不同图像灰度-密度校准曲线对螺旋断层放疗系统剂量计算的影响  

Effect of different image value-density calibration table on dose calculation of helical tomotherapy system

作　　者：叶柳清 洪文松[1] 黎静[2] 文婷[2] 张晋建[2] 

机构地区：[1]广东省第二人民医院放疗科,广东广州510317 [2]广州军区广州总医院螺旋断层放疗中心,广东广州510010

出　　处：《中国医学物理学杂志》2016年第5期505-509,共5页Chinese Journal of Medical Physics

基　　金：广东省社会发展领域科技计划项目(2013B021800051)

摘　　要：目的:探讨不同图像灰度-密度校准曲线(IVDT)对螺旋断层放疗系统(Tomo)计划剂量计算的影响。方法:用3台不同CT设备分别以头部、胸部、腹部的扫描条件扫描含有已知密度插件的Tomo phantom模体,采集所有密度插件CT值并取其平均值,并在Tomo计划系统中建立IVDT曲线。然后选取头部、胸部、腹部各5例患者,同时用3种不同的IVDT曲线在Tomo计划系统中用相同的射野宽度、螺距和调制因子进行计划设计,比较3种方案计划靶区的均匀性指数、适形度指数、最大值、最小值、出束时间和危及器官的剂量体积直方图指标的差异。结果:两台千伏级CT机所得IVDT曲线基本一致,而兆伏级CT所得IVDT曲线在密度为0~1.2 g/cm^3处与其它两条IVDT曲线几乎相近,在密度为1.2 g/cm^3(CT值200 HU)附近有明显的拐点。采用单因素方差分析可得:3种方案靶区均匀性指数、适形度指数、最大值、最小值和头部、胸部、腹部各正常组织的剂量学参数差异均无统计学意义(P>0.05)。结论:用不同CT机、不同扫描条件定位时,用采集的CT值建立IVDT曲线有微小差异,但是不同IVDT曲线对剂量计算无统计学差异,故无需重新建立新的IVDT曲线,可提高物理工作者的工作效率。Objective To research on the effect of different image value-density calibration table（IVDT） on the dose calculation of tomotherapy system. Methods Tomo phantom with plug-ins of known density was scanned by three different CT machines respectively based on the scan conditions of head, chest and abdomen to gather the CT values of all plug-ins and take the average. And IVDT was established in tomotherapy planning system. Fifteen patients respectively treated with tomotherapy for head, chest and abdomen were selected, each of five patients. Three different IVDT with the same field width, pitch, modulation factorwere applied in tomotherapy planning system to design plans. The differences in homogeneity index（HI）, conformal index（CI）, maximum, minimum, delivered time and the dose-volume histogram of organs at risk were compared among three plans. Results The two k V-CT machines obtained the similar IVDT, almost similar with the IVDT obtained by the m V-CT at density of 0-1.2 g/cm^3. Nearby the density of 1.2 g/cm^3（CT value=200HU）, the IVDT obtained by the m V-CT showed significant turning point. The analyze results of single factor analysis of variance available showed no significant differences were found in HI, CI, maximum, minimum, and the dose parameters of head, chest, abdomen among the three plans（P0.05）. Conclusion With different CT machines and scanning conditions of positioning, the IVDT curve established based on the collected CT values has a small difference. The analyzed results proves IVDT has no significant effects on dose calculation, so IVDT don＇t need to be re-established, which improves the work efficiency of physical workers.

关 键 词：图像灰度-密度校准曲线 螺旋断层放疗系统 剂量体积直方图 电子密度 危及器官 剂量学 

分 类 号：R815.6[医药卫生—放射医学]