Degrees Intervals Research Articles

SU‐E‐J‐148: Tools for Development of 4D Proton CT

Purpose:To develop tools for performing 4D proton computed tomography (CT).Methods:A suitable patient with a tumor in the right lower lobe was selected from a set of 4D CT scans. The volumetric CT images formed the basis for calculating the parameters of a breathing model that allows reconstruction of a static reference CT and CT images in each breathing phase. The images were imported into the TOPAS Monte Carlo simulation platform for simulating an experimental proton CT scan with 45 projections spaced by 4 degree intervals. Each projection acquired data for 2 seconds followed by a gantry rotation for 2 seconds without acquisition. The scan covered 180 degrees with individual protons passing through a 9‐cm slab of the patient's lung covering the moving tumor. An initial proton energy sufficient for penetrating the patient from all directions was determined. Performing the proton CT simulation, TOPAS provided output of the proton energy and coordinates registered in two planes before and after the patient, respectively. The set of projection data was then used with an iterative reconstruction algorithm to generate a volumetric proton CT image set of the static reference image and the image obtained under breathing motion, respectively.Results:An initial proton energy of 230 MeV was found to be sufficient, while for an initial energy of 200 MeV a substantial number of protons did not penetrate the patient. The reconstruction of the static reference image set provided sufficient detail for treatment planning.Conclusion:We have developed tools to perform studies of proton CT in the presence of lung motion based on the TOPAS simulation toolkit. This will allow to optimize 4D reconstruction algorithms by synchronizing the acquired proton CT data with a breathing signal and utilizing a breathing model obtained prior to the proton CT scan.This research has been supported by the National Institute Of Biomedical Imaging And Bioengineering of the National Institutes of Health under Award Number R01EB013118.

SU‐E‐T‐494: Influence of Proton Track‐Cell Nucleus Incidence Angle On Relative Biological Effectiveness

Purpose:To explain a Monte Carlo (MC) simulation artifact whereby differences in relative biological effectiveness (RBE) in the induction of initial double strand breaks are observed as a function of the proton track incidence angles in a geometric cell nucleus model. Secondly, to offer an alternative isotropic irradiation procedure to mitigate this effect.Methods:MC tracks of 1 MeV protons were generated in an event‐by‐event mode. They were overlaid on a cylindrical model of a cell nucleus containing 6×109 nucleotide base pairs. The tracks incidence angle θ with respect to the cell nucleus's axis was varied in 10 degrees intervals, each time generating one hundred fractions of ∼2 Gy. Strand breaks were scored in the modeled DNA sugar‐phosphate groups and further sub‐classified into single or double strand breaks (ssbs or dsbs). For each angle, an RBE for the induction of initial dsbs with reference to Co‐60 was calculated.Results:Our results show significant angular dependencies of RBE, with maximum values for incidence angles parallel to the nucleus central axis. Further examination shows that the higher cross‐sections for the creation of dsbs is due to the preferential alignment of tracks with geometrical sub‐parts of the cell nucleus model, especially the nucleosomes containing the sugar‐phosphate groups. To alleviate the impact of this simulation artifact, an average RBE was calculated with a procedure based on a weighted sampling of the angular data.Conclusion:This work demonstrates a possible numerical artifact in estimated RBE if the influence of the particle incidence angle is not correctly taken into account. A correction procedure is presented to better conform the simulations to real‐life experimental conditions.We would like to acknowledge support from the Fonds de recherche du Quebec Sante (FRQS), from the CREATE Medical Physics Research Training Network grant (number 432290) of NSERC, support from NSERC under grants RGPIN 397711‐11 and RGPIN‐2014‐06475 and support from the CIHR under grants MOP‐114910, MOP‐136774 and MOP‐102550.

Lipid accumulation in response to nitrogen limitation and variation of temperature in Nannochloropsis salina.

