Surface dose in intracavitary orthovoltage radiotherapy.
Surface dose in intracavitary orthovoltage radiotherapy.
复制标题
腔内正电压放射治疗中的表面剂量。
DOI：
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
E. Podgoršak
中科院分区：
文献类型：
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作者：
M. Podgorsak;L. Schreiner;E. Podgoršak
正电压技术放射治疗通常是局部浅表恶性肿瘤的主要治疗方法。表面剂量和深度剂量测量与圆柱形和端窗法默室的各种正电压的X射线束的范围从80至300 kVp，无论是开放的光束和光束准直与商业腔内铅玻璃锥。对于由定位在距患者表面一定距离处的隔膜准直的辐射场（开放射束），存在小的皮肤保护效应。另一方面，表面剂量与商业铅玻璃腔内锥可以表现出五倍的开放束剂量最大值相比，增加。在组织等效体模中超过约0.2 mm的深度时，对于开放射束和用腔内锥体准直的射束测得的剂量基本相同。观察到的表面剂量的增加与腔内锥是由于光电子和反冲电子产生的锥。高表面剂量是由薄壁平行板电离室测量的，但不能用圆柱形法默室测量，因为这些室的壁厚太大，无法传输锥体中产生的电子。由于圆柱形法默腔室通常用于辐射输出的校准，腔内锥体产生的高表面剂量可能会被忽略;然而，它们可以通过简单的锥体修改减少到开放射束值。
Radiotherapy with orthovoltage techniques is often the prime treatment for localized superficial malignancies. Surface doses and depth doses measured with cylindrical and end-window Farmer chambers are presented for various orthovoltage x-ray beams in the range from 80 to 300 kVp, both for open beams and beams collimated with commercial intracavitary leaded-glass cones. For radiation fields collimated by a diaphragm positioned at a distance from the patient surface (open beams) there is a small skin-sparing effect. On the other hand, the surface doses with commercial leaded-glass intracavitary cones can exhibit a fivefold increase compared to the open-beam dose maxima. Beyond a depth of approximately 0.2 mm in a tissue-equivalent phantom, the doses measured for open beams and beams collimated with intracavitary cones are essentially identical. The increase in the surface dose observed with intracavitary cones is attributed to photoelectrons and recoil electrons produced in the cones. The high surface doses are measured by thin-wall parallel-plate ionization chambers but cannot be measured with cylindrical Farmer chambers since these chambers have wall thicknesses too large for the transmission of electrons produced in the cone. Since cylindrical Farmer chambers are typically used for calibration of radiation output, the high surface doses produced by the intracavitary cones may be overlooked; they can, however, be reduced to open-beam values by simple modifications to the cones.