SU‐E‐J‐163: The Imaging Dose to Patients Resulting From the ExacTrac X‐Ray System
SU‐E‐J‐163: The Imaging Dose to Patients Resulting From the ExacTrac X‐Ray System
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SU-E-J-163：ExacTrac X 射线系统对患者产生的成像剂量
DOI：
10.1118/1.4814375
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发表时间：
2013
期刊：
影响因子：
3.8
通讯作者：
G. Luo
中科院分区：
文献类型：
--
作者：
G. Ding;G. Luo
目的：缺乏关于Novalis ExacTrac用于图像引导放疗的成像剂量的报告数据。本研究旨在评估ExacTrac X射线成像系统中各种临床默认成像采集方案对患者造成的成像剂量。方法：研究Novalis TX ExacTrac X射线系统（BrainLab，Feldkirchen，德国）。该系统由两个安装在地板上的千伏级X射线管组成，倾斜地投射到安装在天花板上的两个平板探测器上。使用插入体模中的离子室进行剂量测量。由半值层规定的X射线束的离子室空气比释动能校准因子从经认可的剂量学校准实验室获得。研究了临床默认方案（包括颅骨、胸部和腹部）的成像剂量。体模尺寸为30×12×30 cm 3，由低能量X射线用水等效材料制成，PW-LR（CIRS，诺福克，VA）。结果：在等中心点，每个射线管的X射线射野尺寸为20×20 cm 2。观察到两个X射线管之间等中心处测量的辐射剂量存在5- 10%的微小差异。在距治疗台1 cm深度处的体模中测量的剂量分别为0.05 cGy、0.16 cGy和0.19 cGy，这是由一对倾斜射束的颅骨重、胸部重和腹部重临床方案产生的。结果发现，通过选择Abdomen‐Light而不是Abdomen‐Heavy采集方案，剂量减少高达77%。结论：尽管单对射束对患者产生的成像剂量较低，但多次采集（10 - 20对）的总和仍然很大，如果使用非共面射束，这对于一个治疗部分可能很常见。成像剂量强烈依赖于图像采集协议。在治疗过程中，如果图像质量不受影响，则应选择低剂量方案。
Purpose: There is a lack of reported data on imaging dose from Novalis ExacTrac use for image guided radiotherapy. This investigation is to assess the imaging doses to patients resulting from a variety of clinical default imaging acquisition protocols in the ExacTrac x‐ray imaging system. Methods: Novalis TX ExacTrac x‐ray system (BrainLab, Feldkirchen, Germany) is investigated. This system consists of two floor‐mounted kilovoltage X‐ray tubes projecting obliquely onto two flat‐panel detectors mounted on the ceiling. The dose measurements were performed using an ion chamber inserted in a phantom. The air kerma calibration factor of the ion chamber for x‐ray beams specified by the half‐value layer was obtained from an Accredited Dosimetry Calibration Laboratory. The imaging dose from clinical default protocols including Cranium, Thorax and Abdomen were studied. The phantom, in the size of 30×12×30 cm3, was made from slabs of water‐equivalent materials for low energy x‐rays, PW‐LR (CIRS, Norfolk, VA). Results: The field size of x‐rays from each tube is 20×20 cm2 at the isocenter. Small differences of 5–10 % in measured radiation dose at the isocenter between two x‐ray tubes were observed. The doses measured in the phantom at a depth of 1 cm from the treatment table were 0.05 cGy, 0.16 cGy, and 0.19 cGy resulting from a pair of obliquely beams of Cranium‐heavy, Thorax‐Heavy and Abdomen‐Heavy clinical protocols respectively. It was found that there was up to 77% dose reduction by selecting Abdomen‐Light instead of Abdomen‐Heavy acquisition protocols. Conclusion: Although the imaging doses to patients resulting from a single pair of beams are low, the sum of multiple acquisitions (10‐20 pairs) is still significant, which can be common for one treatment fraction if non‐coplanar beams are used. The imaging doses strongly depend on the image acquisition protocols. During treatment, the low dose protocols should be chosen, given that image quality is not compromised.