BackgroundThis batch study deals with the relation between lipid as well as triglyceride contents in Nannochloropsis salina and variation in culture conditions such as nitrogen concentration and temperature.ResultsThe tested parameters caused reduction in growth expressed as cell count, optical density and dry weight, as well strongly involved in lipids and triglycerides accumulation and significantly affected the lipid productivity. At the beginning of the work, the concentration of nitrogen in the medium was reduced to three quarter, half and quarter of the original f2 medium while the temperature kept constant. After that, the optimal nitrogen concentration (quarter of the original media) giving high lipid yield was tested with different temperature degrees from 15 to 35°C with five degree intervals. Although the growth was insignificantly influenced, a considerable increase in lipid and triglyceride (56.1 and 15.1% of dry weight respectively) was observed when the concentration of nitrogen in the medium was reduced to the quarter. Moreover, 59.3% lipid and 17.1% triglyceride on the basis of dry weight were obtained by the combination of 25% nitrogen concentration and 30°C. Simple regressions recommended that the interaction effect of nitrogen limitation and temperature on lipid and triglyceride accumulation was not as fundamental as for nitrogen limitation stress.ConclusionThe degree of nitrogen availability in the combination of temperature effect has been identified as the critical determinant for the maximal production of lipid in N. salina. Nevertheless, major advances in this field can be considered by studying more stresses techniques and genetic strategies.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0085-7) contains supplementary material, which is available to authorized users.

Teaching Hands-on Urban Forestry Health Assessment Using the Resistograph and the CTLA Method

Undergraduate students were instructed how to assess the health of 24 urban willow oak trees. Students received hands-on training using the Resistograph 400 on two sites: a depressional site and a well-drained site on the campus of Stephen F. Austin State University in an upper division Urban Forestry course. Students followed the instructed and prescribed method of drilling three holes at 120 degree intervals at 3.5 feet in height above ground in each oak tree. Tree condition data were recorded on paper strips and analyzed in laboratory for percent decay measured for each sample. The results were averaged for the three samples per tree and the percent of soundwood was determined. Resistograph data were then analyzed by the students using SAS ANOVA for the 24 trees within the two sites. Results indicted a significantly higher amount of decay on the depressional sites compared to the well-drained sites. Data collected using the standard CTLA tree health assessment method indicated willow oaks in depressional sites had a significantly lower condition rating based on six measured tree variables. This study demonstrated that incorporating intensive hands-on instruction within an undergraduate student’s education increases retention rates, enhances their educational experience, and produces a more well-rounded urban forester.

Correlation between bone apposition of the acetabular rim and morphological indicators of femoroacetabular impingement in the japanese asymptomatic population

Purpose: Acetabular rim ossification has been generally accepted as an osteophyte, which appeared in advanced osteoarthritis of the hip. On the contrary, it is suggested that bone apposition of the acetabular rim was induced by femoroacetabular impingement (FAI), abnormal abutment of the femoral neck against the acetabulum. FAI has been well described as a pathologic process that can lead to early osteoarthritic changes. To date, the association between the bone apposition of the acetabular rim and FAI is still unknown. The purpose of this study is to evaluate the association between the presence of bone apposition of the acetabular rim and morphological indicators of FAI based on computed tomography (CT) examination. Methods: We reviewed the CT scans of 245 consecutive subjects (490 hips, age: 21–83 years) who underwent abdominal and pelvic CT from September, 2010 to June, 2011. These subjects were mainly examined for abdominal disorders. We confirmed that no subject had any symptoms for the hip joint by the questionnaire survey. We reviewed them to evaluate the presence of bone apposition of the acetabular rim and the morphological abnormalities of the femoral head and acetabulum. The multi-detector CT adjusted for the anterior and lateral inclination of the acetabulum was obtained. On these images, 3 radial sections, antero-, mid-, and postero-superior, were determined at 30 degrees interval. Each section passed through the midpoint of the acetabulum and crossed vertically to the acetabular margin. Bone apposition of the acetabular rim was diagnosed by the recess sign, which is characterized as a gap between the native acetabular rim and the extension of the osseous apposition. We measured following three signs as indicators for FAI: a angle, center edge angle (CE angle), and acetabular index (AI). At the time of measurement, the position of the pelvis was standardized. We defined an anterior pelvic plane involving the anterior superior iliac spines and the top of the pubis as a reference plane (coronal section). Mann–Whitney U-test was used for statistical analysis. Results: Bone apposition was observed in 156 hips (32%) in total of the three parts. The prevalence at each part, anterior, middle, and posterior was 3.4%, 13.6%, and 24.6% respectively. When we divided the subjects into the younger group (<60 years old) and the elderly group (S60years old), there was significant difference at the prevalence of bone apposition between two groups (younger: 18.3%, elderly: 44.6%; p < 0.01). In terms of the a angle and CE angle, there was no significant difference between the subjects with and without bone apposition (a angle: 45.8 7.3 vs 43.4 8.4 , CE angle: 32.6 5.5 vs 31.7 8.1 , respectively). Interestingly, there was different trend in AI between the younger and elderly groups. The younger group showed no significant difference between the subjects with and without bone appositionwith the AI of 3.1 3.7 vs 4.3 5.2 , whereas the elderly group showed significant difference with the AI of 4.4 2.1 for with the bone apposition group vs 2.9 3.4 for without bone apposition group, p < 0.05. Conclusions: Two different types of FAI have been described, one is cam impingement, which is caused by small offset of femoral head neck junction, and the other is pincer impingement that is attributed by the acetabular over-coverage. Pincer impingement was thought to be associated with ossification of the acetabular rim. It was reported that the bone apposition in FAI initiated from subperiosteal bone formation at the rim, which was distinct from osteophyte formation in OA, which is a result of endochondral ossification from articular cartilage. In the present study, we showed that the prevalence of bone apposition was 32%. It was observed more frequently at the posterior part of the acetabulum and in the elderly subjects of asymptomatic Japanese population. Moreover, statistical analysis revealed significantly larger AI, means shallow joint, in the subjects with bone apposition in the elderly population. These results indicate that the bone apposition of the acetabular rim may have degenerative characteristics without clinical symptoms and might be associated with the instability of the hip joint.

