation is achievable with the applicator described in this work. The use of TG-186 dose calculation made a small improvement in heterogeneous media.



中文翻译：

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用于高剂量率治疗食管癌的新型六通道涂药器的临床前剂量测定

简介
评估六通道高剂量率 (HDR) 涂药器在横向方向性和异质介质方面治疗食管癌的剂量学。

材料和方法
构建了一个与计算机断层扫描 (CT) 和磁共振成像 (MRI) 兼容的食管施药器，该施药器由 2 个可充气部分（锚和治疗球囊）组成，6 个纵向治疗导管在圆周上等距分布。使用Oncentra 4.5 为各种导管负荷和目标位置和尺寸制定治疗计划。将计算的剂量分布与使用胶片和水体模获得的测量分布进行比较。对水和空气的气球充气进行了测试。

结果
当充气气球装满水时，TG-43 剂量计算与测量值匹配得很好。当使用空气充气时，基于模型的剂量计算 (TG-186) 改进了与测量的比较。与单个中央导管相比，具有模拟环形靶标的几个案例表明对非均匀靶标的剂量一致性更好。此外，与单个导管相比，使用该涂药器在保留非目标组织方面产生了相当大的改进。

结论
使用本工作中描述的涂药器可以实现横向剂量调制。TG-186 剂量计算的使用对异质介质进行了小幅改进。