胸部肿瘤三维适形放疗剂量造影剂影响的研究

目的:探讨CT造影剂对胸部肿瘤三维适形放疗剂量的影响.方法:共有40例患者入组,其中食管癌患者34例,肺癌患者6例,中位年龄62岁.在相同扫描条件下分别行CT平扫及增强扫描.在图像融合状态下,分别勾画大体靶区(GTV)、临床靶区(CTV)、计划靶区(PTV)以及危及器官,以平扫图像为基础图像进行剂量计算和计划优化,PTV边缘剂量1.8～2.0 Gy/次,总量45～66 Gy,并以此计划进行治疗.利用计划系统图像融合的功能,将在平扫图像(C-)上勾画的靶区及照射野设计复制到增强图像上,在增强图像(C+)上重新进行剂量计算；分别比较C+和C-图像中相对应的单次治疗照射野MU的不同(按照2 Gy/次计算),肿瘤中心点的剂量、肿瘤边缘点的CT值及剂量的不同；并进行统计学分析.结果:40例患者共有205个照射野,其平扫及增强图像射野MU分别为284.55±63.64和283.00±63.21,P=0.120；肿瘤中心点的剂量分别为平扫(45.219 5±9.561 4) Gy、增强(45.211 7±9.614 5)Gy,P=0.772；肿瘤边缘点的剂量分别为平扫(43.837 2±9.304 9)Gy、增强(42.904 5±9.164 5)Gy,P=0.001；边缘点的CT值分别为平扫(140.83±40.55) HU、增强(39.20±20.82) HU,P=0.00.结论:采用适当的扫描条件,对于胸部肿瘤,可以采用直接增强扫描的方式进行CT定位,使用CT增强扫描对放疗计划的优化影响不明显.

Effect of contrast media on 3-dimensional conformal radiotherapy dose for thoracic cancer

OBJECTIVE:To evaluate the radiation dose changes after the use of CT intravenous contrast for patients with thoracic cancer who received 3-dimensional conformal radiotherapy(3DCRT).METHODS:Forty patients were enrolled in our study,including 34 patients with esophageal cancer and 6 with lung cancer.The median age was 62.Each patient received CT scan with or without contrast at the same condition,respectively.Gross tumor volume(GTV),clinical target volume(CTV),planning target volume(PTV) and organs at risk(OAR) were countered on image fusion condition.The dose was calculated and optimized on CT image without contrast.The margin dose of PTV was 1.8-2.0 Gy per fraction and total dose was 45-66 Gy.The targets and beams were copied to CT image with contrast using TPS image fusion function and the doses were re-calculated.The MU of every beam per fraction(according to 2 Gy per fraction),the dose of tumor center,the dose of tumor margin,and the CT value of tumor margin using CT image with or without contrast were calculated and compared.RESULTS:There were 205 beams in 40 patients.The MU of every beam per fraction were 284.55±63.64 for CT image without contrast and 283.00±63.21 for CT image with contrast(P=0.120).The dose of tumor center were(45.219 5±9.561 4) Gy and(45.211 7±9.614 5) Gy,respectively(P=0.772).The dose of tumor margin were(43.837 2±9.304 9) Gy and(42.904 5±9.164 5) Gy(P=0.001).The CT value of tumor margin were(140.83±40.55) HU and(39.20±20.82) HU,respectively(P=0.00).CONCLUSION:Directly CT scan with contrast can be used for thoracic cancer radiotherapy at suitable scan conditions.