The use of active breathing control (ABC) to reduce margin for breathing motion
The use of active breathing control (ABC) to reduce margin for breathing motion
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DOI：
10.1016/s0360-3016(99)00056-5
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发表时间：
1999-07-01
影响因子：
7
通讯作者：
Martinez, AA
中科院分区：
文献类型：
--
作者：
Wong, JW;Sharpe, MB;Martinez, AA
目的：对于胸部和腹部的肿瘤，减少由于呼吸引起的器官运动的治疗裕度会减少将被照射的正常组织的体积。在不增加边际漏失风险的前提下，可以向靶点输送更高剂量。为了确保安全裕度降低，我们研究了使用主动呼吸控制（ABC）暂时抑制患者呼吸的可行性。治疗计划和交付，然后可以在相同的ABC条件下进行，最小限度的呼吸motion.Methods和Materials：ABC装置的构造包括2对流量监测器和呼吸阀，1每个控制到病人的吸气和呼气路径。患者通过连接到ABC设备的吸嘴呼吸。使用个人计算机连续处理呼吸信号，该个人计算机实时显示变化的肺体积。在患者的呼吸模式变得稳定之后，操作员在呼吸循环中的预选阶段激活ABC。然后关闭两个阀门，以减少呼吸运动。12例患者用ABC法保持呼吸运动，以检查他们对手术的接受程度。应用ABC治疗的可行性进行了测试，在主动屏气期间，通过螺旋计算机断层扫描（CT）扫描仪采集体积扫描5例患者。2例患者患有霍奇金病，2例患有转移性肝癌，1例患有肺癌。在接近正常或深吸气结束时的相同呼吸时相采集两次分次内ABC扫描。2例患者在接近正常呼气末时进行了额外的ABC扫描。1周后，对1例霍奇金病患者重复ABC扫描。在1例肝脏患者中，在呼吸周期的7个不同阶段采集ABC扫描，以便于检查与通气相关的肝脏运动。如适用，绘制肺和肝的轮廓。结果：12例患者对ABC法的耐受性良好。当在正常呼气末应用ABC时，1例肺癌患者的最短主动屏气时间为15 s，所有其他患者的最短主动屏气时间为20 s或更长。2例何杰金氏病患者深吸气时应用ABC持续时间> 40 s。在ABC扫描中未观察到与正常呼吸运动相关的扫描伪影。对一小组分次内扫描数据的分析表明，使用ABC，肝脏体积的可重复性约为1%，肺体积的可重复性在6%以内。肝脏的“目标中心”参数的偏移在相同的呼吸阶段小于1 mm，但在呼吸周期的极端情况下大于4 mm。分数间扫描研究表明，每日设置变化的不确定性评估与ABC治疗fractions.Conclusion之间的器官固定的再现性：结果是令人鼓舞的，ABC提供了一种简单的方法，以尽量减少呼吸运动。当应用于CT扫描和治疗时，ABC程序只需要CT扫描仪或医用加速器的标准操作。ABC扫描没有快速螺旋CT扫描常见的运动伪影。当在呼吸周期的不同点采集时，这些ABC扫描显示三维（3D）器官运动，可用于增强治疗计划。在整个治疗过程中，必须量化ABC器官固定的再现性，然后才能应用该程序以减少适形治疗的边缘。(C)1999 Elsevier Science Inc.
Purpose: For tumors in the thorax and abdomen, reducing the treatment margin for organ motion due to breathing reduces the volume of normal tissues that will be irradiated. A higher dose can be delivered to the target, provided that the risk of marginal misses is not increased. To ensure safe margin reduction, we investigated the feasibility of using active breathing control (ABC) to temporarily immobilize the patient's breathing. Treatment planning and delivery can then be performed at identical ABC conditions with minimal margin for breathing motion.Methods and Materials: An ABC apparatus is constructed consisting of 2 pairs of flow monitor and scissor valve, 1 each to control the inspiration and expiration paths to the patient. The patient breathes through a mouth-piece connected to the ABC apparatus. The respiratory signal is processed continuously, using a personal computer that displays the changing lung volume in real-time. After the patient's breathing pattern becomes stable, the operator activates ABC at a preselected phase in the breathing cycle. Both valves are then closed to immobilize breathing motion. Breathing motion of 12 patients were held with ABC to examine their acceptance of the procedure. The feasibility of applying ABC for treatment was tested in 5 patients by acquiring volumetric scans with a spiral computed tomography (CT) scanner during active breath-hold. Two patients had Hodgkin's disease, 2 had metastatic liver cancer, and 1 had lung cancer. Two intrafraction ABC scans were acquired at the same respiratory phase near the end of normal or deep inspiration. An additional ABC scan near the end of normal expiration was acquired for 2 patients. The ABC scans were also repeated 1 week later for a Hodgkin's patient. In 1 liver patient, ABC scans were acquired at 7 different phases of the breathing cycle to facilitate examination of the liver motion associated with ventilation. Contours of the lungs and livers were outlined when applicable. The variation of the organ positions and volumes for the different scans were quantified and compared.Results: The ABC procedure was well tolerated in the 12 patients. When ABC was applied near the end of normal expiration, the minimal duration of active breath-hold was 15 s far 1 patient with lung cancer, and 20 s or more for all other patients. The duration was greater than 40 s for 2 patients with Hodgkin's disease when ABC was applied during deep inspiration. Scan artifacts associated with normal breathing motion were not observed in the ABC scans. The analysis of the small set of intrafraction scan data indicated that with ABC, the liver volumes were reproducible at about 1%, and lung volumes to within 6%. The excursions of a "center of target" parameter for the livers were less than 1 mm at the same respiratory phase, but were larger than 4 mm at the extremes of the breathing cycle. The inter-fraction scan study indicated that daily setup variation contributed to the uncertainty in assessing the reproducibility of organ immobilization with ABC between treatment fractions.Conclusion: The results were encouraging; ABC provides a simple means to minimize breathing motion. When applied for CT scanning and treatment, the ABC procedure requires no more than standard operation of the CT scanner or the medical accelerator. The ABC scans are void of motion artifacts commonly seen on fast spiral CT scans. When acquired at different points in the breathing cycle, these ABC scans show organ motion in three-dimension (3D) that can be used to enhance treatment planning. Reproducibility of organ immobilization with ABC throughout the course of treatment must be quantified before the procedure can be applied to reduce margin for conformal treatment. (C) 1999 Elsevier Science Inc.