Fox Timothy, Simon Edmund L, Elder Eric, Riffenburgh Robert H, Johnstone Peter A S
Radiation Oncology Department, Emory University School of Medicine, Atlanta, GA 30322, United States.
Lung Cancer. 2007 Apr;56(1):69-75. doi: 10.1016/j.lungcan.2006.11.019. Epub 2006 Dec 28.
Accurate radiation targeting and delivery within the chest and abdomen is greatly affected by the respiratory cycle. Prior methods to minimize respiratory effect include breath-hold and abdominal compression techniques; these are subject to error secondary to variable inspiration/expiration volumes, or by the nature of many cancer patients having inherently poor respiratory function. However, advanced technology called free breathing gated delivery (FBGD) allows patients to breath normally during treatment. The photon beam is on only during a particular prescribed percentage of the respiratory cycle where the target tumor volume is minimized. Consequently, by using an intermittent beam, the time required to treat a patient is increased. No previous study has described the patient throughput ramifications of FBGD.
At Emory clinic, a gated treatment delivery system was inaugurated into clinical use beginning in June 2004. As of 12/31/2004, 15 patients have completed treatment with FBGD. The majority of patients had lung cancer (n=12) with single cases of adrenal metastasis, thymoma, and atypical carcinoid. Over 900 gated treatment fields (approximately 375 treatment sessions) were reviewed on an IRB-approved retrospective protocol. Records from the record-and-verify (R&V) system were queried using automated database mining software to obtain the treatment room time, treatment field time, beam-on time (BOT), dose rate, and monitor units (MU) for each treatment. The presence or absence of a dynamic wedge was also noted, as was the prescribed percent of the respiratory cycle treated. For comparison purposes, 13 non-gated lung cancer patients (lesions were not moving with respiration) were selected from the R&V database.
Patients receiving FBGD required significantly more time for treatment delivery. The time required for FBGD was, on average, 5.5 times greater (range 1.2-12.2) than calculated BOT without gating. Time was further increased with the use of a dynamic wedge, which occurred in 45% (28/62) of the planned fields. The use of MV imaging also increased the time for FBGD treatment sessions by more than 7.5 min on average.
FBGD uniformly increases the time required for RT delivery, and MV imaging and dynamic wedging even more so. Even though this technology more accurately targets tumor volumes while sparing normal tissue, the patient throughput issue may deter this technology from being implemented into busy clinical practices.
胸部和腹部内精确的放射靶向和投送会受到呼吸周期的极大影响。以往尽量减少呼吸影响的方法包括屏气和腹部压迫技术；但由于吸气/呼气量变化，或者许多癌症患者本身呼吸功能较差，这些方法容易出现误差。然而，一种名为自由呼吸门控投送（FBGD）的先进技术可让患者在治疗期间正常呼吸。光子束仅在呼吸周期中目标肿瘤体积最小化的特定规定百分比期间开启。因此，通过使用间歇光束，治疗患者所需的时间会增加。此前尚无研究描述FBGD对患者通量的影响。
在埃默里诊所，一种门控治疗投送系统于2004年6月开始投入临床使用。截至2004年12月31日，15例患者已完成FBGD治疗。大多数患者患有肺癌（n = 12），还有1例肾上腺转移瘤、胸腺瘤和非典型类癌患者各1例。根据一项经机构审查委员会批准的回顾性方案，对900多个门控治疗野（约375个治疗疗程）进行了审查。使用自动化数据库挖掘软件查询记录与验证（R&V）系统中的记录，以获取每次治疗的治疗室时间、治疗野时间、束流开启时间（BOT）、剂量率和监测单位（MU）。还记录了是否使用动态楔形板以及治疗的呼吸周期规定百分比。为作比较，从R&V数据库中选取了13例非门控肺癌患者（病灶不随呼吸移动）。
接受FBGD治疗的患者需要显著更多的治疗投送时间。FBGD所需时间平均比无门控时计算出的BOT长5.5倍（范围为1.2 - 12.2倍）。使用动态楔形板会进一步增加时间，在45%（28/62）的计划野中使用了动态楔形板。MV成像的使用也使FBGD治疗疗程的时间平均增加超过7.5分钟。
FBGD一致地增加了放疗投送所需时间，MV成像和动态楔形板更是如此。尽管这项技术能更精确地靶向肿瘤体积同时保护正常组织，但患者通量问题可能会阻碍该技术在繁忙的临床实践中得到应用。
