bluuebunny/crossref_metadata_2025 huggingface dataset:
LTCC Microfluidic System
Authors: Golonka Leszek J. , Zawada Tomasz , Radojewski Jacek , Roguszczak Henryk , Stefanow Marcin
Published: April 2006

A simple and inexpensive low‐temperature cofired ceramic (LTCC) microfluidic device with integrated optical fibers is designed, manufactured, and tested with positive results. Fluidic channels, mixer, detector, optical fiber, light source, light detector, heater, and temperature sensor are integrated in one LTCC module. The optical system in the LTCC microsystem permits measurements of light transmittance and fluorescence. The design, technology, and results of the module's evaluation are presented.
Thermal Barrier Coatings Design with Increased Reflectivity and Lower Thermal Conductivity for High‐Temperature Turbine Applications
Authors: Kelly Matthew J. , Wolfe Douglas E. , Singh Jogender , Eldridge Jeff , Zhu Dong‐Ming , Miller Robert
Published: April 2006

High reflectance thermal barrier coatings consisting of 7% Yittria‐Stabilized Zirconia (7YSZ) and Al2O3 were deposited by co‐evaporation using electron beam physical vapor deposition (EB‐PVD). Multilayer 7YSZ and Al2O3 coatings with fixed layer spacing showed a 73% infrared reflectance maxima at 1.85 μm wavelength. The variable 7YSZ and Al2O3 multilayer coatings showed an increase in reflection spectrum from 1 to 2.75 μm. Preliminary results suggest that coating reflectance can be tailored to achieve increased reflectance over a desired wavelength range by controlling the thickness of the individual layers. In addition, microstructural enhancements were also used to produce low thermal conductive and high hemispherical reflective thermal barrier coatings (TBCs) in which the coating flux was periodically interrupted creating modulated strain fields within the TBC. TBC showed no macrostructural differences in the grain size or faceted surface morphology at low magnification as compared with standard TBC. The residual stress state was determined to be compressive in all of the TBC samples, and was found to decrease with increasing number of modulations. The average thermal conductivity was shown to decrease approximately 30% from 1.8 to 1.2 W/m‐K for the 20‐layer monolithic TBC after 2 h of testing at 1316°C. Monolithic modulated TBC also resulted in a 28% increase in the hemispherical reflectance, and increased with increasing total number of modulations.
Tropical Forests of Xishuangbanna, China1
Authors: Cao Min , Zou Xiaoming , Warren Matthew , Zhu Hua
Published: April 2006

Lowland tropical forests once covered a large fraction of tropical southern China, but currently have an extent of ca 633,800 ha, mostly in Xishuangbanna of southern Yunnan. The Xishuangbanna region has a typical monsoon climate with a mean annual temperature ranging between 15.1°C and 21.7°C, and precipitation between 1200 and 2500 mm. There is a pronounced dry season between November and April with frequent occurrence of heavy fog. Rainfall during the wet season between May and October accounts for over 80 percent of total annual precipitation. Water deposition from fog accounts for over one‐third of total water input during the dry season in the forests, suggesting an important role that fog may play in pushing up the northern limit of tropical rain forest in Southeast Asia.
Forest Structure and Biomass of a Tropical Seasonal Rain Forest in Xishuangbanna, Southwest China1
Authors: Zheng Zheng , Feng Zhili , Cao Min , Li Zhongfei , Zhang Jianhou
Published: April 2006

Xishuangbanna is a region located at the northern edge of tropical Asia. Biomass estimates of its tropical rain forest have not been published in English literature. We estimated forest biomass and its allocation patterns in five 0.185–1.0 ha plots in tropical seasonal rain forests of Xishuangbanna. Forest biomass ranged from 362.1 to 692.6 Mg/ha. Biomass of trees with diameter at 1.3 m breast height (DBH) ≥ 5 cm accounted for 98.2 percent of the rain forest biomass, followed by shrubs (0.9%), woody lianas (0.8%), and herbs (0.2%). Biomass allocation to different tree components was 68.4–70.0 percent to stems, 19.8–21.8 percent to roots, 7.4–10.6 percent to branches, and 0.7–1.3 percent to leaves. Biomass allocation to the tree sublayers was 55.3–62.2 percent to the A layer (upper layer), 30.6–37.1 percent to the B layer (middle), and 2.7–7.6 percent to the C layer (lower). Biomass of Pometia tomentosa, a dominant species, accounted for 19.7–21.1 percent of the total tree biomass. The average density of large trees (DBH ≥100 cm) was 9.4 stems/ha on two small plots and 3.5 stems/ha on two large plots, illustrating the potential to overestimate biomass on a landscape scale if only small plots are sampled. Biomass estimations are similar to typical tropical rain forests in Southeast Asia and the Neotropics.
Floral Visitors and Pollination of Psychotria tenuinervis (Rubiaceae): Distance from the Anthropogenic and Natural Edges of an Atlantic Forest Fragment1
Authors: Ramos Flavio Nunes , Santos Flavio A. Maës
Published: April 2006

