Application Of Spectral Computed Tomography In Diagnosis Of Thyroid Nodular Lesions

BackgroundsThyroid disease is increasing year by year in China and around the world,its diagnosis、treatment hotspots and disputes are becoming increasingly prominent.Especially for thyroid papillary carcinoma(PTC),the treatment options are not uniform.Some scholars believe that PTC is mostly in a subclinical state,and can be actively followed up and observed,and the timing of surgery is to be determined.Some scholars believe that cervical lymph node metastasis occurs early in PTC and should be operated actively,but there are still controversies about the choice of surgical resection for primary lesions and the scope of cervical lymph node dissection.In the past,the diagnosis and differential diagnosis of thyroid diseases were mainly based on ultrasound,CT and MRI,which were mainly evaluated by pathological changes,morphology and blood supply.They were subjective and lacked objective data.Optimum single-energy imaging combined with energy spectrum parameters(iodine base map,water base map,effective atomic number,energy spectrum curve)of spectral CT can distinguish benign and malignant thyroid nodules from subjective morphology and objective energy spectrum parameters,which can provide guidance for the choice of clinical diagnosis and treatment methods and the scope of lymph node dissection.ObjectiveTo explore the value of optimal spectral CT monochromatic imaging combined with spectral imaging parameters(standardized iodine content,slope of spectral curve)in the diagnosis of benign and malignant thyroid nodules.,and the diagnostic value of Spectral CT imaging in thyroid microcarcinoma.MethodThe clinical data of 90 cases of thyroid nodules diagnosed and treated in our hospital from December 2017 to January 2019 were collected,a total of 172 nodules.According to the benign and malignant results of pathological diagnosis,the nodules were divided into malignant group(84)and benign group(88).All patients underwent Spectral CT GSI mode scan before operation.Obtain and compare the images in the arterial and venous phases of 70 keV and optimal keV(Opti keV)photon energies.Compare the image noise(SD),contrast-to-noise ratio(CNR),and subjective evaluation(Micro calcifications of the nodules,complete or interrupted enhancing capsule,Visualization of the margin)of the two photon energy groups in each phase.Recorded the nodules’ s iodine concentration,and calculated standardized iodine concentration,which was defined as nodules ’ average iodine concentration /ipsilateral arteria carotis communis’ average iodine concentration.Then used 40 and 100 keV as a reference point to calculate spectral curve slope.The slope was defined as(HU40keV-HU100keV)/60.Compared the differences of iodine concentration,standardized iodine concentration and slope of energy spectrum curve between the benign and malignant nodules.At the same time,the image characteristics of thyroid microcarcinoma were further analyzed,and the diagnostic value of Spectral CT in thyroid microcarcinoma was discussed.Results1.Opti keV of Spectral CT imaging of thyroid nodules in venous and arterial phases were 64.57+4.28 keV and 64.35+5.07 keV,respectively.2.Compared with 70 keV imaging,the displaying rates of Micro calcifications of the nodules,complete or interrupted enhancing capsule,Visualization of the margin in the venous and arterial phase images of Opti keV imaging were higher,and the difference was statistically significant(P < 0.05).3.Compared with 70 keV imaging,the subjective score and SD of Opti keV imaging were higher in both venous and arterial phases,while the CNR was lower(P < 0.05).4.The results showed that the IC and NIC in venous and arterial phases of malignant thyroid nodules(PTC)were 28.34±5.11(100μg/cm3),36.48±12.52(100μg/cm3),0.43±0.35,0.50±0.31,respectively.The IC and NIC in venous and arterial phases of benign nodules were 34.12±4.57(100μg/cm3),56.12±13.71(100μg/cm3),0.55±0.21,0.60±0.25,respectively.The IC and NIC of malignant group were lower than those of benign group,and the difference was statistically significant(P < 0.05).5.The results showed that the static and arterial phases of λHU in malignant thyroid nodules were 3.42±1.27,and 3.41±1.80,respectively;the static and arterial phases of λHU in benign thyroid nodules were 5.12±1.75,and 5.87±1.90,respectively;And the phases of λHU in malignant thyroid nodules were lower than those in benign thyroid nodules(P<0.05).6.In the study,34 papillary microcarcinomas(PTMC)accounted for about 45.33% of PTC,7 cases had " Irregular shape,Corner-like protrusion sign of the nodule",and 6 cases had cervical lymph node metastasis.Preoperative diagnosis of PTMC was completely consistent with post-operative diagnosis.It can be seen that " Irregular shape,Corner-like protrusion sign of the nodule “can be used as a sensitive diagnostic basis for thyroid microcarcinoma.Conclusion1.The best single-energy imaging(Opti keV)of energy-spectrum CT before thyroid nodule surgery can improve the image quality,display the details of nodules clearly(Micro calcifications of the nodules,complete or interrupted enhancing capsule,Visualization of the margin),and improve the subjective evaluation of the image.2.The iodine content of malignant group was lower than that of benign group,and the slope of energy spectrum curve of malignant group was lower than that of benign group.The difference was statistically significant(P < 0.05).The benign and malignant thyroid nodules could be distinguished from objective data.3.Opti keV imaging combined with spectral CT imaging parameters(standardized iodine content and slope of spectral curve)can improve the diagnostic value of thyroid nodules in both subjective and objective aspects.4.Compared with 70 keV imaging,Opti keV imaging has more diagnostic information for thyroid microcarcinoma,which is helpful for the detection of small lesions."Corner-like protrusion sign near the local margin of thyroid capsule" has certain significance in the diagnosis of thyroid microcarcinoma.