Comparison of neutron contamination in small photon fields of secondary collimator jaws and circular cones

IF 0.3 Q4 RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING

Journal of Radiotherapy in Practice Pub Date : 2023-01-01 DOI:10.1017/s1460396923000328

Nooshin Banaee, Kiarash Goodarzi, Elham Hosseinzadeh

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引用次数: 0

Abstract

Abstract Introduction: Advanced treatment modalities involve applying small fields which might be shaped by collimators or circular cones. In these techniques, high-energy photons produce unwanted neutrons. Therefore, it is necessary to know neutron parameters in these techniques. Materials and methods: Different parts of Varian linac were simulated by MCNPX, and different neutron parameters were calculated. The results were then compared to photoneutron production in the same nominal fields created by circular cones. Results: Maximum neutron fluence for 1 × 1, 2 × 2, 3 × 3 cm 2 field sizes was 165, 40.4, 19.78 (cm –2 .Gy -1 × 10 6 ), respectively. The maximum values of neutron equivalent doses were 17.1, 4.65, 2.44 (mSv/Gy of photon dose) for 1 × 1, 2 × 2, 3 × 3 cm 2 field size, respectively, and maximum neutron absorbed doses reached 903, 253, 131 (µGy/Gy photon dose) for 1 × 1, 2 × 2, 3 × 3 cm 2 field sizes, respectively. Conclusion: Comparing the results with those in the presence of circular cones showed that circular cones reduce photoneutron production for the same nominal field sizes.

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二次准直钳口和圆锥小光子场中子污染的比较

摘要:先进的治疗方式包括应用小场，可能是由准直器或圆锥形。在这些技术中，高能光子产生不需要的中子。因此，在这些技术中有必要了解中子参数。材料与方法:采用MCNPX软件对瓦里安直线发电机的不同部位进行模拟，计算出不同的中子参数。然后将结果与由圆锥形产生的相同名义场中的光子中子产生进行比较。结果:1 × 1、2 × 2、3 × 3 cm 2场尺寸的最大中子通量分别为165、40.4、19.78 (cm -2 . gy -1 × 10.6)。在1 × 1、2 × 2、3 × 3 cm 2场尺寸下，中子当量剂量最大值分别为17.1、4.65、2.44 (mSv/Gy);在1 × 1、2 × 2、3 × 3 cm 2场尺寸下，中子吸收剂量最大值分别为903、253、131(µGy/Gy光子剂量)。结论:与圆锥存在时的结果比较表明，在相同的名义场尺寸下，圆锥减少了光子中子的产生。

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来源期刊

Journal of Radiotherapy in Practice RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING-

CiteScore

0.80

自引率

0.00%

发文量

期刊介绍： Journal of Radiotherapy in Practice is a peer-reviewed journal covering all of the current modalities specific to clinical oncology and radiotherapy. The journal aims to publish research from a wide range of styles and encourage debate and the exchange of information and opinion from within the field of radiotherapy practice and clinical oncology. The journal also aims to encourage technical evaluations and case studies as well as equipment reviews that will be of interest to an international radiotherapy audience.