Mori Shinichiro, Chen George T Y, Endo Masahiro
Department of Radiation Oncology, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA.
Int J Radiat Oncol Biol Phys. 2007 Sep 1;69(1):308-17. doi: 10.1016/j.ijrobp.2007.05.018.
To analyze the water equivalent pathlength (WEL) fluctuations resulting from cardiac motion and display these variations on a beam's-eye-view image; the analysis provides insight into the accuracy of lung tumor irradiation with heavy charged particle beams.
Volumetric cine computed tomography (CT) images were obtained on 7 lung cancer patients under free-breathing conditions with a 256-multislice CT scanner. Cardiac phase was determined by selecting systole and diastole. A WEL difference image (DeltaWEL) was calculated by subtracting the WEL image at end-systole from that at end-diastole at respiratory exhalation phase. Two calculation regions were defined: Region 1 was limited to the volume defined by planes bounding the heart; Region 2 included the entire body thickness for a given beam's-eye-view angle.
The DeltaWEL values observed in Region 1 showed fluctuations at the periphery of the heart that varied from 20.4 (SD, 5.2) mm WEL to -15.6 (3.2) mm WEL. The areas over which these range perturbation values were observed were 36.8 (32.4) mm(2) and 6.0 (2.8) mm(2) for positive and negative WEL, respectively. The WEL fluctuations in Region 2 increased by approximately 3-4 mm WEL, whereas negative WEL fluctuations changed by approximately -4 to -5 mm WEL, compared with WEL for Region 1; areas over 20 mm WEL changes in Region 2 increased by 9 mm(2) for positive DeltaWEL and 2 mm(2) for negative DeltaWEL.
Cine CT with a 256-multislice CT scanner captures both volumetric cardiac and respiratory motion with a temporal resolution sufficient to estimate range fluctuations by these motions. This information can be used to assess the range perturbations that charged particle beams may experience in irradiation of lung or esophageal tumors adjacent to the heart.
分析心脏运动引起的水等效路径长度（WEL）波动，并在射野视角图像上显示这些变化；该分析有助于深入了解重带电粒子束对肺部肿瘤照射的准确性。
使用256层CT扫描仪在7例肺癌患者自由呼吸状态下获取容积电影计算机断层扫描（CT）图像。通过选择收缩期和舒张期来确定心脏相位。通过在呼气末相位从舒张末期的WEL图像中减去收缩末期的WEL图像来计算WEL差值图像（DeltaWEL）。定义了两个计算区域：区域1限于由包围心脏的平面所界定的体积；区域2包括给定射野视角角度下的整个身体厚度。
在区域1中观察到的DeltaWEL值显示心脏周边存在波动，范围从20.4（标准差，5.2）mm WEL到 -15.6（3.2）mm WEL。观察到这些范围扰动值的区域，对于正WEL和负WEL分别为36.8（32.4）mm²和6.0（2.8）mm²。与区域1的WEL相比，区域2中的WEL波动增加了约3 - 4 mm WEL，而负WEL波动变化约为 -4至 -5 mm WEL；区域2中WEL变化超过20 mm的区域，对于正DeltaWEL增加了9 mm²，对于负DeltaWEL增加了2 mm²。
256层CT扫描仪的电影CT能够以足够的时间分辨率捕捉心脏和呼吸的容积运动，以估计这些运动引起的射程波动。该信息可用于评估带电粒子束在照射心脏附近的肺部或食管肿瘤时可能经历的射程扰动。
