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MATERIALS AND METHODSPLACE OF STUDY:The study was conducted in the Department of Radiology and Imaging, Bharat Scans between June 2016 and May 2018 over a period of 2 years.STUDY POPULATIONCases being referred from government hospital (Madras medical college), Chennai Tamil Nadu.SAMPLE SIZE: The sample size of study is 40 cases.DATA COLLECTION: Data was collected as and when cases were performed after choosing patients who were eligible for study. Observation and follow up of cases was done.TYPE OF STUDY:Prospective observational study with some of the data collected retrospectively. The study was submitted to the scientific and ethical committee and was approved.INCLUSION CRITERIA:Potentially resectable Gastro Esophageal Junction adenocarcinoma.Patients with good performance status (No evidence of metastasis on clinical examination, chest X-ray and Ultrasound Abdomen).EXCLUSION CRITERIA:Evidence of metastasis by clinical examination, X-ray chest and ultrasound abdomen. Patients with co-existent malignancies in other organ system.Patients with biopsy proven squamous cell carcinoma.METHODS OF ENROLLMENT:All patients who met the eligibility criteria and underwent PET/CT imaging during the above mentioned period were enrolled in the study.Criteria for CECT- For locoregional lesions and metastasisMorphological changes such as the presence of an enhancing soft tissue mass as opposed to streaking of the fat in the Gastroesophageal junction.Length and thickness of the mass.Invasion of adjacent structures like, pleura, pericardium, azygos vein, diaphragm, aorta, airway or peritoneum. Regional lymph node metastases. Any paraesophageal lymph nodes from the lower cervical nodes to the celiac nodes were considered as regional lymph nodes for esophageal cancer [According to the AJCC (American Joint Committee of Cancer) staging for esophageal cancer, 8th edition].--Lymph nodes smaller than 1 cm in short-axis diameter and having smooth well-defined border, uniform homogeneous attenuation and a central fatty hilum were considered as benign lymph nodes. Furthermore, lymph nodes with a fatty hilum or with calcifications were regarded as benign.Regional lymph nodes (mentioned below) appearing as round and/or >10 mm in short axis diameter were considered as metastatic lymph nodes. The specific regional lymph nodes are as follows: REGIONAL LYMPHNODES FOR CA ESOPHAGUSLOCATIONRight lower cervical paratracheal nodesBetween the supraclavicular paratracheal space and apex of the lungLeft lower cervical paratracheal nodesBetween the supraclavicular paratracheal space and apex of the lungRight upper paratracheal nodesBetween the intersection of the caudal margin of the brachiocephalic artery with the trachea and the apex of the lungLeft upper paratracheal nodesBetween the top of the aortic arch and apex of the lungRight lower paratracheal nodesBetween the intersection of the caudal margin of the brachiocephalic artery with the trachea and cephalic border of the azygos veinLeft lower paratracheal nodesBetween the top of the aortic arch and the carinaSubcarinal nodesCaudal to the carina of the tracheaUpper thoracic paraesophageal nodesFrom the apex of the lung to the tracheal bifurcationMiddle thoracic paraesophageal nodes From the tracheal bifurcation to the caudal margin of the inferior pulmonary veinLower thoracic paraesophageal lymph nodesFrom the caudal margin of the inferior pulmonary vein to the EGJPulmonary ligament nodeswithin the right or left inferior pulmonary ligamentDiaphragmatic nodesLying on the dome o f the diaphragm and adjacent to or behind its cruraParacardial nodesImmediately adjacent to the gastroesophageal junctionLeft gastric nodesAlong the course o f the left gastric arteryCommon hepatic nodesImmediately on the proximal common hepatic arterySplenic nodesImmediately on the proximal splenic arteryCeliac nodesAt the base of the celiac arteryCervical periesophageal level VI & VII lymph nodesPre-paratracheal, esophageal groove, precricoid (Delphian) and the perithyroidal nodes, including the lymph nodes along the recurrent laryngeal nervesCriteria for CECT - for distant metastasisHypo-attenuating liver lesions with irregular margins and predominant peripheral contrast enhancement with washout in delayed phases were considered as metastasis. Multiple randomly distributed rounded predominantly parenchymal / subpleurally located, non-calcified pulmonary nodules were considered as metastasis. Focal heterogeneous enlargement of the adrenal gland on CT was considered as adrenal metastasis.Detection of soft-tissue masses to the distant sites (other than localized structures) with contrast enhancement or further suggestive signs (e.g., surrounding tissue infiltration, localization) were also considered as malignant. Nodal metastasis other than regional lymph nodes (mentioned above) were considered as distant metastasis.Criteria for PET/CT