bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of multislice computed tomography dose index (CTDI) using optically stimulated luminescence technology
Authors: Ruan Chun , Yukihara Eduardo G. , Clouse William J. , Gasparian Patricia B. R. , Ahmad Salahuddin 
Published: July 2010

PurposeThe extensive use of multislice computed tomography (MSCT) and the associated increase in patient dose calls for an accurate dose evaluation technique. Optically stimulated luminescence (OSL) dosimetry provides a potential solution to the arising concerns over patient dose. This study was intended to evaluate the feasibility and accuracy of OSL dosimeter systems in the diagnostic CT x‐ray beam energy range.MethodsMSCT dose profiles were measured by irradiating OSL strips placed inside the extended PMMA head and body phantoms at different scan conditions by varying kVp settings (100, 120, and 140 kVp) and collimated beam widths (5, 10, 20, and 40 mm). All scans in this study were performed using a GE Lightspeed VCT scanner in axial mode. The exposed strips were then read out using a custom‐made OSL strip reader and corrected with field‐specific conversion factors. Based on the corrected OSL dose profile, the and were evaluated. was also obtained using a 100 mm long pencil ionization chamber for accuracy verification. can be further evaluated by calculating the ratio of and , which was compared to results from previous studies as well.ResultsThe OSL detectors were found to have good sensitivity and dose response over a wide range of diagnostic CT x‐ray beam energy viz. the primary beam and the scatter tail section of the dose profile. The differences between values obtained using the OSL strips and those obtained with 100 mm long pencil ionization chamber were for all scan conditions, indicating good accuracy of the OSL system. It was also found that the did not significantly change as the beam width increased and tube voltage changed. The average at the center of the head and body phantoms were 72.6% and 56.2%, respectively. The corresponding values for the periphery of the head and body phantoms were 85.0% and 81.7%. These results agreed very well with previous results from the literature using other detection techniques or Monte Carlo simulations.ConclusionsThe LED‐based OSL system can be an accurate alternative device for CT dose evaluations. measurement with the use of a 100 mm pencil ionization chamber substantially underestimates the value even with 5 mm collimated beam width. The established complete set of correction factors for various scan parameters allows for accurately estimating with the current use of pencil chamber and dose phantoms. Combined with the simple calibration, it gives this work great potential to be used not only in routine clinical quality assurance checks but also as a promising tool for patient organ dose assessment.
Fast and memory‐efficient Monte Carlo‐based image reconstruction for whole‐body PET
Authors: Zhang Long , Staelens Steven , Van Holen Roel , De Beenhouwer Jan , Verhaeghe Jeroen , Kawrakow Iwan , Vandenberghe Stefaan 
Published: July 2010

PurposeSeveral studies have shown the benefit of an accurate system modeling using Monte Carlo techniques. For state‐of‐the‐art whole‐body positron emission tomography (PET) scanners, Monte Carlo‐based image reconstruction is associated with a significant computational cost to calculate the system matrix as well as a large memory capacity to store it. In this article, the authors present a simulation‐reconstruction framework to solve these problems on the Philips Gemini GS PET scanner.MethodsA fast, realistic system matrix simulation module was developed using egs_pet, which is an efficient PET simulation code based on EGSnrc. The generated system matrix was then used in a rotator‐based ordered subset expectation maximization (OS‐EM) algorithm, which exploits the rotational symmetry of a cylindrical PET scanner. The system matrix was further compressed by using sparse storage techniques.ResultsThe system matrix simulation took five days on 50 cores of Xeon 2.66 GHz, resulting in a system matrix of 2.01 GB. The entire system matrix could be stored in the main memory of a standard personal computer. The image quality in terms of contrast‐noise trade‐offs was considerably improved compared to a standard OS‐EM algorithm. The image quality was also compared to the clinical software on the scanner using routine parameter settings. The contrast recovery coefficient of small hot spheres and cold spheres was significantly improved.ConclusionsThe results indicated that the proposed framework could be used for this PET scanner with improved image quality. This method could also be applied to other state‐of‐the‐art whole‐body PET scanners and preclinical PET scanners with a similar shape.
In vivo quantitative imaging of normal and cancerous breast tissue using broadband diffuse optical tomography
Authors: Wang Jia , Jiang Shudong , Li Zhongze , diFlorio‐Alexander Roberta M. , Barth Richard J. , Kaufman Peter A. , Pogue Brian W. , Paulsen Keith D. 
Published: July 2010