Pollinators, especially insects, could be influenced by forest fragmentation. The aim of this paper was to examine whether there were differences in 1) the communities of floral visitors; 2) the frequency of visits; and 3) the fruit and seed sets of individuals of Psychotria tenuinervis occurring at anthropogenic edges (AEs), natural edges (NEs), and in the forest interior (FI) in 2 yr of study. In 2002, the total number of flower visits was greater in NE and lower in AE, while no difference among habitats was found in 2003. There were differences among sample plots, within habitats, in both years. Bees were the most frequent visitors of P. tenuinervis flowers, and the introduced honeybee Apis mellifera was the most common species observed. There were no differences in the fruit and seed sets, or in the density of reproductive individuals of P. tenuinervis among habitats. However, in 2002, NE showed the greatest proportion of fruits per flower and AE the smallest. The similarity among the habitats was probably due to the marked variation or heterogeneity among the sample plots and among the plants within the habitats, which may have masked any interhabitat differences. The observed heterogeneity and the likely importance of other factors, such as gaps and the age of the edge, on the fragment studied, could be viewed as important issues for conservation programs.
Zonation Patterns of Belizean Offshore Mangrove Forests 41 Years After a Catastrophic Hurricane1
Authors: Piou Cyril , Feller Ilka C. , Berger Uta , Chi Faustino
Published: April 2006

Mangroves are prone to bearing frequently the full brunt of hurricanes and tropical storms. The extent of destruction and early regeneration are widely studied. The purpose of this study was to add a long‐term view of mangrove regeneration and assess the potential effects on mangrove horizontal zonation patterns of catastrophic destruction. Hattie, a category five hurricane, hit the Belizean coast in 1961. It passed directly over the Turneffe Atoll where our study area, Calabash Cay, is located. At four sites on this island, we analyzed mangrove forest structure along transects parallel to the shoreline within zones delineated by species dominance and tree height. We propose an index based on the Simpson index of diversity to express changes in the heterogeneity of the species dominance. Physical–chemical parameters and nutrient availability were also measured. The destruction levels were estimated by analysis of the distribution of diameter at breast heights of the bigger trees in the inland zones. Variations in species dominance among sites and zones could be explained by interactions of various factors. Further, different levels of destruction between the two sides of the island had a significant effect on current patterns of species and structural zonation at Calabash. We conclude that disturbance regime in general should be considered as a factor potentially influencing mangrove horizontal zonation patterns.
Growth Rates and Body Condition in Norops polylepis (Polychrotidae) Vary with Respect to Sex but not Mite Load1
Authors: Schlaepfer Martin A.
Published: April 2006

Norops polylepis is a common anoline lizard that occupies both forest and pasture habitats at various elevations in southern Costa Rica. Previous studies have documented significant spatial variation in mite loads (Eutrombicula chiggers) on N. polylepis. My objective was to investigate whether mite load has a negative impact on growth rates and body condition. Growth rates were estimated in three sites using mark‐recapture with three intensive sampling periods over 12 mo. Nine hundred and forty lizards were captured and 200 individuals were recaptured across sampling periods. Mite load was significantly higher in forests than in pastures, and varied significantly among study sites. Males grew faster than females, and females and juveniles had higher body condition than males. I was unable, however, to detect any influence of mite load on growth rates or body condition. I conclude that Eutrombicula chiggers are either largely benign for N. polylepis or, if they do exert a negative effect on fitness, it is mediated through a trait other than growth or body condition.
Method for transforming CT images for attenuation correction in PET/CT imaging
Authors: Carney Jonathan P. J. , Townsend David W. , Rappoport Vitaliy , Bendriem Bernard
Published: April 2006

A tube‐voltage‐dependent scheme is presented for transforming Hounsfield units (HU) measured by different computed tomography (CT) scanners at different x‐ray tube voltages (kVp) to linear attenuation values for attenuation correction in positron emission tomography (PET) data reconstruction. A Gammex 467 electron density CT phantom was imaged using a Siemens Sensation 16‐slice CT, a Siemens Emotion 6‐slice CT, a GE Lightspeed 16‐slice CT, a Hitachi CXR 4‐slice CT, and a Toshiba Aquilion 16‐slice CT at kVp ranging from 80 to . All of these CT scanners are also available in combination with a PET scanner as a PET/CT tomograph. HU obtained for various reference tissue substitutes in the phantom were compared with the known linear attenuation values at . The transformation, appropriate for lung, soft tissue, and bone, yields the function below a threshold of and above the threshold, where and are fixed parameters that depend on the kVp setting. The use of the kVp‐dependent scaling procedure leads to a significant improvement in reconstructed PET activity levels in phantom measurements, resolving errors of almost 40% otherwise seen for the case of dense bone phantoms at . Results are also presented for patient studies involving multiple CT scans at different kVp settings, which should all lead to the same linear attenuation values. A linear fit to values obtained from CT images using the kVp‐dependent scaling plotted as a function of the corresponding values obtained from CT images yielded with an value of 0.999, indicating that the same values are obtained to a high degree of accuracy.
Characterization of the phantom material Virtual Water™ in high‐energy photon and electron beams
Authors: McEwen M. R. , Niven D.
Published: April 2006

