Cross-validation of a non-invasive positron detector to measure the arterial input function for pharmacokinetic modelling in dynamic positron emission tomography.

Kinetic modeling of positron emission tomography (PET) data can assess index rate of uptake, metabolism and predict disease progression more accurately than conventional static PET. However, it requires knowledge of the time-course of the arterial blood radioactivity concentration, called the arterial input function (AIF). The gold standard to acquire the AIF is by invasive means. The purpose of this study was to validate a previously developed dual readout scintillating fiber-based non-invasive positron detector, hereinafter called non-invasive detector (NID), developed to determine the AIF for dynamic PET measured from the human radial artery. The NID consisted of a 3 m long plastic scintillating fiber with each end coupled to a 5 m long transmission fiber followed by a silicon photomultiplier. The scintillating fiber was enclosed inside the grooves of a plastic cylindrical shell. Two sets of experiments were performed to test the NID against a previously validated microfluidic positron detector. A closed-loop microfluidic system combined with a wrist phantom was used. During the first experiment, the three PET radioisotopes 18F, 11C and 68Ga were tested. After optimizing the detector, a second series of tests were performed using only 18F and 11C. The maximum pulse amplitude to electronic noise ratio was 52 obtained with 11C. Linear regressions showed a linear relation between the two detectors. These preliminary results show that the NID can accurately detect positrons from a patient's wrist and has the potential to non-invasively measure the AIF during a dynamic PET scan. The accuracy of these measurements needs to be determined.

Characterization of scintillating fibers for use as positron detector in positron emission tomography.

PURPOSE: Manual and automatic blood sampling at different time intervals is considered the gold standard to determine the arterial input function (AIF) in dynamic positron emission tomography (PET). However, blood sampling is characterized by poor time resolution and is an invasive procedure. The aim of this study was to characterize the scintillating fibers used to develop a non-invasive positron detector. METHODS: The detector consists of a scintillating fiber coupled at each end to transmission fiber-optic cables that are connected to photo multiplier tubes in a dual readout setup. The detector is designed to be wrapped around the wrist of the patient undergoing dynamic PET. The attenuation length and bending losses were measured with excitation from gamma radiation (137Cs) and ultraviolet (UV) light. The response to positron-emitting radio-tracers was evaluated with 18F and 11C. RESULTS: The attenuation length for a 3.0 m and 1.5 m long scintillating fiber both coincides with the attenuation length given by the manufacturer when excited with the 137Cs source, but not with the UV source due to the differences in scintillation mechanisms. The bending losses are smaller than the measurement uncertainty for the 137Cs source irradiation, and increase when the bending radius decrease for the UV source irradiation. The signal-to-noise ratio for 18F and 11C solutions are 1.98 and 22.54 respectively. The measured decay constant of 11C agrees with its characteristic value. CONCLUSION: The performed measurements in the dual readout configuration suggest that scintillating fibers may be suitable to determine the AIF non-invasively.

Supporting knowledge into action: The Canadian Best Practices Initiative for Health Promotion and Chronic Disease Prevention.

Public health practitioners and policy-makers working to address the burden of chronic disease are increasingly seeking to use best practices given the need to make thoughtful program and policy choices with limited resources. While the evidence base in chronic disease prevention is growing through a number of different information sources, there is often a disconnect between the desire to use best practices and their implementation. This is related not only to individual and organizational barriers in terms of time and resources, but also to lack of agreement on what constitutes best practice and what sources of evidence are valid guides for practice. This is compounded by lack of user-friendly and streamlined access to credible best practice evidence and decision making/practice supports. In response to these needs, six years ago Canadian researchers, policy-makers and practitioners came together to begin working on creating a best practice system in Canada for health promotion and chronic disease prevention. This article presents an overview of the development of the Canadian Best Practices Portal and in particular how an evolution in thinking about best practice methodology and evidence will contribute to an enriched knowledge base for health promotion and chronic disease prevention policy, practice and research.