Trouette R, Récaldini L, Beaumont G, Dahan O, Abdiche S, Pan Z, Wang Y, Maire J P, Demeaux H, Caudry M
Service de radiothérapie, hôpital Saint-André, Bordeaux, France.
Bull Cancer Radiother. 1995;82(1):20-7.
Treatment reproducibility is a major criterion of quality assurance in radiation therapy. During each course, the same dose should be delivered in the same volume of irradiation. Today, portal imaging devices can be used routinely to check and correct patient positioning before much of the daily irradiation has been delivered. In this study we used the Portal Vision Varian (PVV) system during pelvic irradiation in 16 patients. This device can automatically acquire portal images in the first seconds of each course. Observed discrepancies are directly classified by the radiation oncologist according to their type (cranio-caudal, lateral, antero-posterior) and severity (correction of patient positioning is necessary or not). In case of error, patient positioning is corrected before the end of irradiation. Of the 922 portals analysed with PVV, 901 could be analysed (97%). Two hundred and ninety-nine positioning discrepancies were observed (33%) with 59 of them leading to correction (6%). Most of the time, these errors concerned antero-posterior portals. Finally, each patient had an average of 18 to 19 discrepancies which were mainly of no importance for treatment quality. Nevertheless, real errors leading to correction were observed in 14 patients (88%) with an average of four per patient. In some patients many errors occurred, while in others only a few. These shifts were not related to patient weight and thickness but probably a portal dimension. In summary, we think that during pelvic irradiation a portal imaging device should be used daily to improve treatment quality. This system can help the radiation oncologist to discover many positioning errors (an average of four) in the majority of patients (88%) and to correct them before the end of irradiation.
治疗的可重复性是放射治疗质量保证的主要标准。在每个疗程中，相同体积的照射区域应给予相同剂量的辐射。如今，在大部分日常照射开始前，可常规使用射野成像设备来检查和校正患者体位。在本研究中，我们在16例患者盆腔照射期间使用了瓦里安公司的Portal Vision（PVV）系统。该设备能够在每个疗程的最初几秒自动采集射野图像。放射肿瘤学家可根据观察到的差异类型（头脚方向、左右方向、前后方向）和严重程度（是否需要校正患者体位）直接进行分类。如有错误，在照射结束前校正患者体位。在用PVV分析的922个射野中，901个可进行分析（97%）。观察到299个体位差异（33%），其中59个导致了体位校正（6%）。大多数情况下，这些误差涉及前后方向的射野。最后，每位患者平均有18至19个差异，这些差异大多对治疗质量无重要影响。然而，在14例患者（88%）中观察到了导致校正的实际误差，每位患者平均有4个。有些患者出现了许多误差，而另一些患者则很少。这些位移与患者体重和厚度无关，但可能与射野尺寸有关。总之，我们认为在盆腔照射期间应每日使用射野成像设备以提高治疗质量。该系统可帮助放射肿瘤学家在大多数患者（88%）中发现许多体位误差（平均4个），并在照射结束前进行校正。
