The Experts below are selected from a list of 171 Experts worldwide ranked by ideXlab platform
J Schuemann - One of the best experts on this subject based on the ideXlab platform.
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biological modeling of gold nanoparticle enhanced radiotherapy for proton therapy
Physics in Medicine and Biology, 2015Co-Authors: Stephen J Mcmahon, H Paganetti, J SchuemannAbstract:Gold nanoparticles (GNPs) have shown potential as a radiosensitizer for radiation therapy using photon beams. Recently, experimental studies have been carried out using proton beams showing the GNP enhanced responses in proton therapy. In this work, we established a biological model to investigate the change in survival of irradiated cells due to the radiosensitizing effect of gold nanoparticles. Results for proton, megavoltage (MV) photon and kilovoltage (kV) photon beams are compared. For each particle source, we assessed various treatment depths, GNP cellular uptakes and sizes. We showed that kilovoltage photons caused the highest enhancement due to the high Interaction Probability between GNPs and kV photons. The cell survival fraction can be significantly reduced for both proton and MV photon irradiations if GNPs accumulate in the cell. For instance, the sensitizer enhancement ratio (SER) is 1.33 for protons in the middle of a spread out Bragg peak for 1 µM of internalized 50 nm GNPs. If the GNPs can all be internalized into the cell nucleus, the SER for proton therapy increases from 1.33 to 1.81. The results also show that for the same mass of GNPs in the cells, one can expect the greatest sensitization by smaller GNPs, i.e. a SER of 1.33 for 1 µM of internalized 50 nm GNPs and a SER of 3.98 for the same mass of 2 nm GNPs. We concluded that if the GNPs cannot be internalized into the cytoplasm, no GNP enhancement will be observed for proton treatment. Meanwhile, proton radiotherapy can potentially be enhanced with GNPs if they can be internalized into cells, and especially the cell nucleus.
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we g bre 02 biological modeling of gold nanoparticle radiosensitization for proton therapy
Medical Physics, 2014Co-Authors: Yuting Lin, H Paganetti, J SchuemannAbstract:Purpose: The aim of this work is to investigate the radiosensitization effect of gold nanoparticles (GNP) in a proton beam. A computational model was built using the Local Effect Model (LEM) to predict the biological outcome of gold nanoparticle (GNP) sensitization. We present the results using a clinical proton beam, 6MV photon beam and two kilovoltage photon beams. Methods: First, Monte Carlo simulations were carried out using TOPAS (TOol for PArticle Simulation) to obtain the spatial dose distribution in the vicinity of GNPs. The dose distribution was then used as an input for LEM, which predicts dose-response curves for high linear energy transfer radiation using the track structure. The cell survival curves were evaluated for three particle sources (proton beam, MV photon beam and kV photon beam), various treatment depths for each particle source, various GNP uptakes and two different GNP sizes. Results: For proton therapy, the GNP sensitization effect is highly dependent on the treatment depth due to the energy-dependent Interaction Probability. We predict that if GNPs can be taken up by the cell nucleus, proton therapy can be significantly enhanced. If GNPs are only internalized into the cytoplasm, proton therapy can still be enhanced by GNPs and if GNPs are not internalized into cells, there will be no direct damage to the nucleus. For the same GNP uptake and concentration, the cell survival at 2Gy is reduced by 80% using kilovoltage photons, 50% using protons and only 2% using clinical MV photons. Finally, for the same weight of GNPs taken up by the cells, 10 nm GNPs causes 3 times more damage than 50 nm GNPs. Conclusion: We showed that GNPs have potential to be used to enhance radiation therapy for clinical proton beams.
Marc A N Korevaar - One of the best experts on this subject based on the ideXlab platform.
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experimental comparison of high density scintillators for emccd based gamma ray imaging
Physics in Medicine and Biology, 2012Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Marlies C Goorden, R Kreuger, Samuel Salvador, Zachary M Seeley, Nerine J CherepyAbstract:Detection of x-rays and gamma rays with high spatial resolution can be achieved with scintillators that are optically coupled to electron-multiplying charge-coupled devices (EMCCDs). These can be operated at typical frame rates of 50 Hz with low noise. In such a set-up, scintillation light within each frame is integrated after which the frame is analyzed for the presence of scintillation events. This method allows for the use of scintillator materials with relatively long decay times of a few milliseconds, not previously considered for use in photon-counting gamma cameras, opening up an unexplored range of dense scintillators. In this paper, we test CdWO4 and transparent polycrystalline ceramics of Lu2O3:Eu and (Gd,Lu)2O3:Eu as alternatives to currently used CsI:Tl in order to improve the performance of EMCCD-based gamma cameras. The tested scintillators were selected for their significantly larger cross-sections at 140 keV (99mTc) compared to CsI:Tl combined with moderate to good light yield. A performance comparison based on gamma camera spatial and energy resolution was done with all tested scintillators having equal (66%) Interaction Probability at 140 keV. CdWO4, Lu2O3:Eu and (Gd,Lu)2O3:Eu all result in a significantly improved spatial resolution over CsI:Tl, albeit at the cost of reduced energy resolution. Lu2O3:Eu transparent ceramic gives the best spatial resolution: 65 µm full-width-at-half-maximum (FWHM) compared to 147 µm FWHM for CsI:Tl. In conclusion, these ‘slow’ dense scintillators open up new possibilities for improving the spatial resolution of EMCCD-based scintillation cameras.
