bluuebunny/crossref_metadata_2025 huggingface dataset:
Optical spectroscopy of the breast in premenopausal women reveals tissue variation with changes in age and parity
Authors: Knight Julia A. , Blackmore Kristina M. , Wong Jody , Tharmalingam Sukirtha , Lilge Lothar
Published: January 2010

Purpose:

Variations during breast tissue development can influence later breast cancer risk. In particular, prolonged nulliparity increases risk. The authors used optical spectroscopy to compare breast tissue in 115 nulliparous women aged 31–40 (group 2) to 140 nulliparous women aged 18–21 (group 1), and also to 36 parous women aged 31–40 (group 3), and to evaluate the relationship between IGF‐1 and optical breast tissue properties. IGF‐1 has been linked in particular to premenopausal breast cancer.

Methods:

The authors measured the transmission spectra from 625 to 1050 nm wavelengths in each breast and determined regions of interindividual variation using principal components analysis. Spectral differences represent variation in lipid, water, oxyhemoglobin, deoxyhemoglobin, and collagen content. Group differences and the relationship with IGF‐1 were estimated by linear regression after adjustment for multiple factors including height, weight, ethnicity, hormonal contraceptive use, and days since last menstrual period.

Results:

Principal component 3 scores were more negative in the older nulliparous women compared to either younger nulliparous women or to parous women of the same age (, for group 2 vs group 1 and , for group 3 vs group 2). These differences appear to indicate increased deoxyhemoglobin relative to oxyhemoglobin content in the tissue of the older, nulliparous premenopausal women compared to the other groups, which may be an indicator of proportionally increased proliferative tissue. Principal component 4 also differed between older and younger nulliparous women (, for group 2 vs group 1) and was negatively associated with IGF‐1 in younger women (, ) and positively associated with IGF‐1 in older women (, ).

Conclusions:

Optical spectroscopy may be useful to identify breast tissue at increased risk of cancer development and track changes over time, particularly in young women where exposure to radiation is of particular concern. Additional work is needed to confirm the observed breast tissue differences and to determine the specific tissue chromophore changes with age and parity.
Dose‐rate distribution of ‐glass microspheres for intra‐arterial brachytherapy
Authors: Guimarães Carla C. , Moralles Maurício , Sene Frank F. , Martinelli José R.
Published: January 2010

Purpose:

The intra‐arterial administration of radioactive glass microspheres is an alternative therapy option for treating primary hepatocellular carcinoma, the main cause of liver cancer death, and metastatic liver cancer, another important kind of cancer induced in the liver. The technique involves the administration of radioactive microspheres in the hepatic artery, which are trapped preferentially in the tumor.

Methods:

In this work the GEANT4 toolkit was used to calculate the radial dose‐rate distributions in water from‐loaded glass microspheres and also from ‐loaded glass microspheres. To validate the toolkit for this application, the authors compared the dose‐rate distribution of and point sources in water with data from the International Commission on Radiation Units and Measurements report 72.

Results:

Tables of radial dose‐rate distributions are provided for practical use in brachytherapy planning with these microspheres.

Conclusions:

The simulations with the microspheres show that the shape of the beta ray energy spectra with respect to the and sources is significantly modified by the glass matrix.
Automated aortic calcium scoring on low‐dose chest computed tomography
Authors: Išgum Ivana , Rutten Annemarieke , Prokop Mathias , Staring Marius , Klein Stefan , Pluim Josien P. W. , Viergever Max A. , van Ginneken Bram
Published: January 2010

Purpose:

Thoracic computed tomography (CT) scans provide information about cardiovascular risk status. These scans are non‐ECG synchronized, thus precise quantification of coronary calcifications is difficult. Aortic calcium scoring is less sensitive to cardiac motion, so it is an alternative to coronary calcium scoring as an indicator of cardiovascular risk. The authors developed and evaluated a computer‐aided system for automatic detection and quantification of aortic calcifications in low‐dose noncontrast‐enhanced chest CT.

Methods:

The system was trained and tested on scans from participants of a lung cancer screening trial. A total of 433 low‐dose, non‐ECG‐synchronized, noncontrast‐enhanced 16 detector row examinations of the chest was randomly divided into 340 training and 93 test data sets. A first observer manually identified aortic calcifications on training and test scans. A second observer did the same on the test scans only. First, a multiatlas‐based segmentation method was developed to delineate the aorta. Segmented volume was thresholded and potential calcifications (candidate objects) were extracted by three‐dimensional connected component labeling. Due to image resolution and noise, in rare cases extracted candidate objects were connected to the spine. They were separated into a part outside and parts inside the aorta, and only the latter was further analyzed. All candidate objects were represented by 63 features describing their size, position, and texture. Subsequently, a two‐stage classification with a selection of features and‐nearest neighbor classifiers was performed. Based on the detected aortic calcifications, total calcium volume score was determined for each subject.

Results:

The computer system correctly detected, on the average, out of (97.9%) calcified plaque volume in the aorta with an average of of false positive volume per scan. Spearman rank correlation coefficient was between the system and the first observer compared to between the two observers.

