bluuebunny/crossref_metadata_2025_split huggingface dataset:
A radiobiological investigation on dose and dose rate for permanent implant brachytherapy of breast using or sources
Authors: Baltas Dimos , Lymperopoulou Georgia , Löffler Edgar , Mavroidis Panayiotis 
Published: June 2010

PurposeThe present report addresses the question of what could be the appropriate dose and dose rate for and permanent seed implants for breast cancer as monotherapy for early stage breast cancer. This is addressed by employing a radiobiological methodology, which is based on the linear quadratic model, to identify a biologically effective dose (BED) to the prescription point of the brachytherapy implant, which would produce equivalent cell killing (or same cell survival) when compared to a specified external radiotherapy scheme.MethodsIn the present analysis, the tumor and normal tissue BED ratios of brachytherapy and external radiotherapy are examined for different combinations of tumor proliferation constant , ratios, initial dose rate , and reference external radiotherapy scheme (50 or 60 Gy in 2 Gy per fraction). The results of the radiobiological analysis are compared against other reports and clinical protocols in order to examine possible opportunities of improvement.ResultsThe analysis indicates that physical doses of approximately 100–110 Gy delivered with an initial dose rate of around and 78–80 Gy delivered at for and permanent implants, respectively, are equivalent to 50 Gy external beam radiotherapy (EBRT) in 2 Gy per fraction. Similarly, for physical doses of approximately 115–127 Gy delivered with an initial dose rate of around and 92 Gy delivered at for and , respectively, are equivalent to 60 Gy EBRT in 2 Gy per fraction. It is shown that the initial dose rate required to produce isoeffective tumor response with 50 or 60 Gy EBRT in 2 Gy per fraction increases as the repopulation factor increases, even though repopulation is also considered in EBRT. Also, the initial dose rate increases as the value of the ratio decreases. The impact of the different ratios on the ratio of the tumor BEDs is significantly large for both the and implants with the deviation between the ratios and those using the 4.0 and 3.5 Gy values ranging between 18% and 22% in most of the cases.ConclusionsFor the cases of and , the equivalent physical doses to 50 Gy EBRT in 2 Gy per fraction are associated with an overdosage of the involved normal tissue in the range of 4%–16% and an underdosage by 10%–15% for a BED for normal tissue, using an value of 3.0 Gy of 100 Gy. These values are lower by 10%–20% than the published value of 124 Gy for and by about 13% when compared to the published isoeffective dose of 90 Gy for . Similarly, the equivalent physical doses to 60 Gy EBRT in 2 Gy per fraction are associated with an overdosage of the involved normal tissue by 10%–20% and an underdosage by 4%–10% for of 110 Gy.
Dynamic contrast enhanced–MRI in head and neck cancer patients: Variability of the precontrast longitudinal relaxation time
Authors: Craciunescu Oana , Brizel David , Cleland Esi , Yoo David , Muradyan Naira , Carroll Madeline , Barboriak Daniel , MacFall James 
Published: June 2010

