The role of gastric distention in differentiating recurrent tumor from physiologic uptake in the remnant stomach on 18F-FDG PET.
Physiologic (18)F-FDG uptake in the stomach can often cause false-positive results and lowers the usefulness of (18)F-FDG PET in evaluating the remnant stomach. We assessed the role of gastric distension to see whether it is beneficial for the differentiation of recurrent tumors from physiologic (18)F-FDG uptake in the remnant stomach.


METHODS
Thirty patients (22 men and 8 women; age range, 27-80 y; mean age, 58.3 y) with a history of subtotal gastrectomy for gastric cancer underwent (18)F-FDG PET for various clinical indications. After whole-body imaging, the patients were asked to drink water, and then spot imaging of the stomach was performed. (18)F-FDG uptake in the remnant stomach was considered positive for malignancy if it was persistently increased, whether focal or diffuse, after water ingestion. We used 2 standardized uptake value (SUV) criteria to differentiate benign from malignant uptake. First, a lesion was considered benign if its SUV was less than 2 on whole-body imaging. Second, for a lesion with an SUV of 2 or above, it was classified as benign if SUV decreased by more than 10% after water ingestion.


RESULTS
Visual analysis of whole-body images produced 9 true-negative, 4 false-positive, 16 true-positive, and 1 false-negative results. Use of additional spot images produced 12 true-negative, 1 false-positive, 15 true-positive, and 2 false-negative results. When an SUV cutoff of 2 was applied for malignancy before water ingestion, all 17 patients with local recurrence were correctly identified, but 11 of the 13 patients without local recurrence were falsely considered to have a recurrent tumor in the remnant stomach. To reduce the false-positive results, we used the second SUV criterion after water ingestion. Use of that criterion produced 4 false-negative results although it correctly identified the 11 false-positive results as true negative.


CONCLUSIONS
Gastric distension by having patients drink a glass of water seems to be a simple, cost-effective way of improving the diagnostic accuracy of (18)F-FDG PET in patients with suspected recurrence in the remnant stomach. Visual analysis with special attention to the configuration of (18)F-FDG activity after water ingestion seems to be more useful than the change in SUV in evaluating the remnant stomach.
Yun
Mijin
M
Division of Nuclear Medicine, Department of Diagnostic Radiology, Yonsei University College of Medicine, 134 Shinchon-dong, Seodaemoon-ku, Seoul, Korea 120-752.
Choi
Hyun Seok
HS
Yoo
Eunhye
E
Bong
Jung Kyun
JK
Ryu
Young Hoon
YH
Lee
Jong Doo
JD
D000230:Adenocarcinoma / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005189:False Positive Reactions; D005260:Female; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics; D005743:Gastrectomy; D018530:Gastric Stump / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013274:Stomach Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000378:metabolism; D014915:Whole-Body Counting
D005462:Fluorine Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18