Conclusions:

Automatic calcium scoring in the aorta thus appears feasible with good correlation between manual and automatic scoring.
Technical Note: Development of a tidal volume surrogate that replaces spirometry for physiological breathing monitoring in 4D CT
Authors: Werner René , White Benjamin , Handels Heinz , Lu Wei , Low Daniel A.
Published: January 2010

Purpose:

Spirometry exhibits baseline drift and frequent measurement errors so it cannot be used by itself to provide tidal volume‐based image sorting or breathing motion modeling. Other breathing surrogates, in this study an abdominal bellows system, are drift free but do not measure tidal volume. Simultaneously using spirometry and the bellows system allows the user to convert the recorded bellows signal to tidal volume but still relies on spirometry measurements. The authors therefore propose to use CT‐based air content, rather than a spirometer, to convert the bellows signal to tidal volume.

Methods:

41 4D CT data sets are acquired, while the breathing cycle is simultaneously measured using spirometry and an abdominal pressure bellows system. The assumptions underlying the conversion of the bellows measurement to tidal volume by CT‐based air content are analyzed. This comprises of detailed correlation studies of the spirometry‐measured tidal volume, the bellows signal, and CT‐based air content.

Results:

For patients, the spirometry signals are not consistently acquired during the 4D CT session, so correlating spirometry to bellows measurements and CT‐based air content leads to erroneous conversion coefficients. After introducing a minimum correlation threshold to remove these data, good correlations are obtained between the remaining breathing signals. The ratio of CT‐based air content to tidal volume is measured to be ; the expected value is 1.11 because room air is 11% more dense than air in the lungs.

Conclusions:

The observed problems of spirometry recording illustrate the challenges encountered when using spirometers as breathing surrogate for 4D CT acquisition. The high correlation between spirometry and bellows breathing signals and the verified factor of 1.11 between CT‐based air content and tidal volume mean that the bellows measurement (or other equivalent surrogates) can be reliably converted to tidal volume using the CT‐based air content, avoiding the need for a spirometer.
Biological effect of different IMRT delivery techniques: SMLC, DMLC, and helical tomotherapy
Authors: Shaikh Mubin , Burmeister Jay , Joiner Michael , Pandya Shalini , Zhao Bo , Liu Qiang
Published: January 2010

Purpose:

Intensity‐modulated radiotherapy (IMRT) is delivered using a variety of techniques with differing temporal dose characteristics. Spatial dose metrics are generally used to evaluate treatment plan quality. However, the use of this information alone neglects the effects of the significant differences in dose delivery duration and dose accumulation patterns, both of which can impact cell survival. This study uses the linear‐quadratic model with dose protraction corrections to evaluate the biological effectiveness of different IMRT delivery techniques, including fixed gantry IMRT in SMLC (step‐and‐shoot) and DMLC (sliding window) modes and a rotational IMRT technique (helical tomotherapy) for the treatment of prostate and head/neck sites.

Methods:

The temporal dose pattern was measured using a small volume ion chamber (A1SL—) to calculate the protraction factor, and biological equivalent dose (BED) was calculated for a range of repair half‐times and ratios. The treatment BED is compared to an ideal delivery of the target prescription dose, in which dose is delivered instantaneously , to evaluate loss in biological effectiveness due to protraction in delivery. In the case of a conventional prescription, the loss in biological effectiveness was further evaluated using published tumor control probability (TCP) data.

Results:

With SMLC and DMLC IMRT delivery, for both prostate and head/neck, the expected additional loss in BED is about 1% compared to 3D CRT, which corresponds to a predicted 2%–3% reduction in TCP. For tomotherapy, the prostate BED loss is smaller in comparison to 3D CRT; hence, the authors expect a TCP increase of the order of 2%–3%. The aforementioned differences are due to the dose accumulation time.

Conclusions:

While it is theoretically possible to compensate for changes in biologically effective dose, this would be hindered by large uncertainties in parameters used for such calculations; therefore, it is advantageous to irradiate target volume elements as rapidly as possible. The results of this study indicate that temporal dose delivery pattern is an important component in determining the biological effects of IMRT treatment.
Nonlinear registration of serial coronary CT angiography (CCTA) for assessment of changes in atherosclerotic plaque
Authors: Woo Jonghye , Dey Damini , Cheng Victor Y. , Hong Byung‐Woo , Ramesh Amit , Sundaramoorthi Ganesh , Nakazato Ryo , Berman Daniel S. , Germano Guido , Kuo C.‐C. Jay , Slomka Piotr J.
Published: January 2010

Purpose: Coronary CT angiography (CCTA) is a high‐resolution three‐dimensional imaging technique for the evaluation of coronary arteries in suspected or confirmed coronary artery disease (CAD). Coregistration of serial CCTA scans would allow precise superimposition of images obtained at two different points in time, which could aid in recognition of subtle changes and precise monitoring of coronary plaque progression or regression. To this end, the authors aimed at developing a fully automatic nonlinear volume coregistration for longitudinal CCTA scan pairs.

Methods: The algorithm combines global displacement and local deformation using nonlinear volume coregistration with a volume‐preserving constraint. Histogram matching of intensities between two serial scans is performed prior to nonlinear coregistration with dense nonparametric local deformation in which sum of squared differences is used as a similarity measure. The approximate segmentation of coronary arteries obtained from commercially available software provides initial anatomical landmarks for the coregistration algorithm that help localize and emphasize the structure of interest. To avoid possible bias caused by incorrect segmentation, the authors convolve the Gaussian kernel with the segmented binary coronary tree mask and define an extended weighted region of interest. A multiresolution approach is employed to represent coarse‐to‐fine details of both volumes and the energy function is optimized using a gradient descent method. The authors applied the algorithm in ten paired CCTA datasets (20 scans in total) obtained within from each other on a dual source CT scanner to monitor progression of CAD.

