bluuebunny/crossref_metadata_2025 huggingface dataset:
The Predictions of Air Pollution Levels by Nonphysical Models Based on Kalman Filtering Method
Authors: Sawaragi Y. , Soeda T. , Yoshimura T. , Ohe S. , Chujo Y. , Ishihara H.
Published: July 2010

We describe the applications of multiple linear regression model and auto-regressive model which may be of use for the on-line prediction and control of concentration levels of pollutants of air pollution. At the beginning of these researches, in this paper, are presented the prediction of air pollution levels at a few hours in advance. The state variables of the multiple linear regression model are determined by considering the contribution of the component analysis. Practical data measured in Tokyo and Tokushima prefecture in Japan are used, respectively. Kalman filtering method is utilized for the prediction by the multiple linear regression model. Auto-regressive model is fitted to the time series which is processed by subtracting the moving average from the original observed data sequence. Accuracy and characteristic of the prediction by the models presented here are compared with the model of the Box and Jenkins, and with that obtained by the principle of persistence, respectively. Both are found to be significantly more accurate and useful than these models.
Vibratory Identification of Beam Boundary Conditions
Authors: Sweet A. L. , Genin J. , Mlakar P. F.
Published: July 2010

In previous work, by means of stochastic and deterministic models, the authors presented a system identification theory for performing nondestructive testing of elastic systems. The procedure requires identification of the structure’s boundary conditions. Herein, the mathematical models are improved, and vibration data are presented for the determination of the boundary parameters. These experimentally derived results are shown to validate the models.
Analytical Model for Guideway Surface Roughness
Authors: Bala Krishna M. , Hullender D. A.
Published: July 2010

An analytical model is presented for calculating the power spectral density of relatively short wavelength guideway irregularities associated with surface roughness. The results are presented in terms of design tolerances which can be interpreted in terms of the familiar California profile index or in terms of measurable deviations from a straight edge. Digital computer numerical simulation techniques are used to verify the model.
Optimal Control in the Presence of Nondifferentiable State Constraints
Authors: Eyman E. D. , Sudhakar D. P.
Published: July 2010

Necessary conditions are derived for optimality of differential control processes in the presence of nondifferentiable state (or phase) constraints. The techniques of general Mathematical Programming and the Dubovitskii-Milyutin Theorem are employed. The necessary conditions derived are in the form of an adjoint integral equation and a pointwise maximal condition. It is found that the gradient of the state (or phase) constraint can be replaced by the Gateaux differential of a certain form in the adjoint equation.
On Using the ISO Standard To Evaluate the Ride Quality of Broad-Band Vibration Spectra in Transportation Vehicles
Authors: Smith Craig C.
Published: July 2010

The International Standards Organization “Guide for the Evaluation of Human Exposure to Whole-Body Vibrations”, ISO 2631, is converted to a form usable for direct comparison with vibration data represented in power spectral density form. Comparisons are made between the ISO standard, the Urban Tracked Air Cushion Vehicle (UTACV) specification, and measured vibrations at the floorboard and seat of an automobile over smooth and rough roads. The data indicate that the ISO standard is less restrictive than the UTACV specification, and generally not restrictive enough to indicate the roughness of an automobile ride on a rough country road.
Chromatography Column System With Controlled Flow and Temperature for Engineering Scale Application
Authors: Watanabe Sou , Goto Ichiro , Sano Yuichi , Koma Yoshikazu
Published: July 2010

The Japan Atomic Energy Agency is conducting research and development study on the engineering scale extraction chromatography system, which uses silica-based adsorbents impregnated with an extractant for the minor actinides (Am and Cm) recovery from the high level liquid waste generated in the spent fast breeder reactor (FBR) fuel reprocessing, as a part of the fast reactor cycle technology development project. A bench scale testing system was made and provided for the first step of development. The column of the test system (inside diameter of 480 mm or 200 mm with height of 650 mm) was equipped with ports for six external sensors at its top, middle, and bottom levels for measuring the flow velocity or temperature, and for additional six heaters for simulating the decay heat of Am and Cm at the middle level of the column. The flow velocity distribution was almost constant except for the part that is very near the column wall, and it was almost uniform when the liquid flew from top to bottom direction with 4 cm/min of the velocity. The heaters scarcely influenced the temperature profile inside the column when the power applied to the heater simulated the decay heat of Am, Cm, and fission products (FPs). The decay heat generated in the column was transported to the effluents, and the temperature inside the column was kept almost constant.
Recent Moisture Separator Reheater Design Technologies
Authors: Manabe Jun , Kasahara Jiro , Fujita Issaku , Kojima Toshiki
Published: July 2010

