Search results for "Image resolution"
showing 10 items of 377 documents
Analysis of spatial diffusion of ferric ions in PVA-GTA gel dosimeters through magnetic resonance imaging
2017
Abstract This work focused on the analysis of the temporal diffusion of ferric ions through PVA-GTA gel dosimeters. PVA-GTA gel samples, partly exposed with 6 MV X-rays in order to create an initial steep gradient, were mapped using magnetic resonance imaging on a 7T MRI scanner for small animals. Multiple images of the gels were acquired over several hours after irradiation and were analyzed to quantitatively extract the signal profile. The spatial resolution achieved is 200 μm and this makes this technique particularly suitable for the analysis of steep gradients of ferric ion concentration. The results obtained with PVA-GTA gels were compared with those achieved with agarose gels, which …
First Compton telescope prototype based on continuous LaBr3-SiPM detectors
2013
Abstract A first prototype of a Compton camera based on continuous scintillator crystals coupled to silicon photomultiplier (SiPM) arrays has been successfully developed and operated. The prototype is made of two detector planes. The first detector is made of a continuous 16×18×5 mm 3 LaBr 3 crystal coupled to a 16-elements SiPM array. The elements have a size of 3×3 mm 3 in a 4.5×4.05 mm 2 pitch. The second detector, selected by availability, consists of a continuous 16×18×5 mm 3 LYSO crystal coupled to a similar SiPM array. The SPIROC1 ASIC is employed in the readout electronics. Data have been taken with a 22 Na source placed at different positions and images have been reconstructed with…
High performance detector head for PET and PET/MR with continuous crystals and SiPMs
2012
International audience; A high resolution PET detector head for small animal PET applications has been developed. The detector is composed of a 12 mm x 12 mm source continuous LYSO crystal coupled to a 64-channel monolithic SiPM matrix from FBK-irst. Crystal thicknesses of 5 mm and 10 mm have been tested, both yielding an intrinsic spatial resolution around 0.7 mm FWHM with a position determination algorithm that can also provide depth-of-interaction information. The detectors have been tested in a rotating system that makes it possible to acquire tomographic data and reconstruct images of 22Na sources. An image reconstruction method specifically adapted for continuous crystals has been emp…
Time-resolved acousto-optic interaction in single-mode optical fibers: characterization of axial nonuniformities at the nanometer scale.
2014
We report on a time-resolved acousto-optic interaction technique for the detection of axial nonuniformities in single-mode fibers. It is based on the propagation of short packets of flexural acoustic waves. Small axial nonuniformities (of the order of nanometers) are detected by measuring the transmittance of the fundamental mode as a function of time. It is shown that the technique allows the detection of axial nonuniformities along sections of single-mode fiber exceeding 1 m long with spatial resolution of the order of a few centimeters.
THREE-DIMENSIONAL INTEGRAL MICROSCOPY WITH ENHANCED RESOLUTION AND DEPTH OF FIELD
2016
In this contribution we explain two new techniques developed by our group, which permit to increase the two-dimensional spatial resolution of the computed depth images in integral microscopy.
Spatial information transmission using axial temporal coherence coding
2007
We present an approach that can be used for transmission of information through space-limited systems or for superresolution. The spatial information is coded with different axial temporal coherence by interfering every spatial region in the input with the same region, but with a certain known delay in the longitudinal axis. Every spatial region has different delay. After mixing all of the spatial information, it is transmitted through the space-limited system. At the detection the information is passed through a similar interference setup containing certain axial delay. By temporally scanning along the longitudinal axis, each time a different spatial region that was coded with the correspo…
Multiple Cost Functions and Regularization Options for Improved Retrieval of Leaf Chlorophyll Content and LAI through Inversion of the PROSAIL Model
2013
Abstract: Lookup-table (LUT)-based radiative transfer model inversion is considered a physically-sound and robust method to retrieve biophysical parameters from Earth observation data but regularization strategies are needed to mitigate the drawback of ill-posedness. We systematically evaluated various regularization options to improve leaf chlorophyll content (LCC) and leaf area index (LAI) retrievals over agricultural lands, including the role of (1) cost functions (CFs); (2) added noise; and (3) multiple solutions in LUT-based inversion. Three families of CFs were compared: information measures, M-estimates and minimum contrast methods. We have only selected CFs without additional parame…
Evaluation of a multispectral diffuse optical spectroscopy device for assessment of cardiometabolic risk related alterations of body composition
2013
Cardiometabolic diseases encompass a combination of conditions which lead to an increase in the risk of cardiovascular disease and diabetes. With the increasing percentage of the population becoming overweight, it is important to diagnose when the excess adipose tissue becomes malign. The development of a safe, mobile, non-invasive method that would be easy to perform, and low-cost, but also would offer an accurate assessment of subcutaneous adipose tissue (SAT) both in lean and in obese persons is required. A prototype device using an optical method for measurement of the SAT in vivo has been developed, it contains multiple LEDs with four wavelengths (660nm, 780nm, 870nm, 940nm) distribute…
Structured-light imaging through scattering
2016
We present a structured illumination technique to image objects hidden beneath scattering. The sample is computationally retrieved from a known ensemble of light patterns codified onto a digital micromirror device and photocurrent fluctuations provided by a detector with no spatial resolution. Results of laboratory experiments will be shown. Article not available.
Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array
2013
NEXT-DEMO is a high-pressure xenon gas TPC which acts as a technological test-bed and demonstrator for the NEXT-100 neutrinoless double beta decay experiment. In its current configuration the apparatus fully implements the NEXT-100 design concept. This is an asymmetric TPC, with an energy plane made of photomultipliers and a tracking plane made of silicon photomultipliers (SiPM) coated with TPB. The detector in this new configuration has been used to reconstruct the characteristic signature of electrons in dense gas, demonstrating the ability to identify the MIP and "blob" regions. Moreover, the SiPM tracking plane allows for the definition of a large fiducial region in which an excellent e…