The material Virtual Water™ has been characterized in photon and electron beams. Range‐scaling factors and fluence correction factors were obtained, the latter with an uncertainty of around 0.2%. This level of uncertainty means that it may be possible to perform dosimetry in a solid phantom with an accuracy approaching that of measurements in water. Two formulations of Virtual Water™ were investigated with nominally the same elemental composition but differing densities. For photon beams neither formulation showed exact water equivalence—the water/Virtual Water™ dose ratio varied with the depth of measurement with a difference of over 1% at depth. However, by using a density (range) scaling factor very good agreement between water and Virtual Water™ at all depths was obtained. In the case of electron beams a range‐scaling factor was also required to match the shapes of the depth dose curves in water and Virtual Water™. However, there remained a difference in the measured fluence in the two phantoms after this scaling factor had been applied. For measurements around the peak of the depth‐dose curve and the reference depth this difference showed some small energy dependence but was in the range 0.1%–0.4%. Perturbation measurements have indicated that small slabs of material upstream of a detector have a small ( effect) on the chamber reading but material behind the detector can have a larger effect. This has consequences for the design of experiments and in the comparison of measurements and Monte Carlo‐derived values.
An analytical algorithm for skew‐slit imaging geometry with nonuniform attenuation correction
Authors: Huang Qiu , Zeng Gengsheng L.
Published: April 2006

The pinhole collimator is currently the collimator of choice in small animal single photon emission computed tomography (SPECT) imaging because it can provide high spatial resolution and reasonable sensitivity when the animal is placed very close to the pinhole. It is well known that if the collimator rotates around the object (e.g., a small animal) in a circular orbit to form a cone‐beam imaging geometry with a planar trajectory, the acquired data are not sufficient for an exact artifact‐free image reconstruction. In this paper a novel skew‐slit collimator is mounted instead of the pinhole collimator in order to significantly reduce the image artifacts caused by the geometry. The skew‐slit imaging geometry is a more generalized version of the pinhole imaging geometry. The multiple pinhole geometry can also be extended to the multiple‐skew‐slit geometry. An analytical algorithm for image reconstruction based on the tilted fan‐beam inversion is developed with nonuniform attenuation compensation. Numerical simulation shows that the axial artifacts are evidently suppressed in the skew‐slit images compared to the pinhole images and the attenuation correction is effective.
Monte Carlo study of photon fields from a flattening filter‐free clinical accelerator
Authors: Vassiliev Oleg N. , Titt Uwe , Kry Stephen F. , Pönisch Falk , Gillin Michael T. , Mohan Radhe
Published: April 2006

In conventional clinical linear accelerators, the flattening filter scatters and absorbs a large fraction of primary photons. Increasing the beam‐on time, which also increases the out‐of‐field exposure to patients, compensates for the reduction in photon fluence. In recent years, intensity modulated radiation therapy has been introduced, yielding better dose distributions than conventional three‐dimensional conformal therapy. The drawback of this method is the further increase in beam‐on time. An accelerator with the flattening filter removed, which would increase photon fluence greatly, could deliver considerably higher dose rates. The objective of the present study is to investigate the dosimetric properties of 6 and photon beams from an accelerator without a flattening filter. The dosimetric data were generated using the Monte Carlo programs BEAMnrc and DOSXYZnrc. The accelerator model was based on the Varian Clinac 2100 design. We compared depth doses, dose rates, lateral profiles, doses outside collimation, total and collimator scatter factors for an accelerator with and without a flatteneing filter. The study showed that removing the filter increased the dose rate on the central axis by a factor of 2.31 and 5.45 at a given target current. Because the flattening filter is a major source of head scatter photons, its removal from the beam line could reduce the out‐of‐field dose.
Automated detection of lung nodules in CT scans: False‐positive reduction with the radial‐gradient index
Authors: Roy Arunabha S. , Armato Samuel G. , Wilson Andrew , Drukker Karen
Published: April 2006

We present a number of approaches based on the radial gradient index (RGI) to achieve false‐positive reduction in automated CT lung nodule detection. A database of 38 cases was used that contained a total of 82 lung nodules. For each CT section, a complementary image known as an “RGI map” was constructed to enhance regions of high circularity and thus improve the contrast between nodules and normal anatomy. Thresholds on three RGI parameters were varied to construct RGI filters that sensitively eliminated false‐positive structures. In a consistency approach, RGI filtering eliminated 36% of the false‐positive structures detected by the automated method without the loss of any true positives. Use of an RGI filter prior to a linear discriminant classifier yielded notable improvements in performance, with the false‐positive rate at a sensitivity of 70% being reduced from 0.5 to 0.28 per section. Finally, the performance of the linear discriminant classifier was evaluated with RGI‐based features. RGI‐based features achieved a substantial improvement in overall performance, with a 94.8% reduction in the false‐positive rate at a fixed sensitivity of 70%. These results demonstrate the potential role of RGI analysis in an automated lung nodule detection method.
A novel respiratory detection method based on automated analysis of ultrasound diaphragm video
Authors: Xu Qianyi , Hamilton Russell J.
Published: April 2006

