Our aim was to compare the effect of orally taken 1% diatrizoate meglumine, 5% mannitol and water before positron emission tomography/computerized tomography (PET/CT) scan on gastrointestinal tract delineation and fluorine-18-fluorodeoxyglucose ((18)F-FDG) uptake. Our methods were as follows: Sixty-one patients referred for PET/CT scan without gastrointestinal diseases were divided into three groups. One thousand mL of 1% diatrizoate meglumine was orally taken 50 min before PET/CT scan in Group 1 (n=25), 1000 mL 2.5% mannitol was orally taken before scan in Group 2 (n=20) and 1000 mL water was orally taken before scan in Group 3 (n=16). Serum glucose and insulin were tested before and 45 min after taking mannitol in Group 2 patients. Paired t test was used to compare the glucose and insulin changes. The degree of gastrointestinal filling and (18)F-FDG uptake were evaluated by three nuclear medicine physicians using a 4 grade classification standard. Kruskal-Wallis and Mann- Whitney none parametric test was used to compare the filling condition and (18)F-FDG uptake difference among the three groups and between each group.
Results: the differences of serum glucose and insulin levels were not significant before and after contrast taken, in Group 2 patients. Group 2 patients had better gastrointestinal filling than patients of Group 1. Also, Group 2 patients' gastrointestinal filling was better than in Group 3 except in rectum. The jejunum, ascending, transverse and descending colon were better filled in Group 1 patients than in Group 3 patients. The degree of (18)FFDG uptake in stomach, jejunum and ileum, in Group 2 were significantly lower than those of Group 3 (P<0.05). (18)F-FDG uptake in jejunum, in Group 1 was also lower than in Group 3 (P<0.05). (18)F-FDG uptake in ascending colon in Group 1 was higher than in Group 3 (P<0.05). (18)F-FDG uptake in transverse and descending colon, in both Group 1 and Group 2 was significantly higher than in Group 3 (P<0.05). (18)F-FDG uptake in rectum, in Group 2 was significantly higher than in Group 3 (P<0.01). The average maximum CT values in stomach, jejunum, ileum and ascending colon in Group 1 patients were: 132+/-23, 191+/-31, 313+/-47 and 374+/-53 Hounsfield units respectively (Mean+/-SD, P<0.01 between every two groups). In conclusion, patients who take iso-osmia mannitol have good gastrointestinal filling, less physiological (18)F-FDG uptake and may thus have better (18)F-FDG images displaying gastrointestinal abnormalities and differentiating pathological from physiological lesions.