Results: Serial CCTA coregistration was successful in 9/10 cases as visually confirmed. The global displacement and local deformation of target registration error obtained from four anatomical landmarks were and , respectively, and the inverse consistency error of local deformation was . The observer variability between two expert observers was .

Conclusions: The proposed coregistration algorithm demonstrates potential to accurately register serial CCTA scans, which may allow direct comparison of calcified and noncalcified atherosclerotic plaque changes between the two scans.
Real‐time tumor tracking: Automatic compensation of target motion using the Siemens 160 MLC
Authors: Tacke Martin B. , Nill Simeon , Krauss Andreas , Oelfke Uwe
Published: January 2010

Purpose:

Advanced high quality radiation therapy techniques such as IMRT require an accurate delivery of precisely modulated radiation fields to the target volume. Interfractional and intrafractional motion of the patient's anatomy, however, may considerably deteriorate the accuracy of the delivered dose to the planned dose distributions. In order to compensate for these potential errors, a dynamic real‐time capable MLC control system was designed.

Methods:

The newly developed adaptive MLC control system contains specialized algorithms which are capable of continuous optimization and correction of the aperture of the MLC according to the motion of the target volume during the dose delivery. The algorithms calculate the new leaf positions based on target information provided online to the system. The algorithms were implemented in a dynamic target tracking control system designed for a Siemens 160 MLC™. To assess the quality of the new target tracking system in terms of dosimetric accuracy, experiments with various types of motion patterns using different phantom setups were performed. The phantoms were equipped with radiochromic films placed between solid water slabs. Dosimetric results of exemplary deliveries to moving targets with and without dynamic MLC tracking applied were compared in terms of the gamma criterion to the reference dose delivered to a static phantom.

Results:

Our measurements indicated that dose errors for clinically relevant two‐dimensional target motion can be compensated by the new control system during the dose delivery of open fields. For a clinical IMRT dose distribution, the gamma success rate was increased from 19% to 77% using the new tracking system. Similar improvements were achieved for the delivery of a complete IMRT treatment fraction to a moving lung phantom. However, dosimetric accuracy was limited by the system's latency of 400 ms and the finite leaf width of 5 mm in the isocenter plane.

Conclusions:

Different experimental setups representing different target tracking scenarios proved that the tracking concept, the new algorithms and the dynamic control system make it possible to effectively compensate for dose errors due to target motion in real‐time. These early results indicate that the method is suited to increasing the accuracy and the quality of the treatment delivery for the irradiation of moving tumors.
Quantification of breast density with dual energy mammography: An experimental feasibility study
Authors: Ducote Justin L. , Molloi Sabee
Published: January 2010

Purpose:

Breast density, the percentage of glandular breast tissue, has been shown to be a strong indicator of breast cancer risk. A quantitative method to measure breast density with dual energy mammography was investigated using physical phantoms.

Methods:

The dual energy mammography system used a tungsten anode x‐ray tube with a rhodium beam filter for low energy images and a copper beam filter for high energy images. Glandular and adipose equivalent phantoms of uniform thickness were used to calibrate a dual energy basis decomposition algorithm. Four different phantom studies were used to evaluate the technique. The first study consisted of phantoms with thicknesses of 2.5–8.5 cm in 0.5 cm steps with variable densities centered at a mean of 28%. The second study consisted of phantoms at a fixed thickness of 4.0 cm, which ranged in densities from 0% to 100% in increments of 12.5%. The third study consisted of 4.0 cm thick phantoms at densities of 25%, 50% and 75% each imaged at three areal sizes, approximately 62.5, 125, and , in order to assess the effect of breast size on density measurement. The fourth study consisted of step phantoms designed to more closely mimic the shape of a female breast with maximal thicknesses from 3.0 to 7.0 cm at a fixed density of 50%. All images were corrected for x‐ray scatter.

Results:

The RMS errors in breast density measurements were 0.44% for the variable thickness phantoms, 0.64% for the variable density phantoms, 2.87% for the phantoms of different areal sizes, and 4.63% for step phantoms designed to closely resemble the shape of a breast.

Conclusions:

The results of the phantom studies indicate that dual energy mammography can be used to measure breast density with an RMS error of approximately 5%.
Semiautomatic vessel wall detection and quantification of wall thickness in computed tomography images of human abdominal aortic aneurysms
Authors: Shum Judy , DiMartino Elena S. , Goldhammer Adam , Goldman Daniel H. , Acker Leah C. , Patel Gopal , Ng Julie H. , Martufi Giampaolo , Finol Ender A.
Published: January 2010

Purpose:

Quantitative measurements of wall thickness in human abdominal aortic aneurysms (AAAs) may lead to more accurate methods for the evaluation of their biomechanical environment.

Methods:

The authors describe an algorithm for estimating wall thickness in AAAs based on intensity histograms and neural networks involving segmentation of contrast enhanced abdominal computed tomography images. The algorithm was applied to ten ruptured and ten unruptured AAA image data sets. Two vascular surgeons manually segmented the lumen, inner wall, and outer wall of each data set and a reference standard was defined as the average of their segmentations. Reproducibility was determined by comparing the reference standard to lumen contours generated automatically by the algorithm and a commercially available software package. Repeatability was assessed by comparing the lumen, outer wall, and inner wall contours, as well as wall thickness, made by the two surgeons using the algorithm.

