| The combination between the original image of multi-slice spiral computed tomography (MSCT) and post-processing image, can clearly manifest the exact location of lymph nodes suffering from gastric cancer, reveal the relationship between the enlarged lymph nodes and tissue structure around them, and show the size, the shape and the enhanced degree. Therefore, it is one of the practical and reliable methods to diagnose the lymph nodes metastasis of gastric cancer. In recent years, judging the lymph nodes metastasis of gastric cancer by means of multi-slice spiral computed tomography (MSCT) has been studied by scholars home and abroad, but the uniform standard doesn't achieved. Periods'scanning with 64-slice spiral CT can well assess various indexes of lymph nodes suffering from gastric cancer in name for the size, the shape and the enhanced degree, etc. Therefore, MSCT specificity in diagnosing lymph node metastasis of gastric cancer has been improved significantly.Objective: To study the relationship between lymph node metastasis and lymph node size, shape, and enhanced degree of multi-slice CT so as to improve the overall accuracy in Preoperative N staging, and to provide a great deal of more valuable information for choosing proper preclinical surgical technique and assessing the prognosis.Subjects and Methods: Triphasic spiral CT scan was performed on 45 patients (including: 39 males and 6 females;range of age: 39~83 years old; average age: 61.5 years old)who have pathologically turned out to suffer from gastric cancer during the period from January, 2009 to January, 2010. Pathological examination confirmed 37 of all cases had suffered from lymph node metastasis, while the rest had not. All the subjects, who had been fasting for 6~8 hours before examination, were intramuscular injected 654-2 20mg and drank 800~1000ml warm water 10 minutes before the scan via Siemens 64-slice spiral CT. In general, most of patients took the supine position, while some selected the different positions according to different lesion parts. Then venous channel was established through the antecubital vein, non-ionic contrast media ultavist or omnipaque, whose iodine content is 300mg/l and total dose is 80-100ml, was injected by automatic high pressure injector at a speed of 3ml/s and. After that, the data of arterial phase, venous phase and balance phase are respectively 29s,35s and 80s. Scan range: During the flat scanning, arterial phase and venous phase, it ranges from the lower esophagus to the lower levels of kidney, including the entire stomach, while during the balance phase it ranges from diaphragmatic dome to the cavitas pelvis. The slice thickness is 5mm, and slice distance is also 5mm. The original scanning data was reconstructed with 1mm thickness and then transmitted to the workstation (ADW4.2). The indexes of lymph nodes of gastric cancer patients (the distribution, number, size, shape and enhanced degree, etc. on MSCT), are observed by the combination between the axial images and MPR reconstruction images. All the patients were implemented the resection of all or part of stomach after the CT examination. The Excision of lymph nodes were classified and sent to pathology. Analysis by the software SPSS17.0 .With the Kappa test method to evaluate MSCT diagnosis of gastric and pathological diagnosis of metastatic lymph node consistency of results.Results:1. A total of 535 lymph nodes obtained have been checked on MSCT, and divided into three groups according to the size of diameters. The statistical analysis shows two methods to judge the uniformity of metastatic lymph nodes between the analytical result from the group (diameter≥8mm) and pathological findings (Kappa = 0.831). The sensitivity of MSCT to diagnose the lymph nodes metastasis of gastric cancer is 79.6%, and the specificity is 78.8%. The conclusion of this study supports that it can be a standard for MSCT to decide lymph node metastasis that the length of diameter is or over 8mm. 2. The lymph nodes on MSCT were classified into three groups according to the enhanced degree. The statistical analysis shows that there was uniformity between the analyzed result from the group (the average value difference of enhanced density≥80Hu) and pathological findings (Kappa = 0.849). The sensitivity of MSCT to diagnose the lymph nodes metastasis of gastric cancer is 81.6%, and the specificity is 75.6%.The author recommends that 80Hu should be the enhanced threshold to decide lymph nodes of gastric cancer metastasis. 3. The lymph nodes on MSCT were classified into two groups according to the short diameter ratio, and compared with pathological findings. The result shows that there was uniformity between the analyzed result from the group (short diameter ratio≥0.7) and pathological findings (Kappa = 0.873). The sensitivity of MSCT to diagnose the lymph nodes metastasis of gastric cancer is 85.6%, and the specificity is 71.8%. Therefore, the author recommends that short diameter ratio is or over 0.7 should be a reasonable indicator to decide lymph nodes of gastric cancer metastasis. 4. The location of the lymph nodes also affected the detection rate of lymph nodes on MSCT. Celiac main artery and lesser curvature lymph nodes were in the higher sensitivity of detection, and their rates were respectively 89.4% and 90.3%. However, the gastric cardiac the right area and the greater curvature lymph nodes showed lower rates, respectively 57.8% and 45.0%.Conclusion: As a kind of simple, noninvasive method, based on diameter, short diameter ratio and enhanced degree of lymph nodes, MSCT can preliminarily judge and stage the lymph node metastasis for gastric cancer patients, and offer the valuable reference for choosing proper preclinical surgical technique and assessing the prognosis.
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