Differential Bioaccumulation of Mercury and Selenium in Stomach Contents and Tissues of Three Colorado, USA, Cutthroat Trout Populations.

Total mercury (THg) and selenium (TSe) levels were measured in stomach contents (SC) and twelve tissues of cutthroat trout (Oncorhynchus clarkii) occurring in three high-elevation lakes of Colorado, USA, inhabiting watersheds absent past and current mining activities. For 32 of 36 tissues, including muscle, mean THg wet weight (ww) concentrations were greater than in the diet (SC) for all sites, indicating biomagnification. Ranges of THg (µg/kg ww) for SC and stomach tissue (ST) were 1.23-73.54 and 14.55-61.35, respectively. Selenium concentrations in fish muscle were not greater than in the SC indicating a trophic transfer factor < 1.0. However, in several other tissues, mean Se dry weight (dw) levels were greater than in SC for all three lakes. Ranges of TSe for SC and ST were 166-7544 and 797-7523 (µg/kg dw), respectively. The muscle to egg/ovary ratio for Se averaged 2.30, 4.60, and 2.68 for the three populations. The variability of SC (planktonic vs. benthic) and differential distributions of THg and TSe in SC and organ-tissues generated questions focusing on the seasonal, physiological, and genetic drivers of these organometal(loid)s in subalpine trout.

Accurate group velocity estimation for unmanned aerial vehicle-based acoustic atmospheric tomography.

Acoustic atmospheric tomography calculates temperature and wind velocity fields in a slice or volume of atmosphere based on travel time estimates between strategically located sources and receivers. The technique discussed in this paper uses the natural acoustic signature of an unmanned aerial vehicle as it overflies an array of microphones on the ground. The sound emitted by the aircraft is recorded on-board and by the ground microphones. The group velocities of the intersecting sound rays are then derived by comparing these measurements. Tomographic inversion is used to estimate the temperature and wind fields from the group velocity measurements. This paper describes a technique for deriving travel time (and hence group velocity) with an accuracy of 0.1% using these assets. This is shown to be sufficient to obtain highly plausible tomographic inversion results that correlate well with independent SODAR measurements.

Anti-platelet and anti-hypertension medication use in patients with fibromuscular dysplasia: Results from the United States Registry for Fibromuscular Dysplasia.

Fibromuscular dysplasia (FMD), a non-inflammatory arterial disease, may lead to renovascular hypertension (HTN) and cerebrovascular disease. Little is known about medication use in FMD. Clinical features and medication use were reviewed in a national FMD registry (12 US sites). Medication usage was assessed in raw and adjusted analyses. Covariates included demographic characteristics, co-morbid conditions and vascular bed involvement. A total of 874 subjects (93.6% female) were included in the analysis. Mean age was 55.6±13.1 years, 74.5% had HTN, 25.4% had a history of transient ischemic attack or stroke, and 7.5% had a history of coronary artery disease (CAD). Renal and cerebrovascular arteries were affected in 70.4% and 74.7%, respectively. Anti-platelet agents were administered to 72.9% of patients. In multivariate analyses, factors associated with a greater likelihood of anti-platelet agent use were older age (OR=1.02 per year, p=0.005), CAD (OR=3.76, p=0.015), cerebrovascular artery FMD involvement in isolation (OR=2.31, p<0.0001) or a history of previous intervention for FMD (OR=1.52, p=0.036). A greater number of anti-HTN medications was evident in isolated renal versus isolated cerebrovascular FMD patients. Factors associated with a greater number of anti-HTN medications were older age (OR=1.03 per year, p<0.0001), history of HTN (OR=24.04, p<0.0001), history of CAD (OR=2.71, p=0.0008) and a history of a previous therapeutic procedure (OR=1.72, p=0.001). In conclusion, in FMD, medication use varies based on vascular bed involvement. Isolated renal FMD patients receive more anti-HTN agents and there is greater anti-platelet agent use among patients with cerebrovascular FMD. Further studies correlating medication use in FMD with clinically meaningful patient outcomes are necessary.

The feasibility of unmanned aerial vehicle-based acoustic atmospheric tomography.

A technique for remotely monitoring the near-surface air temperature and wind fields up to altitudes of 1 km is presented and examined. The technique proposes the measurement of sound spectra emitted by the engine of a small unmanned aerial vehicle using sensors located on the aircraft and the ground. By relating projected and observed Doppler shifts in frequency and converting them into effective sound speed values, two- and three-dimensional spatially varying atmospheric temperature and wind velocity fields may be reconstructed using tomography. The feasibility and usefulness of the technique relative to existing unmanned aerial vehicle-based meteorological techniques using simulation and trials is examined.

Epidemiology of peripheral arterial disease and critical limb ischemia in an insured national population.

