Application Of Spectral Computed Tomography In Diagnosis And Differential Diagnosis Of Thyroid Lesions

Part 1The value of spectral CT in differentiating between benign and malignant thyroid lesionsObjective To analyze the morphological features and spectral parameters of benign and malignant thyroid lesions,and to explore the value of spectral CT in the differential diagnosis of thyroid lesions.Materials and Methods Patients with thyroid lesions underwent neck CT scan on a spectral CT(GE Discovery 750HD)with spectral mode from March 2014 to December 2016.The polychromatic images and a set of monochromatic images were obtained and the morphological features and spectrum parameters were analyzed on the PACS terminal and AW4.6 workstation.The iodine concentration(IC)of lesions,the normal thyroid and common carotid arteries were measured on the iodine-based material images.The water concentration(WC)of the lesions,normal thyroid and common carotid arteries were measured on the water-based material images.The normalized iodine concentration to arterial(NICA),the normalized iodine concentration to normal thyroid(NICT)and slope of spectral curve(λHU)were calculated.The statistical analysis was performed by using SPSS 19.0 software.The area under the receiver operating characteristic(ROC)curve was used to determine the diagnostic capability of the lesion.A value of P<0.05 for the difference was statistically significant.Logistic regression analysis was used to evaluate the diagnostic efficacy of spectral parameters and morphological features.Results A total of 230 lesions were found in 225 patients(57benign lesions,173 malignant lesions).There were significant differences between benign and malignant lesions in the border,microcalcifications and lymph node metastasis(P<0.05).The sensitivity of differential malignant tumors from benign ones was 76.3%,25.4%and 68.8%respectively.The specificity was 63.2%,96.5%and 94.7%respectively.The accuracy was 73.0%,43.0%and 75.2%respectively.The sensitivity,specificity and accuracy of combined the three features were 73.4%,93.0%and 82.6%,respectively.There was no significant difference in the parameters between the three benign groups except the IC values(P<0.05).There was no significant difference in IC between nodular goiter and adenoma,nodular goiter and thyroiditis,while the IC value of adenoma was significantly higher than that of thyroiditis,the difference was statistically significant(P=0.006,P<0.05).The differences of IC,NICT and λHU were statistically significant between nodular goiter and malignant tumor,adenoma and malignant tumor,while there were no statistical differences between the thyroiditis and malignant tumors in all the parameters.The threshold of IC<3.2 mg/ml,NICT<0.55 and λHU<3.73 were the predictor of malignancy that demonstrating 71.1%,46.2%and 68.2%in sensitivity respectively,the specificity was 68.4%,84.2%and 75.4%,respectively,the accuracy was 70.4%,55.7%and 70.0%.The diagnostic parameters of IC,NICT,λHU combined with morphological features included unclear borders,microcalcification and cervical lymph nodes metastatic were higher in the diagnosis of malignancy,the sensitivity,specificity and accuracy were 86.1%,86.0%and 83.9%respectively.Conclusion Spectral CT quantitatively evaluates the iodine concentration of thyroid lesions,which is valuable for benign and malignant identification.Combining the spectral parameters with the morphological features is helpful for differentiating the thyroid lesions.Part 2Preliminary study on spectral parameters of various pathological types of malignant tumors of thyroidObjective To analyze the imaging manifestations and spectral parameters of various pathological types of malignant tumors of thyroid.Materials and Methods 67 cases of malignant thyroid tumors were included in the retrospective study.The morphological manifestations and the spectral parameters were analyzed.All the patients underwent spectral CT scan on a Discovery 750HD scanner in GSI mode.The morphological manifestations of lesions were analyzed on the optimal monochromatic images.The iodine concentration(IC),water concentration(WC),spectral HU curve slope values(λHU)were measured and analyzed by GSI Viewer.SPSS 19.0 software was used for statistical analysis.Results The morphological features of malignant thyroid tumors were as follows:single lesion(57 cases,85.1%),irregular shape(46 cases,68.7%),indistinct margin(45 cases,67.2%),heterogeneous density(48 cases,71.6%)and detection of calcification(21 cases,31.3%).There was no significant difference among various types of malignant tumors on water concentration(P>0.05).The IC and λHU values of papillary carcinoma,follicular carcinoma and medullary carcinoma were higher than those of anaplastic carcinoma and lymphoma,the difference was statistically significant(P<0.05).The IC values of the lesions from more to less were follicular carcinoma,medullary carcinoma.papillary carcinoma,lymphoma and anaplastic carcinoma,respectively.The λHU values were also consistent with the IC.There were no significant differences in the IC and λHU between papillary carcinoma,follicular carcinoma and medullary carcinoma(P>0.05).There was no significant difference between lymphoma and anaplastic carcinoma(P>0.05).However anyone of medullary carcinoma,papillary carcinoma and follicular carcinoma,compared with anyone of lymphoma and anaplastic carcinoma,respectively,the difference was statistically significant(P<0.05).Conclusion The morphological features and spectrum parameters are different in various pathological types of thyroid malignant tumors,and it is helpful for the diagnosis and differential diagnosis.Part 3Preliminary study on spectral CT in the diagnostic value of papillary thyroid microcarcinomaObjective To retrospectively analyze the clinical value of spectral CT imaging for detecting and diagnosing papillary thyroid microcarcinoma(PTMC).Materials and Methods 33 cases(35 lesions)with PTMC confirmed by surgical pathology from January 2015 to January 2016 were included in this retrospective study.All the patients underwent Spectral CT scan on a Discovery 750HD scanner.The spectral CT images were divided into 3 groups:polychromatic image(group A),optimal monochromatic image(group B),and the fused image which blended optimal monochromatic image with iodine-based material decomposition image together(group C).The image qualities of group A and B were evaluated objectively,and the detection abilities of the 3 groups were evaluated subjectively.The image manifestations and lesion spectral parameters were analyzed.SPSS 19.0 software was used for statistical analysis.Results The optimal CNR level was(65.96±4.01)keV(range from 62 to 75keV).The CNR of the optimal monochromatic image of spectral CT was higher than that of the polychromatic image(t=-5.626,P=0.000),and the noise of optimal monochromatic image was lower than that of polychromatic image(t=12.00,P=0.000),and the differences were significant(P<0.05).The detection rate of the 3 groups of images for microcarcinoma lesions were 91.4%(32/35),97.1%(34/35),and 100%(35/35)respectively,while the subjective scores of the 3 image groups of images were 2.54±1.15,3.31±0.93,and 3.46±0.74 respectively.The detection ability of fused image was better than that of polychromatic image and similar to that of optimal monochromatic image.The characteristics of microcarcinoma were irregular shape(19 cases,54.3%),indistinct margin(24 cases,68.6%),heterogeneous density(24 cases,68.6%),detection of microcalcification(16 cases,45.7%),and lymph node metastasis(20 cases,60.6%).The lesions’ average iodine concentration and the average spectral HU curve slope values were 2.5±l.Omg/ml(range from 0.9～4.3mg/ml)and 2.99±1.59(-0.83～5.38),respectively.Conclusion Spectral CT could provides more detailed information for the diagnosis of PTMC,and the fused image with the optimal monochromatic image and iodine-based material decomposition image may be useful for detecting and diagnosing PTMC.