PET imaging of 18F-florbetapir in cognitively impaired individuals: Lack of activity within the cerebellar cortex.

Ten individuals suspected of having possible Alzheimer disease underwent PET imaging using 18F-Flubetapir. Only one of ten individuals had a pattern typical for normal elderly control subjects with 9 of the 10 showing a Alzheimer type pattern for the cerebral cortex yet all 10 subjects had uniformly low to absent tracer localization to the cerebellar cortex; significantly high tracer activity was noted within the subcortical white matter of the cerebellum in a symmetric manner in all cases. In consideration of studies that have shown amyloid deposits within the cerebellar cortex in 90% of pathologically proven cases of Alzheimer's disease, these findings raise questions about the actual clinical value of florbetapir PET imaging in evaluating cerebellar involvement and raises questions whether PET imaging of this tracer accurately portrays patterns of amyloid deposition, as there is rapid hepatic metabolism of the parent compound after intravenous injection. Possible links to Alzheimer's disease related alterations in blood-brain barrier permeability to the parent compound and subsequent radiolabelled metabolites are discussed as potential mechanisms that could explain the associated localization of the tracer to the brainstem and subcortical white matter within the cerebrum and cerebellum of Alzheimer's disease patients.

Systemic Immune Response to Vaccination on FDG-PET/CT.

A patient with newly diagnosed right lung cancer had transient 18F-fluorodeoxyglucose (FDG)-avid left axillary lymph nodes and intense splenic FDG uptake on positron emission tomography (PET)/computed tomography (CT). History revealed that the patient received a left-sided influenza vaccine 2-3 days before the examination. Although inflammatory FDG uptake in ipsilateral axillary nodes is reported, to our knowledge, this is the first report of visualization of the systemic immune response in the spleen related to the influenza vaccination on FDG-PET/CT. The history, splenic uptake and time course on serial FDG-PET/CT helped to avoid a false-positive interpretation for progressing lung cancer and alteration of the radiation therapy plan.

Sirolimus-induced interstitial pneumonitis in a renal transplant patient.

We report interstitial pneumonitis caused by sirolimus (Rapamune, an immunosuppressive agent) in a renal transplant patient. This rare manifestation was recently recognized as a troublesome adverse effect of sirolimus in many solid-organ transplant recipients, the majority of whom are kidney transplant recipients. While on sirolimus our patient developed cough, fever, and patchy infiltrates, which failed to respond to multiple courses of antibiotic therapy. Biopsy showed findings characteristic of drug-induced hypersensitivity pneumonitis, and excluded other entities, such as opportunistic infection. Improvement occurred only upon discontinuation of the sirolimus.

Accurate detection of metabolically active "brown" and "white" adipose tissues with computed tomography.

BACKGROUND: Adipose tissues (AT) are highly metabolically active complex endocrine organs and are classified into white (WAT) and brown AT (BAT) with proinflammatory and anti-inflammatory characteristics. The current study investigated the accuracy of computed tomography (CT) to quantitatively detect BAT and WAT based on Hounsfield unit (HU) threshold compared to standardized uptake values (SUVs) of corresponding AT with the use of positron emission tomography (PET). METHODS: One hundred twenty-four patients who underwent whole-body (18)F-fluorodeoxyglucose ((18)F-FDG) PET/CT were studied. The SUVs and HUs of regions of BAT and WAT were measured and compared in these scans. The receiver operator characteristic (ROC) analysis was used to detect the HU threshold values for the detection of BAT and WAT. RESULTS: The CT HU of BAT, with high (18)F-FDG uptake, was significantly higher compared to WAT (-67.1 ± 8.2 [-10 to -87] versus -93.5 ± 10.1 [-88 to -190], P = .0006). Generalized linear-regression models revealed that mean CT HU of BAT was 26.4 HU higher than that of WAT (P = .001). A strong agreement between CT HU and PET SUV in measuring metabolically active AT (r(2) = 0.81, P = .0001) was observed. The ROC curve showed that the optimal cutoff value of CT HU to detect BAT was HU ≥-87 with sensitivity of 83.3% and specificity of 100%, and the negative CT HU below -87 is highly specific for WAT. CONCLUSION: In our study, CT can accurately and quantitatively detect BAT and WAT based on CT HU threshold, which is -10 to -87 for BAT and -88 to -190 for WAT.