Results:

There was high correspondence between automatic and manual measurements for the lumen area ( and for ruptured and unruptured aneurysms, respectively) and between vascular surgeons ( and for ruptured and unruptured aneurysms, respectively). The authors’ automatic algorithm showed better results when compared to the reference with an average lumen error of 3.69%, which is less than half the error between the commercially available application Simpleware and the reference (7.53%). Wall thickness measurements also showed good agreement between vascular surgeons with average coefficients of variation of 10.59% (ruptured aneurysms) and 13.02% (unruptured aneurysms). Ruptured aneurysms exhibit significantly thicker walls than unruptured ones , .

Conclusions:

While further refinement is needed to fully automate the outer wall segmentation algorithm, these preliminary results demonstrate the method's adequate reproducibility and low interobserver variability.
The effects of dose calculation resolution on dose accuracy for radiation therapy treatments of the lung. Part I. A Monte Carlo model of the lung
Authors: Babcock Kerry , Sidhu Narinder
Published: January 2010

Purpose: The purpose of this work was to create an anatomically detailed EGSnrc Monte Carlo based model of the right lung. The resulting model, called BRANCH, includes an accurate representation of the right bronchial, arterial, and venous branching networks down to a scale of 0.1 mm. The model may be varied to represent lung shape and density at any phase of the respiration cycle.

Methods: Polynomial surfaces were used to approximate the anatomic boundaries that define the right lung surface at several phases of the respiration cycle. A branching network algorithm was used to generate the bronchial, arterial, and venous trees within the anatomic boundaries. The branching networks were modeled as a series of bifurcating cylinders connected by spherical junctions. The validity of the BRANCH dose calculation was verified using an all‐water version of the model.

Results: The geometric dimensions of the BRANCH model corresponded well with published data. The bronchial tree model contained 27 798 branches ranging from 0.02 to 0.54 cm in diameter. The arterial tree model had 27 957 branches ranging from 0.02 to 1.2 cm in diameter. The venous model tree had 26 347 branches ranging from 0.02 to 0.34 cm in diameter. A gamma analysis indicated that the all‐water BRANCH Monte Carlo code produced dose distributions that agreed within 0.1 cm and 0.5% to conventional DOSXYZnrc results.

Conclusions: The BRANCH model is a useful tool for performing detailed dosimetric studies within a realistic representation of the lung.
An intraoperative 3D ultrasound system for tumor margin determination in breast cancer surgery
Authors: DeJean Paul , Brackstone Muriel , Fenster Aaron
Published: January 2010

Purpose:

The purpose of this study was to analyze the clinical utility of a portable three‐dimensional ultrasound (3DUS) system to be used for surgical guidance of lumpectomy surgeries. In 11%–60% of lumpectomy surgeries, a second surgery is required to fully resect the tumor. Previous studies have used 3DUS as a guidance tool with the hope of more accuracy in resecting the entire tumor during the first surgery. However, they utilized larger systems, which are not easily integrated into the operating room.

Methods:

The portable 3DUS scanning system we developed consisted of a motorized “tilt” scanner coupled to a Terason t3000 portable ultrasound machine (Terason Ultrasound, Burlington, MA). The 3DUS system was evaluated by measuring agar “tumor” phantoms of known volumes and acquiring and segmenting images from nine patients undergoing lumpectomy.

Results:

Experiments on simulated agar tumor phantoms have shown that our device could be used to measure objects with smooth, well‐defined boundaries of known volume with an error of 3%. It was possible to view and segment estimated tumor margins from the clinical images in three dimensions. Correspondence between measurements obtained in the laboratory and the operating room varied with tumor geometry and the degree of spiculation in the ultrasound image. The measured values obtained by the system did not correspond closely with those obtained using histology. However, a more accurate histological measurement using 3D histology may provide a better basis for comparison.

Conclusions:

The results of imaging simulated agar tumor phantoms indicate the system's consistency in measuring objects of known volume and geometry. The system could be used for segmenting the approximate boundary of lumpectomy patients’ breast tumors relative to inserted guide wires. The potential advantages of this system are a reduction in the number of re‐excision surgeries required and a reduction in the operative time with the patient under anesthesia.
Stereotactic targeting and dose verification for age‐related macular degeneration
Authors: Gertner Michael , Chell Erik , Pan Kuang‐Hung , Hansen Steve , Kaiser Peter K. , Moshfeghi Darius M.
Published: January 2010

Purpose:

Validation of the targeting and dose delivery of the IRay™ low voltage age‐related macular degeneration treatment system.

Methods:

Ten human cadaver eyes were obtained for this study and mounted in the IRay™ system. Using gel and vacuum, an I‐Guide™ immobilization device was coupled to the eyes and radiochromic film was affixed to the posterior aspect of the globes. Three narrow x‐ray beams were delivered through the pars plana to overlap on the predicted nominal fovea. A needle was placed through the center of the film's beam spot and into the eye to register the film and the inner retina. The process was performed three times for each of the ten eyes (30 simulated treatments; 90 individual beams). The globes were dissected to assess the targeting accuracy by measuring the distances from the needles to the fovea. The dose to the fovea was calculated from the radiochromic film.

Results:

X‐ray targeting on the retina averaged from the fovea. Repeated treatments on the same eye showed a reproducibility of . The optic nerve was safely avoided, with the 90% isodose edge of the beam spot between 0.4 and 2.6 mm from the edge of the optic disk. Measured dose matched that prescribed.