Purpose: Calculation of the precontrast longitudinal relaxation times is an integral part of the Tofts‐based pharmacokinetic (PK) analysis of dynamic contrast enhanced–magnetic resonance images. The purpose of this study was to investigate the interpatient and over time variability of in head and neck primary tumors and involved nodes and to determine the median for primary and nodes . The authors also looked at the implication of using voxel‐based values versus region of interest (ROI)‐based on the calculated values for vascular permeability and extracellular volume fraction .Methods: Twenty head and neck cancer patients receiving concurrent chemoradiation and molecularly targeted agents on a prospective trial comprised the study population. Voxel‐based 's were generated using a gradient echo sequence on a 1.5 T MR scanner using the variable flip angle method with two flip angles [J. A. Brookes et al., “Measurement of spin‐lattice relaxation times with FLASH for dynamic MRI of the breast,” Br. J. Radiol. 69, 206–214 (1996)]. The voxel‐based , , and were calculated using iCAD's® (Nashua, NH) software. The mean 's in muscle and fat ROIs were calculated . To assess reliability of ROI drawing, values from ROIs delineated by 2 users (A and B) were calculated as the average of the 's for 14 patients. For a subset of three patients, the variability from baseline to end of treatment was also investigated. The and from primary and node ROIs were calculated using voxel‐based values and and differences reported.Results: The calculated values for fat and muscle are within the range of values reported in literature for 1.5 T, i.e., and . The average over 14 patients of the 's based on drawings by users A and B were , , , and . The absolute percentage difference between and calculated with voxel‐based versus ranged from 6% to 81% and from 2% to 24%, respectively.Conclusions: There is a certain amount of variability in the median values between patients, but the differences are not significant. There were also no statistically significant differences between the values for primary and nodes at baseline and the subsequent time points ( Friedman test). Voxel‐based calculations are essential when quantitative Tofts‐based PK analysis in heterogeneous tumors is needed. In the absence of mapping capability, when a relative, qualitative analysis is deemed sufficient, a value of can be used as an estimate for for both the primary tumor and the affected nodes in head and neck cancers at all the time points considered.
On the feasibility of MRI‐guided navigation to demarcate breast cancer for breast‐conserving surgery
Authors: Alderliesten Tanja , Loo Claudette , Paape Anita , Muller Sara , Rutgers Emiel , Peeters Marie‐Jeanne Vrancken , Gilhuijs Kenneth 
Published: June 2010

PurposeThe aim of this study was to investigate the feasibility of image‐guided navigation approaches to demarcate breast cancer on the basis of preacquired magnetic resonance (MR) imaging in supine patient orientation.MethodsStrategies were examined to minimize the uncertainty in the instrument‐tip position, based on the hypothesis that the release of instrument pressure returns the breast tissue to its predeformed state. For this purpose, four sources of uncertainty were taken into account: (1) : Uncertainty in the reproducibility of the internal mammary gland geometry during repeat patient setup in supine orientation; (2) : Residual uncertainty in registration of the breast after compensation for breathing motion using an external marker; (3) : Uncertainty in the reconstructed location of the tip of the needle using an optical image‐navigation system (phantom experiments, ); and (4) : Uncertainty in displacement of breast tumors due to needle‐induced tissue deformations (patients, ). A Monte Carlo study was performed to establish the 95% confidence interval (CI) of the combined uncertainties. This region of uncertainty was subsequently visualized around the reconstructed needle tip as an additional navigational aid in the preacquired MR images. Validation of the system was performed in five healthy volunteers (localization of skin markers only) and in two patients. In the patients, the navigation system was used to monitor ultrasound‐guided radioactive seed localization of breast cancer. Nearest distances between the needle tip and the tumor boundary in the ultrasound images were compared to those in the concurrently reconstructed MR images.ResultsBoth and were normally distributed with and , respectively. Taking prior estimates for and into account, the combined impact resulted in 3.9 mm uncertainty in the position of the needle tip (95% CI) after release of pressure. The volunteer study showed a targeting accuracy comparable to that in the phantom experiments: versus , respectively. In the patient feasibility study, the deviations were within the 3.9 mm CI.ConclusionsImage‐guided navigation to demarcate breast cancer on the basis of preacquired MR images in supine orientation appears feasible if patient breathing is tracked during the navigation procedure, positional uncertainty is visualized and pressure on the localization instrument is released prior to verification of its position.
The effect of limited MR field of view in MR/PET attenuation correction
Authors: Delso Gaspar , Martinez‐Möller Axel , Bundschuh Ralph A. , Nekolla Stephan G. , Ziegler Sibylle I. 
Published: June 2010

