Salvatore U. Berlangieri

UNLABELLED: Amyloid-beta (Abeta) imaging with N-methyl-(11)C-2-(4'-methylamino-phenyl)-6-hydroxy-benzothiazole ((11)C-6-OH-BTA-1; also known as (11)C-PIB) shows a robust increase in cortical binding in Alzheimer's disease (AD). The aim of this study was to explore the clinical potential of Abeta imaging for the diagnosis of AD by comparison of the accuracy of visual reading of (11)C-PIB images with quantitative analysis and (18)F-FDG. METHODS: Fifteen AD patients (age, 71.1 +/- 11.3 y [mean +/- SD]; mini-mental state examination [MMSE], 18.9 +/- 9.3 [mean +/- SD]) and 25 healthy control (HC) subjects (age, 71.9 +/- 6.82 y; MMSE >or= 28) underwent 90-min dynamic (11)C-PIB PET and 20-min static (18)F-FDG PET. (11)C-PIB images, generated from data acquired between 40 and 70 min after injection, and (18)F-FDG images were rated separately by 2 readers as normal, possible AD, or probable AD. Quantitative analyses used the distribution volume ratio (DVR) of frontal cortex, parietotemporal cortex, posterior cingulate, and caudate nucleus for (11)C-PIB and standardized uptake value ratio (SUVR) of parietotemporal cortex and posterior cingulate for (18)F-FDG, using cerebellar cortex as the reference region. Receiver-operating-characteristic (ROC) analysis was performed to compare the accuracy of quantitative measures. To determine the effect of age on diagnostic accuracy, the median age of the AD subjects (74 y) was chosen to separate the cohort into younger (64.4 +/- 5.8 y) and older (78.6 +/- 4.1 y) groups. RESULTS: Visual agreement between readers was excellent for (11)C-PIB (kappa = 0.90) and good for (18)F-FDG (kappa = 0.56). (11)C-PIB was more accurate than (18)F-FDG both on visual reading (accuracy, 90% vs. 70%, P = 0.05) and ROC analysis (95% vs. 83%, P = 0.02). Accuracy declined more with (18)F-FDG than with (11)C-PIB in the older group. CONCLUSION: Visual analysis of (11)C-PIB images appears more accurate than visual reading of (18)F-FDG for identification of AD and has accuracy similar to quantitative analysis of a 90-min dynamic scan. The accuracy of (11)C-PIB PET is limited by cortical binding in some healthy elderly subjects, consistent with postmortem studies of cerebral Abeta. Longitudinal follow-up is required to determine if this represents detection of preclinical AD.

PURPOSE: We evaluate the accuracy of F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) for staging and management of renal cell carcinoma. MATERIALS AND METHODS: FDG-PET was performed in 25 patients with known or suspected primary renal tumors and/or metastatic disease and compared with conventional imaging techniques, including computerized tomography (CT). Histopathological confirmation was obtained in 18 patients and confirmation of the disease was by followup in the remainder. The impact of FDG-PET on disease management was also assessed. RESULTS: Of the 17 patients with known or suspected primary tumors FDG-PET was true positive in 15, true negative in 1 and false-negative in 1. Comparative CT was true positive in 16 patients and false-positive in 1. The accuracy of FDG-PET and CT was similar (94%). All patients would have undergone radical nephrectomy after conventional imaging findings but FDG-PET results altered treatment decisions for 6 (35%), of whom 3 underwent partial nephrectomy and 3 avoided surgery due to confirmation of benign pathology or detection of unsuspected metastatic disease. Of the 8 cases referred for evaluation of local recurrence and/or metastatic disease FDG-PET changed treatment decisions in 4 (50%), with disease up staged in 3 and recurrence excluded in 1. Compared with CT, FDG-PET was able to detect local recurrence and distant metastases more accurately and differentiated recurrence from radiation necrosis. CONCLUSIONS: FDG-PET accurately detected local disease spread and metastatic disease in patients with renal cell carcinoma and altered treatment in 40%. FDG-PET may have a role in the diagnostic evaluation of patients with renal cell carcinoma preoperatively and staging of metastatic disease.

UNLABELLED: PET offers a noninvasive means to assess neoplasms, in view of its sensitivity and accuracy in staging tumors and potentially in monitoring treatment response. The aim of this study was to evaluate newly diagnosed primary brain tumors for the presence of hypoxia, as indicated by the uptake of 18F-fluoromisonidazole (18F-FMISO) and to examine the relationship of hypoxia to the uptake of 18F-FDG and molecular markers of hypoxia. METHODS: Seventeen patients with suspected primary glioma were enrolled prospectively in this study. Sixteen patients had histology, with 2 having metastatic disease. All patients had PET studies with 18F-FMISO and 18F-FDG and MRI studies. Immunohistochemistry was undertaken with tumor markers of angiogenesis and hypoxia. Patients were monitored for disease progression and statistical analysis of data was performed. RESULTS: Of the 14 patients with histology, 8 died with a median time of 16 mo (range, 2-30 mo) until death. Of those who died, 7 had positive and 1 had negative 18F-FMISO uptake. 18F-FMISO uptake was observed in all high-grade gliomas but not in low-grade gliomas. A significant relationship was found between 18F-FDG or 18F-FMISO uptake and expression of VEGF-R1 and Ki67 expression. Other immunohistochemical markers demonstrated a trend toward increased uptake but none was significant. CONCLUSION: 18F-FMISO PET provides a noninvasive assessment of hypoxia in glioma and was prognostic for treatment outcomes in the majority of patients. 18F-FMISO PET may have a role not only in directing patients toward targeted hypoxic therapies but also in monitoring response to such therapies.