The moisture separator reheater (MSR) is a key piece of equipment in reheat systems in nuclear steam turbines that use saturated main steam, where it helps improve turbine efficiency and suppress flow-accelerated corrosion. Fundamental to achieving a compact, reliable MSR design are methods for predicting mist separator vane performance and suppressing tube drainage instability. First, we devised a method for predicting separator performance based on the observation of mist separation behavior under an air-water test. We then developed a method for predicting performance under steam conditions from air-water test data and verified it by means of a comparison with the actual results of a steam condition test. The instability of tube drainage associated with both subcooling and temperature oscillation at turbine partial load, which might adversely affect the seal welding of the tubes to the tube sheet due to thermal fatigue, was measured on an existing unit to clarify the behavior. We then developed a technique for increasing venting steam, which had been operating at a constant flow rate, to suppress instability and verified its effectiveness. Both methods were applied to current MSR models, which were adopted for nuclear power plant turbines commercially placed in service from 1984 to 2009, and the effectiveness of the methods was demonstrated. The separator vane mist carryover rate was less than 0.1%, and tube drainage instability was suppressed, demonstrating the effectiveness of the simple design concept of a two-flow U-tube instead of the prevailing four-flow U-tube design. We put forth a new concept in the design of MSRs for 1700 MW class advanced pressurized water reactor (APWR) units based on associated technologies, along with advanced technology for the compact design of pressure vessels and multidisciplinary optimum design for evaluating heat exchanger tube bundles.
Numerical Solution on Spherical Vacuum Bubble Collapse Using MPS Method
Authors: Tian Wen xi , Qiu Sui-zheng , Su Guang-hui , Ishiwatari Yuki , Oka Yoshiaki
Published: July 2010

Single vacuum bubble collapse in subcooled water has been simulated using the moving particle semi-implicit (MPS) method in the present study. The liquid is described using moving particles, and the bubble-liquid interface was set to be the vacuum pressure boundary without interfacial heat mass transfer. The topological shape of the vacuum bubble is determined according to the location of interfacial particles. The time dependent bubble diameter, interfacial velocity, and bubble collapse time were obtained within a wide parametric range. Comparison with Rayleigh’s prediction indicates a good consistency, which validates the applicability and accuracy of the MPS method. The potential void-induced water hammer pressure pulse was also evaluated, which is instructive for the cavitation erosion study. The present paper discovers fundamental characteristics of vacuum bubble hydrodynamics, and it is also instructive for further applications of the MPS method to complicated bubble dynamics.
Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery
Authors: Sarfehnia A. , Clasie B. , Chung E. , Lu H. M. , Flanz J. , Cascio E. , Engelsman M. , Paganetti H. , Seuntjens J.
Published: July 2010

Purpose

The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard.

Methods

The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDR brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS‐398 protocol.

Results

The overall 1‐sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS‐398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS‐398 well to within 1‐sigma uncertainty.

Conclusions

This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.
Peak SNR in automated coronary calcium scoring: Selecting CT scan parameters and statistically defined scoring thresholdsa)
Authors: Arnold Ben A. , Xiang Ping , Mao Song S. , Budoff Matthew J.
Published: July 2010

Purpose

Development and verification of peak signal‐to‐noise ratio equations for determining optimum CT scanning and scoring parameters for a new automated coronary calcium scoring program (N‐vivo™). Experimental evaluation of the new program for scoring small calcium hydroxyapatite (CaHA) microspheres with small voxel CT images.

Methods

Theoretical equations were developed using measures of noise, resolution, contrast, scatter, and x‐ray photon energy. A coronary calcium scoring test phantom containing very small CaHA microspheres was scanned simultaneously with a calibration phantom at three kVps, three voxel sizes, and three phantom sizes. Agatston and calibrated mass scores, noise standard deviations, peak noise, and peak signal voxel intensities were measured by the N‐vivo method for individual microspheres and in patient CT scans.

Results

The equation was predictive of the optimum voxel size, kVp, and phantom size, and allowed automated computation of mass scoring thresholds specific to each patient and CT scan. The smallest microcalcification scored in the full sized phantom with the N‐vivo method by calibrated mass score (volume , mass 0.17 mg) was approximately four times smaller than that scored with the Agatston method (, mass 0.63 mg).