Conclusions:

This study provides confidence that the IRay™, with an average accuracy of 0.6 mm and a precision of 0.4 mm, can reliably treat most AMD lesions centered on the fovea. With the exception of motion, all sources of error are included.
Time‐efficient patient‐specific quantification of regional carotid artery fluid dynamics and spatial correlation with plaque burden
Authors: LaDisa John F. , Bowers Mark , Harmann Leanne , Prost Robert , Doppalapudi Anil Vamsi , Mohyuddin Tayyab , Zaidat Osama , Migrino Raymond Q.
Published: January 2010

Purpose:

Low wall shear stress (WSS) and high oscillatory shear index (OSI) influence plaque formation, yet little is known about their role in progression/regression of established plaques because of lack of practical means to calculate them in individual patients. Our aim was to use computational fluid dynamics (CFD) models of patients with carotid plaque undergoing statin treatment to calculate WSS and OSI in a time‐efficient manner, and determine their relationship to plaque thickness (PT), plaque composition (PC), and regression.

Methods:

Eight patients (, one female) underwent multicontrast 3 T MRI at baseline and six‐month post statin treatment. PT and PC were measured in carotid segments (common–CC, bifurcation–B, internal–IC) and circumferentially in nonoverlapping 60° angles and correlated with CFD models created from MRI, ultrasound, and blood pressure.

Results:

PT was highest in B ( versus CC: , IC: , ). Circumferentially, plaque was greatest opposite the flow divider , where the lowest WSS and highest OSI were observed. In B and IC, PT was inversely related to WSS ( and −0.37, ) and directly related to OSI ( and 0.52, ). The total plaque volume changed from to at six months . Baseline WSS, but not OSI, correlated with changes in PT, necrotic tissue, and hemorrhage in B and IC, but not CC. CFD modeling took per patient.

Conclusions:

PT and PC correspond to adverse WSS and OSI in B and IC, and WSS is modestly but significantly related to changes in PT after short‐term statin treatment. Regional hemodynamics from CFD can feasibly augment routine clinical imaging for comprehensive plaque evaluation.
Simultaneous navigation of multiple Pareto surfaces, with an application to multicriteria IMRT planning with multiple beam angle configurations
Authors: Craft David , Monz Michael
Published: January 2010

Purpose:

To introduce a method to simultaneously explore a collection of Pareto surfaces. The method will allow radiotherapy treatment planners to interactively explore treatment plans for different beam angle configurations as well as different treatment modalities.

Methods:

The authors assume a convex optimization setting and represent the Pareto surface for each modality or given beam set by a set of discrete points on the surface. Weighted averages of these discrete points produce a continuous representation of each Pareto surface. The authors calculate a set of Pareto surfaces and use linear programming to navigate across the individual surfaces, allowing switches between surfaces. The switches are organized such that the plan profits in the requested way, while trying to keep the change in dose as small as possible.

Results:

The system is demonstrated on a phantom pancreas IMRT case using 100 different five beam configurations and a multicriteria formulation with six objectives. The system has intuitive behavior and is easy to control. Also, because the underlying linear programs are small, the system is fast enough to offer real‐time exploration for the Pareto surfaces of the given beam configurations.

Conclusions:

The system presented offers a sound starting point for building clinical systems for multicriteria exploration of different modalities and offers a controllable way to explore hundreds of beam angle configurations in IMRT planning, allowing the users to focus their attention on the dose distribution and treatment planning objectives instead of spending excessive time on the technicalities of delivery.
A photon spectrometric dose‐rate constant determination for the Advantage™ Pd‐103 brachytherapy source
Authors: Chen Zhe Jay , Bongiorni Paul , Nath Ravinder
Published: January 2010

Purpose:

Although several dosimetric characterizations using Monte Carlo simulation and thermoluminescent dosimetry (TLD) have been reported for the new Advantage™ Pd‐103 source (IsoAid, LLC, Port Richey, FL), no AAPM consensus value has been established for the dosimetric parameters of the source. The aim of this work was to perform an additional dose‐rate constant determination using a recently established photon spectrometry technique (PST) that is independent of the published TLD and Monte Carlo techniques.

Methods:

Three Model IAPD‐103A Advantage™ Pd‐103 sources were used in this study. The relative photon energy spectrum emitted by each source along the transverse axis was measured using a high‐resolution germanium spectrometer designed for low‐energy photons. For each source, the dose‐rate constant was determined from its emitted energy spectrum. The PST‐determined dose‐rate constant was then compared to those determined by TLD and Monte Carlo techniques. A likely consensus value was estimated as the arithmetic mean of the average values determined by each of three different techniques.

Results:

The average value for the three Advantage™ sources was found to be . Intersource variation in was less than 0.01%. The was within 2% of the reported values determined by PTRAN, EGSnrc, and MCNP5 codes. It was 3.4% lower than the reported . A likely consensus value was estimated to be , similar to the AAPM consensus values recommended currently for the Theragenics (Buford, GA) Model 200 , the NASI (Chatsworth, CA) Model MED3633 , and the Best Medical (Springfield, VA) Model 2335 sources.

Conclusions:

An independent determination has been performed for the Advantage™ Pd‐103 source. The obtained in this work provides additional information needed for establishing a more accurate consensus value for the Advantage™ Pd‐103 source.
Organ doses to adult patients for chest CT
Authors: Huda Walter , Sterzik Alexander , Tipnis Sameer , Schoepf U. Joseph
Published: January 2010

Purpose:

The goal of this study was to estimate organ doses for chest CT examinations using volume computed tomography dose index data as well as accounting for patient weight.