PurposeA NIR tomography system that combines frequency domain (FD) and continuous wave (CW) measurements was used to image normal and malignant breast tissues.MethodsFD acquisitions were confined to wavelengths less than 850 nm because of detector limitations, whereas light from longer wavelengths (up to 948 nm) was measured in CW mode with CCD‐coupled spectrometer detection. The two data sets were combined and processed in a single spectrally constrained reconstruction to map concentrations of hemoglobin, water, and lipid, as well as scattering parameters in the breast.ResultsChromophore concentrations were imaged in the breasts of nine asymptomatic volunteers to evaluate their intrasubject and intersubject variability. Normal subject data showed physiologically expected trends. Images from three cancer patients indicate that the added CW data is critical to recovering the expected increases in water and decreases in lipid content within malignancies. Contrasts of 1.5 to twofold in hemoglobin and water values were found in cancers.ConclusionsIn vivo breast imaging with instrumentation that combines FD and CW NIR data acquisition in a single spectral reconstruction produces more accurate hemoglobin, water, and lipid results relative to FD data alone.
Estimation of microscopic dose enhancement factor around gold nanoparticles by Monte Carlo calculations
Authors: Jones Bernard L. , Krishnan Sunil , Cho Sang Hyun 
Published: July 2010

PurposeAn approach known as gold nanoparticle‐aided radiation therapy (GNRT) is a recent development in radiation therapy which seeks to make a tumor more susceptible to radiation damage by modifying its photon interaction properties with an infusion of gold nanoparticles (GNPs). The purpose of this study was to quantify the energy deposition due to secondary electrons from GNPs on a nanometer scale and to calculate the corresponding microscopic dose enhancement factor around GNPs.MethodsThe Monte Carlo code EGSnrc was modified to obtain the spectra of secondary electrons from atoms of gold approximating GNPs and molecules of water under photon irradiation of a tumor loaded with GNPs. Six different photon sources were used: , , , , 50 kVp, and 6 MV x rays. Treating the scored electron spectra as point sources within an infinite medium of water, the event‐by‐event Monte Carlo code NOREC was used to quantify the radial dose distribution, giving rise to gold/water electron dose point kernels and corresponding microscopic dose enhancement factors. These kernels were applied to a test case based on a scanning electron microscope image of a GNP distribution in tissue, enabling the determination of the microscopic dose enhancement at each dose point.ResultsFor the lower energy sources , , , and 50 kVp, the secondary electron fluence within a GNP‐loaded tumor was increased by as much as two orders of magnitude, leading to two orders of magnitude increase in electron energy deposition over radial distances up to . For the test case considered, the dose was enhanced by factors ranging from 2 to 20 within of GNPs, and by 5% as far away as .ConclusionsThis study demonstrates a remarkable microscopic dose enhancement due to GNPs and low energy photon sources. By quantifying the microscopic dose enhancement factor for a given photon source as a function of distance from GNPs, it also enables the selection of either a passive or an active tumor targeting strategy using GNPs which will maximize the radiobiological benefit from GNRT.
Variability in PET quantitation within a multicenter consortium
Authors: Fahey Frederic H. , Kinahan Paul E. , Doot Robert K. , Kocak Mehmet , Thurston Harold , Poussaint Tina Young 
Published: July 2010

