Image Analysis Of 18 F-FDG PET/CT Subacute Thyroiditis With 99m TcO 4 -Clinical Significance Of SPECT/CT In The Diagnosis And Follow-up Of Subacute Thyroiditis

Part I ¹⁸F-FDG PET/CT imaging characteristics of subacute thyroiditisObjective The clinical manifestations of subacute thyroiditis?SAT?are variable,and are easily missed and misdiagnosed.To investigate the imaging characteristics of subacute thyroiditis?SAT?features on ¹⁸F-FDG PET/CT,and discuss the value of staging diagnosis,identified with other thyroid diseases.Methods From March 2012 to September 2017,it was retrospectively studied that 36 patients?9 males and 27 females;average age?41.5 ± 10.2?years,median age 42 years?who underwent ¹⁸F-FDG PET/CT,combined with surgical pathological findings,typical clinical presentations,laboratory tests,and treatment procedures,diagnosed as SAT.The patients according to thyroid function tests,glucose metabolism,etc.were divided into three stages: acute stage,medium stage,and recovery stage.To investigate the imaging characteristics of ¹⁸F-FDG PET/CT in three different stages of subacute thyroiditis,and involvement of thyroid.The ROI of the lesion was delineated and the SUVmax value was calculated.The semi-quantitative analysis compared the differences between groups in each stage.Data were analyzed using the analysis of variance F-test with mean ± standard deviation and completely random design data.Results The involvement of thyroid in 12 patients with subacute thyroiditis in the acute stage were: 8/12,3/12,1/12,respectively.7 cases of low density focus were diffuse,and 5 cases were nodular?multiple or single?,of which SUVmax value were 3.6 to 8.3 and the average was 5.48 ± 1.28.In two cases,a single lymph node in the right cervical root showed increased FDG uptake,with an SUVmax of 3,2.8,respectively.In 12 cases with subacute thyroiditis,the proportion involvement of thyroid gland in the medium stage in two lobes,a single lobe and part of a lobe were 7/12,4/12,1/12.8 cases of low density focus were diffuse,and 4 cases were nodular?multiple or single?,of which SUVmax value were2.0 to 4.5 and the average was 3.2±0.8.One patient,multiple right neck lymph nodes showed increased FDG uptake,with an SUVmax of 2.5.The other,the left cervical lymph node showed a single increase with FDG uptake,with an SUVmax of 1.7.12 cases with subacute thyroiditis are in the recovery stages,of which the density of the two lobes of thyroid in 9 cases basically recovered with no or mild FDG uptake,of which the proportion involvement of thyroid in 3 cases in two lobes,a single lobe and part of a lobe were 2/12,1/12,0/12.2 cases of low density focus were diffuse,and 1 cases were nodular?multiple or single?,of which SUVmax value were1.2 to 2.3 and the average was 1.63±0.48.There were no lymph nodes showed or increased FDG uptake.The imaging findings of the involvement of thyroid in three different statges were as follows:?1?Two lobes: The patient presented with asymmetric enlargement of the two lobes of thyroid,with diffuse or nodular low density in the lesion.It was not clear with normal thyroid tissue,and the density was lower than the adjacent soft tissue,in the corresponding to which the uptake increased.?2?Single lobe: The patients showed an irregular enlargement of the single of the thyroid gland,the density evenly or the inhomogeneously decreased with increased uptake obviously,and the less clear boundary.?3?Part of a lobe: the patient showed a nodular low density in the single lobe of the thyroid gland.The boundary between the lesion and the normal thyroid gland was unclear,in the corresponding to wich the uptake was mildly increased.It can be seen that with the progression of disease,semi-quantitative SUVmax values showed a decreasing trend in the acute stage,medium stage,and recovery stage of subacute thyroiditis,and the SUVmax values were 6.58±0.89,3.2±0.8,and 1.63±0.48,respectively.The differences between the groups were statistically significant?F=53.94,P<0.001?.The diffuse or focal irregular low density gradually restored to normal density,and the enlarged thyroid gland gradually restored to normal or slightly smaller with clear boundary to the surrounding tissue,which was the morphological changes of CT.Conclusion ¹⁸F-FDG is a good imaging agent for inflammation.