Classifying Asian dust aerosols and their columnar optical properties using fuzzy clustering

AbstractThe Gustafson‐Kessel fuzzy clustering algorithm is used to classify Asian dust aerosols from Aerosol Robotic Network inversions, and properties within different membership degree intervals are analyzed. Five typical Asian dust sites are selected for source data. Based on dust aerosol physics, seven key parameters are selected as clustering inputs. The two clusters, dust and nondust, are then divided by a membership degree threshold of 0.5 on a scale of 0 to 1. The membership degree denotes the level of confidence that a record belongs to a cluster. The degree of mixing is denoted by diminishing membership values; e.g., the classified dust aerosol associated with higher membership degree denotes the purer dust. The two‐dimensional principle component projections, together with the properties of the clusters, show the capability of fuzzy clustering to classify a pure aerosol type based on a membership degree. Then the detailed dust properties within different membership degree intervals are analyzed. The results show that both the optical properties and volume size distributions vary significantly with membership degrees and range diversities can be reduced within each interval. The proposed method can also be used to determine weights in an aerosol fitting model to improve the parameterization. The method is most suited to air masses with multicomponent aerosol mixtures and can easily be extended to other types of aerosols.

Study on thermo physical and excess molar properties of binary systems of ionic liquids. I: [Cnmim][PF6] (n = 6, 8) and alkyl acetates

The measurements of densities, ρ, speeds of sound, u and refractive indices, nD for binary mixtures containing 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6mim][PF6]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6])+ethyl acetate (EA) and butyl acetate (BA) were reported over full range of concentrations. The measurements were performed at atmospheric pressure and seven different temperatures of five degree intervals between (293.15 and 323.15)K. The excess properties on mixing were derived from measured values of these properties. The values of density were utilized to obtain excess molar volumes, VmE, speeds of sound to obtain excess molar isentropic compressibilities, κS,mE and refractive index to get refractive index deviations, ΔφnD. The binary co-efficients of excess properties were obtained by Redlich–Kister polynomial equation. The influences of temperature and addition of –CH2 group in imidazolium cation of ionic liquids as well as acetate on excess properties have been discussed. The VmE and κS,mE are negative and decease with increase in temperature while ΔφnD are positive and increase with increase in temperature. For common acetate, The VmE increases with each increment of –CH2 group in imidazolium cation of IL and similar is true when –CH2 group increases in alkyl acetate for common IL. The deviation in VmEwas investigated by employing Prigogine–Flory–Patterson theory.