Conclusions

The equation can be used to model and optimize calcium scoring and CT scan parameters. The common assumptions that noise is too high in thin slice CT or requires high radiation dose for CAC scoring are shown to be misleading. The N‐vivo method showed higher detection sensitivity for small microspheres and more consistent mass scores at different beam energies than the conventional Agatston method. Advanced calcium scoring methods with higher sensitivity may allow improved monitoring of plaque changes and provide earlier detection of atherosclerosis.
Noise variance analysis using a flat panel x‐ray detector: A method for additive noise assessment with application to breast CT applications
Authors: Yang Kai , Huang Shih‐Ying , Packard Nathan J. , Boone John M.
Published: July 2010

Purpose

A simplified linear model approach was proposed to accurately model the response of a flat panel detector used for breast CT (bCT).

Methods

Individual detector pixel mean and variance were measured from bCT projection images acquired both in air and with a polyethylene cylinder, with the detector operating in both fixed low gain and dynamic gain mode. Once the coefficients of the linear model are determined, the fractional additive noise can be used as a quantitative metric to evaluate the system's efficiency in utilizing x‐ray photons, including the performance of different gain modes of the detector.

Results

Fractional additive noise increases as the object thickness increases or as the radiation dose to the detector decreases. For bCT scan techniques on the UC Davis prototype scanner (80 kVp, 500 views total, 30 frames/s), in the low gain mode, additive noise contributes 21% of the total pixel noise variance for a 10 cm object and 44% for a 17 cm object. With the dynamic gain mode, additive noise only represents approximately 2.6% of the total pixel noise variance for a 10 cm object and 7.3% for a 17 cm object.

Conclusions

The existence of the signal‐independent additive noise is the primary cause for a quadratic relationship between bCT noise variance and the inverse of radiation dose at the detector. With the knowledge of the additive noise contribution to experimentally acquired images, system modifications can be made to reduce the impact of additive noise and improve the quantum noise efficiency of the bCT system.
Validation of 3D reconstructions of a mimicked femoral artery with an ultrasound imaging robotic system
Authors: Janvier Marie‐Ange , Soulez Gilles , Allard Louise , Cloutier Guy
Published: July 2010

Purpose

The degree of stenosis is the most important criterion to assess peripheral arterial disease manifested by atherosclerosis mainly in lower limb arteries. Ultrasound (U.S.) imaging offers low‐cost, safe, and convenient options to evaluate this disease, but most U.S. freehand approaches cannot optimally locate stenoses and map lower limb arterial geometries. A 3D‐U.S. imaging robotic system that can control and standardize image acquisition by scanning typically encountered diseased arterial lower limb segments is presented and validated with phantoms.

Methods

A Z‐phantom calibration procedure was used to characterize spatial transformation of the U.S. probe image plane for different clinical image acquisition settings. Moreover, the accuracy of the calibration transform to reconstruct a lower‐limb‐mimicking vessel geometry was evaluated with a vascular phantom.

Results

A 3D calibration precision of was achieved. Reconstruction errors were less than in all 3D vessel representations and the cross‐sectional areas of each image section were close to those of gold standard phantom measures. The best reconstruction accuracy (smallest error) was .

Conclusion

Altogether, these results demonstrate the potential of the robotic scanner to adequately represent lower limb vessels for the clinical evaluation of stenoses.
Evaluation of the peripheral dose in stereotactic radiotherapy and radiosurgery treatmentsa)
Authors: Di Betta Erika , Fariselli Laura , Bergantin Achille , Locatelli Federica , Del Vecchio Antonella , Broggi Sara , Fumagalli Maria Luisa
Published: July 2010

Purpose

The main purpose of this work was to compare peripheral doses absorbed during stereotactic treatment of a brain lesion delivered using different devices. These data were used to estimate the risk of stochastic effects.

Methods

Treatment plans were created for an anthropomorphic phantom and delivered using a LINAC with stereotactic cones and a multileaf collimator, a CyberKnife® system (before and after a supplemental shielding was applied), a TomoTherapy® system, and a Gamma Knife® unit. For each treatment, 5 Gy were prescribed to the target. Measurements were performed with thermoluminescent dosimeters inserted roughly in the position of the thyroid, sternum, upper lung, lower lung, and gonads.

Results

Mean doses ranged from of 4.1 (Gamma Knife) to 62.8 mGy (LINAC with cones) in the thyroid, from 2.3 (TomoTherapy) to 30 mGy (preshielding CyberKnife) in the sternum, from 1.7 (TomoTherapy) to 20 mGy (preshielding CyberKnife) in the upper part of the lungs, from 0.98 (Gamma Knife) to 15 mGy (preshielding CyberKnife) in the lower part of the lungs, and between 0.3 (Gamma Knife) and 10 mGy (preshielding CyberKnife) in the gonads.