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a pinhole gamma camera with optical depth of Interaction elimination
Physics in Medicine and Biology, 2009Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Freek J BeekmanAbstract:The performance of pinhole single photon emission computed tomography (SPECT) depends on the spatial resolution of the gamma-ray detectors used. Pinhole cameras suffer from strong resolution loss due to the varying depth-of-Interaction (DOI) of gamma quanta that enter the detector material at an angle. We eliminate DOI effects in a scintillation gamma camera via a dedicated optic fiber bundle that acts as a focusing collimator for light generated in a scintillation crystal. A curved crystal is connected to a concavely shaped fiber-optic bundle such that the fibers connect perpendicularly to the crystal's convex surface and point straight at the pinhole opening. Limiting the fiber numerical apertures can be used to suppress resolution losses due to light spread. Here we demonstrate experimentally that this prototype position-sensitive gamma sensor successfully eliminates DOI effects, and has an intrinsic resolution of better than 280 µm full width at half maximum with an Interaction Probability of 67% for 140 keV photons. Therefore, the detector has great potential for increasing the resolution of pinhole SPECT.
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multi scale algorithm for improved scintillation detection in a ccd based gamma camera
Physics in Medicine and Biology, 2009Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Marlies C Goorden, Freek J BeekmanAbstract:Gamma cameras based on charge-coupled devices (CCDs) and micro-columnar CsI scintillators can reach high spatial resolutions. However, the gamma Interaction Probability of these scintillators is low (typically <30% at 141 keV) due to the limited thickness of presently available micro-columnar scintillators. Continuous scintillators can improve the Interaction Probability but suffer from increased light spread compared to columnar scintillators. In addition, for both types of scintillators, gamma photons incident at an oblique angle reduce the spatial resolution due to the variable depth of Interaction (DOI). To improve the spatial resolution and spectral characteristics of these detectors, we have developed a fast analytic scintillation detection algorithm that makes use of a depth-dependent light spread model and as a result is able to estimate the DOI in the scintillator. This algorithm, performing multi-scale frame analysis, was tested for an electron multiplying CCD (EM-CCD) optically coupled to CsI(Tl) scintillators of different thicknesses. For the thickest scintillator (2.6 mm) a spatial resolution of 148 µm full width half maximum (FWHM) was obtained with an energy resolution of 46% FWHM for perpendicularly incident gamma photons (Interaction Probability 61% at 141 keV). The multi-scale algorithm improves the spatial resolution up to 11%, the energy resolution up to 36% and the signal-to-background counts ratio up to 46% compared to a previously implemented algorithm that did not model the depth-dependent light spread. In addition, the multi-scale algorithm can accurately estimate DOI. As a result, degradation of the spatial resolution due to the variable DOI for gamma photons incident at a 45° angle was improved from 2.0 103 to 448 µm FWHM. We conclude that the multi-scale algorithm significantly improves CCD-based gamma cameras as can be applied in future SPECT systems.
Jan W T Heemskerk - One of the best experts on this subject based on the ideXlab platform.
