Intense F-18 FDG accumulation in the stomach in a patient with Menetrier's disease

Unusually Elevated Gastric Radioactivity on 18F-FDG PET/CT in Diffuse Large B-Cell Lymphoma

A 41-year-old woman presented with abdominal distention, inappetence, and rapid emaciation for 1 month. Diffuse bulky gastric wall thickening with lymph nodes enlargement and peritoneal nodules were revealed using abdominal CT. Staging F-FDG PET/CT performed after admission demonstrated intensely diffuse FDG uptake in stomach, FDG-avid lymph nodes, and peritoneal nodular lesions. Postoperatively, these lesions were diagnosed as diffuse large B-cell lymphoma.

18F-fluorodeoxyglucose positron emission tomography/computed tomography findings of gastric lymphoma: Comparisons with gastric cancer

The role of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in numerous malignant tumors, including gastric lymphoma, is well-established. However, there have been few studies with regard to the ¹⁸F-FDG PET/CT features of gastric lymphoma. The aim of the present study was to characterize the ¹⁸F-FDG PET/CT features of gastric lymphoma, which were compared with those of gastric cancer. Prior to treatment, ¹⁸F-FDG PET/CT was performed on 24 patients with gastric lymphoma and 43 patients with gastric cancer. The ¹⁸F-FDG PET/CT pattern of gastric wall lesions was classified as one of three types: Type I, diffuse thickening of the gastric wall with increased FDG uptake infiltrating more than one-third of the total stomach; type II, segmental thickening of the gastric wall with elevated FDG uptake involving less than one-third of the total stomach; and type III, local thickening of the gastric wall with focal FDG uptake. The incidence of the involvement of more than one region of the stomach was higher in the patients with gastric lymphoma than in those with gastric cancer. Gastric FDG uptake was demonstrated in 23 of the 24 patients (95.8%) with gastric lymphoma and in 40 of the 43 patients (93.0%) with gastric cancer. Gastric lymphoma predominantly presented with type I and II lesions, whereas gastric cancer mainly presented with type II and III lesions. The maximal thickness was larger and the maximal standard uptake value (SUV_max) was higher in the patients with gastric lymphoma compared with those with gastric cancer. A positive correlation between the maximal thickness and SUV_max was confirmed for the gastric cancer lesions, but not for the gastric lymphoma lesions. There was no difference in the maximal thickness and SUV_max of the gastric wall lesions between the patients without and with extragastric involvement, for gastric lymphoma and gastric cancer. Overall, certain differences exist in the findings between gastric lymphoma and gastric cancer patients on ¹⁸F-FDG PET/CT images, which may contribute to the identification of gastric lymphoma.

Role of gastric distention with additional water in differentiating locally advanced gastric carcinomas from physiological uptake in the stomach on 18F-fluoro-2-deoxy-D-glucose PET

PURPOSE

In this study, we investigated the role of gastric distention with additional water to determine whether it is beneficial for the differentiation of locally advanced gastric carcinomas from physiological 18F-fluoro-2-deoxy-D-glucose (FDG) uptake in the stomach and to characterize the FDG uptake of gastric carcinomas by relating it to the histopathological properties of the tumours.

METHODS

Sixteen patients with locally advanced gastric carcinomas and 20 control patients were studied by FDG-PET. After whole-body PET imaging, the patients drank 400 ml of water and then spot imaging with additional water of the stomach was performed. The final diagnosis was determined from the results of surgery. The gastric areas were divided into the upper, middle, and lower parts. The degree of FDG uptake in the stomach was qualitatively evaluated by visual grading into three degrees. For quantitative analysis, the regional tumour uptake was measured by mean standardized uptake values using a region of interest technique.

RESULTS

In visual analysis, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of PET without additional water ingestion were 100, 50, 62, 100 and 72%, respectively, and those of PET with additional water ingestion were 88, 100, 100, 91 and 94%, respectively. Using spot imaging under the condition with additional water ingestion, four gastric carcinomas were depicted more clearly.

CONCLUSION

Gastric distention as a result of patients drinking a glass of water is a simple and noninvasive method for improving the diagnostic accuracy of FDG-PET in patients with locally advanced gastric carcinoma.

Gastric distension by ingesting food is useful in the evaluation of primary gastric cancer by FDG PET

Gastric carcinoma is the second leading cause of cancer-related death worldwide. Detection and surgical resection of gastric cancer in the early stage provides the only hope for improved survival in patients with gastric cancer. Positron emission tomography (PET) with F-18 2-deoxy-2-fluoro-D-glucose (FDG) has been shown to be essential in the evaluation of a variety of malignancies. However, conventional FDG PET has limited value for detecting a primary tumor of the stomach, mostly because of the relatively high levels of physiological uptake by the contracted stomach. We report 3 cases of primary gastric carcinomas detected successfully by FDG PET after the ingestion of food. The PET images of the stomach after ingesting food were compared with the routine fasting-state whole-body PET images for each patient. When the stomach was distended by food, the malignant lesions were more discernible. These cases indicate that gastric distension by ingesting food may be a simple method that can help to detect a primary gastric malignancy by FDG PET.

Malignant Lesions Can Mimic Gastric Uptake on FDG PET

Gastric FDG uptake is a common observation on positron emission tomography (PET), which is most frequently caused by a nonmalignant etiology. However, a malignant lesion in the region of the stomach must not be overlooked. A 48-year-old woman with a history of melanoma in the esophagus and status postesophagectomy underwent FDG PET to evaluate for tumor recurrence. The images demonstrated hypermetabolism in the region of the location of the stomach. However, considering that the patient had a history of a stomach pullthrough procedure, we felt that this activity was nongastric and represented tumor recurrence, which was subsequently confirmed by computed tomography scan and histopathologic examination.

An analysis of the physiological FDG uptake pattern in the stomach

The purpose of this study was to clarify the normal gastric FDG uptake pattern to provide basic information to make an accurate diagnosis of gastric lesions by FDG PET. We examined 22 cases, including 9 of malignant lymphoma, 8 of lung cancer, 2 of esophageal cancer, and 3 of other malignancies. No gastric lesions were observed in any of the 22 cases on upper gastrointestinal examinations using either barium meal or endoscopic techniques. The intervals between FDG PET and the gastrointestinal examination were within one week in all cases. The stomach regions were classified into the following three areas: U (upper)-area, M (middle)-area, and L (lower)-area. The degree of FDG uptake in these three gastric regions was qualitatively evaluated by visual grading into 4 degrees, and then a semiquantitative evaluation was carried out using the standardized uptake value (SUV). Based on a visual grading evaluation, the mean FDG uptake score in the U-, M-, and L-areas was 1.14 +/- 0.96, 0.82 +/- 0.96, and 0.36 +/- 0.49 (mean +/- S.D.), respectively. The FDG uptake scores obtained in the three areas were significantly different (Friedman test, p < 0.05). Furthermore, the rank order of the FDG uptake score in each case (U > or = M > or = L) was found to be statistically significant (Cochran-Armitage trend test, p < 0.05). The mean SUVs of 11 cases in the three areas were 2.38 +/- 1.03, 1.91 +/- 0.71, and 1.34 +/- 0.44 (mean +/- S.D.), respectively. The SUV in the U-area was significantly higher than that in the L-area (Friedman test, p < 0.05). A significant difference in FDG uptake was observed among the three gastric areas, and the FDG uptake extent in all cases was U > M > L. In conclusion, the physiological gastric FDG uptake was significantly higher at the oral end. A stronger gastric FDG uptake at the anal end may therefore be suggestive of a pathological uptake.