Introduction
3D printing has become a popular and widely available technique of rapid prototyping. The impact of used materials on the dose distribution has been studied for high energy sources. However, brachytherapy sources emit lower energy photons, and materials used in 3D printing may differ. This study was conducted to analyze the influence of common materials (polylactic acid – PLA and acrylonitrile butadiene styrene – ABS) used in stereolitho­graphy.

Material and methods
A 3D-printed phantom was designed, printed, and used to calibrate Gafchromic films. In the next step, a range of 1 mm thick plates of PLA and ABS (from zero to thirty) were inserted between source and detector to measure the impact of studied materials on delivered dose. Measurements were performed using a calibrated radiochromic film and Farmer ionization chamber in water.

Results
No statistically significant correlation (p = 0.4854) between the thickness of inserted PLA and the dose delivered to the film was obtained. With ionization chamber, Spearman’s rank order test showed a significant correlation (p = 0.00004); however, the correlation was found weak. In case of ABS measurement, a statistically significant (p = 0.0159), yet weak negative correlation was found between the thickness of used material and the dose delivered to the film. On the other hand, a weak statistically significant (p = 0.0212) but positive correlation was found when the dose was measured with Farmer ionization chamber. We find these correlations false, as all measured doses were within the measurement uncertainty range (film ±8.0%, Farmer ±8.8%) from 100% of the prescribed dose.

Conclusions
According to obtained results, with the accuracy of measurement under clinical conditions, the impact of highly filled PLA and ABS printed objects on the dose distribution from an 192Ir source in water can be omitted.



中文翻译：

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高剂量率近距离放射治疗中用于立体光刻的低成本材料的剂量学评估

简介
3D 打印已成为一种流行且广泛使用的快速原型制作技术。已针对高能量源研究了所用材料对剂量分布的影响。然而，近距离放射治疗源会发射较低能量的光子，并且 3D 打印中使用的材料可能会有所不同。本研究旨在分析立体光刻中常用材料（聚乳酸 – PLA 和丙烯腈丁二烯苯乙烯 – ABS）的影响。

材料与方法
设计、打印并用于校准 Gafchromic 薄膜的 3D 打印模型。在下一步中，将一系列 1 毫米厚的 PLA 和 ABS 板（从零到三十）插入源和检测器之间，以测量研究材料对传递剂量的影响。使用校准的放射变色膜和 Farmer 电离室在水中进行测量。

结果
在插入的 PLA 的厚度和传递到薄膜的剂量之间没有获得统计学上显着的相关性 (p = 0.4854)。使用电离室时，Spearman 排序检验显示出显着相关性（p = 0.00004）；但是，发现相关性很弱。在 ABS 测量的情况下，在使用的材料的厚度和传递到薄膜的剂量之间发现了统计学上显着的 (p = 0.0159) 但微弱的负相关性。另一方面，当使用 Farmer 电离室测量剂量时，发现了微弱的统计显着性 (p = 0.0212) 但正相关。我们发现这些相关性是错误的，因为所有测量的剂量都在规定剂量的 100% 的测量不确定范围内（胶片 ±8.0%，Farmer ±8.8%）。

结论
根据获得的结果，在临床条件下测量的准确性，可以忽略高填充 PLA 和 ABS 打印物体对 192Ir 源在水中的剂量分布的影响。