| PurposeFDG PET/CT imaging has been proven of value in many types of tumors. But atypical high uptake of mediastinal lymph nodes might interfere with image interpretation. This study was designed to compare the FDG PET/CT results between Atypical or Non-specific High Uptake of Aged Mediastinal Lymph Nodes (AUAL) and Metastases of Mediastinal Lymph Nodes (MLNM) ,then make out a method for differential diagnosis of AUAL and MLNM.Materials and MethodsRetrospectively studied 409 patients who received examination of FDG PET/CT had high uptake of mediastinal lymph nodes (LN) in the Center of PET/CT Diagnosis and Therapy of Shandong Provencal Hospital from October 2003 to November 2006.Excluding 11 cases of lymphoma, 10 cases of sarcoid and 16 cases of reactive lymphoid follicular hyperplasia caused by pulmonary TB or lung inflammation. Among them 243 cases of MLNM, aged from 28 to 89, mean age is 58.28±11.805 years old, median age is 59 years old.104 cases of AUAL, aged from 38 to 90, mean age is 68.93±11.093 years old, median age is 74 years old. 25 cases of both had MLNM and AUAL, aged from 62 to 82, mean age is 73.64±4.434 years old, median age is 74 years old.104 cases of AUAL, aged from 38 to 90, mean age is 68.93±11.093 years old, median age is 74 years old. All of them proved by operation, endueomediascopy, biopsy or follow up for at least 6 months.PET/CT used Discovery LS PET/CT scan machinery General Electrical Medical Systems, Milwaukee, Wis),trace media use 18F-fluorodeoxyglucose (18F-FDG), spiral acceleration used GE MINItrace with Microlab auto combined system.All subjects fasted at more than 46h prior to the examination and had a documented normal serum glucose level prior to injection of FDG Dose counts of 5.6 ～ 7.4MBq/kg and all accounts about 370～555MBq. PET/CT examination performed after 40 minutes. Chest scan view including neck, both lung fields to both adrenal glands. Whole body scan view including cranial base to upper segment of thigh bone. After scan to fuse the images on the work station. After reconstruction got the images of coronary, sagittal and transverse of CT, PET and PET-CT.The measurement points were pointed by 3 experienced doctors major in radiology and nuclear medicine. American Thoracic Society map of regional pulmonary nodes (ATS) was used to the mediastinal lymph nodes and the longest size, shortest size, maximum standard uptake value (SUVmax) ,mean standard uptake value (SUVmean) and CT values were recorded separately.The relationship of the longest size, shortest size, maximum standard uptake value (SUVmax ) ,mean standard uptake value (SUVmean) and CT values between AUAL and MLNM were evaluated statistically. Continuous variables were expressed as the mean±SD and frequencies were analyzed using the Independent-sample T Test. A P<0.05 was considered to be significant. The CT values of normal were analyzed using correction and regression related to age was calculated. All calculations were performed using statistical software(SPSS version 12.0; SPSS Inc. ; Chicago.IL).ResultsAll 673 LNs of AUAL, mean longest size was 12.56±4.09mm, mean shortestsize was 9.44±2.67 mm. mean CT values was 57.55±16.76Hu, mean SUVmax was 4.78±2.48 and mean SUVmean was 3.75±1.95.The values had no significant difference between gender, but the CT values had relations to ages, and as normals, its regression formation was Y=20.816+0.334X (Y=CT value, X=age) .All 1349 LNs of MLNM, mean longest size was 17.49±8.29mm, mean shortest size was 12.86±5.43 mm, mean CT values was 40.78±9.22Hu, mean SUVmax was 6.53±3.57 and mean SUVmean was 5.31±2.95.The SUV values had no significant difference between gender , but the sizes and CT values had significant difference between gender.All of the longest size (t=12.98, P=0.000), shortest size (t=13.75, P=0.000), CT value(t=-18.2; P=0.000), SUVmax(t=9.40, P=0.000), SUVmean (t=10.31, P=0.000) had significant difference between MLNM and AUAL.ConclusionsPET/CT can make differential diagnosis of AUAL and MLNM according to①The population: AUAL most occur in the people senior to 50 years old and their clinical features were normal. MLNM most occur in the people who got malignant tumors and their clinical features were related to the malignant tumor. In this study, MLNM mean age was 58.28±11.805 years old and median age was 59 years old; AUAL mean age was 68.93±11.093 years old and median age was 70 years old. ②The site of lesions: MLNM and AUAL all showed high uptake of FDG, MLNM combined by primary lesions and had a clear chain related to the primary lesions sites; AUAL had no primary lesion or had lesion but the high uptake LNs had no relations to the lesions. ③The SUV values of MLNM were significant higher than that of AUAL. In this study, the mean SUVmax and mean SUVmean of MLNM were 6.53±3.57 and 5.31±2.95; in contrast, the mean SUVmax and mean SUVmean of AUAL were 4.78±2.48 and 3.75±1.95. ④MLNM had multiple morphology, different size and irregular calcifications, their shortest size often > 10mm. AUAL had regularly bargain, same size and mass calcifications, and their shortest size often < 10mm. In this study, the mean longest size and mean shortest size of MLNM were 17.49±8.29mm and 12.86±5.43 mm; in contrast, the mean longest size and mean shortest size of AUAL were 12.56±4.09mm and 9.44±2.67 mm. ⑤The density of AUAL LNs were increased and uniformity. If the density ununiformaty maybe implied of metastases were occurred in the LNs. The LNs of AUAL looked like diffused calcium mineralization but had no sure calcification foci. The LNs distributed bilateral over the mediastinal or in the mediastinal. Their CT values more than 40 to 50 Hu. The density of MLNM LNs were not increased but can find destructions in the center of LNs and show high uptake of FDG. In this study, the mean CT value of MLNM was 40.78±9.22Hu and that of AUAL was 57.55±16.76Hu. From above all, we can draw a conclusion that to make differential diagnosis of AUAL and MLNM should think over about the manifestations of FDG PET/CT and clinical features, and a strict follow-up should be performed. |
PDF Full Text Request