A rapidly converging, iterative deconvolution algorithm with a novel resolution subsets-based approach RSEMD that operates on digital imaging and communications in medicine images to improve the ...quality of clinical CT images is presented. The RSEMD method was tested on Catphan 500 and anthropomorphic 4-D XCAT phantoms to determine the improvements in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The method was applied to preclinical CT images previously reconstructed by conventional software. To test the potential improvement in clinically relevant CT images we employed the 4-D XCAT phantom to simulate a small, low contrast lesion placed in the liver. In all of the phantom studies, the images proved to have higher resolution and lower noise as compared with filtered back projection. In general, the iterative deblurring restoration reaches the highest SNR and CNR values after approximately 20 iterations with an improvement factor of about 1.5 for both CNR and SNR in noisy CT images. We also found improvements in preclinical and clinical CT images after the application of RSEMD. The results obtained with the RSEMD method are in agreement with other iterative algorithms employed either in image space or with hybrid reconstruction algorithms which start in projection space and then follow in image domain. The RSEMD method can be applied to suboptimal routine-dose clinical CT images to improve the image quality to diagnostically acceptable levels.
Modern positron emission tomography (PET) systems, offering high counting rate capabilities, high sensitivity, and near-submillimeter coordinate resolution, require fast image reconstruction software ...that can operate on list-mode data and take into account most of finite resolution effects such as photon scattering, positron range in tissue, and detector features. It has already been demonstrated that the expectation maximization (EM) method with extended system matrix modeling looks very attractive for image resolution recovery in PET imaging studies. In this paper, the performance of EM-based algorithms (in particular, their ability to improve the image resolution) is evaluated for a small animal PET imager with several phantoms. The achievement of a substantial decrease in processing time using an EM deblurring procedure is shown, as is an approach to successfully treat what are essentially nonspace-invariant resolution effects within a shift-invariant model.
Radioarsenic labelled radiopharmaceuticals could be a valuable asset to Positron Emission Tomography (PET). In particular, the long half-lives of
72As (
T
1/2=26
h) and
74As (
T
1/2=17.8 d) allow to ...investigate slow physiological or metabolical processes, like the enrichment and distribution of antibodies in tumor tissue. This work describes the direct production of no-carrier-added (nca) arsenic isotopes *As, with *=71, 72, 73, 74 or 77, the reaction to *AsAsI
3 and its radiochemical separation from the irradiated solid germanium oxide via polystyrene-based solid-phase extraction. The germanium oxide target, irradiated at a cyclotron or a nuclear reactor, is dissolved in concentrated HF and Ge is separated almost quantitatively (99.97%) as GeF
6
2−. *AsAsI
3 is formed by addition of potassium iodide. The radiochemical separation yield for arsenic is >90%. *AsAsI
3 is a versatile radioarsenic labelling synthon.
The electron-multiplying charge-coupled device (EMCCD) offers improved quantum efficiencies (40 to 95%) over a broader range of wavelengths (400 to 900 nm) and a higher intrinsic resolution (<100 mum ...using photon counting) when compared to photomultiplier tubes. The electron gain achieved in the multiplication register of an EMCCD effectively reduces the readout noise to less than 1 electron/pixel, making them sensitive to single photoelectrons. Our prototype camera uses the Texas Instruments Impactrontrade EMCCD model TC253SPD-B0 (7.4 mum square pixels) which is cooled under vacuum to -50degC using a four stage Peltier and liquid heat exchanger. Shuttered lens-coupling is used to image the optical light from a 3 mm thick monolithic CsI(Tl) crystal. Precise clocking for the EMCCD is provided by a National Instruments FPGA controller (PCI-7811R) and LabVIEW FPGA module (version 8.0). A custom built electronics box contains the clock driver circuitry and 16-bit video board for digital conversion of the video signal. Our optical coupling method differs from other EMCCD SPECT systems by using lenses rather than fiber optic bundles for transfer. TC253 characterization tests measured a maximum gain just over 1000times, dark current rate of 0.14 e/p/s, read noise of 18.2 e/p, and spurious charge generation of 4 e/p. A light integration intrinsic resolution of 110 mum FWHM was measured. Light integration images of a line phantom using a single pinhole collimator were used for SPECT reconstruction. We found the relative high spurious charge generation and low quantum efficiency of the TC253 made it incapable of photon counting for low energy sources using lens coupling.
Charged particles and photons have been measured in central Pb + Pb collisions at 158 A GeV in a common (eta-phi)-phase space region in the WA98 experiment at the CERN SPS. The measured distributions ...have been analyzed to quantify the frequency with which phase space regions of varying sizes have either small or large neutral pion fraction. The measured results are compared with VENUS model simulated events and with mixed events. Events with both large and small charged-neutral fluctuations are observed to occur more frequently than expected statistically, as deduced from mixed events, or as predicted by model simulations, with the difference becoming more prominent with decreasing size of the A Delta eta-Delta phi region. (C) 2011 Elsevier B.V. All rights reserved.
Bioluminescent imaging (BLI) of luciferase-expressing cells in live small animals is a powerful technique for investigating tumor growth, metastasis, and specific biological molecular events. ...Three-dimensional imaging would greatly enhance applications in biomedicine since light emitting cell populations could be unambiguously associated with specific organs or tissues. Any imaging approach must account for the main optical properties of biological tissue because light emission from a distribution of sources at depth is strongly attenuated due to optical absorption and scattering in tissue. Our image reconstruction method for interior sources is based on the deblurring expectation maximization method and takes into account both of these effects. To determine the boundary of the object we use the standard iterative algorithm—maximum likelihood reconstruction method with an external source of diffuse light. Depth-dependent corrections were included in the reconstruction procedure to obtain a quantitative measure of light intensity by using the diffusion equation for light transport in semi-infinite turbid media with extrapolated boundary conditions.
Measurements of direct photon production in p + Pb and p + C collisions at root(NN)-N-s = 17.4 GeV are presented. Upper limits on the direct photon yield as a function of p(T) are derived and ...compared to the results for Pb + Pb collisions at root(NN)-N-s = 17.3 GeV. The production of the eta meson, which is an important input to the direct photon signal extraction, has been determined in the eta -> 2 gamma channel for p + C collisions at root(NN)-N-s = 17.4 GeV. (c) 2012 Elsevier B.V. All rights reserved.
Measurements of direct photon production in p+Pb and p+C collisions at sNN=17.4 GeV are presented. Upper limits on the direct photon yield as a function of pT are derived and compared to the results ...for Pb+Pb collisions at sNN=17.3 GeV. The production of the η meson, which is an important input to the direct photon signal extraction, has been determined in the η→2γ channel for p+C collisions at sNN=17.4 GeV.
Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at root s(NN) = 17.4 GeV at midrapidity (2.3 less than or similar to eta(lab)less than or similar to 3.0) over the ...range 0.7 less than or similar to p(T)less than or similar to 3.5 GeV/c. The spectra are compared to pi(0) spectra measured in Pb+Pb collisions at root s(NN) = 17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N-part less than or similar to 300), the yield of pi(0)'s with p(T)greater than or similar to 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N-coll), while for central Pb+Pb collisions with N-part greater than or similar to 350, the pi(0) yield is suppressed.
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