The spatial resolution of a NaI(T1), 25 mm thick bar detector designed for use in positron emission tomography has been studied. The position along the 500 mm long detector is determined from the centroid of the light distribution in the crystal as measured by a linear array of photomultiplier tubes. A Monte Carlo computer simulation was performed to investigate the factors limiting the spatial resolution. The program allowed us to study the effect of various phototube configurations and crystal surfaces. Since the resolution is affected by the width of the light distribution, we studied the effect of sharpening the distribution by modifying the front crystal surface with grooves cut perpendicular to the long axis of the crystal and by using non-linear preamplifiers. The simulation predicts a spatial resolution (FWHM) of 3 mm with this crystal. Experimental measurements of spatial resolution were performed concurrently with the simulations. In particular, a modified grooved crystal was measured to have 4.0 mm spatial resolution, an improvement over the original crystal without grooves. With delay line pulse shortening, which increases the count rate capability of the detector, the grooved crystal was measured to have 5.5 mm spatial resolution.
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PLoS One
January 2025
QUT Centre for Data Science, Queensland University of Technology, Brisbane, Queensland, Australia.
Background: Spatial data are often aggregated by area to protect the confidentiality of individuals and aid the calculation of pertinent risks and rates. However, the analysis of spatially aggregated data is susceptible to the modifiable areal unit problem (MAUP), which arises when inference varies with boundary or aggregation changes. While the impact of the MAUP has been examined previously, typically these studies have focused on well-populated areas.
View Article and Find Full Text PDFEnviron Monit Assess
January 2025
Faculty of Resources Management, Thai Nguyen University of Agriculture and Forestry, Mo Bach Str, Thai Nguyen City, Thai Nguyen Province, 250000, Vietnam.
Drought is a reoccurring natural phenomenon that presents significant challenges to agricultural production, ecosystem stability, and water resource management. The Central Highlands of Vietnam, a major region of industrial crops and vegetation ecosystems, has become increasingly vulnerable to drought impacts. Despite this vulnerability, limited research has explored the specific characteristics of drought and its seasonal effects on vegetation ecosystems in the region.
View Article and Find Full Text PDFAcc Chem Res
January 2025
School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
ConspectusSymmetry is a pervasive phenomenon spanning diverse fields, from art and architecture to mathematics and science. In the scientific realms, symmetry reveals fundamental laws, while symmetry breaking─the collapse of certain symmetry─is the underlying cause of phenomena. Research on symmetry and symmetry breaking consistently provides valuable insights across disciplines, from parity violation in physics to the origin of homochirality in biology.
View Article and Find Full Text PDFJ Opt Soc Am A Opt Image Sci Vis
August 2024
Compressed ultrafast photography (CUP) is a high-speed imaging technique with a frame rate of up to ten trillion frames per second (fps) and a sequence depth of hundreds of frames. This technique is a powerful tool for investigating ultrafast processes. However, since the reconstruction process is an ill-posed problem, the image reconstruction will be more difficult with the increase of the number of reconstruction frames and the number of pixels of each reconstruction frame.
View Article and Find Full Text PDFLife Metab
December 2024
Key Laboratory of Phytochemistry and Natural Medicines, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China.
Metabolic dysfunction-associated steatotic liver disease (MASLD) is a metabolic disease that can progress to metabolic dysfunction-associated steatohepatitis (MASH), cirrhosis, and cancer. The zonal distribution of biomolecules in the liver is implicated in mediating the disease progression. Recently, G-protein-coupled receptor 35 (GPR35) has been highlighted to play a role in MASLD, but the precise mechanism is not fully understood, particularly, in a liver-zonal manner.
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