PurposeThe purpose of this study was to evaluate the variability in quantitation of positron emission tomography (PET) data acquired within the context of a multicenter consortium.MethodsPET quantitation phantoms designed by American Association of Physicists in Medicine/Society of Nuclear Medicine Task Group 145 were sent to the ten member sites of the Pediatric Brain Tumor Consortium (PBTC), a NIH‐funded research consortium investigating the biology and therapies for brain tumors in children. The phantoms were water‐filled cylinders (18.6 cm inside height and 20.4 cm inside diameter) based on the standard ACR phantom with four small, “hot” cylinders of varying diameters (8, 12, 16, 25 mm, all with 38 mm height), consisting of an equilibrium mixture of in an epoxy matrix. At each site, the operator added the appropriate amount of to the water in the background in order to attain a feature‐to‐background ratio of roughly 4:1. The phantom was imaged and reconstructed as if it were a brain PET scan for the PBTC. An approximately 12 mm circular region of interest (ROI) was placed over each feature and in a central area in the background. The mean and maximum pixel values for each ROI were requested from local sites in units of activity concentration (Bq/ml) and the standard uptake value (SUV) (g/mL) based on bodyweight. The activity concentration was normalized by the decay‐corrected known activity concentration for the features, and reported as the absolute recovery coefficient (RC). In addition, central analyses were performed by two observers.ResultsThe ten sites successfully imaged the phantom within 5 months and submitted the quantitative results and the phantom image data to the PBTC Operations and Biostatistics Center. The local site‐based and central analyses yielded similar mean values for RC. Local site‐based SUV measurements of the hot cylindrical features yielded greater variability than central analysis (COV range of 29.9%–42.8% compared to 7.7%–23.2%). Correcting for miscalculations in the local site reported SUVs substantially reduced the variation to levels similar to the central analysis (COV range of 8.8%–18.4%) and also led to the local sites providing a similar mean of the SUV values to those from the central analysis. In the central analysis, the use of mean SUV in place of maximum SUV for an ROI of fixed size substantially reduced the variation in the SUV values (COV ranges of 7.7%–11.3% vs 9.3%–23.2%).ConclusionsBased on this investigation, a SUV variability in the range of 10%–25% due solely to instrument and analysis factors can be expected in the context of a multicenter consortium if a central reading is used and quality assurance and quality control procedures are followed. The overall SUV variability can be expected to be larger than this due to biological and protocol factors.
Ant colony algorithm implementation in electron and photon Monte Carlo transport: Application to the commissioning of radiosurgery photon beams
Authors: García‐Pareja S. , Galán P. , Manzano F. , Brualla L. , Lallena A. M. 
Published: July 2010

PurposeIn this work, the authors describe an approach which has been developed to drive the application of different variance‐reduction techniques to the Monte Carlo simulation of photon and electron transport in clinical accelerators.MethodsThe new approach considers the following techniques: Russian roulette, splitting, a modified version of the directional bremsstrahlung splitting, and the azimuthal particle redistribution. Their application is controlled by an ant colony algorithm based on an importance map.ResultsThe procedure has been applied to radiosurgery beams. Specifically, the authors have calculated depth‐dose profiles, off‐axis ratios, and output factors, quantities usually considered in the commissioning of these beams. The agreement between Monte Carlo results and the corresponding measurements is within for the central axis percentage depth dose and the dose profiles. The importance map generated in the calculation can be used to discuss simulation details in the different parts of the geometry in a simple way. The simulation CPU times are comparable to those needed within other approaches common in this field.ConclusionsThe new approach is competitive with those previously used in this kind of problems (PSF generation or source models) and has some practical advantages that make it to be a good tool to simulate the radiation transport in problems where the quantities of interest are difficult to obtain because of low statistics.
Assessment of ultrasound modulation of near infrared light on the quantification of scattering coefficient
Authors: Singh M. Suheshkumar , Yalavarthy Phaneendra K. , Vasu R. M. , Rajan K. 
Published: July 2010

PurposeTo assess the effect of ultrasound modulation of near infrared (NIR) light on the quantification of scattering coefficient in tissue‐mimicking biological phantoms.MethodsA unique method to estimate the phase of the modulated NIR light making use of only time averaged intensity measurements using a charge coupled device camera is used in this investigation. These experimental measurements from tissue‐mimicking biological phantoms are used to estimate the differential pathlength, in turn leading to estimation of optical scattering coefficient. A Monte‐Carlo model based numerical estimation of phase in lieu of ultrasound modulation is performed to verify the experimental results.ResultsThe results indicate that the ultrasound modulation of NIR light enhances the effective scattering coefficient. The observed effective scattering coefficient enhancement in tissue‐mimicking viscoelastic phantoms increases with increasing ultrasound drive voltage. The same trend is noticed as the ultrasound modulation frequency approaches the natural vibration frequency of the phantom material. The contrast enhancement is less for the stiffer (larger storage modulus) tissue, mimicking tumor necrotic core, compared to the normal tissue.ConclusionsThe ultrasound modulation of the insonified region leads to an increase in the effective number of scattering events experienced by NIR light, increasing the measured phase, causing the enhancement in the effective scattering coefficient. The ultrasound modulation of NIR light could provide better estimation of scattering coefficient. The observed local enhancement of the effective scattering coefficient, in the ultrasound focal region, is validated using both experimental measurements and Monte‐Carlo simulations.
ADC response to radiation therapy correlates with induced changes in radiosensitivity
Authors: Larocque Matthew P. , Syme Alasdair , Allalunis‐Turner Joan , Fallone B. Gino 
Published: July 2010

