In this research work, a simple homemade cubic phantom was designed to validate the Image-Guided Radiotherapy (IGRT) set up and verified with the help of tungsten fiducial markers (size 2-3 mm) inserted into the cubic phantom. Phantom made up of Styrofoam, was scanned with the help of 16 slice Toshiba CT scanner where each slice was of 1 mm thickness and HU level set to -1000. A radio-opaque contrast medium was rubbed on the phantom to visualize the scanner images. Once the iso-center had been marked on a phantom with the help of in-room positioning laser and the fields (RT-LAT and AP) were applied on the contoured body of the phantom in Varian's ARIA-11 Eclipse dosimeter software, the same position of the phantom was reproduced on Varian's Linear Accelerator DHX. Known shifts of 3.0 to 30.0 mm from the marked iso-center were applied on the phantom by moving the couch in all six directions one by one. On each applied couch shift, an x-ray image of the phantom was acquired with the help of an MV portal imager of Linac in AP and RT-LAT direction. This image was superimposed with a reference image of phantom and shift accuracy calculated by ARIA-11 software was noted down. It turned out that irrespective of the position of the phantom on the couch, the calculated corrected shift and deviation from reference position was always between ± 1-2 mm which is the required accuracy for IGRT according to International Atomic Energy Agency (IAEA). This process was repeated 40 times and each time, the corrected shift came out to be ± 1-2 mm. We can conclude that our system is safe and accurate enough to perfectly position the actual patient for IGRT.

中文翻译：

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评估和验证基于钨基准标记的图像引导放射治疗。

在这项研究工作中，设计了一个简单的自制立方体模型来验证影像引导放射治疗（IGRT）的设置，并借助插入到立方体模型中的钨基准标记（尺寸为2-3 mm）进行验证。用16片东芝CT扫描仪扫描由泡沫聚苯乙烯组成的幻影，其中每片厚度为1毫米，HU级别设置为-1000。将不透射线的造影剂在体模上摩擦，以使扫描仪图像可视化。在室内定位激光的帮助下，将等中心线标记在体模上，然后在Varian的ARIA-11 Eclipse剂量计软件中将场（RT-LAT和AP）应用到体模的轮廓体上幻影的位置在Varian的Linear Accelerator DHX上进行了复制。已知的3.0到30的偏移量。通过在所有六个方向上一张一张地移动沙发，将距离标记的等中心点0毫米的对象施加到体模上。在每次施加的卧榻移位时，借助Linac的MV门户成像仪在AP和RT-LAT方向上获取体模的X射线图像。该图像与幻像的参考图像叠加，并记下了由ARIA-11软件计算出的偏移精度。事实证明，与人体模型在沙发上的位置无关，计算出的校正偏移和与参考位置的偏差始终在±1-2 mm之间，这是国际原子能机构（IAEA）所要求的IGRT精度。重复该过程40次，每次校正后的偏移量为±1-2 mm。