Leter Edward M, Cademartiri Filippo, Levendag Peter C, Flohr Thomas, Stam Henk, Nowak Peter J
Department of Radiotherapy, Erasmus Medical Center, Rotterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2005 Jul 1;62(3):888-92. doi: 10.1016/j.ijrobp.2005.03.002.
We used four-dimensional multislice spiral computed tomography (MSCT) to determine respiratory lung-tumor motion and compared this strategy to common clinical practice in conformal radiotherapy treatment-planning imaging.
The entire lung volume of 10 consecutive patients with 14 lung metastases were scanned by a 16-slice MSCT. During the scans, patients were instructed to breathe through a spirometer that was connected to a laptop computer. For each patient, 10 stacks of 1.5-mm slices, equally distributed throughout the respiratory cycle, were reconstructed from the acquired MSCT data. The lung tumors were manually contoured in each data set. For each patient, the tumor-volume contours of all data sets were copied to 1 data set, which allowed determination of the volume that encompassed all 10 lung-tumor positions (i.e., the tumor-traversed volume [TTV]) during the respiratory cycle. The TTV was compared with the 10 tumor volumes contoured for each patient, to which an empiric respiratory-motion margin was added. The latter target volumes were designated internal-motion included tumor volume (IMITV).
The TTV measurements were significantly smaller than the reference IMITV measurements (5.2 +/- 10.2 cm(3) and 10.1 +/- 13.7 cm(3), respectively). All 10 IMITVs for 2 of the 4 tumors in 1 subject completely encompassed the TTV. All 10 IMITVs for 3 tumors in 2 patients did not show overlap with up to 35% of the corresponding TTV. The 10 IMITVs for the remaining tumors either completely encompassed the corresponding TTV or did not show overlap with up to 26% of the corresponding TTV.
We found that individualized determination of respiratory lung-tumor motion by four-dimensional respiratory-gated MSCT represents a better and simple strategy to incorporate periodic physiologic motion compared with a generalized approach. The former strategy can, therefore, improve common and state-of-the-art clinical practice in conformal radiotherapy.
我们采用四维多层螺旋计算机断层扫描（MSCT）来确定肺部肿瘤的呼吸运动，并将该策略与适形放疗治疗计划成像中的常规临床实践进行比较。
对连续10例患有14处肺转移瘤的患者的全肺容积进行16层MSCT扫描。扫描过程中，指导患者通过连接到笔记本电脑的肺活量计进行呼吸。对于每位患者，从获取的MSCT数据中重建出10组1.5毫米厚的切片，这些切片在呼吸周期中均匀分布。在每个数据集中手动勾勒出肺部肿瘤的轮廓。对于每位患者，将所有数据集的肿瘤体积轮廓复制到一个数据集中，这样就能确定在呼吸周期中包含所有10个肺部肿瘤位置的体积（即肿瘤遍历体积[TTV]）。将TTV与为每位患者勾勒出的10个肿瘤体积进行比较，并为后者添加经验性呼吸运动边界。后一种靶体积被指定为包含内部运动的肿瘤体积（IMITV）。
TTV测量值显著小于参考IMITV测量值（分别为5.2±10.2立方厘米和10.1±13.7立方厘米）。1名受试者的4个肿瘤中的2个肿瘤的所有10个IMITV完全包含了TTV。2名患者的3个肿瘤的所有10个IMITV与相应TTV的重叠率高达35%时未显示出重叠。其余肿瘤的10个IMITV要么完全包含相应的TTV，要么与相应TTV的重叠率高达26%时未显示出重叠。
我们发现，与通用方法相比，通过四维呼吸门控MSCT对肺部肿瘤呼吸运动进行个体化测定是一种更好且简单的纳入周期性生理运动的策略。因此，前一种策略可以改善适形放疗中的常规和先进临床实践。
