Mageras Gig S, Pevsner Alex, Yorke Ellen D, Rosenzweig Kenneth E, Ford Eric C, Hertanto Agung, Larson Steven M, Lovelock D Michael, Erdi Yusuf E, Nehmeh Sadek A, Humm John L, Ling C Clifton
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
Int J Radiat Oncol Biol Phys. 2004 Nov 1;60(3):933-41. doi: 10.1016/j.ijrobp.2004.06.021.
We investigate the characteristics of lung tumor motion measured with respiration-correlated computed tomography (RCCT) and examine the method's applicability to radiotherapy planning and treatment.
Six patients treated for non-small-cell lung carcinoma received a helical single-slice computed tomography (CT) scan with a slow couch movement (1 mm/s), while simultaneously respiration is recorded with an external position-sensitive monitor. Another 6 patients receive a 4-slice CT scan in a cine mode, in which sequential images are acquired for a complete respiratory cycle at each couch position while respiration is recorded. The images are retrospectively resorted into different respiration phases as measured with the external monitor (4-slice data) or patient surface displacement observed in the images (single-slice data). The gross tumor volume (GTV) in lung is delineated at one phase and serves as a visual guide for delineation at other phases. Interfractional GTV variation is estimated by scaling diaphragm position variations measured in gated radiographs at treatment with the ratio of GTV:diaphragm displacement observed in the RCCT data.
Seven out of 12 patients show GTV displacement with respiration of more than 1 cm, primarily in the superior-inferior (SI) direction; 2 patients show anterior-posterior displacement of more than 1 cm. In all cases, extremes in GTV position in the SI direction are consistent with externally measured extremes in respiration. Three patients show evidence of hysteresis in GTV motion, in which the tumor trajectory is displaced 0.2 to 0.5 cm anteriorly during expiration relative to inspiration. Significant (>1 cm) expansion of the GTV in the SI direction with respiration is observed in 1 patient. Estimated intrafractional GTV motion for gated treatment at end expiration is 0.6 cm or less in all cases; however; interfraction variation estimates (systematic plus random) are more than 1 cm in 3/9 patients.
Respiration-correlated CT can be performed with currently available CT equipment and acquisition settings. RCCT provides not only three-dimensional information on intrafractional tumor motion and deformation, but also allows estimates of interfractional tumor variation when combined with radiographic measurements of diaphragm position variation during treatment.
我们研究了利用呼吸相关计算机断层扫描（RCCT）测量的肺肿瘤运动特征，并检验该方法在放射治疗计划和治疗中的适用性。
6例接受非小细胞肺癌治疗的患者接受了螺旋单层计算机断层扫描（CT），扫描时检查床移动缓慢（1毫米/秒），同时使用外部位置敏感监测器记录呼吸情况。另外6例患者以电影模式接受4层CT扫描，在每个检查床位置采集完整呼吸周期的序列图像，同时记录呼吸情况。图像根据外部监测器测量的结果（4层数据）或图像中观察到的患者体表位移（单层数据），进行回顾性重新分类到不同的呼吸阶段。在一个阶段勾画出肺内的大体肿瘤体积（GTV），并作为其他阶段勾画的视觉指导。通过将治疗时门控X线片上测量的膈肌位置变化按RCCT数据中观察到的GTV:膈肌位移比例进行缩放，来估计分次间GTV的变化。
12例患者中有7例显示GTV随呼吸的位移超过1厘米，主要在上下（SI）方向；2例患者显示前后位移超过1厘米。在所有病例中，GTV在SI方向的位置极值与外部测量的呼吸极值一致。3例患者显示GTV运动存在滞后现象，其中肿瘤轨迹在呼气时相对于吸气向前位移0.2至0.5厘米。在1例患者中观察到GTV在SI方向随呼吸有显著（>1厘米）的扩张。所有病例中，呼气末期门控治疗的分次内GTV运动估计值均为0.6厘米或更小；然而，3/9例患者的分次间变化估计值（系统误差加随机误差）超过1厘米。
利用现有的CT设备和采集设置即可进行呼吸相关CT检查。RCCT不仅能提供关于分次内肿瘤运动和变形的三维信息，而且与治疗期间膈肌位置变化的X线测量相结合时，还能估计分次间肿瘤的变化。