Experimental Investigation of the Loss Coefficients in a Linear Cascade

This paper reports results of experimental investigations on a linear cascade of axial compressor blades. Experiments were conducted in an open circuit subsonic wind tunnel of Aerodynamics Research Laboratory of the Iran University of Science and Technology. Different Reynolds numbers based on the blade chord length were examined, ranging from 80,000 to 500,000. Flow incidences were changed between −8 to +8 degrees with 2 degrees intervals. Freestream turbulence intensity was changed between 1.25 to 4 percent corresponding to different mesh screens mounted upstream of the test model. All the above flow conditions provided to establish various flow regimes, in terms of fully laminar and transitional flows, around the blades. At a specified range of Reynolds numbers laminar separation bubble/bubbles occurred over the blade solid walls. Surface pressure distributions were measured utilizing a computerized data acquisition system. Fluctuating velocities were also measured at various positions around the separation bubble zone, using hot film anemometry. Surface oil flow visualization was carried out for some selected flow conditions. Experimental results were used to study boundary layer characteristics and to determine variations of loss coefficient with each of Reynolds number, flow incidence and turbulence intensity parameters for the test model.

군 지연 및 충실도를 이용한 IR-UWB용 테이퍼 슬롯 안테나 방사패턴 분석

본 논문에서는 IR-UWB를 위한 테이퍼 슬롯 안테나를 Ansoft인 HFFS을 사용하여 설계 및 제작 하였고 안테나의 군 지연 및 충실도를 사용하여 광대역 안테나의 빔 폭에 대해 연구를 제안하였다. 이를 위해 Network Analyzer에서 획득한 데이터를 Chirp Z-transform을 사용하여 시간영역에서의 분석을 하였고 시뮬레이션은 CST microwave studio를 이용하여 이를 확인 하였다. 안테나의 방사패턴의 분석은 두 안테나를 0.5 미터 간격으로 이격시킨 후 송신 안테나를 고정 후 수신 안테나를 10° 간격으로 360° 회전하여 각각의 충실도를 획득하여 안테나의 성능 분석하였다. 분석한 결과 ±40° 미만일 경우 90%이상의 양호한 충실도를 얻었고 ±40° 이상은 90%이하의 낮은 결과를 얻었다. 이러한 충실도를 이용한 방사패턴을 사용함으로 광대역 안테나의 빔 폭을 보다 정확한 분석을 할 수 있다.

Polarimetric heterodyning fiber laser sensor for directional acoustic signal measurement

A DBR fiber grating laser acoustic sensor based on polarization beat signal modulation analysis has been demonstrated for directional acoustic signal measurement. The acoustic sensor was fabricated in birefringent erbium-doped fiber, and the influences of external-acoustic pressure on fiber grating laser sensor were analyzed, considering the effect of relative orientation of the acoustic wave on the degrees of birefringence modulation. In experiment, the birefringence in sensing fiber was modulated by ultrasonic pressure. Agreement between theoretical and experimental results was obtained for ultrasound wave propagating from different directions (0-360 degrees in 15 degrees intervals) corresponding to a nonlinearly change in beat frequency modulation rates. The results demonstrate that the DBR fiber grating laser acoustic sensor has an orientation recognizable ability, offering a potential for acoustic vector signal detection.

SU-E-T-148: Fluence/Dose Comparison

Purpose: To determine if X‐ray beam fluence measured at the CyberKnife is collimator can be used to reliably predict dose FWHM at 800 mm SAD. Method: A camera‐scintillator system (Iris Beam Aperture Caliper‐Logos Systems) was connected to the CyberKnife such that the scintillator surface was within a millimeter of the collimator. X‐ray fluence images were captured for the 12 Ms apertures. The IBAC software measured 72 FWHM diameters at 5 degree intervals on each beam spot in order to develop the average. EDR2 film was used to capture beam images of the 12 aperture sizes at 800 mm SAD. This film was scanned with a Vidar scanner and the images brought into RIT software to measure FWHM dose diameters for each beam. In addition, these film images were input into the IBAC software to measure the agreement between the IBAC and RIT image processing algorithms. Results: The IBAC fluence diameters when projected from 400 to 800 mm SAD were equivalent to the film dose measurements with an average delta of 0.30 mm (standard deviation 0.06 mm). The IBAC measurements of the film diameters matched the RIT measurements with an average delta of 0.032 mm (standard deviation 0.015 mm). The time required to perform the IBAC measurements was 20 minutes while the time needed to expose, scan, and measure the film was 2 hours. Conclusion: This work indicates that the IBAC system can be used to produce fluence FWHM measurements that closely correlate with the Results of conventional film based systems. Since no film is used and the total amount of time saved is more than 1.5 hours, measuring the fluence at the collimator source with the IBAC can be seen as an effective Ms QA alternative, having a lower incremental cost per measurement.

