Florbetapir (F18-AV-45) PET to assess amyloid burden in Alzheimer's disease dementia, mild cognitive impairment, and normal aging.

OBJECTIVE: To evaluate the performance characteristics of florbetapir F18 positron emission tomography (PET) in patients with Alzheimer's disease (AD), mild cognitive impairment (MCI), and healthy control subjects (HCs). METHODS: Florbetapir PET was acquired in 184 subjects (45 AD patients, 60 MCI patients, and 79 HCs) within a multicenter phase 2 study. Amyloid burden was assessed visually and quantitatively, and was classified as positive or negative. RESULTS: Florbetapir PET was rated visually amyloid positive in 76% of AD patients, 38% of MCI patients, and 14% of HCs. Eighty-four percent of AD patients, 45% of MCI patients, and 23% of HCs were classified as amyloid positive using a quantitative threshold. Amyloid positivity and mean cortical amyloid burden were associated with age and apolipoprotein E ε4 carrier status. CONCLUSIONS: : The data are consistent with expected rates of amyloid positivity among individuals with clinical diagnoses of AD and MCI, and indicate the potential value of florbetapir F18 PET as an adjunct to clinical diagnosis.

Assessing the utility of the ventilation phase in ventilation-perfusion imaging for acute pulmonary embolism.

PURPOSE: This study aims to identify patient characteristics that allow the exclusion of the ventilation phase in ventilation-perfusion imaging for the evaluation of acute pulmonary embolism (PE). MATERIALS AND METHODS: A total of 500 consecutive ventilation-perfusion reports with an indication for possible acute PE were retrospectively reviewed. Information on ventilation abnormalities, perfusion defects, PIOPED classification, age, sex, chest radiograph results, and presence of respiratory disease was recorded. Patients with moderate and large perfusion defects were analyzed to assess the utility of the ventilation phase on the final PIOPED classification. RESULTS: Moderate (n=39) or large (n=26) perfusion defects were seen in 65 (13%) studies. Of these, 46 studies (70.8%) had defects unmatched on ventilation and three (4.6%) had triple-match defects, resulting in 49 reports (75.4%) classified as intermediate (n=28) or high (n=21) probability for PE. There was a statistically significant association between unmatched defects and a clear chest radiograph (P=0.03) and an association approaching statistical significance with younger age (P=0.05). There was a strong association with respiratory disease (P=0.12) and no association with patient sex (P=0.82). The percentage of studies with unmatched defects increased from 70.8 to 76.7% (33/43, P=0.39) if patients with respiratory disease were excluded, to 82.4% (28/34, P=0.14) if abnormal chest radiographs were excluded, and to 95.7% (22/23, P=0.01) if both were excluded. CONCLUSION: There may be a subset of patients - younger patients with clear chest radiographs and no respiratory disease - for whom the ventilation phase can be excluded and the determination of a PE is based solely on perfusion abnormalities.