This paper proposes a novel respiratory detection method based on diaphragm motion measurements using a 2D ultrasound unit. The proposed method extracts a respiratory signal from an automated analysis of the internal diaphragm motion during breathing. The respiratory signal may be used for gating. Ultrasound studies of diaphragm breathing motion were performed on four volunteers. The ultrasound video stream was captured and transferred to a personal computer and decomposed into individual image frames. After straightforward image analysis, region of interest selection, and filtering, the mutual information (MI) and correlation coefficients (CCs) between a selected reference frame and all other frames were computed. The resulting MI and CC values were discovered to produce a signal corresponding to the respiratory cycle in both phase and magnitude. We also studied the diaphragm motion of two volunteers during repeated deep inspiration breath holds (DIBH) and found a slight relaxation motion of the diaphragm during the DIBH, suggesting that the residual motion may be important for treatments delivered at this breathing phase. Applying the proposed respiratory detection method to these ultrasound studies, we found that the MI and CC values demonstrate the relaxation behavior, indicating that our method may be used to determine the radiation triggering time for a DIBH technique.
Implications of unchanged detection criteria with CAD as second reader of mammograms
Authors: Bornefalk Hans
Published: April 2006

In this paper we address the use of computer‐aided detection (CAD) systems as second readers in mammography. The approach is based on Bayesian decision theory and its implication for the choice of optimal operating points. The choice of a certain operating point along an ROC curve corresponds to a particular tradeoff between false positives and missed cancers. By minimizing a total risk function given this tradeoff, we determine optimal decision thresholds for the radiologist and CAD system when CAD is used as a second reader. We show that under very general circumstances, the performance of the sequential system is improved if the decision threshold of the latent human decision variable is increased compared to what it would have been in the absence of the CAD system. This means that an initial stricter decision criterion should be applied by the radiologist when CAD is used as a second reader than otherwise. First and foremost, the results in this paper should be interpreted qualitatively, but an attempt is made at quantifying the effect by tuning the model to a prospective study evaluating the use of CAD as a second reader. By making some necessary and plausible assumptions, we are able to estimate the effect of the resulting suboptimal operating point. In this study of women, we estimate that a 15% reduction in callbacks for masses could have been achieved with only about a 1.5% relative decrease in sensitivity compared to that without using a stricter initial criterion by the radiologist. For microcalcifications the corresponding values are 7% and 0.2%.
Method for the evaluation of a average glandular dose in mammography
Authors: Okunade Akintunde Akangbe
Published: April 2006

This paper concerns a method for accurate evaluation of average glandular dose (AGD) in mammography. At different energies, the interactions of photons with tissue are not uniform. Thus, optimal accuracy in the estimation of AGD is achievable when the evaluation is carried out using the normalized glandular dose values, , that are determined for each (monoenergetic) x‐ray photon energy, , compressed breast thickness (CBT), , breast glandular composition, and data on photon energy distribution of the exact x‐ray beam used in breast imaging. A generalized model for the values of that is for any arbitrary CBT ranging from 2 to (with values that are not whole numbers inclusive, say, ) was developed. Along with other dosimetry formulations, this was integrated into a computer software program, GDOSE.FOR, that was developed for the evaluation of AGD received from any x‐ray tube/equipment (irrespective of target‐filter combination) of up to . Results are presented which show that the implementation of GDOSE.FOR yields values of normalized glandular dose that are in good agreement with values obtained from methodologies reported earlier in the literature. With the availability of a portable device for real‐time acquisition of spectra, the model and computer software reported in this work provide for the routine evaluation of AGD received by a specific woman of known age and CBT.
Bone‐composition imaging using coherent‐scatter computed tomography: Assessing bone health beyond bone mineral density
Authors: Batchelar Deidre L. , Davidson Melanie T. M. , Dabrowski Waldemar , Cunningham Ian A.
Published: April 2006

Quantitative analysis of bone composition is necessary for the accurate diagnosis and monitoring of metabolic bone diseases. Accurate assessment of the bone mineralization state is the first requirement for a comprehensive analysis. In diagnostic imaging, x‐ray coherent scatter depends upon the molecular structure of tissues. Coherent‐scatter computed tomography (CSCT) exploits this feature to identify tissue types in composite biological specimens. We have used CSCT to map the distributions of tissues relevant to bone disease (fat, soft tissue, collagen, and mineral) within bone‐tissue phantoms and an excised cadaveric bone sample. Using a purpose‐built scanner, we have measured hydroxyapatite (bone mineral) concentrations based on coherent‐scatter patterns from a series of samples with varying hydroxyapatite content. The measured scatter intensity is proportional to mineral density in true . Repeated measurements of the hydroxyapatite concentration in each sample were within, at most, 2% of each other, revealing an excellent precision in determining hydroxyapatite concentration. All measurements were also found to be accurate to within 3% of the known values. Phantoms simulating normal, over‐, and under‐mineralized bone were created by mixing known masses of pure collagen and hydroxyapatite. An analysis of the composite scatter patterns gave the density of each material. For each composite, the densities were within 2% of the known values. Collagen and hydroxyapatite concentrations were also examined in a bone‐mimicking phantom, incorporating other bone constituents (fat, soft tissue). Tomographic maps of the coherent‐scatter properties of each specimen were reconstructed, from which material‐specific images were generated. Each tissue was clearly distinguished and the collagen‐mineral ratio determined from this phantom was also within 2% of the known value. Existing bone analysis techniques cannot determine the collagen‐mineral ratio in intact specimens. Finally, to demonstrate the in situ potential of this technique, the mineralization state of an excised normal cadaveric radius was examined. The average collagen‐mineral ratio of the cortical bone derived from material‐specific images of the radius was , which is in agreement with the expected value of 0.55 for healthy bones.
Generalized five‐dimensional dynamic and spectral factor analysis
Authors: El Fakhri Georges , Sitek Arkadiusz , Zimmerman Robert E. , Ouyang Jinsong
Published: April 2006