Conclusions

The peripheral dose absorbed in the sites of interest with a 5 Gy fraction is low. Although the risk of adverse side effects calculated for 20 Gy delivered in 5 Gy fractions is negligible, in the interest of optimum patient radioprotection, further studies are needed to determine the weight of each contributor to the peripheral dose.
Combined mixed approach algorithm for in‐line phase‐contrast x‐ray imaging
Authors: De Caro Liberato , Scattarella Francesco , Giannini Cinzia , Tangaro Sabina , Rigon Luigi , Longo Renata , Bellotti Roberto
Published: July 2010

Purpose

In the past decade, phase‐contrast imaging (PCI) has been applied to study different kinds of tissues and human body parts, with an increased improvement of the image quality with respect to simple absorption radiography. A technique closely related to PCI is phase‐retrieval imaging (PRI). Indeed, PCI is an imaging modality thought to enhance the total contrast of the images through the phase shift introduced by the object (human body part); PRI is a mathematical technique to extract the quantitative phase‐shift map from PCI. A new phase‐retrieval algorithm for the in‐line phase‐contrast x‐ray imaging is here proposed.

Methods

The proposed algorithm is based on a mixed transfer‐function and transport‐of‐intensity approach (MA) and it requires, at most, an initial approximate estimate of the average phase shift introduced by the object as prior knowledge. The accuracy in the initial estimate determines the convergence speed of the algorithm. The proposed algorithm retrieves both the object phase and its complex conjugate in a combined MA (CMA).

Results

Although slightly less computationally effective with respect to other mixed‐approach algorithms, as two phases have to be retrieved, the results obtained by the CMA on simulated data have shown that the obtained reconstructed phase maps are characterized by particularly low normalized mean square errors. The authors have also tested the CMA on noisy experimental phase‐contrast data obtained by a suitable weakly absorbing sample consisting of a grid of submillimetric nylon fibers as well as on a strongly absorbing object made of a 0.03 mm thick lead x‐ray resolution star pattern. The CMA has shown a good efficiency in recovering phase information, also in presence of noisy data, characterized by peak‐to‐peak signal‐to‐noise ratios down to a few dBs, showing the possibility to enhance with phase radiography the signal‐to‐noise ratio for features in the submillimetric scale with respect to the attenuation‐based imaging.

Conclusions

It has been shown that phase‐retrieved radiographies can be used both to have quantitative phase information about soft tissues, complementary to the attenuation information, and to enhance the visibility of details inside soft tissues, with higher efficiency with respect to phase radiography.
An attenuation integral digital imaging technique for the treatment portal verification of conventional and intensity‐modulated radiotherapy
Authors: Guan Huaiqun
Published: July 2010

Purpose

To propose an attenuation integral digital imaging (AIDI) technique for the treatment portal verification of conventional and intensity‐modulated radiotherapy (IMRT).

Methods

In AIDI technique, an open in air fluence image and a patient fluence image were acquired under the same exposure. Then after doing the dark field correction for both the and , the AIDI image was simply calculated as , which is the attenuation integral along the ray path from the x‐ray source to a detector pixel element. Theoretical analysis for the low contrast detection and the contrast to noise ratio (CNR) of AIDI was presented and compared to those for the fluence imaging. With AIDI, the variation of x‐ray fluence and the variation of individual detector pixel's response can be automatically compensated without using the flood field correction.

Results

The AIDI image for a contrast detail phantom demonstrated that it can efficiently suppress the background structures such as the couch and generate better visibility for low contrast objects with megavoltage x rays. The AIDI image acquired for a Catphan 500 phantom using a 60° electronic dynamic wedge field also revealed more contrast disks than the fluence imaging did. Finally, AIDI for an IMRT field of a head/neck patient successfully displayed the anatomical structures underneath the treatment portal but not shown in fluence imaging.

Conclusions

For IMRT and high degree wedge beams, direct imaging using them is difficult because their photon fluence is highly nonuniform. But AIDI can be used for the treatment portal verification of these beams.
Prostate and seminal vesicle volume based consideration of prostate cancer patients for treatment with 3D‐conformal or intensity‐modulated radiation therapya)
Authors: Reddy Nandanuri M. S. , Nori Dattatreyudu , Chang Hyesook , Lange Christopher S. , Ravi Akkamma
Published: July 2010

Purpose

The purpose of this article was to determine the suitability of the prostate and seminal vesicle volumes as factors to consider patients for treatment with image‐guided 3D‐conformal radiation therapy (3D‐CRT) or intensity‐modulated radiation therapy (IMRT), using common dosimetry parameters as comparison tools.

