Yin Li-Jie, Yu Xiao-Bin, Ren Yan-Gang, Gu Guang-Hai, Ding Tian-Gui, Lu Zhi
Department of Radiotherapy, Dalian Central Hospital, Dalian 116033, China.
Multidiscip Respir Med. 2013 Mar 18;8(1):21. doi: 10.1186/2049-6958-8-21.
To investigate the utilization of PET-CT in target volume delineation for three-dimensional conformal radiotherapy in patients with non-small cell lung cancer (NSCLC) and atelectasis.
Thirty NSCLC patients who underwent radical radiotherapy from August 2010 to March 2012 were included in this study. All patients were pathologically confirmed to have atelectasis by imaging examination. PET-CT scanning was performed in these patients. According to the PET-CT scan results, the gross tumor volume (GTV) and organs at risk (OARs, including the lungs, heart, esophagus and spinal cord) were delineated separately both on CT and PET-CT images. The clinical target volume (CTV) was defined as the GTV plus a margin of 6-8 mm, and the planning target volume (PTV) as the GTV plus a margin of 10-15mm. An experienced physician was responsible for designing treatment plans PlanCT and PlanPET-CT on CT image sets. 95% of the PTV was encompassed by the 90% isodose curve, and the two treatment plans kept the same beam direction, beam number, gantry angle, and position of the multi-leaf collimator as much as possible. The GTV was compared using a target delineation system, and doses distributions to OARs were compared on the basis of dose-volume histogram (DVH) parameters.
The GTVCT and GTVPET-CT had varying degrees of change in all 30 patients, and the changes in the GTVCT and GTVPET-CT exceeded 25% in 12 (40%) patients. The GTVPET-CT decreased in varying degrees compared to the GTVCT in 22 patients. Their median GTVPET-CT and median GTVPET-CT were 111.4 cm3 (range, 37.8 cm3-188.7 cm3) and 155.1 cm3 (range, 76.2 cm3-301.0 cm3), respectively, and the former was 43.7 cm3 (28.2%) less than the latter. The GTVPET-CT increased in varying degrees compared to the GTVCT in 8 patients. Their median GTVPET-CT and median GTVPET-CT were 144.7 cm3 (range, 125.4 cm3-178.7 cm3) and 125.8 cm3 (range, 105.6 cm3-153.5 cm3), respectively, and the former was 18.9 cm3 (15.0%) greater than the latter. Compared to PlanCT parameters, PlanPET-CT parameters showed varying degrees of changes. The changes in lung V20, V30, esophageal V50 and V55 were statistically significant (Ps< 0.05 for all), while the differences in mean lung dose, lung V5, V10, V15, heart V30, mean esophageal dose, esophagus Dmax, and spinal cord Dmax were not significant (Ps> 0.05 for all).
PET-CT allows a better distinction between the collapsed lung tissue and tumor tissue, improving the accuracy of radiotherapy target delineation, and reducing radiation damage to the surrounding OARs in NSCLC patients with atelectasis.
探讨正电子发射断层显像-计算机断层扫描（PET-CT）在非小细胞肺癌（NSCLC）合并肺不张患者三维适形放疗靶区勾画中的应用。
纳入2010年8月至2012年3月期间接受根治性放疗的30例NSCLC患者。所有患者均经影像学检查病理确诊为肺不张。对这些患者进行PET-CT扫描。根据PET-CT扫描结果，分别在CT和PET-CT图像上勾画大体肿瘤体积（GTV）和危及器官（OARs，包括肺、心脏、食管和脊髓）。临床靶体积（CTV）定义为GTV外放6-8 mm的边界，计划靶体积（PTV）定义为GTV外放10-15 mm的边界。由一名经验丰富的医师负责在CT图像集上设计治疗计划PlanCT和PlanPET-CT。95%的PTV被90%等剂量曲线包绕，两个治疗计划尽可能保持相同的射野方向、射野数、机架角度和多叶准直器位置。使用靶区勾画系统比较GTV，并根据剂量体积直方图（DVH）参数比较OARs的剂量分布。
30例患者的GTVCT和GTVPET-CT均有不同程度变化，其中12例（40%）患者的GTVCT和GTVPET-CT变化超过25%。22例患者的GTVPET-CT较GTVCT有不同程度减小。其GTVPET-CT中位数和GTVCT中位数分别为111.4 cm³（范围37.8 cm³-188.7 cm³）和155.1 cm³（范围76.2 cm³-301.0 cm³），前者较后者小43.7 cm³（28.2%）。8例患者的GTVPET-CT较GTVCT有不同程度增大。其GTVPET-CT中位数和GTVCT中位数分别为144.7 cm³（范围125.4 cm³-178.7 cm³）和125.8 cm³（范围105.6 cm³-153.5 cm³），前者较后者大18.9 cm³（15.0%）。与PlanCT参数相比,PlanPET-CT参数有不同程度变化。肺V20、V30、食管V50和V55的变化有统计学意义（均P<0.05），而平均肺剂量、肺V5、V10、V15、心脏V30、平均食管剂量、食管Dmax和脊髓Dmax的差异无统计学意义（均P>0.05）。
PET-CT能更好地区分萎陷肺组织与肿瘤组织，提高NSCLC合并肺不张患者放疗靶区勾画的准确性，并减少对周围OARs的放射损伤。