PurposeA critical question in the development of combined MR/PET scanners is whether MR can provide the tissue attenuation data required for PET reconstruction. Unfortunately, MR images are often unable to encompass the entire patient. The resulting truncation in the transverse plane leads to incomplete attenuation maps, causing artifacts in the reconstructed PET image. This article describes the experiments performed to quantify these artifacts. A method to compensate the missing data was evaluated to determine whether software correction is possible or whether additional transmission hardware has to be included in the scanner.MethodsThree studies were made. First, simulated PET data were used to quantify the bias due to an incomplete attenuation map. A set of spherical lesions was simulated in the lungs and mediastinum of a patient. The data were reconstructed with complete and partial attenuation maps and the uptake differences were evaluated. Second, clinical data from PET/CT oncology patients were used. To reproduce the expected conditions in an MR/PET scanner, only patients scanned with the arms resting along the body were considered. These scans were then used to create maps of the reconstruction bias due to field of view (FOV) limitations. Lastly, a PET reconstruction with incomplete attenuation data was evaluated as a means to obtain attenuation information beyond the MR FOV. The patient outline was automatically segmented with a three‐dimensional snake algorithm and used to fill the truncated data in the attenuation map.ResultsAverage bias up to 15% and local biases up to 50% were estimated when PET data were reconstructed with incomplete attenuation information. Completing the attenuation map with data extracted from a PET prereconstruction globally reduced these biases to below 10%. This correction proved to be tolerant to inaccuracies in positioning and attenuation values. However, local artifacts up to 20% could still be found near the edges of the MR FOV.ConclusionsMR FOV restrictions can indeed make the reconstructed PET data unacceptable for diagnostic purposes. Biases can be globally compensated by automatic preprocessing of the attenuation map. However, inaccuracies in the correction will result in small artifacts near the periphery of the image that could lead to false‐positive findings.
Regression error estimation significantly improves the region‐of‐interest statistics of noisy MR images
Authors: Juras Vladimir , Zbýň Štefan , Szomolanyi Pavol , Trattnig Siegfried 
Published: June 2010

PurposeThe region‐of‐interest (ROI) selection and evaluation is one of the key factors in the successful evaluation of radiological images. However, the presence of noise in images may lead to incorrect diagnosis. The aim of this study was to test the hypothesis that the weighting by error estimation in ROI assessment might significantly improve the validity of the results.MethodsAs a model, the data maps of the transverse relaxation time constants from patients who underwent a matrix‐associated chondrocyte transplantation procedure on the femoral condyle were analyzed. Artificial noise with a Rician density probability distribution was added to each TE image. ROIs were processed either as a regular arithmetic mean or as a weighted mean, in which weighted coefficients were calculated with regard to fitting error estimates [coefficient of determination (); root mean squared error (RMSE), mean absolute error (MSE), mean squared error (MAE), and chi‐squared error ()].ResultsThe global values in repair tissue (, ; range 51–70 ms) and in healthy cartilage (, ; range 40–60 ms) were significantly different . With a 45% or greater decrease from the original SNR value (corresponding to a noise level of 35% of random value), the statistical significance was lost ; however, the use of the coefficient of determination as a correction factor was able to maintain the p‐value of up to a 56% decrease from the original SNR value.ConclusionsThe results of this study can prospectively be applied in a wide range of radiological imaging techniques in cases when error estimation is possible. Our analysis on MR images with artificially added noise showed that utilization of the correlation of determination as a weighting parameter in ROI evaluation may significantly improve the differentiation between native and transplanted cartilage tissue in noisy images. This could be an added benefit in the non‐invasive monitoring of the post‐operative status of patients with cartilage transplants if the MR images are not ideal (e.g., lower field strength or lower SNR).
Lung cancer and exposure to quartz and diesel exhaust in Swedish iron ore miners with concurrent exposure to radon
Authors: Bergdahl Ingvar A , Jonsson Håkan , Eriksson Kåre , Damber Lena , Järvholm Bengt 
Published: June 2010