PurposeMagnetic resonance imaging was used to compare the responses of human glioma tumor xenografts to a single fraction of radiation, where a change in radiosensitivity was induced by use of a suture‐based ligature.MethodsIschemia was induced by use of a suture‐based ligature. Six mice were treated with 800 cGy of 200 kVp x rays while the ligature was applied. An additional six mice had the ligature applied for the same length of time but were not irradiated. Quantitative maps of each tumor were produced of water apparent diffusion coefficient (ADC) and transverse relaxation time (T2). Mice were imaged before and at multiple points after treatment. Volumetric, ADC, and T2 responses of the ligated groups were compared to previously measured responses of the same tumor model to the same radiation treatment, as well as those from an untreated control group.ResultsApplication of the ligature without irradiation did not affect tumor ADC values, but did produce a temporary decrease in tumor T2 values. Average tumor T2 was reduced by 6.2% 24 h after the ligature was applied. Average tumor ADC increased by 9.6% 7 days after irradiation with a ligature applied. This response was significantly less than that observed in the same tumor model when no ligature is present (21.8% at 7 days after irradiation).ConclusionsThese observations indicate that the response of ADC to radiation therapy is not determined entirely by physical dose deposition, but at least in part by radiosensitivity and resultant biological response.
Stable Synthetic Cationic Bacteriochlorins as Selective Antimicrobial Photosensitizers
Authors: Huang Liyi , Huang Ying-Ying , Mroz Pawel , Tegos George P. , Zhiyentayev Timur , Sharma Sulbha K. , Lu Zongshun , Balasubramanian Thiagarajan , Krayer Michael , Ruzié Christian , Yang Eunkyung , Kee Hooi Ling , Kirmaier Christine , Diers James R. , Bocian David F. , Holten Dewey , Lindsey Jonathan S. , Hamblin Michael R. 
Published: July 2010

ABSTRACT

Photodynamic inactivation is a rapidly developing antimicrobial treatment that employs a nontoxic photoactivatable dye or photosensitizer in combination with harmless visible light to generate reactive oxygen species that are toxic to cells. Tetrapyrroles (e.g., porphyrins, chlorins, bacteriochlorins) are a class of photosensitizers that exhibit promising characteristics to serve as broad-spectrum antimicrobials. In order to bind to and efficiently penetrate into all classes of microbial cells, tetrapyrroles should have structures that contain (i) one or more cationic charge(s) or (ii) a basic group. In this report, we investigate the use of new stable synthetic bacteriochlorins that have a strong absorption band in the range 720 to 740 nm, which is in the near-infrared spectral region. Four bacteriochlorins with 2, 4, or 6 quaternized ammonium groups or 2 basic amine groups were compared for light-mediated killing against a Gram-positive bacterium (
Staphylococcus aureus
), a Gram-negative bacterium (
Escherichia coli
), and a dimorphic fungal yeast (
Candida albicans
). Selectivity was assessed by determining phototoxicity against human HeLa cancer cells under the same conditions. All four compounds were highly active (6 logs of killing at 1 μM or less) against
S. aureus
and showed selectivity for bacteria over human cells. Increasing the cationic charge increased activity against
E. coli
. Only the compound with basic groups was highly active against
C. albicans.
Supporting photochemical and theoretical characterization studies indicate that (i) the four bacteriochlorins have comparable photophysical features in homogeneous solution and (ii) the anticipated redox characteristics do not correlate with cell-killing ability. These results support the interpretation that the disparate biological activities observed stem from cellular binding and localization effects rather than intrinsic electronic properties. These findings further establish cationic bacteriochlorins as extremely active and selective near-infrared activated antimicrobial photosensitizers, and the results provide fundamental information on structure-activity relationships for antimicrobial photosensitizers.
Antifungal Therapy in a Murine Model of Disseminated Infection by
Cryptococcus gattii
Authors: Calvo Enrique , Pastor F. Javier , Rodríguez M. Mar , Pujol Isabel , Guarro Josep 
Published: July 2010

