CT能谱成像在诊断肿瘤淋巴结转移和肿瘤性质中的作用

Preliminary study of spectral CT imaging in the differential diagnosis of metastatic lymphadenopathy due to various tumors

目的通过对淋巴瘤、肺腺癌、肺鳞癌及胆管癌的转移性淋巴结行能谱CT扫描，探讨能谱成像在鉴别不同肿瘤淋巴结转移性肿大中的应用价值。方法回顾性分析2010年10月至12月间淋巴瘤3例（28个淋巴结）、肺腺癌5例（30个淋巴结）、肺鳞癌4例（24个淋巴结）及胆管癌2例（10个淋巴结）行能谱CT扫描，测量混合能量图像上各个淋巴结在不同能量水平下（40～140keV，间隔10keV）淋巴结的CT值及碘基图和水基图各个淋巴结的碘和水含量，分别对不同肿瘤转移性淋巴结在不同keV下淋巴结的CT值、碘和水含量进行方差分析和t检验。结果观察肿大转移淋巴结的最佳对比噪声比对应的单能量水平是70keV。70keV下淋巴瘤、肺腺癌、肺鳞癌及胆管癌CT值分别（81．36±9．81）、（58．33±21．55）、（56．47±10．62）和（73．57±4．43）HU差异有统计学意义（F=17．29，P〈0．01），其中淋巴瘤与肺腺癌、肺鳞癌及肺鳞癌与胆管癌在CT值之间差异有统计学意义（P〈0．05），淋巴瘤与胆管癌及肺腺癌与胆管癌CT值差异有统计学意义（P〈0．05），肺腺癌与肺鳞癌CT值的差异未见统计学意义（P〉0．05）。淋巴瘤、肺腺癌、肺鳞癌及胆管癌的碘含量分别为（1．93±0．04）、（1．16±0．15）、（1．25±0．21）和（1．44±0．04）g／L；淋巴瘤、肺腺癌、肺鳞癌及胆管癌的水含量分别为（1029．40±20．85）、（1024．98±11．19）、（1022．12±12．94）和（1030．87±10．10）g／L；肺腺癌与肺鳞癌的转移性淋巴结的碘含量之间差异未见统计学意义（t=1．77，P〉0．05），其他不同肿瘤转移性淋巴结的碘含量之间有统计学意义（P均〈0．05）；各不同肿瘤转移性淋巴结的水含量之间未见统计学意义（P均〉0．05）。结论CT能谱成像通过应用碘含量及低能量下的CT值，对不同来源的转移性淋巴结的鉴别有较大意义，70keV单能量图像显示肿大转移性淋巴结最清楚。

Objective To investigate the feasibility of differentiating lymph node metastases of four types of primary tumors （lymphoma, lung adenocarcinoma, lung squamous cell carcinoma and cholangiocarcinoma） using gemstone spectral imaging （GSI） . Methods Three cases with lymphoma （28 lymph node）, five cases with lung adenoearcinoma （30 lymph node）, four cases with lung squamous cell carcinoma（24 lymph node） and two cases with cholangiocarcinoma（ 10 lymph node） were evaluated by germstona spectra imaging CT scans. Imaging protocol included unenhanced conventional CT scan （120 kVp） ,enhanced GSI （80/140 kVp） on arterial phase and conventional CT scan （120 kVp） on portal phase. CT attenuation values of lymph nodes in the monochromatic images at 11 sets of keV levels （40- 140 keV, 10 keV step） and the iodine and water contents of these lymph nodes were measured. All results were analyzed with ANOVA and t test. Results The optimal monochromatic level was 70 keV for the optimal contrast-noise ratio （CNR） of metastatic lymphadenopathy. The CT attenuation values of metastatic lymphadenopathy were （81.36 ± 9.81 ）, （58.33 ± 21.55 ）, （ 56.47 ± 10. 62） and （ 73.57 ± 4.43 ） HU, respectively, at 70 keV（ F = 17.29, P 〈0.01 ）. There were significant differences in CT attenuation values between lymphoma and lung adenocarcinoma, between lymphoma and lung squamous cell carcinoma and between lung squamous cell carcinoma and eholangiocareinoma （ P 〈 0. 05 ） . The differences in CT attenuation values were significant between eholangiocarcinoma and lung squamous cell carcinoma, between cholangiocarcinoma and lymphoma （ P 〈 0. 05 ）. There was no difference in CT attenuation values at all 11 sets of keV levels between lung squamous cell carcinoma and lung adenocarcinoma （ P 〉 0. 05 ）. The iodine contents of lymphoma, lung adenocarcinoma, lung squamous cell carcinoma and eholangiocarcinoma were （1.93±0.04）, （1.16±0.15）, （1.25 ±0.21） and （1.44 ±0.04） g/L, respectively. The water contents of lymphoma, lung adenocareinoma, lung squamous cell carcinoma and cholangiocareinoma were （1029.40± 20.85）, （1024.98 ± 11.19）, （1022.12 ± 12.94） and （1030.87 ± 10.10） g/L, respectively. Except between lung squamous cell carcinoma and lung adenoearcinoma, the differences in the iodine contents of metastatic lymphadenopathy were significant among tumors （ P 〈 0. 05 ）. There was no difference in the water contents of metastatic lymphadenopathy among tumors （ P 〉 0. 05 ）. Conclusions Although CT spectral imaging fails to differentiate metastatic lymphadenopathy of lung adenoeareinoma and lung squamous cell carcinoma, it is also a promising method of distinguishing metastatic lymphadenopathy of malignant tumors by CT attenuation values in monochromatic images and iodine contents in material density images. The optimal monochromatic level was determined to be at 70 keV for providing the optimal CNR of metastatic lymphadenopathy.