Improved beta-amyloid PET reproducibility using two-phase acquisition and grey matter delineation.

PURPOSE: We investigated whether the reproducibility of standard visual reporting (STD method) in flutemetamol (FMM) PET can be improved using a newly introduced method that uses grey matter edges derived from the perfusion phase (GM-EDGE method). METHODS: Two-phase FMM PET was performed in 121 patients with mild cognitive impairment. Five nuclear medicine physicians blindly and independently evaluated all late-phase scans, initially employing the STD method and later the GM-EDGE method. A five-point scale was used to express the degree of amyloid positivity, and a binary classification (positive/negative) was used in combination with subjective confidence (five-point scale). Multirater Fleiss' kappa, intraclass correlation coefficient (ICC) and inter-rater reliability (Cohen's kappa) were determined for the STD and GM-EDGE methods. RESULTS: The weighted Cohen's kappa values for the five-point measure of amyloid positivity ranged from 0.63 to 0.73 (median 0.70) for the STD method and from 0.76 to 0.89 (median 0.80) for the GM-EDGE method (ICC 0.84, 95% CI 0.79-0.88, for the STD method; 0.91, 95% CI 0.89-0.94, for the GM-EDGE method). The nonweighted Cohen's kappa value for the binary classification ranged from 0.73 to 0.93 (median 0.82) for the STD method and 0.90 to 0.97 (median 0.93) for the GM-EDGE method (Fleiss' kappa 0.82, 95% CI 0.77-0.88, for the STD method; 0.93, 95% CI 0.87-0.99, for the GM-EDGE method). The GM-EDGE method resulted in significantly greater subjective confidence in the readings of four physicians (p < 0.010). The binary classification was concordant among all five physicians in 80.8% of the scans using the STD method and in 91.6% of the scans using the GM-EDGE method (p = 0.016). CONCLUSION: The newly introduced GM-EDGE method was associated with significantly higher inter-rater agreement among physicians and higher subjective confidence in the reading. The method is easy to implement in clinical practice, especially when the perfusion phase is utilized clinically.

Clinical outcomes of patients with nonseminomatous germ cell tumours and negative postchemotherapy positron emission tomography.

Univariate and multivariate analyses were carried out to identify factors associated with the failure of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) to correctly predict relapse-free survival in patients with nonseminomatous germ cell tumours. Ninety-three patients with negative postchemotherapy FDG-PET scan were analyzed in the retrospective study. The FDG-PET result was validated by long-term follow-up and, in some patients, by resection of the residual tumour mass. The negative predictive value of FDG-PET was 81.7%. Higher tumour marker levels and nodal stage at diagnosis, presence of residual mass, and teratoma or teratocarcinoma in the primary histology were associated with FDG-PET failure.

Prognostic and diagnostic accuracy of [18F]FDG-PET/CT in 190 patients with carcinoma of unknown primary.

PURPOSE: The aim of the study was to determine the accuracy of [(18)F]fluorodeoxyglucose (FDG) PET/CT in the search for the primary and the presence of a malignancy. The prognostic value of FDG-PET/CT information was tested. METHODS: A total of 190 patients were retrospectively analysed: 82 with histologically proven metastases (HPM) and 108 with clinical suspicion of the presence of a malignancy (CSM). The sensitivity and specificity were determined. Overall survival was calculated to evaluate the prognostic value of the FDG-PET/CT findings. RESULTS: In the search for the primary, the sensitivity and specificity were 62.0% and 81.9%, respectively. In the search for the presence of a malignancy, the sensitivity and specificity were 93.6% and 85.7%, respectively. Between the HPM and CSM groups, no significant difference in sensitivity and specificity was found either in the search for the primary or in the search for the presence of a malignancy. No significant difference in the sensitivity and specificity was found between 78 patients who were investigated by contrast-enhanced FDG-PET/CT and the remaining patients. A significantly shorter overall survival was found among patients with positive FDG-PET/CT findings compared with patients with negative findings (p = 0.00001); no significant difference in survival was found between the HPM and the CSM group (p = 0.770). CONCLUSION: FDG-PET/CT imaging is very helpful in the search for the presence of a malignancy in patients with carcinoma of unknown primary syndrome. FDG-PET/CT is less accurate in identifying exactly the site of a primary. Discovery of a hypermetabolic lesion was associated with the worst survival rate.