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experimental comparison of high density scintillators for emccd based gamma ray imaging
Physics in Medicine and Biology, 2012Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Marlies C Goorden, R Kreuger, Samuel Salvador, Zachary M Seeley, Nerine J CherepyAbstract:Detection of x-rays and gamma rays with high spatial resolution can be achieved with scintillators that are optically coupled to electron-multiplying charge-coupled devices (EMCCDs). These can be operated at typical frame rates of 50 Hz with low noise. In such a set-up, scintillation light within each frame is integrated after which the frame is analyzed for the presence of scintillation events. This method allows for the use of scintillator materials with relatively long decay times of a few milliseconds, not previously considered for use in photon-counting gamma cameras, opening up an unexplored range of dense scintillators. In this paper, we test CdWO4 and transparent polycrystalline ceramics of Lu2O3:Eu and (Gd,Lu)2O3:Eu as alternatives to currently used CsI:Tl in order to improve the performance of EMCCD-based gamma cameras. The tested scintillators were selected for their significantly larger cross-sections at 140 keV (99mTc) compared to CsI:Tl combined with moderate to good light yield. A performance comparison based on gamma camera spatial and energy resolution was done with all tested scintillators having equal (66%) Interaction Probability at 140 keV. CdWO4, Lu2O3:Eu and (Gd,Lu)2O3:Eu all result in a significantly improved spatial resolution over CsI:Tl, albeit at the cost of reduced energy resolution. Lu2O3:Eu transparent ceramic gives the best spatial resolution: 65 µm full-width-at-half-maximum (FWHM) compared to 147 µm FWHM for CsI:Tl. In conclusion, these ‘slow’ dense scintillators open up new possibilities for improving the spatial resolution of EMCCD-based scintillation cameras.
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a pinhole gamma camera with optical depth of Interaction elimination
Physics in Medicine and Biology, 2009Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Freek J BeekmanAbstract:The performance of pinhole single photon emission computed tomography (SPECT) depends on the spatial resolution of the gamma-ray detectors used. Pinhole cameras suffer from strong resolution loss due to the varying depth-of-Interaction (DOI) of gamma quanta that enter the detector material at an angle. We eliminate DOI effects in a scintillation gamma camera via a dedicated optic fiber bundle that acts as a focusing collimator for light generated in a scintillation crystal. A curved crystal is connected to a concavely shaped fiber-optic bundle such that the fibers connect perpendicularly to the crystal's convex surface and point straight at the pinhole opening. Limiting the fiber numerical apertures can be used to suppress resolution losses due to light spread. Here we demonstrate experimentally that this prototype position-sensitive gamma sensor successfully eliminates DOI effects, and has an intrinsic resolution of better than 280 µm full width at half maximum with an Interaction Probability of 67% for 140 keV photons. Therefore, the detector has great potential for increasing the resolution of pinhole SPECT.
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multi scale algorithm for improved scintillation detection in a ccd based gamma camera
Physics in Medicine and Biology, 2009Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Marlies C Goorden, Freek J BeekmanAbstract:Gamma cameras based on charge-coupled devices (CCDs) and micro-columnar CsI scintillators can reach high spatial resolutions. However, the gamma Interaction Probability of these scintillators is low (typically <30% at 141 keV) due to the limited thickness of presently available micro-columnar scintillators. Continuous scintillators can improve the Interaction Probability but suffer from increased light spread compared to columnar scintillators. In addition, for both types of scintillators, gamma photons incident at an oblique angle reduce the spatial resolution due to the variable depth of Interaction (DOI). To improve the spatial resolution and spectral characteristics of these detectors, we have developed a fast analytic scintillation detection algorithm that makes use of a depth-dependent light spread model and as a result is able to estimate the DOI in the scintillator. This algorithm, performing multi-scale frame analysis, was tested for an electron multiplying CCD (EM-CCD) optically coupled to CsI(Tl) scintillators of different thicknesses. For the thickest scintillator (2.6 mm) a spatial resolution of 148 µm full width half maximum (FWHM) was obtained with an energy resolution of 46% FWHM for perpendicularly incident gamma photons (Interaction Probability 61% at 141 keV). The multi-scale algorithm improves the spatial resolution up to 11%, the energy resolution up to 36% and the signal-to-background counts ratio up to 46% compared to a previously implemented algorithm that did not model the depth-dependent light spread. In addition, the multi-scale algorithm can accurately estimate DOI. As a result, degradation of the spatial resolution due to the variable DOI for gamma photons incident at a 45° angle was improved from 2.0 103 to 448 µm FWHM. We conclude that the multi-scale algorithm significantly improves CCD-based gamma cameras as can be applied in future SPECT systems.
M Garattini - One of the best experts on this subject based on the ideXlab platform.
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Angular asymmetry of the nuclear Interaction Probability of high energy particles in short bent crystals
Eur.Phys.J.C, 2020Co-Authors: W Scandale, F Cerutti, M Garattini, S Gilardoni, L.s. Esposito, A. Natochii, R. Rossi, G.i. Smirnov, V. Zhovkovska, F. GalluccioAbstract:The rate of inelastic nuclear Interactions in a short bent silicon crystal was precisely measured for the first time using a 180 GeV/c positive hadron beam produced in the North Experimental Area of the CERN SPS. An angular asymmetry dependence on the crystal orientation in the vicinity of the planar channeling minimum has been observed. For the inspected crystal, this Probability is about $\sim 20\%$ larger than in the amorphous case because of the atomic density increase along the particle trajectories in the angular range of volume reflection, whose dimension is determined by the crystal bending angle. Instead, for the opposite angular orientation with respect to the planar channeling, there is a smaller Probability excess of $\sim 4\%$.