MO-D-108-02: A Secondary Monitor Unit Calculation Algorithm Using Superposition of Symmetric, Open Fields for IMRT and VMAT Treatment Plans

Purpose: To perform a secondary dose calculation for an IMRT or VMAT plan to a point on or off axis within 2% using open field data. Methods: The calculation is performed by subdividing dose into the contributions from each opposing leaf pair for a given MLC configuration. Leaf pair dose is determined by drawing four rectangular fields based on leaf positions that are symmetric about the point of calculation. Field dose is determined using isocentric monitor unit calculation formalism with open field data. Superposition of these fields yields the dose from the leaf pair to the point. VMAT plans are approximated by a static MLC configuration at four degree intervals. The algorithm requires standard open field data (e.g., Scps, TPRs), and the MLC control point information. These calculations were done with additional measured small field output factors down to a 1.2 cm2. Algorithm doses were compared with homogeneous and heterogeneous Pinnacle calculations of a series of prostate, head and neck, and chest wall treatment plans. For each treatment plan the calculation point was taken as the isocenter and/or the center of the PTV. Delivery techniques included SMLC‐IMRT and VMAT. Results: Good agreement was obtained between doses calculated by the algorithm and the Pinnacle Treatment Planning System. For homogeneous cases, the total calculated doses were within 2% for all patient plans. Individual beam errors were as high as 7.8% with an average of 2.8%. Larger errors were associated for beam segments with leaf positions very near the calculation point. Larger errors were also found for heterogeneous calculations, where a simple ratio of TPR correction factor was utilized in the algorithm. Conclusion: Results demonstrate that clinically acceptable agreement is obtained using this method. Further improvement could be made with more accurate heterogeneity correction factors and/or incorporation of MLC leaf end effects. This work was supported in part by a research agreement with Oncology Data Systems, Inc.

SU‐E‐T‐367: Dosimetric Comparison of VMAT and S&amp;S IMRT Regarding the Dose Delivered to the Skin in Different Cancer Sites

Purpose: The risk for radiation induced skin complications can limit the effectiveness of radiation therapy when large areas of skin are involved in the treatment. Therefore, the accurate determination of skin dose may be critical in preventing post‐therapy side effects. The purpose of this study is to quantify the skin dose received by the Volumetric Modulated Arc Therapy (VMAT) and a 7 field MLC‐based IMRT step and shoot (S&amp;S) delivery modalities using the same dose prescription. Methods: 5 prostate, 5 head‐and‐neck, and 5 brain cancer patients were used in this study to quantify skin dose for the examined radiation modalities. 30 treatment plans were produced (15 VMAT and 15 IMRT S&amp;S) and for each patient the skin dose was measured using ultra‐thin TLDs. Doses were measured at 11 points on the surface of a cheese phantom at 25 degree intervals using ultra‐thin lithium‐fluoride TLDs with surface dimensions of 0.3cm × 0.3cm and a thickness of 0.01cm, comparable to the thickness of the skin. For each patient, the corresponding doses were also calculated using the Pinnacle treatment planning system. Results: A 36% increase in skin dose was measured on the brain patients using VMAT vs. IMRT S&amp;S while a 38% decrease in skin dose was measured on the H&amp;N patients using VMAT vs. IMRT S&amp;S. The prostate patients showed just a 12% increase in skin dose using VMAT vs. IMRT S&amp;S. The skin doses from Pinnacle showed small differences between the two modalities. The absolute differences of the dose values between the plan and the measurements were within an order of magnitude of the measured doses. Conclusion: The skin dose differences between the VMAT vs. IMRT S&amp;S modalities were found to be significant. However, the direction of the differences was found to be treatment site specific and its magnitude patient specific.