positive statusSoft-tissue masses in conjunction with focally increased glucose metabolism (FDG avid) above the surrounding tissue level were regarded as malignant. A maximum standardized uptake value (SUVmax) of more than 2.5 (for extrahepatic lesions) and 3.5 (intrahepatic lesions) supported the diagnosis of a malignant lesion but was always considered in conjunction with the qualitative appearance of the lesion (e.g., a liver lesion with a SUV max of 3.1 clearly demarcated from the background liver activity was considered malignant).Lymph nodes were assessed for metastatic spread on the basis of an increased glucose metabolism independent of their size. Criteria for CT negative status for recurrent diseaseNo obvious enhancing lesions detected on Contrast enhanced CT study.Criteria for PET/CT negative status for residual / recurrent diseaseNo increased FDG uptake in lesions which were Positive on CT.From June 2015 to May 2018, 40 patients were referred to our institution for PET/CT imaging with suspected gastroesophageal junction tumor. In all 40 of these patients referred for staging / follow up, a reliable reference standard was available. The reference standard was established by histopathological examination of potentially resectable lesion in both locoregional and distant areas.TECHNIQUE :IMAGE ACQUSITION :Figure 3-1. [Actual image of GE Discovery VCT system installed at Bharat Scans, Royapettah, Chennai].CT and PET/CT imaging were performed using the 64 slice PET/CT scanner (GE Discovery VCT, Wisconsin, USA). This system combines a 64 slice-detector CT scanner with a PET scanner.Patient’s random blood glucose levels, serum creatinine and blood urea were analyzed prior to the study and study performed only when random blood glucose levels were <160mg/dl and serum creatinine and blood urea levels within normal limits.While resting on a reclining chair, the patients received a 10 mCi of 18F-FDG intravenously (up to a maximum of 20 mCi) and were asked to drink 900 mL of oral contrast. All possible physical activity was restricted to prevent physiological uptake in muscles.The imaging sequence began 45 min after tracer injection. All patients were positioned on the imaging table with their arms up. After determining the imaging field (Vertex to mid thighs) with an initial scout scan, CT acquisition with intravenous contrast material was performed using the following parameters: 120 kVp, 300 mAs, 0.5sec tube rotation, 3.75 mm slice collimation, pitch and speed of 0.984:1, 39.37mm/rot. The CT scan was followed by the PET emission scan. PET images were acquired in 3D mode. Patients were instructed to breathe shallowly during the PET and CT portions of the study to minimize misregistration between PET and CT images. CT images were reconstructed in axial, sagittal and coronal planes. Axial, Sagittal and Coronal PET reconstructions were interpreted with and without attenuation correction.IMAGE RECONSTRUCTION:CT images were reconstructed using conventional filtered back projection, at 3.4-mm axial intervals to match the slice separation of the PET data. PET images were reconstructed by using iterative algorithms (ordered-subsets expectation maximization, two iterations and eight subsets). Attenuation was corrected by mapping the CT Hounsfield units to the linear attenuation coefficients.Figure 3-2. [Actual image of GE Discovery VCT PET/CT console room installed at Bharat Scans, Royapettah, Chennai].IMAGE INTERPRETATION AND ANALYSISPET, CT, and PET/CT acquired in this retrospectively enrolled population were interpreted as follows: CT and PET images were interpreted independently by one radiologist and one nuclear medicine specialist, respectively, PET/CT studies were read in consensus.QUANTITATIVE ANALYSIS OF FDG UPTAKE:For the calculation of Standard uptake value (SUV), circular regions of interest were placed on consecutive axial images of lesions visually identified to have abnormally increased FDG uptake.The SUV was calculated as:SUV =decay - corrected activity(kBq) / tissue volume(ml)injected – FDG activity (kBq) / bodyweight (g)To minimize partial volume effects and assure reproducibility of measurements, the maximum SUV (SUVmax) was used. STANDARD OF REFERENCE:The standard of reference was diagnostic laparoscopy followed by histopathology examination.A suspected tumor site was considered true-positive if diagnostic laparoscopy followed by histopathology examination were positive.A lesion was considered true-negative if the histologic findings were negative .ANALYSIS:Using the standard of reference, sensitivity, specificity, positive predictive value, negative predictive value were calculated. In addition, comparison between groups was performed using the unpaired t test and Pearson’s chi square test. Correlations were sought using the Pearson correlation. A p value of <0.05 was considered significant. ................
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