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study of inelastic nuclear Interactions of 400 gev c protons in bent silicon crystals for beam steering purposes
European Physical Journal C, 2018Co-Authors: W Scandale, F Andrisani, G Arduini, F Cerutti, M Garattini, S Gilardoni, A Masi, D Mirarchi, S MontesanoAbstract:Inelastic nuclear Interaction Probability of 400 GeV/c protons interacting with bent silicon crystals was investigated, in particular for both types of crystals installed at the CERN Large Hadron Collider for beam collimation purposes. In comparison to amorphous scattering Interaction, in planar channeling this Probability is $$\sim 36\%$$ for the quasi-mosaic type (planes (111)), and $$\sim 27\%$$ for the strip type (planes (110)). Moreover, the absolute inelastic nuclear Interaction Probability in the axial channeling orientation, along the $$\langle 110\rangle $$ axis, was estimated for the first time, finding a value of $$0.6\%$$ for a crystal 2 mm long along the beam direction, with a bending angle of 55 $$\upmu $$ rad. This value is more than two times lower with respect to the planar channeling orientation of the same crystal, and increases with the vertical angular misalignment. Finally, the correlation between the inelastic nuclear Interaction Probability in the planar channeling and the silicon crystal curvature is reported.
Freek J Beekman - One of the best experts on this subject based on the ideXlab platform.
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a pinhole gamma camera with optical depth of Interaction elimination
Physics in Medicine and Biology, 2009Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Freek J BeekmanAbstract:The performance of pinhole single photon emission computed tomography (SPECT) depends on the spatial resolution of the gamma-ray detectors used. Pinhole cameras suffer from strong resolution loss due to the varying depth-of-Interaction (DOI) of gamma quanta that enter the detector material at an angle. We eliminate DOI effects in a scintillation gamma camera via a dedicated optic fiber bundle that acts as a focusing collimator for light generated in a scintillation crystal. A curved crystal is connected to a concavely shaped fiber-optic bundle such that the fibers connect perpendicularly to the crystal's convex surface and point straight at the pinhole opening. Limiting the fiber numerical apertures can be used to suppress resolution losses due to light spread. Here we demonstrate experimentally that this prototype position-sensitive gamma sensor successfully eliminates DOI effects, and has an intrinsic resolution of better than 280 µm full width at half maximum with an Interaction Probability of 67% for 140 keV photons. Therefore, the detector has great potential for increasing the resolution of pinhole SPECT.
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multi scale algorithm for improved scintillation detection in a ccd based gamma camera
Physics in Medicine and Biology, 2009Co-Authors: Marc A N Korevaar, Jan W T Heemskerk, Marlies C Goorden, Freek J BeekmanAbstract:Gamma cameras based on charge-coupled devices (CCDs) and micro-columnar CsI scintillators can reach high spatial resolutions. However, the gamma Interaction Probability of these scintillators is low (typically <30% at 141 keV) due to the limited thickness of presently available micro-columnar scintillators. Continuous scintillators can improve the Interaction Probability but suffer from increased light spread compared to columnar scintillators. In addition, for both types of scintillators, gamma photons incident at an oblique angle reduce the spatial resolution due to the variable depth of Interaction (DOI). To improve the spatial resolution and spectral characteristics of these detectors, we have developed a fast analytic scintillation detection algorithm that makes use of a depth-dependent light spread model and as a result is able to estimate the DOI in the scintillator. This algorithm, performing multi-scale frame analysis, was tested for an electron multiplying CCD (EM-CCD) optically coupled to CsI(Tl) scintillators of different thicknesses. For the thickest scintillator (2.6 mm) a spatial resolution of 148 µm full width half maximum (FWHM) was obtained with an energy resolution of 46% FWHM for perpendicularly incident gamma photons (Interaction Probability 61% at 141 keV). The multi-scale algorithm improves the spatial resolution up to 11%, the energy resolution up to 36% and the signal-to-background counts ratio up to 46% compared to a previously implemented algorithm that did not model the depth-dependent light spread. In addition, the multi-scale algorithm can accurately estimate DOI. As a result, degradation of the spatial resolution due to the variable DOI for gamma photons incident at a 45° angle was improved from 2.0 103 to 448 µm FWHM. We conclude that the multi-scale algorithm significantly improves CCD-based gamma cameras as can be applied in future SPECT systems.