Dosimetry Investigation of MOSFET for Clinical IMRT Dose Verification

In IMRT, patient-specific dose verification is followed regularly at each centre. Simple and efficient dosimetry techniques play a very important role in routine clinical dosimetry QA. The MOSFET dosimeter offers several advantages over the conventional dosimeters such as its small detector size, immediate readout, immediate reuse, multiple point dose measurements. To use the MOSFET as routine clinical dosimetry system for pre-treatment dose verification in IMRT, a comprehensive set of experiments has been conducted, to investigate its linearity, reproducibility, dose rate effect and angular dependence for 6 MV x-ray beam. The MOSFETs shows a linear response with linearity coefficient of 0.992 for a dose range of 35 cGy to 427 cGy. The reproducibility of the MOSFET was measured by irradiating the MOSFET for ten consecutive irradiations in the dose range of 35 cGy to 427 cGy. The measured reproducibility of MOSFET was found to be within 4% up to 70 cGy and within 1.4% above 70 cGy. The dose rate effect on the MOSFET was investigated in the dose rate range 100 MU/min to 600 MU/min. The response of the MOSFET varies from -1.7% to 2.1%. The angular responses of the MOSFETs were measured at 10 degrees intervals from 90 to 270 degrees in an anticlockwise direction and normalized at gantry angle zero and it was found to be in the range of 0.98 ± 0.014 to 1.01 ± 0.014. The MOSFETs were calibrated in a phantom which was later used for IMRT verification. The measured calibration coefficients were found to be 1 mV/cGy and 2.995 mV/cGy in standard and high sensitivity mode respectively. The MOSFETs were used for pre-treatment dose verification in IMRT. Nine dosimeters were used for each patient to measure the dose in different plane. The average variation between calculated and measured dose at any location was within 3%. Dose verification using MOSFET and IMRT phantom was found to quick and efficient and well suited for a busy radiotherapy department.

High Speed Gas Sampling System for Engine Cylinder Emission Analyses

Abstrac t—In this study, high speed gas sampling system was used to collect gas samples in the engine cylinder. C1-C5 base d HC components behaviuor in the engine cylinder were investigated experimentally during the flame period. Model GSD-10 fast response gas sampling system was used to sample gas in the cylinder. The high speed gas sampling valve mounted on the engine cylinder was connected to the gas chromatograph instrument directly, and samplings were continuously gathered at the intended crank shaft angle ranges. The electro-magnetic valve lift time was controlled by setting a time-lag from the TDC reference point of the engine crank angle. Crank pulses were provided by crank pulse generator. The generator consists of a slit disc mounted on the engine shaft and a photo-electric pick-up. It was designed to generate the crank pulse (360 pulses/rev) and the reference pulse (1 pulse/rev). In cylinder gas samples were taken for 10-15 degree intervals after the ignition. Samples taken during the flame period were approximately 60 degrees of crank angle after the spark plug ignited. In this study, Agilent 7890A Gas Chromatography (GC) system was employed to analyze C1-C5 HC component of the sampled gas from th e engine cylinder. GC-FID (Flame Ionization Detector) analysis method was utilized to investigate hydrocarbon components. Response time of hydrocarbon components were listed. HC components variation with respect to crank angle were plotted and interpreted.

Human phase response curve to a 1 h pulse of bright white light

The phase resetting response of the human circadian pacemaker to light depends on the timing of exposure and is described by a phase response curve (PRC). The current study aimed to construct a PRC for a 1 h exposure to bright white light (∼8000 lux) and to compare this PRC to a <3 lux dim background light PRC. These data were also compared to a previously completed 6.7 h bright white light PRC and a <15 lux dim background light PRC constructed under similar conditions. Participants were randomized for exposure to 1 h of either bright white light (n=18) or <3 lux dim background light (n=18) scheduled at 1 of 18 circadian phases. Participants completed constant routine (CR) procedures in dim light (<3 lux) before and after the light exposure to assess circadian phase. Phase shifts were calculated as the difference in timing of dim light melatonin onset (DLMO) during pre- and post-stimulus CRs. Exposure to 1 h of bright white light induced a Type 1 PRC with a fitted peak-to-trough amplitude of 2.20 h. No discernible PRC was observed in the <3 lux dim background light PRC. The fitted peak-to-trough amplitude of the 1 h bright light PRC was ∼40% of that for the 6.7 h PRC despite representing only 15% of the light exposure duration, consistent with previous studies showing a non-linear duration–response function for the effects of light on circadian resetting.

