Delayed (18)F-fluoro-2-deoxy-D-glucose positron emission tomography scan for differentiation between malignant and benign lesions in the pancreas.
BACKGROUND
Positron emission tomography (PET) using (18)F-fluoro-2-deoxy-D-glucose (FDG) has been used for the evaluation of various tumors, but accumulation in inflammatory lesions makes it a controversial modality. The aim of this study was to investigate the usefulness of delayed scanning in differentiation between malignant and benign lesions in the pancreas.


METHODS
Forty-seven patients with suspected pancreatic carcinoma were studied by FDG-PET. All patients received approximately 370 megabequerels of FDG after a transmission scan, and an emission scan was performed 1 hour and 2 hours later for all patients. A subset of 19 patients was also scanned at 3 hours postinjection. The standardized uptake value (SUV) was determined, and the retention index was calculated by dividing the increase in the SUV between 1 hour and 2 hours postinjection by the SUV at 1 hour postinjection.


RESULTS
Of 27 malignant lesions, the SUVs of 22 lesions increased at 2 hours postinjection, whereas the FDG uptake in 17 of 20 benign lesions decreased. The SUVs at 3 hours postinjection were higher than those at 2 hours postinjection in 9 of 14 malignant lesions and in 2 of 5 benign lesions. Malignant lesions showed a higher retention index than benign lesions (mean +/- standard deviation: 12. 36 +/- 13.37 and -7.05 +/- 17.28, respectively; P < 0.0001). Applying an SUV of 2.5 at 1 hour postinjection with the cut-off value for the differentiation between malignant and benign lesions caused one false negative result and seven false positive results, with a diagnostic accuracy of 83.0% (39 of 47 patients). However, combining the retention index with the SUV obtained at 2 hours postinjection provided a higher diagnostic accuracy (91.5%; 43 or 47 patients) than the SUV alone. The false negative rate remained constant when the retention index was taken into account. Images at 3 hours postinjection usually were unhelpful in differentiating further between malignant lesions and benign lesions.


CONCLUSIONS
The current data suggest that delayed FDG-PET scanning at 2 hours postinjection may contribute to differentiation between malignant and benign lesions in the pancreas.
Nakamoto
Y
Y
Department of Nuclear Medicine and Diagnostic Imaging, Graduate School of Medicine, Kyoto University, Kyoto, Japan. nakamoto@kuhp.kyoto-u.ac.jp
Higashi
T
T
Sakahara
H
H
Tamaki
N
N
Kogire
M
M
Doi
R
R
Hosotani
R
R
Imamura
M
M
Konishi
J
J
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003937:Diagnosis, Differential; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000000981:diagnostic imaging / Q000473:pathology*; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D014055:Tomography, Emission-Computed
D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18