We have generalized the spectral factor analysis and the factor analysis of dynamic sequences (FADS) in SPECT imaging to a five‐dimensional general factor analysis model (5D‐GFA), where the five dimensions are the three spatial dimensions, photon energy, and time. The generalized model yields a significant advantage in terms of the ratio of the number of equations to that of unknowns in the factor analysis problem in dynamic SPECT studies. We solved the 5D model using a least‐squares approach. In addition to the traditional non‐negativity constraints, we constrained the solution using a priori knowledge of both time and energy, assuming that primary factors (spectra) are Gaussian‐shaped with full‐width at half‐maximum equal to gamma camera energy resolution. 5D‐GFA was validated in a simultaneous pre‐/post‐synaptic dual isotope dynamic phantom study where and activities were used to model early Parkinson disease studies. 5D‐GFA was also applied to simultaneous perfusion/dopamine transporter (DAT) dynamic SPECT in rhesus monkeys. In the striatal phantom, 5D‐GFA yielded significantly more accurate and precise estimates of both primary and time activity curves (TAC) compared to conventional FADS ( in and in , ). Our technique was also validated in two primate dynamic dual isotope perfusion/DAT transporter studies. Biases of ‐HMPAO and ‐DAT activity estimates with respect to estimates obtained in the presence of only one radionuclide (sequential imaging) were significantly lower with 5D‐GFA ( for ‐HMPAO and for ‐DAT) compared to biases greater than 15% for volumes of interest (VOI) over the reconstructed volumes . 5D‐GFA is a novel and promising approach in dynamic SPECT imaging that can also be used in other modalities. It allows accurate and precise dynamic analysis while compensating for Compton scatter and cross‐talk.
Reduction of bias and variance for evaluation of computer‐aided diagnostic schemes
Authors: Li Qiang , Doi Kunio
Published: April 2006

Computer‐aided diagnostic (CAD) schemes have been developed to assist radiologists in detecting various lesions in medical images. In addition to the development, an equally important problem is the reliable evaluation of the performance levels of various CAD schemes. It is good to see that more and more investigators are employing more reliable evaluation methods such as leave‐one‐out and cross validation, instead of less reliable methods such as resubstitution, for assessing their CAD schemes. However, the common applications of leave‐one‐out and cross‐validation evaluation methods do not necessarily imply that the estimated performance levels are accurate and precise. Pitfalls often occur in the use of leave‐one‐out and cross‐validation evaluation methods, and they lead to unreliable estimation of performance levels. In this study, we first identified a number of typical pitfalls for the evaluation of CAD schemes, and conducted a Monte Carlo simulation experiment for each of the pitfalls to demonstrate quantitatively the extent of bias and/or variance caused by the pitfall. Our experimental results indicate that considerable bias and variance may exist in the estimated performance levels of CAD schemes if one employs various flawed leave‐one‐out and cross‐validation evaluation methods. In addition, for promoting and utilizing a high standard for reliable evaluation of CAD schemes, we attempt to make recommendations, whenever possible, for overcoming these pitfalls. We believe that, with the recommended evaluation methods, we can considerably reduce the bias and variance in the estimated performance levels of CAD schemes.
Effect of edema, relative biological effectiveness, and dose heterogeneity on prostate brachytherapya)
Authors: Wang Jian Z. , Mayr Nina A. , Nag Subir , Montebello Joseph , Gupta Nilendu , Samsami Nina , Kanellitsas Christos
Published: April 2006

