Integrating Information from FDG - and Amyloid PET for Detecting Different Types of Dementia in Older Persons. A Case-series Study.

A significant progress has been made in the understanding of the neurobiology of Alzheimer's disease. The post-mortem studies are the gold standard for a correct histopathological diagnosis, contributing to clarify the correlation with cognitive, behavioral and extra-cognitive domains. However, the relationship between pathological staging and clinical involvement remains challenging. Neuroimaging, including positron emission tomography (PET) and magnetic resonance, could help to bridge the gap by providing in vivo information about disease staging. In the last decade, advances in the sensitivity of neuroimaging techniques have been described, in order to accurately distinguish AD from other causes of dementia. Fluorodeoxyglucose-traced PET (FDG-PET) is able to measure cerebral metabolic rates of glucose, a proxy for neuronal activity, theoretically allowing detection of AD. Many studies have shown that this technique could be used in early AD, where reduced metabolic activity correlates with disease progression and predicts histopathological diagnosis. More recently, molecular imaging has made possible to detect brain deposition of histopathology-confirmed neuritic ß-amyloid plaques (Aß) using PET. Although Aß plaques are one of the defining pathological features of AD, elevated levels of Aß can be detected with this technique also in older individuals without dementia. This raises doubts on the utility of Aß PET to identify persons at high risk of developing AD. In the present case-series, we sought to combine metabolic information (from FDG-PET) and amyloid plaque load (from Aß PET) in order to correctly distinguish AD from other forms of dementia. By selecting patients with Aß PET + / FDG-PET + and Aß PET - / FDG-PET +, we propose an integrated algorithm of clinical and molecular imaging information to better define type of dementia in older persons.

Prognostic value of 18F-FDG standard uptake value by integrated PET/CT in the staging of malignant pleural mesothelioma.

Malignant pleural mesothelioma (MPM) is a rare and aggressive tumor with generally disappointing results in terms of survival, however, there are occasional long-term survivors probably due to the biologic characteristics of the disease. Standard uptake value (SUV) of [(18)F] Fluorodeoxyglucose (FDG) evaluated by photon emission tomography (PET) is now widely accepted as an indicator of biologic behavior in several malignancies. The aim of this study was to verify whether SUV(max) and SUV(mean) are inversely associated with the prognosis of patients with MPM and whether there was a correlation between grading/disease stage and SUV value. Patients with histologically proven MPM underwent integrated PET and computed tomography (CT) scanning. Patients fasted and received 5.18 MBq of FDG per kilogram of body weight. Based on the maximum Chi-Square method, a SUV(max) of 4.21 (range: 2.30-14.74) and a SUV(mean) of 2.78 (range: 1.80-7.00) were used to classify patients as having a good or poor prognosis, respectively. From January 2004 to March 2010, 27 patients were analyzed: median age was 65 years (range: 54-77) and histologic MPM subtypes were epithelioid (23 patients) and biphasic (4 patients). At a median follow-up of 23 months (range: 1-52), there was no difference in median survival for either high or low SUV(max) [26 months (range: 11-not reached) vs.19 months (range: 12-not reached); p=0.811] or for high or low SUV(mean) [26 months (range: 8-not reached) vs.19 months (range: 11-not reached); p=0.831]. High SUV(max) (p=0.018) was statistically correlated with high-stage disease. There was only a trend towards statistical significance between high-grade disease and high SUV(mean) (p=0.083); no such trend was found between advanced stages and SUV(max) (p=0.268). We observed a significant correlation only between high SUV(max) and high-grade disease. No other relationships between SUV(max) and SUV(mean) with biologic and clinical parameters were found. This is probably due to the patient characteristics and to the non-routine use of 18F-FDG PET/CT to stage rare tumors such as MPM.