Methods:

A CT dosimetry spreadsheet (ImPACT CT patient dosimetry calculator) was used to compute organ doses for a 70 kg patient undergoing chest CT examinations, as well as volume computed tomography dose index in a body CT dosimetry phantom at the same CT technique factors. Ratios of organ dose to were generated as a function of anatomical location in the chest for the breasts, lungs, stomach, red bone marrow, liver, thyroid, liver, and thymus. Values of were obtained for x‐ray tube voltages ranging from 80 to 140 kV for 1, 4, 16, and 64 slice CT scanners from two vendors. For constant CT techniques, we computed ratios of dose in water phantoms of differing diameter. By modeling patients of different weights as equivalent water cylinders of different diameters, we generated factors that permit the estimation of the organ doses in patients weighing between 50 and 100 kg who undergo chest CT examinations relative to the corresponding organ doses received by a 70 kg adult.

Results:

For a 32 cm long CT scan encompassing the complete lungs, values of ranged from 1.7 (thymus) to 0.3 (stomach). Organs that are directly in the x‐ray beam, and are completely irradiated, generally had values well above 1 (i.e., breast, lung, heart, and thymus). Organs that are not completely irradiated in a total chest CT scan generally had values that are less than 1 (e.g., red bone marrow, liver, and stomach). Increasing the x‐ray tube voltage from 80 to 140 kV resulted in modest increases in for the heart (9%) and thymus (8%), but resulted in larger increases for the breast (19%) and red bone marrow (21%). Adult patient chests have been modeled by water cylinders with diameters between for a 50 kg patient and for a 100 kg patient. At constant x‐ray techniques, a 50 kg patient is expected to have doses that are higher than those in a 70 kg adult, whereas a 100 kg patient will have doses that are lower.

Conclusions:

We describe a practical method to use CTDI data provided by commercial CT scanners to obtain patient and examination specific estimates of organ dose for chest CT examinations.
Local and Long-Range Reciprocal Regulation of cAMP and cGMP in Axon/Dendrite Formation
Authors: Shelly Maya , Lim Byung Kook , Cancedda Laura , Heilshorn Sarah C. , Gao Hongfeng , Poo Mu-ming
Published: January 2010

Promoting Axon Formation

How do neurons initiate one axon and lots of dendrites? Using an in vitro assay involving stripes of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP),

Shelly
et al.

(p.
547
) show that an increase in cAMP initiates axon formation while an increase in cGMP initiates dendrites. Moreover, cAMP and cGMP reciprocally inhibit each other via the activation of specific phosphodiesterases, as well as protein kinase A and protein kinase G. Finally, long-range self-inhibition of cAMP can explain why only one axon, yet multiple dendrites, is initiated in single hippocampal neurons in culture. Locally increasing cAMP in one neurite causes long-range cAMP reduction in the rest of the neurites, accompanied by corresponding reciprocal changes in cGMP.
The Asynchronous State in Cortical Circuits
Authors: Renart Alfonso , de la Rocha Jaime , Bartho Peter , Hollender Liad , Parga Néstor , Reyes Alex , Harris Kenneth D.
Published: January 2010

Columns, Connections, and Correlations

What is the nature of interactions between neurons in neural circuits? The prevalent hypothesis suggests that dense local connectivity causes nearby cortical neurons to receive substantial amounts of common input, which in turn leads to strong correlations between them. Now two studies challenge this view, which impacts our fundamental understanding of coding in the cortex.

Ecker
et al.

(p.
584
) investigated the statistics of correlated firing in pairs of neurons from area V1 of awake macaque monkeys. In contrast to previous studies, correlations turned out to be very low, irrespective of the stimulus being shown to the animals, the distances of the recording sites, and the similarity of the neuron's receptive fields or response properties. In an accompanying modeling and recording paper,

Renart
et al.

(p.
587
) demonstrate how it is possible to have zero noise correlation, even among cells with common input.
A Tricyclic Aromatic Isomer of Hexasilabenzene
Authors: Abersfelder Kai , White Andrew J. P. , Rzepa Henry S. , Scheschkewitz David
Published: January 2010

Aromatic Silicon

Benzene has long intrigued chemists on account of the energy stabilization, termed aromaticity, which arises from π-electron delocalization around its ring framework. A persistent question has been how such stabilization would be impacted were the carbons to be replaced by heavier atoms such as silicon.

Abersfelder
et al.

(p.
564
) have prepared a benzene analog with Si atoms in place of all six-ring carbons, but a slightly altered bonding framework in which substituents outside the ring are no longer evenly distributed. Instead, the substituents pair up at two Si sites, leaving two other ring sites with no external appendages. The resulting compound no longer has a continuous network of π-electrons, but retains a degree of aromatic stabilization involving sigma and nonbonding electrons.
Platelets Amplify Inflammation in Arthritis via Collagen-Dependent Microparticle Production
Authors: Boilard Eric , Nigrovic Peter A. , Larabee Katherine , Watts Gerald F. M. , Coblyn Jonathan S. , Weinblatt Michael E. , Massarotti Elena M. , Remold-O’Donnell Eileen , Farndale Richard W. , Ware Jerry , Lee David M.
Published: January 2010

Platelet Microparticles Drive Inflammatory Arthritis

Platelets are best known for their critical role in blood clot formation during wound repair, but an appreciation for their role in inflammatory processes is growing. Platelet-derived cellular microparticles (MPs) are small membrane vesicles released from platelets in response to cell activation that can transport biomolecules throughout the body that have also been implicated in inflammatory processes.