Many factors influence response in low‐dose‐rate (LDR) brachytherapy of prostate cancer. Among them, edema, relative biological effectiveness (RBE), and dose heterogeneity have not been fully modeled previously. In this work, the generalized linear‐quadratic (LQ) model, extended to account for the effects of edema, RBE, and dose heterogeneity, was used to assess these factors and their combination effect. Published clinical data have shown that prostate edema after seed implant has a magnitude (ratio of post‐ to preimplant volume) of 1.3–2.0 and resolves exponentially with a half‐life of 4–25 days over the duration of the implant dose delivery. Based on these parameters and a representative dose‐volume histogram (DVH), we investigated the influence of edema on the implant dose distribution. The LQ parameters ( and ) determined in earlier studies were used to calculate the equivalent uniform dose in fractions with respect to three effects: edema, RBE, and dose heterogeneity for and implants. The analysis shows a negative effect of edema and dose heterogeneity on tumor cell killing because the prostate edema degrades the dose coverage to tumor target. For the representative DVH, the (volume covered by 100% of prescription dose) decreases from 93% to 91% and 86%, and the (dose covering 90% of target volume) decrease from 107% to 102% and 94% of prescription dose for and implants, respectively. Conversely, the RBE effect of LDR brachytherapy [versus external‐beam radiotherapy (EBRT) and high‐dose‐rate (HDR) brachytherapy] enhances dose effect on tumor cell kill. In order to balance the negative effects of edema and dose heterogeneity, the RBE of prostate brachytherapy was determined to be approximately for and for implants. These RBE values are consistent with the RBE data published in the literature. These results may explain why in earlier modeling studies, when the effects of edema, dose heterogeneity, and RBE were all ignored simultaneously, prostate LDR brachytherapy was reported to show an overall similar dose effect as EBRT and HDR brachytherapy, which are independent of edema and RBE effects and have a better dose coverage.
Assessment of a new multileaf collimator concept using GEANT4 Monte Carlo simulations
Authors: Tacke Martin B. , Szymanowski Hanitra , Oelfke Uwe , Schulze Carsten , Nuss Susanne , Wehrwein Eugen , Leidenberger Stefan
Published: April 2006

The aim of the work was to investigate in advance the dosimetric properties of a new multileaf collimator (MLC) concept with the help of Monte Carlo (MC) simulations prior to the production of a prototype. The geometrical design of the MLC was implemented in the MC code GEANT4. For the simulation of a treatment beam, an experimentally validated phase space and a virtual spatial Gaussian‐shaped model placed in the origin were used. For the simulation of the geometry in GEANT4, the jaws and the two leaf packages were implemented with the help of computer‐aided design data. First, transmission values for different tungsten alloys were extracted using the simulation codes GEANT4 and BEAMnrc and compared to experimental measurements. In a second step, high‐resolution simulations were performed to detect the leakage at depth of maximum dose. The 20%–80% penumbra along the travel direction of the leaves was determined using fields shifted along the ‐ and ‐axis. The simulated results were compared with measured data. The simulation of the transmission values for different tungsten alloys showed a good agreement with the experimental measurements (within 2.0%). This enabled an accurate estimation of the attenuation coefficient for the various leaf materials. Simulations with varying width of the spatial Gaussian distribution showed that the leakage and the penumbra depend very much on this parameter: for instance, for widths of 2 and , the interleaf leakage is below 0.3% and 0.75%, respectively. The results for the leakage and the penumbra are in good agreement with the measurements. This study showed that GEANT4 is appropriate for the investigation of the dosimetric properties of a multileaf collimator. In particular, a quantification of the leakage, the penumbra, and the tongue‐and‐groove effect and an evaluation of the influence of the beam parameters such as the width of the Gaussian distribution was possible.
Image registration with auto‐mapped control volumes
Authors: Schreibmann Eduard , Xing Lei
Published: April 2006

Many image registration algorithms rely on the use of homologous control points on the two input image sets to be registered. In reality, the interactive identification of the control points on both images is tedious, difficult, and often a source of error. We propose a two‐step algorithm to automatically identify homologous regions that are used as a priori information during the image registration procedure. First, a number of small control volumes having distinct anatomical features are identified on the model image in a somewhat arbitrary fashion. Instead of attempting to find their correspondences in the reference image through user interaction, in the proposed method, each of the control regions is mapped to the corresponding part of the reference image by using an automated image registration algorithm. A normalized cross‐correlation (NCC) function or mutual information was used as the auto‐mapping metric and a limited memory Broyden‐Fletcher‐Goldfarb‐Shanno algorithm (L‐BFGS) was employed to optimize the function to find the optimal mapping. For rigid registration, the transformation parameters of the system are obtained by averaging that derived from the individual control volumes. In our deformable calculation, the mapped control volumes are treated as the nodes or control points with known positions on the two images. If the number of control volumes is not enough to cover the whole image to be registered, additional nodes are placed on the model image and then located on the reference image in a manner similar to the conventional BSpline deformable calculation. For deformable registration, the established correspondence by the auto‐mapped control volumes provides valuable guidance for the registration calculation and greatly reduces the dimensionality of the problem. The performance of the two‐step registrations was applied to three rigid registration cases (two PET‐CT registrations and a brain MRI‐CT registration) and one deformable registration of inhale and exhale phases of a lung 4D CT. Algorithm convergence was confirmed by starting the registration calculations from a large number of initial transformation parameters. An accuracy of was achieved for both deformable and rigid registration. The proposed image registration method greatly reduces the complexity involved in the determination of homologous control points and allows us to minimize the subjectivity and uncertainty associated with the current manual interactive approach. Patient studies have indicated that the two‐step registration technique is fast, reliable, and provides a valuable tool to facilitate both rigid and nonrigid image registrations.
The US radiation dosimetry standards for therapy level beams, and the transfer to the AAPM accredited dosimetry calibration laboratories
Authors: Minniti R. , Chen‐Mayer H. , Seltzer S. M. , Huq M. Saiful , Bryson L. , Slowey T. , Micka J. A. , DeWerd L. A. , Wells N. , Hanson W. F. , Ibbott G. S.
Published: April 2006

