갑상선암 수술 전 진단목적의 ¹⁸F-FDG PET/CT Dual Time Point영상에서 SUV값과 방사능 농도 측정법의 유용성 평가

The Preoperative Diagnosis of Thyroid Cancer in ¹⁸F-FDG PET/CT Dual Time Imaging of SUV and Evaluation of Radioactivity Measurement

Purpose : This study is designed to compare two parameters reflecting ¹⁸F-FDG uptake, SUV and radioactivity, for diagnosis of thyroid cancer in dual time ¹⁸F-FDG PET/CT imaging and to find which parameter is more useful to decide whether the tumor is malignant or not. Materials and Methods : We performed retrospective study for 40 patients. All patients are diagnosed as primary thyroid cancer and examined ¹⁸F-FDG PET/CT. First, we got the dispersion of scattering beam of neck and lung apex to set a background and compared each dispersion, mean value, standard deviation of maxSUV and radioactivity. Also, mean maxSUV, △maxSUV, △ maxBq/ml(%) and radioactivity between groups according to lesion's size based on biopsy are compared with independent-sample t-test. Results : the values that were from maxSUV and radioactivity measurement technique were compensated and calculated to practical values for mean comparison and patients were divided to two groups based on tumor size, Group1 (size≤1 cm, n=21), Group2 (size>1 cm, n=19) for accurate comparison. In Group1, maxSUV (semi-quantitative analysis) was increased from 5.64±5.85 (1.89~17.84) at first image to 5.90±5.01 (1.95~18.22) at second image and radioactivity (Bq/ml) (quantitative analysis) showed similar increase from 5.93±6.38 (2.50~16.75) at first image to 6.01±5.25 (2.66~16.58) at second image. In Group2, TFmaxSUV was 10.54±14.36 (2.54~33.89) in true first image, TSmaxSUV was 9.85±12.88 (2.62~26.20) in true second image separately. The maxSUV showed a significant difference in the mean comparison between the two groups (p=0.035) But, mean radioactivity (Bq/ml) was 5.93±6.38 (4.81~40.99) in true first image, 6.01±5.25 (4.51~36.93) in true second image and didn't show a significant difference statistically (p=0.126) Conclusion : In diagnosis of thyroid tumor, SUV and radioactivity depending on ¹⁸F-FDG uptake showed high similarity with coefficient of determination (R2=0.939) and malignant evaluation results using dual time also showed similar aspect. Radioactivity for evaluation of malignant tumor didn't show better specificity or sensitivity than maxSUV.