SU-E-l-01: Investigating the Dependence of 2D and 3D Scatter-To-Primary Ratios on Breast Density in Clinical Breast CT.

To characterize 2D and 3D scatter-to-primary ratios (SPR) and investigate the dependence of SPR on breast density based on clinicalpatient imaging on our dedicated SPECT-CT mammotomography system. As a part of an on-going IRB approved protocol, 7 consented women underwent a breast imaging study with our SPECT-CT system. Using a quasi-monochromatic x-ray cone beam and flat panel detector, 240 projections were obtained. 6 beam stop array (BSA) projections were also obtained over 40 degree intervals. The CT data were scatter corrected using a phantom-validated algorithm based on the BSA technique. For each projection, 2D scatter fluence was determined behind each beam stop shadow through the patient's breast, and cubic spline interpolated throughout the thresholded breast region. 2D SPRs were calculated as the average of 6 measured ratios of scatter projections to scatter corrected (primary) projections. Angular cubic spline interpolation was performed to obtain the remaining 234 azimuthal BSA projections for reconstruction correction. Corrected and uncorrected projection images were individually reconstructed and 3D SPRs calculated as the ratio of difference between primary and un-corrected volumes to primary volumes. Histograms of the reconstructed patient data-sets yielded distinct peaks representing linear attenuation coefficients of glandular+skin and fatty tissue. Percentage glandular and fatty tissue was estimated by fitting a double Gaussian to the histogram and integrating area under the curve. Only 4 CT data sets devoid of motion and truncation artifacts were suitable for scatter correction. Preliminary results show that 2D SPR values peak at the center of breast volumes and were greatest (∼50%) for the most glandular breast, whereas 3D SPR values remained fairly constant throughout the breast and did not obviously correlate with density, consistent with prior phantom results. 2D SPR values are greater in breasts with higher glandular tissue composition, whereas 3D SPR values appear independent of breast composition. This work is funded by the National Cancer Institute of the National Institutes of Health grant RO1-CA096821, with partial support (JHP) from NIH T32-EB001040. MPT is the inventor of this CT technology, and is named as an inventor on the patent for this technology awarded to Duke University. If this technology becomes commercially successful, MPT and Duke could benefit financially.

Characterization of low-temperature vapour pressure estimates for secondary organic aerosol applications

Many models of secondary organic aerosol (SOA) formation, adhering to gas-particle equilibrium partitioning theory, require known vapour pressures for low volatility products of volatile organic compound (VOC) oxidation. Since the majority of such products have yet to be isolated and analysed, few experimental determinations of pertinent vapour pressures have been achieved, and models are forced to rely on vapour pressure estimates, such as those available through the common, computer-based SPARC and MPBPWIN property calculators. Thus, the accuracy of the respective estimation methods must be measured and evaluated, in order to determine the consequences in the resulting models. However, published evaluations, and most models themselves, typically focus on moderate to high ambient temperatures, which may not be applicable year-round in colder regions, where the rate of VOC oxidation slows, while the vapour pressures of the products decrease, indicating an increased tendency to condense into the aerosol phase. In this paper, the accuracy of the SPARC and MPBPWIN methods is evaluated over a broad temperature range, from 248.15 to 298.15K, in five degree intervals using a test set of 45 compounds. The results are reported in terms of mean average error (MAE) and mean bias error (MBE), and given for alcohol, carboxylic acid, aldehyde, and ketone compound classes at each temperature. Specific trends in MAE and MBE with regard to compound class and changing temperature are discussed. More generally, the evaluation indicates that SPARC, with MAE decreasing from 0.288 at 248.15K to 0.165 at 298.15K and MBE increasing from −0.180 at 248.15K to a peak of −0.081 at 293.15K, is more accurate at low to moderate temperatures than MPBPWIN, with MAE decreasing from 0.436 at 248.15K to 0.272 at 298.15K and MBE increasing from −0.328 at 248.15K to −0.213 at 298.15K. Decreasing accuracy at lower temperatures emphasizes a need for focused experimental and model efforts in this temperature range.