Boilard
et al.

(p.
580
; see the Perspective by

Zimmerman and Weyrich

) have now found that platelet-derived MPs probably contribute to the inflammatory processes underlying rheumatoid arthritis, an autoimmune disease. The majority of MPs in synovial fluid from patients with various types of inflammatory arthritis were platelet-derived and, importantly, platelet-derived MPs were lacking in synovial fluid from osteoarthritis patients. Furthermore, platelet depletion abrogated disease development in a mouse model of inflammatory arthritis.
Apes Among the Tangled Branches of Human Origins
Authors: Harrison Terry
Published: January 2010

The evolution of apes between 23 and 5 million years ago set the scene for the emergence of the first hominins in Africa.
Bundling with X-rays
Authors: Safinya Cyrus R. , Li Youli
Published: January 2010

High-brilliance synchrotron radiation is used to trigger a reversible transition from randomly oriented filaments to hexagonal bundles.
Arsonists in Rheumatoid Arthritis
Authors: Zimmerman Guy A. , Weyrich Andrew S.
Published: January 2010

Inflammation associated with rheumatoid arthritis is stoked by platelets, expanding their roles into the immune system.
Measuring Subjective Well-Being
Authors: Layard Richard
Published: January 2010

How should human happiness and life-satisfaction be assessed?
Edwin G. Krebs (1918–2009)
Authors: Catterall William A. , Scott John D.
Published: January 2010

Defining how protein phosphorylation is regulated led to an explosion of knowledge about most cellular processes.
Bird-Dinosaur Link Firmed Up, And in Brilliant Technicolor
Authors: Stone Richard
Published: January 2010

On page
571
of this week's issue of
Science
, paleontologists unveil
Haplocheirus sollers
, a new genus of alvarezsauroid—a group of dinosaurs once thought to be flightless birds. The nearly complete skeleton is about 15 million years older than the earliest known bird,
Archaeopteryx
.
Climate Science Leader Rajendra Pachauri Confronts the Critics
Authors: Bagla Pallava
Published: January 2010

Intergovernmental Panel on Climate Change (IPCC) head Rajendra Kumar Pachauri has recently come under attack in the U.K. press for his lucrative stints as an adviser to companies including the Toyota Motor Corp. and Deutsche Bank. Earlier this week, Pachauri defended IPCC's work and shot back at critics who want to see him ousted as panel chair.
NRC Urges U.S. to Rethink Sale of Helium Reserve
Authors: Cho Adrian
Published: January 2010

The price of the heavier isotope of helium, helium-4, is artificially low and encouraging waste of a substance indispensable for numerous scientific and technological applications, says a U.S. National Research Council report released last week.
In Central California, Coho Salmon Are on the Brink
Authors: Miller Greg
Published: January 2010

As this year's winter spawning season draws to an end, biologists who've been surveying the subspecies of coho salmon that lives along the central California coast are reporting dismal numbers. A federal species recovery plan to be released next month has morphed into a species survival plan.
Test Shots Show Laser-Fusion Experiment Is on Target
Authors: Clery Daniel
Published: January 2010

In a
study
published online this week by
Science
, researchers at the National Ignition Facility, a huge laser for nuclear fusion experiments at Lawrence Livermore National Laboratory, describe their first experiments using all 192 of the facility's beams on test targets empty of fuel.
In the Deep Blue Sea
Authors: Pennisi Elizabeth
Published: January 2010

A survey of corals and their kin is showing the surprising evolutionary potential of the ocean's deepest waters, where no sunlight penetrates.
Little Castle on the Prairie
Authors: Kean Sam
Published: January 2010

Can $400 million and a “Manhattan Project for diabetes” transform South Dakota into a research hub?
Dose Response of Attenuated
Bordetella pertussis
BPZE1-Induced Protection in Mice
Authors: Mielcarek Nathalie , Debrie Anne-Sophie , Mahieux Severine , Locht Camille
Published: January 2010

Despite the availability of efficacious vaccines, the incidence of whooping cough is still high in many countries and is even increasing in countries with high vaccine coverage. Most severe and life-threatening pertussis cases occur in infants who are too young to be sufficiently protected by current vaccine regimens. As a potential solution to this problem, we have developed an attenuated live
Bordetella pertussis
vaccine strain, named BPZE1. Here, we show that after a single administration, BPZE1 induces dose-dependent protection against challenge with virulent
B. pertussis
in low-dose and in high-dose intranasal mouse lung colonization models. In addition, we observed BPZE1 dose-dependent antibody titers to
B. pertussis
antigens, as well as cell-mediated immunity, evidenced by the amounts of gamma interferon (IFN-γ) released from spleen cells upon stimulation with
B. pertussis
antigens. These two parameters may perhaps be used as readouts in clinical trials in humans that are currently being planned.
Development of a Bead Immunoassay To Measure Vi Polysaccharide-Specific Serum IgG after Vaccination with the
Salmonella enterica
Serovar Typhi Vi Polysaccharide
Authors: Staats Herman F. , Kirwan Shaun M. , Whisnant Carol C. , Stephenson James L. , Wagener Diane K. , Majumder Partha P.
Published: January 2010

