49 research outputs found
ARAS: an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes.
BackgroundAutomated protocols for measuring and dispensing solutions containing radioisotopes are essential not only for providing a safe environment for radiation workers but also to ensure accuracy of dispensed radioactivity and an efficient workflow. For this purpose, we have designed ARAS, an automated radioactivity aliquoting system for dispensing solutions containing positron-emitting radioisotopes with particular focus on fluorine-18 ((18)F).MethodsThe key to the system is the combination of a radiation detector measuring radioactivity concentration, in line with a peristaltic pump dispensing known volumes.ResultsThe combined system demonstrates volume variation to be within 5 % for dispensing volumes of 20 ÎŒL or greater. When considering volumes of 20 ÎŒL or greater, the delivered radioactivity is in agreement with the requested amount as measured independently with a dose calibrator to within 2 % on average.ConclusionsThe integration of the detector and pump in an in-line system leads to a flexible and compact approach that can accurately dispense solutions containing radioactivity concentrations ranging from the high values typical of [(18)F]fluoride directly produced from a cyclotron (~0.1-1 mCi ÎŒL(-1)) to the low values typical of batches of [(18)F]fluoride-labeled radiotracers intended for preclinical mouse scans (~1-10 ÎŒCi ÎŒL(-1))
Energy-sensitive GaSb/AlAsSb separate absorption and multiplication avalanche photodiodes for X-Ray and gamma-ray detection
Demonstrated are antimonyâbased (Sbâbased) separate absorption and multiplication avalanche photodiodes (SAMâAPDs) for Xâray and gammaâray detection, which are composed of GaSb absorbers and large bandgap AlAsSb multiplication regions in order to enhance the probability of stopping highâenergy photons while drastically suppressing the minority carrier diffusion. Wellâdefined Xâray and gammaâray photopeaks are observed under exposure to 241Am radioactive sources, demonstrating the desirable energyâsensitive detector performance. Spectroscopic characterizations show a significant improvement of measured energy resolution due to reduced highâpeak electric field in the absorbers and suppressed nonradiative recombination on surfaces. Additionally, the GaSb/AlAsSb SAMâAPDs clearly exhibit energy response linearity up to 59.5 keV with a minimum fullâwidth halfâmaximum of 1.283 keV. A further analysis of the spectroscopic measurement suggests that the device performance is intrinsically limited by the noise from the readout electronics rather than that from the photodiodes. This study provides a first understanding of Sbâbased energyâsensitive SAMâAPDs and paves the way to achieving efficient detection of highâenergy photons for Xâray and gammaâray spectroscopy
Quantitative assessments of glycolysis from single cells
The most common positron emission tomography (PET) radio-labeled probe for molecular diagnostics in patient care and research is the glucose analog, 2-deoxy-2-[F-18]fluoro-D-glucose (^(18)F-FDG). We report on an integrated microfluidics-chip/beta particle imaging system for in vitro ^(18)F-FDG radioassays of glycolysis with single cell resolution. We investigated the kinetic responses of single glioblastoma cancer cells to targeted inhibitors of receptor tyrosine kinase signaling. Further, we find a weak positive correlation between cell size and rate of glycolysis
Significant suppression of surface leakage in GaSb/AlAsSb heterostructure with Al2O3 passivation
This work develops a (NH4)2S/Al2O3 passivation technique for photodiode-based GaSb/AlAsSb heterostructure. Surface-sulfurated GaSb/AlAsSb heterostructure mesas show a significant suppression of reversed-bias dark current by 4â5 orders of magnitude after they are further passivated by Al2O3 layers. So the mesa sidewalls treated with (NH4)2S/Al2O3 layers can effectively inhibit the shunt path of dark carriers. The activation energies for both bulk and surface components are extracted from temperature-dependent currentâvoltage characteristics, which suggest that the bulk characteristics remain unchanged, while Fermi-level pinning at surfaces is alleviated. Additionally, temperature coefficients of the breakdown voltage are extracted, confirming that the breakdown process is confined entirely in the large bandgap AlAsSb regions. This study shows that the implementation of (NH4)2S/Al2O3 passivation can lead to room temperature GaSb-based photodiodes and GaSb/AlAsSb-based avalanche photodiodes for highly efficient photodetection
Fast Metabolic Response to Drug Intervention Through Analysis on a Miniaturized, Highly Integrated Molecular Imaging System
We report on a radiopharmaceutical imaging platform designed to capture the kinetics of cellular responses to drugs. Methods: A portable in vitro molecular imaging system comprising a microchip and a ÎČ-particle imaging camera permitted routine cell-based radioassays of small numbers of either suspended or adherent cells. We investigated the kinetics of responses of model lymphoma and glioblastoma cancer cell lines to ^(18)F-FDG uptake after drug exposure. Those responses were correlated with kinetic changes in the cell cycle or with changes in receptor tyrosine kinase signaling. Results: The platform enabled direct radioassays of multiple cell types and yielded results comparable to those from conventional approaches; however, the platform used smaller sample sizes, permitted a higher level of quantitation, and did not require cell lysis. Conclusion: The kinetic analysis enabled by the platform provided a rapid (âŒ1 h) drug screening assay
Quantitative assessments of glycolysis from single cells
The most common positron emission tomography (PET) radio-labeled probe for molecular diagnostics in patient care and research is the glucose analog, 2-deoxy-2-[F-18]fluoro-D-glucose (^(18)F-FDG). We report on an integrated microfluidics-chip/beta particle imaging system for in vitro ^(18)F-FDG radioassays of glycolysis with single cell resolution. We investigated the kinetic responses of single glioblastoma cancer cells to targeted inhibitors of receptor tyrosine kinase signaling. Further, we find a weak positive correlation between cell size and rate of glycolysis
NEMA NU 4-2008 Comparison of preclinical PET imaging systems
The National Electrical Manufacturers Association (NEMA)
standard NU 4-2008 for performance measurements of smallanimal
tomographs was recently published. Before this standard,
there were no standard testing procedures for preclinical
PET systems, and manufacturers could not provide clear
specifications similar to those available for clinical systems
under NEMA NU 2-1994 and 2-2001. Consequently, performance
evaluation papers used methods that were modified ad
hoc from the clinical PET NEMA standard, thus making
comparisons between systems difficult. Methods: We acquired
NEMA NU 4-2008 performance data for a collection of commercial
animal PET systems manufactured since 2000: micro-
PET P4, microPET R4, microPET Focus 120, microPET Focus
220, Inveon, ClearPET, Mosaic HP, Argus (formerly eXplore
Vista), VrPET, LabPET 8, and LabPET 12. The data included
spatial resolution, counting-rate performance, scatter fraction,
sensitivity, and image quality and were acquired using settings
for routine PET. Results: The data showed a steady improvement
in system performance for newer systems as compared
with first-generation systems, with notable improvements in
spatial resolution and sensitivity. Conclusion: Variation in system
design makes direct comparisons between systems from
different vendors difficult. When considering the results from
NEMA testing, one must also consider the suitability of the
PET system for the specific imaging task at hand.This work was funded by the Natural Sciences and Engineering Research Council of Canada under Discovery Grant 341628-2007. No other potential conflict of interest relevant to this article was reported.En prens