An international group of experts in pharmacokinetic modeling recommends a consensus nomenclature to describe in vivo molecular imaging of reversibly binding radioligands.

No abstract

No abstract

The aim of this guideline is to provide a minimum standard for the acquisition and interpretation of PET and PET/CT scans with [18F]-fluorodeoxyglucose (FDG). This guideline will therefore address general information about [18F]-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) and is provided to help the physician and physicist to assist to carrying out, interpret, and document quantitative FDG PET/CT examinations, but will concentrate on the optimisation of diagnostic quality and quantitative information.

Regional cerebral blood flow (CBF), oxygen extraction ratio (OER), oxygen utilization (CMRO2) and blood volume (CBV) were measured in a group of 34 healthy volunteers (age range 22-82 yrs) using the 15O steady-state inhalation method and positron emission tomography. Between subjects CBF correlated positively with CMRO2, although the interindividual variability of the measured values was large. OER was not dependent on CMRO2, but highly negatively correlated with CBF. CBV correlated positively with CBF. When considering the values of all the regions of interest within a single subject, a strict coupling between CMRO2 and CBF, and between CBF and CBV was found, while OER was constant and independent of CBF and CMRO2. In 'pure' grey and white matter regions CMRO2, CBF and CBV decreased with age approximately 0.50% per year. In other regions the decline was less evident, most likely due to partial volume effects. OER did not change or showed a slight increase with age (maximum in the grey matter region 0.35%/yr). The results suggest diminished neuronal firing or decreased dendritic synaptic density with age.

No abstract

No abstract

Summary: In order to localize cerebral cognitive or sen sorimotor function, activation paradigms are being used in conjunction with PET measures of cerebral activity (e.g., rCBF). The changes in local cerebral activity have two components: a global, region independent change and a local or regional change. As the first step in local izing the regional effects of an activation, global variance must be removed by a normalization procedure. A simple normalization procedure is division of regional values by the whole brain mean. This requires the dependence of local activity on global activity to be one of simple pro portionality. This is shown not to be the case. Further more, a systematic deviation from a proportional relation ship across brain regions is demonstrated. Consequently, any normalization must be approached on a pixel by-pixel basis by measuring the change in local activity and change in global activity. The changes associated with an activation can be partitioned into global and local effects according to two models: one assumes that the increase in local activity depends on global values and the other assumes independence. It is shown that the inThere is an increasing use of specific activation paradigms in positon emission tomography (PET) studies of local cerebral function. Activation stud ies permit analysis of local changes in function brought about by cognitive, pharmacological, or sensorimotor challenge. One obstacle to the inter pretation of regional data is the confounding effect of global changes.Received September 18, 1989; revised December 13, 1989; ac cepted December 14, 1989.Address correspondence and reprint requests to Dr. K. J. Friston at MRC Cyclotron Unit, Hammersmith Hospital, Du Cane Rd., London W12 OHS, U.K.Abbreviations used: ANCOVA, analysis of covariance; PET, positron-emission tomography; rCBF, regional cerebral blood flow; ROI, region of interest; SSM, scaled subprofile model. 458crease in activity due to a cognitive activation is indepen dent of global activity. This independence of the (activa tion) condition effect and the confounding linear effect of global activity on observed local activity meet the re quirements for an analysis of covariance, with the "nuisance" variable as global activity and the activation condition as the categorical independent variable. These conclusions are based on analysis of data from 24 scans: six conditions over four normal subjects using a verbal fluency paradigm. A technique is described based on ANCOVA and using statistical parametric mapping to lo calize foci in the brain that have been significantly per turbed by the cognitive tasks. This technique represents a fundamental and necessary departure from ROI-based approaches allowing the separation of global and local effects pixel by pixel, and provides an image of affected regions whose significance can be quantified. The speci ficity and sensitivity of the described method of change detection is assessed.