Abstract 3160: Tolerance to a Tilt Table Standing Protocol In an Acute Stroke-Unit Setting: A Pilot Study

Background: objective was set to describe and examine physiological and self-reported indices of tolerance of a standing tilt table protocol (STTP) among patients following an acute stroke. Design: Prospective, observational pilot study of patients admitted to a stroke unit of a single academic medical center. Methods: A clinical protocol for the use of the tilt table was developed and applied to subjects in the acute phase following a stroke. The protocol involved a step-wise process to gradually raise the subject into a standing position with lower extremities in a weight bearing position on the tilt table platform, at 10 degree intervals from 60 to 90 degrees. The STTP clinical indices of tolerance were operationally defined as: Systolic blood pressure (SBP) maintained within 20 mmHg of baseline, diastolic blood pressure (DBP) maintained within 10 mmHg of baseline, heart rate (HR) maintained within 10 beats per minute of baseline, oxygen saturation (SpO 2 ) maintained at 90% or above while on supplemental O 2 or room air, absence of pallor. Subjective indices of tolerance were operationally defined as: rating of perceived exertion (RPE) &lt; 15 per Borg Rating of Perceived Exertion Scale, pain &lt; 5 using a numerical pain rating scale ranging from 0 to 10, and absence of angina, dizziness, nausea, dyspnea, or request to discontinue the STTP. No single measure was considered to be of primary importance, and any value falling outside the predetermined parameter was considered indicative of intolerance. Overall, tolerance of the STTP was defined as the ability to sustain 60 degrees or greater of tilt table inclination (minimum of 87% total weight bearing) for a minimum 5 minutes, without signs or symptoms of intolerance. Specifically, frequencies of the highest angle achieved, the duration of standing time tolerated, and physiologic response were recorded. Results: Thirty-six patients with ischemic or hemorrhagic stroke (22 females, 14 males) aged 24 to 87 years (62 + 16 years) enrolled. Fifty three percent of subjects (N = 19) attained 60 degrees or higher on the standing tilt table. Ten subjects were unable to achieve 45 degrees. Subjects tolerated a mean total standing time at or above 60 degrees of 8.9 + 7.2 minutes. All subjects met tolerance criteria for dyspnea, pain, pallor, perceived effort, and nausea at 60 degrees or higher. All subjects were tolerant by heart rate criteria at 70, 80 and 90 degrees; 96% were tolerant at 60 degrees. For diastolic blood pressure, tolerance ranged from 72% (80 degrees) to 90% (70 degrees). For systolic blood pressure, tolerance ranged from 84% (70 degrees) to 100% (90 degrees). Oxygen saturation tolerance was achieved in 100% of subjects at each angle. Conclusion: This pilot study suggests that use of a tilt table is well tolerated among patients in the acute stroke phase, and may be an effective tool for introducing early mobilization to a medically fragile patient population.

MULTI-POD CONFERENCE SYSTEMS

This disclosure describes a multi-pod conferencing system for local conference participants to communicate with remote conference participants that includes a plurality of pods for local conference participants where an individual pod connects to one or more plurality of pods through a data communication means. The individual pods further include the following: pod processor means; an input device and a display; a loudspeaker that couples to a digital to analog converter; 3 physical bi-polar microphones positioned at 120 degree intervals in the horizontal resting plane of the pod, each individual physical microphone connects to a pair of audio ports with each audio port being equal distance from the loudspeaker, the physical microphones couple to analog to digital converting mean and pod processor means; 3 virtual microphones; pod echo cancellation means; and microphone gating means. The disclosed system further includes a base unit that couples to the plurality of pods through the data communication means. The base unit further includes base controller means, where the base controller means couples to the converting means. The system further includes the command input and display information from the individual pod that distributed to the plurality of pods such that the plurality of pods can be operated in tandem and where the computed values of the pod gating means is distributed to other pods to gate the pods on and or off.