ObjectivesStudies of underground miners have documented an increased risk of lung cancer mainly linked to radon exposure but possibly influenced by other concurrent exposures.MethodsA cohort study was carried out in 8321 iron ore miners with low exposure to radon, employed in 1923–1998 and followed up for lung cancer in 1958–2000. Historical exposures to radon, crystalline silica and diesel exhaust were assessed. Data including exposure to radon, quartz and diesel exhaust from another mine with higher exposure to radon were reanalysed.ResultsMiners had increased risk for lung cancer (SIR 1.48 (95% CI 1.22 to 1.78), based on 112 cases during 227 000 person-years). The increased risk could not be explained by exposure to radon or diesel exhaust but was associated with exposure to crystalline silica: SIR 0.96 (0.53 to 1.62), 1.45 (1.10 to 1.87), 1.99 (1.31 to 2.90) and 1.77 (0.92 to 3.10) in groups with exposure to 0, 0–2, 2–5 and >5 mg years/m3, respectively. Reanalysis of data from the other mine indicated that quartz was a possible confounder in the analysis of relationship between radon and lung cancer. In the highest radon exposed group, the point estimate for the RR decreased from 5.65 to 3.90 when adjusting for concurrent exposure to quartz.ConclusionsCrystalline silica, a known carcinogen, probably affects lung cancer risk in iron ore miners. The main implication of the results is for interpretation of the dose–response curve for radon and lung cancer in underground iron ore miners. Since exposure to radon and quartz is often correlated, quartz exposure can be an important confounder.
Systemic inflammation, heart rate variability and air pollution in a cohort of senior adults
Authors: Luttmann-Gibson Heike , Suh Helen H , Coull Brent A , Dockery Douglas W , Sarnat Stefanie Ebelt , Schwartz Joel , Stone Peter H , Gold Diane R 
Published: June 2010

ObjectivesShort-term elevation of ambient particulate air pollution has been associated with autonomic dysfunction and increased systemic inflammation, but the interconnections between these pathways are not well understood. We examined the association between inflammation and autonomic dysfunction and effect modification of inflammation on the association between air pollution and heart rate variability (HRV) in elderly subjects.Methods25 elderly subjects in Steubenville, Ohio, were followed up to 24 times with repeated 30-min ECG Holter monitoring (545 observations). C-reactive protein (CRP), fibrinogen, interleukin-6 (IL-6), soluble inter-cellular adhesion molecule 1 (sICAM-1), and white blood cell and platelet counts were measured in peripheral blood samples collected in the first month of the study. Increased systemic inflammation was defined for subjects within the upper 20% of the distribution for each marker. A central ambient monitoring station provided daily fine particle (PM2.5) and sulphate (SO42−) data. Linear mixed models were used to identify associations between inflammatory markers and HRV and to assess effect modification of the association between air pollution and HRV due to inflammatory status.ResultsA 5.8 mg/l elevation in CRP was associated with decreases of between −8% and –33% for time and frequency domain HRV outcomes. A 5.1 μg/m3increase in SO42−on the day before the health assessment was associated with a decrease of −6.7% in the SD of normal RR intervals (SDNN) (95% CI −11.8% to −1.3%) in subjects with elevated CRP, but not in subjects with lower CRP (p value interaction=0.04), with similar findings for PM2.5.ConclusionsIncreased systemic inflammation is associated with autonomic dysfunction in the elderly. Air pollution effects on reduced SDNN are stronger in subjects with elevated systemic inflammation.
Long-term effects of mechanized stump treatment against Heterobasidion annosum root rot in Picea abies
Authors: Oliva Jonàs , Thor Magnus , Stenlid Jan 
Published: June 2010

Airborne Heterobasidion annosum (Fr.) Bref. sensu lato infections can be controlled by winter thinning or by mechanically spreading urea or Phlebiopsis gigantea (Fr.) Jülich spores on stump surfaces during summer thinning operations. The long-term outcomes of these control methods when applied as part of the conventional forest operations are unclear. We studied the rot incidence and population structure of H. annosum in plots of Picea abies (L.) Karst. thinned in winter or thinned in summer with and without treatment of the stumps. Plots were distributed among 11 stands in Sweden representing two different land use histories: forest and agricultural. After 13 years, the effect of stump treatment on rot incidence was only evident in stands on former agricultural land. In stands planted on former forest land with higher levels of preexisting rot than on former agricultural land, the expansion of preexisting genets of H. annosum might have masked the effects of stump protection. In former forest land, unprotected summer plots showed a greater diversity of H. annosum genotypes and a smaller number of trees infected by each genet than in protected plots, suggesting that protection treatments prevented the establishment of new genets, which may result in a reduced rot incidence in the future.
Changes in community structure of ectomycorrhizal fungi associated with Pinus montezumae across a volcanic soil chronosequence at Sierra Chichinautzin, Mexico
Authors: Reverchon Frédérique , Ortega-Larrocea María del Pilar , Pérez-Moreno Jesús , Peña-Ramírez Víctor Manuel , Siebe Christina 
Published: June 2010