¹⁸F-FDG PET/CT can directly reflect the location and range of the involvement in the progression of SAT,and quantitatively,dynamically observe the progression of the disease.It also plays a role in differiential diagnosis?especially solitary nodules?.Part II The value of ^99mTcO₄^-SPECT/CT in the diagnosis and follow-up of subacute thyroiditisObjective: To investigate the value of ^99mTcO₄^-SPECT/CT in the diagnosis and follow-up of subacute thyroiditis.METHODS: From September 2015 to December 2017,65 patients?15 males and 50 females;age range 25 to 66 years,mean age?43.1±8.8?years.44 years old?suspected as subacute thyroiditis in preliminary diagnosed were separately underwent ^99mTcO₄^-thyroid plain imaging and ^99mTcO₄^-SPECT/CT fusion imaging in our department of nuclear medicine,whose diagnostic efficacy was compared.^99mTcO₄^-SPECT/CT examination was performed for patients with confirmed SAT after treatment,and all patients were followed up for 1 years.The SPSS 17 statistical software was used to analyze the data.The measurement data were expressed as mean ± standard deviation?x±s?.The chi square test was used to compare the diagnostic accuracy and the percentage of ^99mTcO₄^-planar imaging and ^99mTcO₄^-SPECT/CT imaging,and the results were statistically significant?P < 0.05?.The value of the two methods for the diagnosis of subacute thyroiditis was compared by using the area under the receiver operating characteristic curve?ROC?.RESULTS: The sensitivity,specificity,accuracy,positive predictive value,and negative predictive value of SAT in ^99mTcO₄^-planar imaging diagnosis were 72.7%,57.1%,67.7%,78.0%,and 50.0%,respectively.To ^99mTcO₄^-SPECT/CT,the sensitivity,specificity,accuracy,positive predictive value,and negative predictive value were 93.2%,90.5%,92.3%,95.3%,and 86.4%,respectively.By the Mc Nemar test,the sensitivity of ^99mTcO₄^-SPECT/CT in diagnosing SAT was higher than that of ^99mTcO₄^-planar imaging. The difference in sensitivity between the two examinations was statistically significant??2=7.1,P<0.05?.The specificity of ^99mTcO₄^-SPECT/CT in diagnosing SAT was also higher than that of ^99mTcO₄^-planar imaging.The specificity of the two images was statistically significant??2=5.1,P<0.05?.The area under the ROC curve of ^99mTcO₄^-planar imaging and ^99mTcO₄^-SPECT/CT were 0.649±0.075 and 0.918±0.043,respectively.The value of ^99mTcO₄^-SPECT/CT in the diagnosis of SAT was superior to that of ^99mTcO₄^-planar imaging,and the difference was statistically significant??2=12.0,P<0.01?.In a 1-year follow-up after treatment,no complete recovery of ^99mTcO₄^-thyroid SPECT/CT imaging was found in 24 cases.The recurrence rate was 25%?6/24?in approximately 4-11 months after onset,while 14 cases of ^99mTcO₄^-SPECT/CT imaging recoveried completely without recurrence,of which the difference was statistically significant??2=4.2,P<0.05?.Conclusion: The diagnostic accuracy of ^99mTcO₄^-SPECT/CT on SAT is significantly higher than that of ^99mTcO₄^-planar imaging,proved gain value,which could better distinguish between benign and malignant lesions.The ^99mTcO₄^-SPECT/CT fusion imaging can also be used to observe and evaluate the therapeutic effect of SAT,based on which greatly reducing the recurrence rate by tapering the dose of glucocorticoid.