A study of scintillation beta microprobes Woody, C.L.; Stoll, S.P.; Schlyer, D.J. ...
IEEE transactions on nuclear science,
10/2002, Letnik:
49, Številka:
5
Journal Article
Recenzirano
Several types of scintillation microprobes have recently been developed to directly measure positron activity from radiotracers in live animals. These probes consist of either a small lutetium ...oxyorthosilicate (LSO) crystal or plastic scintillator coupled to an optical fiber that is read out with a photomultiplier tube operated in a single photon counting mode. In this paper, a comparison is made between the two types of probes in terms of their sensitivity to both positrons and gammas. It was found that LSO offers very high sensitivity to positrons due to its high density and light output, and allows the construction of very small probes for certain applications. The LSO probe can also provide effective discrimination between positrons and gammas, and provide better localization of positron decays, using pulse height discrimination. Results are also given on the use of the microprobe on live laboratory animals.
We have built and evaluated a gamma-ray imaging detector for PET and simultaneous PET-MRI with the goal of providing sub-mm spatial resolution in all 3 dimensions. It consists of a solid slab of LYSO ...coupled to arrays of silicon photomultipliers (SiPMs) on both sides. The design is relatively cost-effective because it requires minimal mechanical processing of the scintillator, and because the photosensors are relatively large resulting in a small number of readout channels. Positioning algorithms employed include simple Anger centroid and a unique maximum likelihood approach with a measured system model which was developed for a previous generation APD-based detector. The design and construction of the detector, front-end electronics, data acquisition, and data processing methods are presented. The SiPM arrays are characterized and preliminary measures of energy, timing, and spatial resolution have been obtained, indicating promising performance.
This report presents recent progress of a study on the radiation damage in lead tungstate (PbWO/sub 4/) crystals. The dose rate dependence of radiation damage in PbWO/sub 4/ has been observed. An ...optimization of the oxygen compensation through post-growth thermal annealing has led to PbWO/sub 4/ samples with significantly improved radiation hardness. Front irradiation is found to cause a factor of 2 to 6 times less severe damage than uniform irradiation. Lanthanum doping was found not to be a determining factor for PbWO/sub 4/ radiation hardness improvement. Finally, a TEM/EDS analysis revealed that the radiation damage in PbWO/sub 4/ crystals is caused by oxygen vacancies.
A study has been carried out to investigate the possibility of using a pair of LSO + APD detector arrays to obtain a noninvasive measurement of the arterial input function for use in PET. The main ...focus of this study was to determine the spatial resolution and sensitivity required to obtain a high quality image that would permit a precise determination of the region of interest around the wrist artery. From these data a quantitative arterial input function that has minimal interference from the tissue and vein background can be obtained. The detector arrays were operated in coincidence counting mode to obtain planar images of various phantoms to demonstrate the feasibility of the concept.
US health care spending has continued to increase and now accounts for 18% of the US economy, although little is known about how spending on each health condition varies by payer, and how these ...amounts have changed over time.
To estimate US spending on health care according to 3 types of payers (public insurance including Medicare, Medicaid, and other government programs, private insurance, or out-of-pocket payments) and by health condition, age group, sex, and type of care for 1996 through 2016.
Government budgets, insurance claims, facility records, household surveys, and official US records from 1996 through 2016 were collected to estimate spending for 154 health conditions. Spending growth rates (standardized by population size and age group) were calculated for each type of payer and health condition.
Ambulatory care, inpatient care, nursing care facility stay, emergency department care, dental care, and purchase of prescribed pharmaceuticals in a retail setting.
National spending estimates stratified by health condition, age group, sex, type of care, and type of payer and modeled for each year from 1996 through 2016.