Ectomycorrhizal (ECM) communities of Pinus montezumae Lamb. var. montezumae were studied across a volcanic soil chronosequence at Sierra del Chichinautzin, Mexico, to investigate differences in community structure at sites with different soil quality. Study sites were located on volcanic soils of different ages. Both aboveground and belowground fungal communities were compared for 3 years. Species abundance, richness, and diversity were compared among sites. Significant differences were found among the three sites for sporocarp abundance and biomass but not for total ECM root tips. The more diverse sporocarp community was found at the youngest, less fertile site. Dominant species at the sporocarp and ECM morphotype levels differed across the chronosequence. The largest proportion of sporocarp species was site-exclusive, which suggests that aboveground communities depend upon soil conditions. Contrarily, 85% of ECM morphotypes were present at least at two sites. The poor correspondence between the aboveground and belowground views of the ECM fungal community may be due to differences in sampling methodology and level of identification. Inocybe and Laccaria species were abundant fruiters at all sites, and as multisite fungi, they may be tested for inoculum efficiency to be used in reforestation programs in the surroundings of Mexico City.
Evaluation of two risk mitigation strategies for dealing with fire-related uncertainty in timber supply modelling
Authors: Savage David W. , Martell David L. , Wotton B. Mike 
Published: June 2010

We embedded a linear programming timber harvest scheduling model into an aspatial stochastic simulation model of a flammable forest to evaluate two fire risk mitigation strategies. The harvest scheduling model is solved repeatedly to produce harvest schedules within a rolling planning horizon framework. The risk mitigation strategies we examined were (1) whether or not to account for fire in the planning model and (2) replanning interval. We evaluated those strategies under four representative fire regimes. We found that accounting for fire in the planning model reduced the harvest volume variability as fire activity increased (i.e., for average annual burn fractions ≥0.45%), but replanning intervals over a range of 1 to 10 years had little impact on harvest volume variability. We also developed a risk analysis decision-making aid that forest managers can use to help deal with fire-related uncertainty. Our results suggest that risk-averse forest managers should account for fire while planning, especially when burn fractions exceed 0.45%.
Production ecology ofThuja occidentalis
Authors: Hofmeyer Philip V. , Seymour Robert S. , Kenefic Laura S. 
Published: June 2010

Equations to predict branch and tree leaf area, foliar mass, and stemwood volume were developed from 25 destructively sampled northern white-cedar ( Thuja occidentalis L.) trees, a species whose production ecology has not been studied. Resulting models were applied to a large sample of 296 cored trees from 60 sites stratified across a soil gradient throughout northern Maine. Nonlinear regression analysis was used to assess alternative forms of the relationship between volume increment (VINC) and projected leaf area (PLA); analysis of covariance was used compare stemwood growth efficiency (GE) among soil-site classes, light exposure classes, and the presence of decay. Stem volume was estimated with Honer’s equation ( T.G. Honer. 1967. Forest Management Research and Services Institute ) with refitted parameters. PLA was best predicted with Maguire and Bennett’s nonlinear model ( D.A. Maguire and W.S. Bennett. 1996. Can. J. For. Res. 26: 1991–2005 ) using sapwood area or crown length and the ratio of tree height to diameter at breast height. A sigmoid model form captured the relationship between VINC and PLA more precisely and with less bias than the simple power function; this implies that the relationship between GE and PLA reaches a peak rather than decreases monotonically. At PLAs >50 m2, GE gradually declined with increasing crown size and was significantly influenced by site and light exposure. With PLA, site, and light held constant, decayed trees had a significantly lower (by 11%) GE than sound stems, a finding not previously reported for other tree species.