目的 分析双能CT（dual-energy CT，DECT）对下咽癌光子调强放射治疗（intensity modulated radiation therapy， IMRT）剂量计算的差异及剂量学特点。 方法 选取2019年6月‒12月在山东省第二人民医院接受根治性放疗的下咽癌患者18例，应用双能CT对患者进行模拟定位，将双能CT图像重建为单能40、60、80、100、120、140 keV的单序列 CT图像，获得不同能量下电子密度曲线并对CT图像赋值获得不同kV级和keV级的单能CT图像。将所有患者调强计划分别复制到不同能级CT图像并进行剂量计算，比较计划靶区（planning target volume， PTV）和危及器官（organ at risk， OAR）的剂量学差异。 结果 脑干、甲状腺和下颌骨等组织在不同能级CT图像上CT值差异较大，平均变化幅度为55.32% ~ 85.61%；不同keV能级CT图像PTV的2%靶区体积所对应剂量（D_2%）、、98%靶区体积所对应剂量（D_98%）、适形指数（conformal index， CI）和均匀性指数（homogeneity index， HI）等剂量学指标的差异无统计学意义（P > 0.05）；下颌下腺平均剂量（D_mean）、下颌骨最小剂量（D_min）和脑干最大剂量（D_max）在不同kV级能级CT图像变化显著，分别为2.5%、2.1%和4.2%（P 均 < 0.05），其余器官变化均 < 1.4%（P > 0.05）；下颌下腺D_mean、下颌骨D_min和脑干D_max不同keV伪CT图像变化显著，分别为5.41%、6.56%和4.21%（P < 0.05），其余器官变化均 < 1.52%（P > 0.05）；相同能量下不同电子密度曲线图像比较OAR剂量时，除40 、60 kV/keV图像外，下颌骨D_max、D_min和D_mean在所有同能量的图像间差异均有统计学意义（P均< 0.05）。 结论 CT值计算误差对下咽癌IMRT计划剂量计算影响显著，尤其是对靠近骨性结构或被骨性结构包绕的器官，双能CT可提高CT值及IMRT剂量计算的精确度。

Objective To quantitatively analyze the differences of dose calculation and dosimetric characteristics of dual-energy CT （DECT） images for photon intensity modulated radiation therapy （IMRT） of hypopharyngeal carcinoma. Methods Eighteen hypopharyngeal cancer patients who received radical radiotherapy from June 2019 to December 2019 in Shandong second provincial general hospital were selected. DECT was used to simulate for the patients. The DECT images were reconstructed into single-energy CT images of 40， 60， 80， 100， 120 and 140 keV. The electron density curves at different energy levels were obtained. Single-energy CT images of different kV and keV grades can be obtained by assigning the electron density curves to CT images. The IMRT plans of all patients were copied respectively to the different energy images. The dosimetry was recalculated to compare and analyze the dosimetric differences between planning target volume（PTV） and organ at risk（OAR）. Results The CT value of brainstem， thyroid and mandible were significant difference in different energy levels， with the average change range of 55.32% ⁃ 85.61%.The dosimetry indexes of PTV such as dose corresponding to 2% of the target area volume（D_2%）， dose corresponding to 2% of the target area volume（D_98%）， conformal index（CI） and homogeneity index （HI） in different keV images were similar （P > 0.05）.The differences of Dmean to submandibular gland， Dmin to mandible and Dmax to brainstem were significant in different kV images， which were 2.52%， 2.1% and 4.2%， respectively（P < 0.05）. The changes in other organs were less than 1.4% （P > 0.05）.Dmean of submandibular gland， Dmin of mandible and Dmax of brainstem in keV CT images showed significant changes， which were 5.41%， 6.56% and 4.21%， respectively（P < 0.05）. The changes in other organs were all less than 1.52% （P > 0.05）.Comparing the dose of OARsin the same energy images with different electron density curves， there were significant difference in Dmax， Dmin and Dmean of mandible among all images with the same energy （P < 0.05）， except 40 and 60 kV /keV images. Conclusion The calculation error of CT value has a significant influence on the IMRT dose calculation of hypopharyngeal carcinoma， especially for the bone structure or the organ with bone structure surrounding. Dual-energy CT can improve the estimation accuracy of CT value and further improve the calculation accuracy of dose.