Vi polysaccharide from
Salmonella enterica
serotype Typhi is used as one of the available vaccines to prevent typhoid fever. Measurement of Vi-specific serum antibodies after vaccination with Vi polysaccharide by enzyme-linked immunosorbent assay (ELISA) may be complicated due to poor binding of the Vi polysaccharide to ELISA plates resulting in poor reproducibility of measured antibody responses. We chemically conjugated Vi polysaccharide to fluorescent beads and performed studies to determine if a bead-based immunoassay provided a reproducible method to measure vaccine-induced anti-Vi serum IgG antibodies. Compared to ELISA, the Vi bead immunoassay had a lower background and therefore a greater signal-to-noise ratio. The Vi bead immunoassay was used to evaluate serum anti-Vi IgG in 996 subjects from the city of Kolkata, India, before and after vaccination. Due to the location being one where
Salmonella
serotype Typhi is endemic, approximately 45% of the subjects had protective levels of anti-Vi serum IgG (i.e., 1 μg/ml anti-Vi IgG) before vaccination, and nearly 98% of the subjects had protective levels of anti-Vi serum IgG after vaccination. Our results demonstrate that a bead-based immunoassay provides an effective, reproducible method to measure serum anti-Vi IgG responses before and after vaccination with the Vi polysaccharide vaccine.
An Oral versus Intranasal Prime/Boost Regimen Using Attenuated Human Rotavirus or VP2 and VP6 Virus-Like Particles with Immunostimulating Complexes Influences Protection and Antibody-Secreting Cell Responses to Rotavirus in a Neonatal Gnotobiotic Pig Model
Authors: Azevedo Marli S. P. , Gonzalez Ana Maria , Yuan Lijuan , Jeong Kwang-il , Iosef Cristiana , Van Nguyen Trang , Lovgren-Bengtsson Karin , Morein Bror , Saif Linda J.
Published: January 2010

We determined the impact of mucosal prime/boost regimens and vaccine type (attenuated Wa human rotavirus [AttHRV] or nonreplicating Wa 2/6 rotavirus-like particles [VLP]) on protection and antibody-secreting cell (ASC) responses to HRV in a neonatal gnotobiotic pig disease model. Comparisons of delivery routes for AttHRV and evaluation of nonreplicating VLP vaccines are important as alternative vaccine approaches to overcome risks associated with live oral vaccines. Groups of neonatal gnotobiotic pigs were vaccinated using combinations of oral (PO) and intranasal (IN) inoculation routes as follows: (i) 3 oral doses of AttHRV (AttHRV3×PO); (ii) AttHRV3×IN; (iii) AttHRVPO, then 2/6VLP2×IN; (iv) AttHRVIN, then 2/6VLP2×IN; and (v) mock-inoculated controls. Subsets of pigs from each group were challenged with virulent Wa HRV [P1A(8) G1] (4 weeks post-primary inoculation) to assess protection. The AttHRVPO+2/6VLP2×IN pigs had the highest protection rates against virus shedding and diarrhea (71% each); however, these rates did not differ statistically among the vaccine groups, except for the AttHRVIN+2/6VLPIN group, which had a significantly lower protection rate (17%) against diarrhea. The isotype, magnitude, and tissue distribution of ASCs were analyzed by enzyme-linked immunospot assay. The highest mean numbers of virus-specific IgG and IgA ASCs were observed pre- and postchallenge in both intestinal and systemic lymphoid tissues of the AttHRVPO+2/6VLPIN group. Thus, the AttHRVPO+2/6VLPIN vaccine regimen using immunostimulating complexes (ISCOM) and multiple mucosal inductive sites, followed by AttHRV3×PO or IN regimens, were the most effective vaccine regimens, suggesting that either AttHRVPO+2/6VLPIN or AttHRV3×IN may be an alternative approach to AttHRV3×PO for inducing protective immunity against rotavirus diarrhea.
Impact of a Pneumococcal Conjugate Vaccination Program on Carriage among Children in Norway
Authors: Vestrheim Didrik F. , Høiby E. Arne , Aaberge Ingeborg S. , Caugant Dominique A.
Published: January 2010

In July 2006, the seven-valent pneumococcal conjugate vaccine (PCV7) was introduced in Norway with a reduced (2 doses + 1 boost) dose schedule. Post-PCV7 shifts in pneumococcal reservoirs were assessed by two point prevalence studies of nasopharyngeal colonization among children in day care centers, before (2006) and after (2008) widespread use of PCV7. Nasopharyngeal swabs were obtained from 1,213 children, 611 in 2006 and 602 in 2008. A total of 1,102 pneumococcal isolates were recovered. Serotyping, multilocus sequence typing, and antimicrobial drug susceptibility testing were performed on all isolates. Although carriage of PCV7 serotypes decreased among both vaccinated and unvaccinated children, the overall prevalence of pneumococcal carriage remained high (80.4%) after vaccine introduction. The pneumococcal populations were diverse, and in the shift toward non-PCV7 serotypes, expansion of a limited number of established clonal complexes was observed. While non-antimicrobial-susceptible clones persisted among PCV7 serotypes, antimicrobial resistance did not increase among non-PCV7 serotypes. Direct and indirect protection of PCV7 against nasopharyngeal colonization was inferred from an overall decrease in carriage of PCV7 serotypes. No preference was found for nonsusceptible clones among the replacing non-PCV7 serotypes.