Total health care spending increased from an estimated $1.4 trillion in 1996 (13.3% of gross domestic product GDP; $5259 per person) to an estimated $3.1 trillion in 2016 (17.9% of GDP; $9655 per person); 85.2% of that spending was included in this study. In 2016, an estimated 48.0% (95% CI, 48.0%-48.0%) of health care spending was paid by private insurance, 42.6% (95% CI, 42.5%-42.6%) by public insurance, and 9.4% (95% CI, 9.4%-9.4%) by out-of-pocket payments. In 2016, among the 154 conditions, low back and neck pain had the highest amount of health care spending with an estimated $134.5 billion (95% CI, $122.4-$146.9 billion) in spending, of which 57.2% (95% CI, 52.2%-61.2%) was paid by private insurance, 33.7% (95% CI, 30.0%-38.4%) by public insurance, and 9.2% (95% CI, 8.3%-10.4%) by out-of-pocket payments. Other musculoskeletal disorders accounted for the second highest amount of health care spending (estimated at $129.8 billion 95% CI, $116.3-$149.7 billion) and most had private insurance (56.4% 95% CI, 52.6%-59.3%). Diabetes accounted for the third highest amount of the health care spending (estimated at $111.2 billion 95% CI, $105.7-$115.9 billion) and most had public insurance (49.8% 95% CI, 44.4%-56.0%). Other conditions estimated to have substantial health care spending in 2016 were ischemic heart disease ($89.3 billion 95% CI, $81.1-$95.5 billion), falls ($87.4 billion 95% CI, $75.0-$100.1 billion), urinary diseases ($86.0 billion 95% CI, $76.3-$95.9 billion), skin and subcutaneous diseases ($85.0 billion 95% CI, $80.5-$90.2 billion), osteoarthritis ($80.0 billion 95% CI, $72.2-$86.1 billion), dementias ($79.2 billion 95% CI, $67.6-$90.8 billion), and hypertension ($79.0 billion 95% CI, $72.6-$86.8 billion). The conditions with the highest spending varied by type of payer, age, sex, type of care, and year. After adjusting for changes in inflation, population size, and age groups, public insurance spending was estimated to have increased at an annualized rate of 2.9% (95% CI, 2.9%-2.9%); private insurance, 2.6% (95% CI, 2.6%-2.6%); and out-of-pocket payments, 1.1% (95% CI, 1.0%-1.1%).
Estimates of US spending on health care showed substantial increases from 1996 through 2016, with the highest increases in population-adjusted spending by public insurance. Although spending on low back and neck pain, other musculoskeletal disorders, and diabetes accounted for the highest amounts of spending, the payers and the rates of change in annual spending growth rates varied considerably.
sPHENIX is a new experiment under construction for the Relativistic Heavy Ion Collider at Brookhaven National Laboratory which will study the quark-gluon plasma to further the understanding of QCD ...matter and interactions. A prototype of the sPHENIX electromagnetic calorimeter (EMCal) was tested at the Fermilab Test Beam Facility in Spring 2018 as experiment T-1044. The EMCal prototype corresponds to a solid angle of \( \Delta \eta \times \Delta \phi = 0.2 \times 0.2\) centered at pseudo-rapidity \(\eta = 1\). The prototype consists of scintillating fibers embedded in a mix of tungsten powder and epoxy. The fibers project back approximately to the center of the sPHENIX detector, giving 2D projectivity. The energy response of the EMCal prototype was studied as a function of position and input energy. The energy resolution of the EMCal prototype was obtained after applying a position dependent energy correction and a beam profile correction. Two separate position dependent corrections were considered. The EMCal energy resolution was found to be \(\sigma(E)/\langle E\rangle = 3.5(0.1) \oplus 13.3(0.2)/\sqrt{E}\) based on the hodoscope position dependent correction, and \(\sigma(E)/\langle E\rangle = 3.0(0.1) \oplus 15.4(0.3)/\sqrt{E}\) based on the cluster position dependent correction. These energy resolution results meet the requirements of the sPHENIX physics program.
The effects of radiation damage in silicon photomultipliers (SiPMs) from gamma rays have been measured and compared with the damage produced by neutrons. Several types of MPPCs from Hamamatsu were ...exposed to gamma rays and neutrons at the Solid State Gamma Ray Irradiation Facility (SSGRIF) at Brookhaven National Lab and the Institute for Nuclear Research (Atomki) in Debrecen, Hungary. The gamma ray exposures ranged from 1 krad to 1 Mrad and the neutron exposures ranged from 10\(^8\) n/cm\(^2\) to 10\(^{12}\) n/cm\(^2\). The main effect of gamma ray damage is an increase in the noise and leakage current in the irradiated devices, similar to what is seen from neutron damage, but the level of damage is considerably less at comparable high levels of exposure. In addition, the damage from gamma rays saturates after a few hundred krad, while the damage from neutrons shows no sign of saturation, suggestive of different damage mechanisms in the two cases. The change in optical absorption in the window material of the SiPMs due to radiation was also measured. This study was carried out in order to evaluate the use of SiPMs for particle physics applications with moderate levels of radiation exposures.
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