| [Objective]To analyse the imaging diagnosis findings of 18F-FDG PET/CT in 92 unknown primary tumors with lymph nodes metastasis to appraises the possible clinical valuation of 18F-FDG PET/CT in detecting primary tumor.[Materials and Methods]1. Study objective1.1 Control groupSelect 30 cases of the healthy physical examines to analyse the normal 18F-FDG PET/CT image, whose clinical examination, Electrocardiogram, X-Rays, B-ultrasound, serum tumor markers were all normal. Ages ranged from 27 to 62 years. Median age was 43 years.1.2 Lymph nodes metastasis groupRetrospective analysis 92 cases with Lymph nodes metastasis with unknown primary tumors between May 2003 and October 2008, who hadn't been treated and hadn't malignancy history.57 were male and 35 were female. Ages ranged from 19 to 81 years. Median age was 51.Histologic findings of at least one lymph node metastatic site were available in all patients and revealed squamous cell carcinoma in 41 patients, adenocarcinoma in 32 patients, small cell cancer in 3 patients and indefinite pathology cancer in 16 patients.All patients were taken whole body 18F-FDG PET/CT scan. 2. Main equipments and imaging agentDiscovery LS PET/CT Scanner and PET tracerlab F-X F-N from General Electric Company,18F-FDG was made by Automatic synthesis with a radiochemical purity over 95%.3. Imaging methods and image reconstructionSubject with more than 6 hours fasting, in a quite state, should be injected body weight* 0.15 (mci)18F-FDG at the hand vein by using the three-way pipe, later lying down in a darkroom for around an hour. The PET/CT scan was performed after the urination. The scan included CT plain scan and PET scan with a scan range from the middle of the femur to the calotte,6 to 8 bed positions. And the CT scan conditions were:140kV,160mA, pitch 0.75,0.8 second for tube lab rotation,5mm thickness, each emission scan time was 4minutes per bed position. The PET images were reconstructed by OSEM method and images attenuation correction used CT data. CT images were reconstructed by the standard reconstrucion method. The matrix was 512 by 512, and the reconstructed slice thickness was 4.25mm. The PET and CT images were transmitted to Xeleris workstation to have the frame to frame image fusion display.4. Image analysis and Diagnostic CriteriaPET images and CT images were fused by frame to frame. And the images were analyzed by two experienced senior physicians in the filed of PET/CT diagnosis. The positive lesions uptake higher to that of the nearby normal tissue and was considered with integrated CT image. The standardized uptake value (SUV) was calculated with the PET sanner software and average values in the ROIs were measured and record for each patients. Lesions were more than 3 months follow-up.5. Statistical MethodSPSS13.0 Statistical Processing Software was used in this study. Multiple comparison of sample rates were tested by x2 test. The value of PET/CT in diagnosing the nature of palpable lymph node was tested by diagnostic performance and with pathology results as gold standard. All the statistics tests were seen statically significant when test level was less than 0.05.[Results] 1. 18FDG PET/CT imaging1.1 Normal PET/CT studyA good understanding of the normal physiology is important. From right to left the different planar images are a useful way to survey lesions on PET/CT. The brain is also a site of high FDG uptake due to marked glucose utilization, particularly in gray matter. FDG is cleared primarily through the renal system, so the renal calices, ureters and bladder are seen. There is mild generalized uptake in the liver, bone marrow and spleen. Normal variant uptake in the heart and bowel can be seen (fig 1). Abnormal soft tissue mass was not seen on CT scan.2.92 cases of lymph node metastasis with PET/CT diagnosis and follow-up results92 cases of lymph node metastasis, PET/CT diagnosis of primary tumors were 74 cases (80.4%):25 cases of nasopharyngeal carcinoma (fig 2),22 cases of lung cancer (fig 3,4), breast cancer (fig 5) and ovarian cancer (fig 6) four cases each, three cases of gastric cancer (fig 7), larynx, esophagus cancer (fig 8), prostate cancer (fig 9) and colon cancer two cases each, submandibular gland cancer (fig 10), tongue cancer, parotid gland cancer (fig 11), thyroid cancer (fig 12,13), pancreatic cancer (fig 14) and endometrial cancer (fig 15) one case each; PET/CT can not determine the primary tumor in 18 cases, of which one case was followed up as lung cancer, one case as nasopharyngeal carcinoma,12 cases were died,2 cases survive,2 cases are actively treatment.2.1 The relationship between the PET/CT positive rate of diagnosis and pathological type2.1.1 Primary diagnosis of metastatic lymph node squamous cell carcinoma were 41 cases:20 cases of nasopharyngeal carcinoma,3 cases of lung cancer, cervical cancer and esophageal cancer two cases each, one case of submandibular gland carcinoma,11 cases (26.8%) primary tumor could not be determined, positive diagnosis rate of 73.2%. One case was followed up as nasopharyngeal cancer and one case was followed as nasopharyngeal carcinoma in 11 cases of unknown primary tumor, and one patient was followed up as the lung cancer, the other 9 cases of primary tumors and death has not yet been out found.2.1.2 Primary diagnosis of metastatic lymph node adenocarcinoma were 32 cases:11 cases of lung cancer,4 cases of breast cancer, gastric cancer and ovarian cancer (fig 6) 3 cases each,2 cases of prostate cancer (fig 9), parotid gland,thyroid cancer (fig 12,13),endometrial cancer (fig 15),colon and pancreatic cancer (fig 14) one case each.4 cases (12.5%) primary tumor could not be determined. Positive diagnostic rate was 87.5%.2 cases are followed-up alively of 4 cases of primary tumor is still unknown so far in the body and 2 cases of death.2.1.3 Primary diagnosis of metastatic lymph node small cell carcinoma were 3 cases:2 cases of lung cancer, primary tumor of one case could not be determined and follow-up as death.2.1.4 Primary diagnosis of non-specific pathological types with lymph node metastasis were 16 cases:6 cases of lung cancer,5 cases of nasopharyngeal carcinoma, ovarian cancer, tongue cancer and colon cancer 1 case each, the primary of 2 cases (12.5%) tumor could not be determined. Positive diagnostic rate was 87.5%.2 cases of unknown primary tumor are now being treated and the primary tumor is still unknown.2.1.5 The PET/CT positive diagnosis rate of metastatic lymph nodes for squamous cell carcinoma, adenocarcinoma, small cell carcinoma, non-specific pathological types were tested by x 2-test:x2=3.22, P=0.36, diagnostic performance of PET/CT for 4 different types above of lymph node metastasis pathological were no significant difference.2.2 The relationship between the PET/CT positive diagnosis rate of tumor and the differentiation degree92 cases of lymph node metastasis pathological in differentiated were 45 cases of clear, specific for the 41 cases of poorly differentiated, in 4 cases of middle differentiation cancer. Of poorly differentiated carcinoma, PET/CT diagnosed 33 cases (80.5%) primary tumors.Of middle differentiation cancer, PET/CT diagnosed 3 cases (75.0%) primary tumors.2.3 The relationship between the first part of lymph node metastases and primary lesion.The first part of lymph node metastases were in line with the conventional primary carcinoma metastatic sites of 66 cases (71.7%) and the not(fig,6,9,15) were 8 cases (8.7%)[Conclusions]1.18F-FDG PET/CT has a higher application value in looking for the primary tumor for lymph node metastases.2. Diagnosis of primary cancer by 18F-FDG PET/CT for lymph node metastasis do not been influenced by the histological types of metastatic carcinoma. |
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