Is there an impact of 18F-FDG PET/CT on the surveillance and clinical management of recurrent ovarian cancer? Research based on a large sample in a single PET/CT center.

OBJECTIVES: The aim of the study was to evaluate the use of F-fluorodeoxyglucose ((18)F-FDG) PET/computed tomography (CT) in the follow-up and clinical management of ovarian cancer patients after therapy. MATERIALS AND METHODS: A total of 152 ovarian cancer patients who had undergone therapy were evaluated. Clinical information, CA-125 levels, and traditional imaging findings were analyzed. According to the indication for PET/CT the patients were divided into five groups for assessing the role of (18)F-FDG PET/CT in the clinical management of ovarian cancer patients after therapy. A comparison was made between the PET/CT findings and the results of clinical follow-up. RESULTS: Of the 152 patients, 137 had follow-up results and 15 were lost to follow-up. A total of 105 patients were found to have recurrent tumor and 32 were found to be disease-free after long-term follow-up. The diagnostic sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were 98.3, 91.2, 96.8, 97.5, and 93.9%, respectively. PET/CT was especially useful in patients when indications were to diagnose suspected recurrence, assess disease progression, and evaluate therapeutic response. CONCLUSION: PET/CT has been proven to be extremely valuable in the evaluation of patients with recurrent ovarian cancer and is particularly helpful in guiding treatment planning.

Comparison of the effect of positive and negative oral contrast agents on (18)F-FDG PET/CT scan.

UNLABELLED: 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.

Optimizing delayed scan time for FDG PET: comparison of the early and late delayed scan.

OBJECTIVES: Although dual-time-point scans have been widely used to improve the diagnostic efficacy of FDG PET in differentiating between malignant and benign lesions, no optimized delayed scan time-point has yet been recommended in clinical practice. Our study aimed to explore the most appropriate time for a delayed scan by comparing early and late delayed scans. METHODS: Eighty patients with suspected malignancy were given a three-phase (64 min, 110 min, 233 min after FDG injection) PET/CT scan. The maximum standardized uptake values (SUVs) in the three-phase scans were recorded as SUV1, SUV2 and SUV3, respectively, and compared among three-phase imaging. Retention indices (RIs) of each lesion in two delayed phases were calculated according to the formulae: RI1=SUV2-SUV1/SUV1 x100% and RI2=SUV3-SUV1/SUV1 x100%. RI1 and RI2 in both malignant and benign groups were assessed through correlation analysis. The diagnostic values of two delayed scans were compared through the analysis of the receiver operating characteristic curves. RESULTS: One hundred and nine of 148 lesions were malignant, and 39/148 lesions benign, which were verified by pathological, clinical, laboratory or radiological examination. RI1 and RI2 in malignancy were 14.8+/-13.1% and 10.8+/-20.5% respectively, and the correlation coefficient was 0.6 (P=0.0001). RI1 and RI2 in benign lesions were 11.3+/-28.2% and 9.3+/-42.4%, respectively, and the correlation coefficient was 0.6 (P=0.0001). The area under the ROC curve for RI1 was 0.627+/-0.050 (null hypothesis: true area=0.5, P=0.0130); whereas the area under the ROC curve for RI2 was 0.563+/-0.052 (null hypothesis: true area=0.5, P=0.2321), suggesting that the late delayed scan may have no diagnostic value. CONCLUSION: The retention index values in the two delayed phases have good relativity. The diagnostic value of early delayed imaging is higher than that of late delayed imaging. An early delayed scan, according to our research, should be recommended in clinical practice.