This work reports the transfer of the primary standard for air kerma from the National Institute of Standards and Technology (NIST) to the secondary laboratories accredited by the American Association of Physics in Medicine (AAPM). This transfer, performed in August of 2003, was motivated by the recent revision of the NIST air‐kerma standards for gamma‐ray beams implemented on July 1, 2003. The revision involved a complete recharacterization of the two NIST therapy‐level gamma‐ray beam facilities, resulting in new values for the air‐kerma rates disseminated by the NIST. Some of the experimental aspects of the determination of the new air‐kerma rates are briefly summarized here; the theoretical aspects have been described in detail by Seltzer and Bergstrom [“Changes in the U.S. primary standards for the air‐kerma from gamma‐ray beams,” J. Res. Natl. Inst. Stand. Technol. 108, 359–381 (2003)]. The standard was transferred to reference‐class chambers submitted by each of the AAPM Accredited Dosimetry Calibration Laboratories (ADCLs). These secondary‐standard instruments were then used to characterize the gamma‐ray beams at the ADCLs. The values of the response (calibration coefficient) of the ADCL secondary‐standard ionization chambers are reported and compared to values obtained prior to the change in the NIST air‐kerma standards announced on July 1, 2003. The relative change is about 1.1% for all of these chambers, and this value agrees well with the expected change in chambers calibrated at the NIST or at any secondary‐standard laboratory traceable to the new NIST standard.
Effect of scatter and an antiscatter grid on the performance of a slot‐scanning digital mammography system
Authors: Shen Sam Z. , Bloomquist Aili K. , Mawdsley Gord E. , Yaffe Martin J. , Elbakri Idris
Published: April 2006

The use of a grid increases perceptibility of low contrast objects in mammography. Slot‐scan mammography provides a more dose efficient reduction of the scattered radiation reaching the detector than obtained with an antiscatter grid in screen‐film or flat‐panel digital mammography. In this paper, the potential of using a grid in a slot‐scan system to provide a further reduction of scattered radiation is investigated. The components of the digital signal: primary radiation, off‐focus radiation, scattered radiation, and optical fluorescence glare in a detector were quantified. Based on these measurements, the primary and scatter transmission factors , scatter‐to‐primary ratio (SPR), signal‐difference‐to‐noise ratio (SDNR), and the SDNR improvement factor were obtained. Our results showed that the SPR ranged from 0.05 to 0.19 for breast thicknesses between 2 and , respectively. The values of ranged from 0.85 to 0.94. Because the slot‐scanning system has an inherently low SPR, the increase in dose required when the grid is used outweighs the benefit of the small increase in SDNR. It is possible that greater benefit could be achieved by using a grid with a higher , such as obtained using air‐core technology.
Camphor-Palladium Complexes as Catalysts for Cyclization of Alkynes
Authors: Carvalho M. Fernanda N. N. , Duarte M. Teresa , Herrmann Rudolf
Published: April 2006

Catalytic properties of the camphor-derived complexes trans-[PdCl2(L1)2], R = Me2N (1), i-Pr (3), C6H5 (4), in PhC≡CMe cyclotrimerization are highly dependent on the characteristics of the R group. Their activity decreases in the order 1 > 3 > 4. The effects of geometric and/or electronic parameters on the catalytic activity of the complexes are evaluated on the basis of X-ray and electrochemical data.
1,6-Anhydro-1-thio-β-D-glucopyranose (Thiolevoglucosan) and the Corresponding Sulfoxides and Sulfone
Authors: Buděšínský Miloš , Poláková Jana , Hamerníková Michaela , Císařová Ivana , Trnka Tomáš , Černý Miloslav
Published: April 2006

Starting 1,2,3,4-tetra-O-acetyl-6-O-tosyl-β-D-glucopyranose (3) was converted into 2,3,4-tri-O-acetyl-1-thio-6-O-tosyl-β-D-glucopyranose (6) via intermediate glycosyl bromide 4 and S-thiouronium salt 5. Treatment of compound 6 with sodium methoxide gave 1,6-anhydro-1-thio-β-D-glucopyranose (thiolevoglucosan 2a). The isomeric sulfoxides 7 and 8 were prepared by selective oxidation of thiolevoglucosan 2a with hydrogen peroxide or 3-chloroperoxybenzoic acid. The structure of new compounds was confirmed by 1H and 13C NMR spectroscopy or by X-ray analysis; magnetic anisotropy of the sulfinyl and sulfonyl group has been discussed.
A comparison of information on motor vehicle crashes as reported by written or telephone interviews
Authors: Alonso A , Laguna S , Seguí-Gómez M
Published: April 2006

Objective:To compare information about traffic crash injuries and kilometers driven reported in a written questionnaire with information reported in a telephone interview.