Methods

Dosimetry of 3D and IMRT plans for 48 patients was compared. Volumes of prostate, SV, rectum, and bladder, and prescriptions were the same for both plans. For both 3D and IMRT plans, expansion margins to (CTV) and prostate were 0.5 cm posterior and superior and 1 cm in other dimensions to create PTV and CDPTV, respectively. Six‐field 3D plans were prepared retrospectively. For 3D plans, an additional 0.5 cm margin was added to PTV and CDPTV. Prescription for both 3D and IMRT plans was the same: 45 Gy to CTV followed by a 36 Gy boost to prostate. Dosimetry parameters common to 3D and IMRT plans were used for comparison: Mean doses to prostate, CDPTV, SV, rectum, bladder, and femurs; percent volume of rectum and bladder receiving 30 , 50 , and 70 Gy , dose to 30% of rectum and bladder, minimum and maximum point dose to CDPTV, and prescription dose covering 95% of CDPTV .

Results

When the data for all patients were combined, mean dose to prostate and CDPTV was higher with 3D than IMRT plans . Mean to CDPTV was the same for 3D and IMRT plans . On average, among all cases, the minimum point dose was less for 3D‐CRT plans and the maximum point dose was greater for 3D‐CRT than for IMRT . Mean dose to 30% rectum with 3D and IMRT plans was comparable . was less , was the same , and was more for rectum with 3D than IMRT plans. Mean dose to bladder was less with 3D than IMRT plans . for bladder with 3D plans was less than that of IMRT plans . and for 3D plans were the same for 3D and IMRT plans . Mean dose to femurs was more with 3D than IMRT plans . For a given patient, mean dose and dose to 30% rectum and bladder were less with 3D than IMRT plans for prostate or volumes (38/48) and (39/48), respectively . The larger the dose to rectum or bladder with 3D plans, the larger also was the dose to these structures with IMRT . For both 3D and IMRT plans, dose to rectum and bladder increased with the increase in the volumes of prostate and seminal vesicles ( to 0.001).

Conclusions

Volumes of prostate and seminal vesicles provide a reproducible and consistent basis for considering patients for treatment with image‐guided 3D or IMRT plans. Patients with prostate and volumes and , respectively, would be suitable for 3D‐CRT. Patients with prostate and volumes and , respectively, might get benefit from IMRT.
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

Purpose

The 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.

Methods

MSCT 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.

Results

The 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.

Conclusions

The 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

Purpose

Several 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.

Methods

A 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.

Results

The 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.

Conclusions

The 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

Purpose

A NIR tomography system that combines frequency domain (FD) and continuous wave (CW) measurements was used to image normal and malignant breast tissues.

Methods

FD 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.

Results

Chromophore 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.

Conclusions

In 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

Purpose

An 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.

Methods

The 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.

Results

For 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 .

Conclusions

This 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

Purpose

The 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.

Methods

PET 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.

Results

The 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%).

Conclusions

Based 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

Purpose

In 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.

Methods

The 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.

Results

The 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.

Conclusions

The 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

Purpose

To assess the effect of ultrasound modulation of near infrared (NIR) light on the quantification of scattering coefficient in tissue‐mimicking biological phantoms.

Methods

A 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.

Results

The 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.

Conclusions

The 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

Purpose

Magnetic 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.

Methods

Ischemia 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.

Results

Application 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).

Conclusions

These 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.
Pricking Out Pain with Adenosine
Authors: Gough Nancy R.
Published: July 2010

By stimulating the production of adenosine, acupuncture stimulates a class of pain-relieving receptors in the periphery.
Organized Randomness
Authors: Foley John F.
Published: July 2010

The self-organization of phosphatidylinositol lipids along the membranes of
Dictyostelium
cells enables spontaneous cell migration.
Correcting a Liver Problem
Authors: Hurtley Stella M.
Published: July 2010

A mouse model of a human liver disease can be treated using a drug known to be well tolerated.
Out-FoxO1ing Cancer from the Cytoplasm
Authors: Adler Elizabeth M.
Published: July 2010

FoxO1 acts in the cytoplasm to stimulate autophagy and cancer cell death.
Stuck on You
Authors: VanHook Annalisa M.
Published: July 2010

Cleavage of the zona pellucida component ZP2 is required to prevent sperm binding to fertilized eggs.
BK Channel Cytoplasmic Domain
Authors: Vinson Valda K.
Published: July 2010

A tetramer of two regulatory domains forms a gating ring that regulates calcium ion activation.
Righting Repair Pathways
Authors: Riddihough Guy
Published: July 2010

A specific pathway protects damaged DNA from error-prone repair.
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

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

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

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.