ABSTRACT

We have evaluated the efficacy of posaconazole (PSC), voriconazole (VRC), and amphotericin B (AMB) in a murine model of systemic infection by
Cryptococcus gattii
using immunocompromised animals and three clinical strains of the fungus. AMB was the most effective drug in prolonging the survival of mice and also in reducing tissue burden in all organs tested. To a lesser degree, VRC at 60 mg/kg of body weight in lung tissue and PSC at 40 mg/kg also in spleen demonstrated good efficacy in reducing the fungal load. The PSC and VRC levels in serum and brain tissue, determined by an agar diffusion bioassay method at 4 h after the last dose of the therapy, were above the corresponding MIC values. However, these drugs were not able to reduce the fungal load in brain tissue. Our results demonstrated that PSC and, to a lesser degree, VRC, have fungistatic activity and potential for the treatment of human pulmonary cryptococcosis.
Purification and Characterization of Avian β-Defensin 11, an Antimicrobial Peptide of the Hen Egg
Authors: Hervé-Grépinet Virginie , Réhault-Godbert Sophie , Labas Valérie , Magallon Thierry , Derache Chrystelle , Lavergne Marion , Gautron Joël , Lalmanach Anne-Christine , Nys Yves 
Published: July 2010

ABSTRACT

Natural antimicrobial peptides are present in different compartments (eggshell, egg white, and vitelline membranes) of the hen egg and are expected to be involved in the protection of the embryo during its development and to contribute to the production of pathogen-free eggs. In the present study, we used vitelline membranes from hen (
Gallus gallus
) eggs as a source of avian β-defensin 11 (AvBD11). A purification scheme using affinity chromatography and reverse-phase chromatography was developed. Purified AvBD11 was analyzed by a combination of mass spectrometry approaches to characterize its primary sequence and structure. A monoisotopic molecular species at [M + H]
+
of 9,271.56 Da was obtained, and its N- and C-terminal sequences were determined. We also examined posttranslational modifications and identified the presence of 6 internal disulfide bonds. AvBD11 was found to exhibit antimicrobial activity toward both Gram-positive and Gram-negative bacteria.
International Retrospective Analysis of 73 Cases of Invasive Fusariosis Treated with Voriconazole
Authors: Lortholary Olivier , Obenga Gaelle , Biswas Pinaki , Caillot Denis , Chachaty Elisabeth , Bienvenu Anne-Lise , Cornet Muriel , Greene John , Herbrecht Raoul , Lacroix Claire , Grenouillet Frédéric , Raad Issam , Sitbon Karine , Troke Peter 
Published: July 2010

ABSTRACT

The outcomes for 73 invasive fusariosis patients treated with voriconazole were investigated. Patients with proven (
n
= 67) or probable (
n
= 6) infections were identified from the voriconazole clinical database (
n
= 39) and the French National Reference Center for Mycoses and Antifungals database (
n
= 34). Investigator-determined success was a complete or partial response. Survival was determined from day 1 of voriconazole therapy to the last day known alive. Patients were 2 to 79 years old (median, 43 years), and 66% were male. Identified
Fusarium
species (62%) were
F. solani
,
F. moniliforme
,
F. proliferatum
, and
F. oxysporum
. Underlying conditions analyzed included hematopoietic stem cell transplant (HSCT; 18%), hematologic malignancy (HM; 60%), chronic immunosuppression (CI; 12%), or other condition (OC; 10%). Infection sites were brain (5%), disseminated excluding brain (67%), lungs/sinus (15%), and other (12%). Most patients (64%) were or had recently been neutropenic (<500 cells/mm
3
). Therapy duration was 1 to 480 days (median, 57 days), with a 47% success rate. Baseline neutropenia impacted success adversely (
P
≤ 0.03). Success varied by underlying condition (HSCT, 38%; HM, 45%; CI, 44%; OC, 71%) and infection site (brain, 0%; disseminated, 45%; other, 56%; lung/sinus, 64%) (
P
> 0.05). Combination therapy (13 patients) was no better than treatment with voriconazole alone. Overall, 59% of the patients died (49% died of fusariosis), and 90-day survival was 42%. Site of infection influenced survival (
P
= 0.02). Median survival (in days) by species was as follows:
F. solani
, 213;
F. oxysporum
, 112;
Fusarium
spp., 101;
F. proliferatum
, 84;
F. moniliforme
, 76. We conclude that voriconazole is a therapeutic option for invasive fusariosis.