Design:Telephone and paper surveys.

Setting:TheSeguimiento Universidad de Navarra(SUN, University of Navarra Follow-up) study, in Spain. The SUN study is an open enrollment cohort study with 17 000 enrolled graduates followed through biennial mailed questionnaires.

Subjects:A sample of 542 individuals from the SUN study participants.

Main outcome measure:Agreement on information about traffic crash injuries and mileage driven in a mailed questionnaire and a telephone survey.

Results:Participation was 90.4%. Considering the phone survey as the gold standard, data on traffic crash injuries in the mailed questionnaire had 83% sensitivity (95% CI 77% to 89%), 77% specificity (95% CI 71% to 82%), 74% positive predictive value (95% CI 67% to 80%), and 89% negative predictive value (95% CI 83% to 93%). Agreement beyond chance, measured by the kappa statistic, was 0.63 (95% CI 0.56 to 0.70). Correlation between questionnaire and telephone surveys and kilometers driven on average during a year assessed by the intraclass correlation coefficient was 0.64 (95% CI 0.57 to 0.70), p<0.001.

Conclusions:Information on sustained traffic crash injuries and traveled mileage over the previous two years as reported through mailed questionnaires in a highly educated population could be used in the study of associations between traffic crash injuries and a variety of risk factors.
Ascertainment of intimate partner violence using two abuse measurement frameworks
Authors: Bonomi A E , Thompson R S , Anderson M , Rivara F P , Holt V L , Carrell D , Martin D P
Published: April 2006

Objective:To estimate prevalence of intimate partner violence (IPV) according to two abuse ascertainment tools, and agreement between the tools.

Methods:2504 women randomly selected from a health maintenance organization were asked about IPV exposure in their most recent intimate relationship using five questions on physical and sexual abuse, and fear due to partner’s threats and controlling behavior from the Behavioral Risk Factor Surveillance Survey (BRFSS) and 10 questions from the Women’s Experience with Battering (WEB) scale. IPV prevalence was estimated according to the BRFSS and WEB, and the proportion of women who were WEB+/BRFSS+, WEB−/BRFSS−, WEB−/BRFSS+, and WEB+/BRFSS−.

Results:In their most recent relationship, 14.7% of women reported abuse of any type on the BRFSS versus 7.0% on the WEB scale. In direct comparisons of the WEB and BRFSS questions, a higher percentage of abused women reported any IPV on the five BRFSS questions (88.4%) compared to the 10 WEB questions (42.0%). However, both the BRFSS and WEB identified some women as abused that would have been missed by the other instrument.

Conclusions:Intimate partner violence prevalence depends on how women are asked about abuse. Resources permitting, more than one abuse ascertainment strategy (for example, both the BRFSS and WEB questions) should be tried in order to broadly identify as many women as possible who interpret themselves as abused.
Estimating injury severity using the Barell matrix
Authors: Clark D E , Ahmad S
Published: April 2006

Objective:To determine whether the Barell matrix (Inj Prev2002;8:91–6) could effectively categorize injuries by severity.

Methods:Injury diagnoses of cases in the 2002 US Nationwide Inpatient Sample were classified according to the Barell matrix. For each cell of the matrix, the authors used ICDMAP-90 to determine the predominant Abbreviated Injury Score (AIS) and body region, and calculated the weighted proportion surviving (bPScell) among patients with any diagnosis in that cell. These findings were used to estimate maximum AIS (bAISmax), ISS (bISS), and the minimum or product of bPScell (bPSmin, bPSprod) for injured patients in the 1996–2000 US National Hospital Discharge Surveys. Case survival was determined for different scores, and outcome models using age, sex, comorbidity, mechanism, and bISS or bPSmin were compared to models using ISS calculated from ICDMAP-90 (mISS) or using ICISS.

Results:Case survival decreased with increasing bAISmax or bISS; survival was closely approximated by bPSmin, and also increased monotonically with bPSprod. Outcome models using bISS or bPSmin were similar to those using mISS or ICISS. An Abbreviated Barell Categorization, with only four groups, was also effective.

Conclusion:Barell matrix categorization of administrative data allows severity scoring similar to that obtainable with ICDMAP-90 or ICISS.
Incidence of trampoline related pediatric fractures in a large district general hospital in the United Kingdom: lessons to be learnt
Authors: Bhangal K K , Neen D , Dodds R
Published: April 2006

Aim:To test the observation that the incidence of trampoline related pediatric fractures is increasing—both nationally and in a large district general hospital.

Method:A retrospective analysis was undertaken of patient records establishing mechanism of injury of pediatric fractures over three consecutive summers from 2000–03. Theatre records of fractures treated operatively were used as the initial data source.

Results:A statistically significant increase in trampoline related injuries was discovered. This reflects the rising incidence of injuries from national data and furthermore corresponds to the growing popularity of domestic use trampolines in the UK.

Conclusion:The incidence of injuries is increasing. There are lessons to be learnt from existing work from countries where trampoline prevalence has been greater for longer. The authors recommend various safety measures that may reduce children’s injuries.