| Purpose:This study was focused on the comparison of CT,SPECT and PET images,by which we can evaluate the applical value of PET/CT fusion images in the research field of thyroid carcinoma. Methods:The analysis was based on 12 cases of the thyroid carcinoma(4 males,8 females,age range 22-73y, mean ages 35.8y)which were collected from July, 2003 to January, 2005.The final diagnosises were confiromed by clinical followed up(over 6 months),surgery,biopsy and pathology.Serum thyroglobulin, thyriod gland functional test,CT (computed tomography),SPECT(single photon emission computed tomography), PET(positron emission tomography)and PET/CT were applied in all cases. In which spiral CT scanning was applied in 12 cases, these spiral CT scanners were respectively from sele CT/sp(Marconi),sensation(Siemens), Prospeed(GE)and Heli CAT Flash(Felscint),there were 6 plain examinations, on the base of that, the other 6 cases were applied enhancement scanning with a 100ml bolus injection of contrast material at 3ml/s, the scan slice thickness was 5mm and the pitch was 1.0.SPECT was applied in 5 cases, the scanners were starcam 3200i(GE),Diacam(Siemens) and Apex-Sp4 (Elscin).There were also another 7 cases which were applied by GE Advance PET scanner.Combined PET/CT examinations were performed in 12 cases, the scanner was Discovery Ls(GE)which included Advance 2 PET scanner and Light speed spiral CT scanner, the scan parameters were as following: tube voltage 140Kv, tube current 90mA～200mA, slice thickness 5mm,patch 0.75,rotating time per ring 0.8s, scanning field of view(FOV)50cm;the PET thickness 4.25mm,matrix 128×128,emission scan time was 4min～6min per bed position.Fusion images were constructed by combining the PET and CT images on the Entegra computer workstation after scanning. In that way, transaxial, sagittal and coronal fusion images were obtained. PET/CT was separatedly compared with CT,SPECT and PET findings, then we recorded the tumor lesions of its numbers, localization, size, the distrubution of radionuclide, calcification, the involvement of lymph node in neck and metastatic in other organs. From the statistically analyzed by SAS software,there was a significant difference when P<0.05. Results:(I)The manifestation of primary lesion: there were 19 lesions in 12 cases thyroid carcinom, including 16(84.2%)with papillary carcinoma, 2(10.5%)with follicular carcinoma and 1(5.3%)with undifferentiated carcinoma. Of 19 lesions, there were 13(68.4%)positive lesions on CT images, all of them appeared in a low density, 9 seen irregular shape anduntidy margin,7 showed heterogeneous density, of which 5(26.3%)were detected calcifications; there were 7 lesions in 6 cases enhancement scanning,4 lesions were detected no complete enhanced ring around the tumor, and 2 lesions showed peninsular tubercles around the tumor. In addition,7 cases 58.3%)infiltrated the adjacent structure;Of 6 positive lesions(31.6%)on SPECT static image, 3 showed cold nodules and 3 cool nodules, all lesions revealed increasing perfusion on dynamic imaging;7 cases underwent PET examination,9lesions(68.4%)showed focal abnormal radiophamceutical uptake in pathologic sites; On PET/CT images, 19 positive lesions(100%)showed abnormal intense high metabolic region, 6 (31.6%)of them showed heterogeneous density and 5(26.3%)showed untidy margin.(II)Metastatic lymph node on the neck: PET/CT fusion images allowed precise localization in 5cases(100%),CT image showed 2 cases, whereas 2 cases were detected intense radiophamceutical uptake in 5 cases underwent SPECT examination,and 2 cases showed radiophamceutical uptake in 7 cases underwent PET examination.(III)Metastatics on other organs: 3 cases, on SPECT or PET, PET/CT images showed abnormal radiophamceutical uptake,but CT scan only found 2 cases of them. Conclusion:The density and shape of thyroid neoplasms lesion can be clearly detected on CT image, nuclear medicine images such as SPECT, PET can provides excellent information on functional biology about primary lesion and metastatic lesion, but precise localization w...
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