BACKGROUND: Critical limb ischemia (CLI) represents the most severe clinical manifestation of peripheral arterial disease (PAD) and is the major cause of ischemic amputation in the United States. Risk factors and the associated incidence and prevalence of CLI have not been well described in the general population. This study describes the risk factors for PAD progression to CLI and estimates the annual incidence and prevalence of CLI in a representative United States patient cohort. METHODS: This was a retrospective cohort analysis of adults with commercial, Medicare supplemental, or Medicaid health insurance who had at least one PAD or CLI health care claim from January 1, 2003, through December 31, 2008, and 12 months of continuous coverage. Two subgroups of CLI presentation were identified: primary CLI (patients without any prior PAD or subsequent PAD diagnostic code >30 days after CLI diagnostic code) and secondary CLI (patients with prior PAD or subsequent PAD diagnostic codes ≤30 days of a CLI diagnostic code). Patterns of presentation, annual incidence, and prevalence of CLI were stratified by health care plan. Risk factors for progression to CLI were compared by presentation type. RESULTS: From 2003 to 2008, the mean annual incidence of PAD was 2.35% (95% confidence interval [CI], 2.34%-2.36%) and the incidence of CLI was 0.35% (95% CI, 0.34%-0.35%) of the eligible study population, with primary and secondary presentations occurring at similar rates. The mean annualized prevalence of PAD was 10.69% (95% CI, 10.67%10.70%) and the mean annualized prevalence of CLI was 1.33% (95% CI, 1.32%-1.34%) of the eligible study population, and two-thirds of the cases presented as secondary CLI. CLI developed in 11.08% (95% CI, 11.30%-11.13%) of patients with PAD. A multivariable model demonstrated that diabetes, heart failure, stroke, and renal failure were stronger predictors of primary rather than secondary CLI presentation. CONCLUSIONS: These data establish new national estimates of the incidence and prevalence of CLI and define key risk factors that contribute to primary or secondary presentations of CLI within a very large contemporary insured population cohort in the United States.

Blood pressure response to renal artery stenting in 901 patients from five prospective multicenter FDA-approved trials.

BACKGROUND: Renal artery stent revascularization is commonly used for renovascular hypertension. Clinical predictors associated with blood pressure (BP) improvement after renal artery stent revascularization are not well understood. METHODS: Patient-level data from 901 patients in five prospective multicenter Food and Drug Administration-approved investigational device exemption studies of renal artery stent revascularization was pooled. BP response was defined as reduction of systolic BP (SBP) by >10 mm Hg. Stent patency was defined within each study. Associations of BP reduction were determined by logistic regression. RESULTS: Of 901 patients, complete outcome information was available in 527. Of these, 212/527 (40%) were male, mean age was 63 ± 13 years, 196/544 (36%) were diabetic and 504/527 (96%) had a SBP ≥ 140 mm Hg or DBP ≥ 90 mm Hg at baseline. Compared to baseline, 9-month systolic (164 ± 21 mm Hg vs. 146 ± 22 mm Hg, P < 0.0001) and diastolic (79 ± 13 mm Hg vs. 76 ± 12 mm Hg, P < 0.0001) BP declined significantly. Nine-month stent patency was 90% (305/339). In a univariate analysis, baseline SBP >150 mm Hg (OR = 4.09, CI = 2.74-6.12, P < 0.0001) was positively associated with BP response following renal artery stent revascularization. In a multivariable analysis, baseline SBP remained associated with a positive BP response (OR = 1.76, CI = 1.53-2.03, P < 0.0001). CONCLUSIONS: In the largest pooled dataset of patients treated with renal artery stent revascularization, SBP and DBP were significantly lower at 9-months. Elevated baseline SBP (>150 mm Hg) was strongly associated with BP reduction after the procedure.

Effect of tirasemtiv, a selective activator of the fast skeletal muscle troponin complex, in patients with peripheral artery disease.

Tirasemtiv (CK-2017357), a novel small-molecule activator of the fast skeletal muscle troponin complex, slows the rate of calcium release from troponin, thus sensitizing fast skeletal muscle fibers to calcium. In preclinical studies, tirasemtiv increased muscle force and delayed the onset and reduced the extent of muscle fatigue during hypoxia in vitro and muscle ischemia in situ. This study evaluated the effect of single doses of tirasemtiv on measures of skeletal muscle function and fatigability in patients with stable calf claudication due to peripheral artery disease (PAD). Sixty-one patients with an ankle-brachial index ≤0.90 in the leg with claudication received single double-blind doses of tirasemtiv 375 mg and 750 mg and matching placebo in random order about 1 week apart. After 33 patients were treated, the 750 mg dose was decreased to 500 mg due to adverse events and these dose groups were combined for analysis. On each study day, bilateral heel-raise testing was performed before and at 3 and 6 hours after dosing; a 6-minute walk test was performed at 4 hours after dosing. Claudicating calf muscle performance was increased at the highest dose and plasma concentration of tirasemtiv; however, the 6-minute walk distance decreased with both the dose and plasma concentration of tirasemtiv, possibly due to dose-related adverse events, particularly dizziness, that could impede walking ability. In conclusion, the mechanism of fast skeletal muscle troponin activation improved muscle function but not 6-minute walking distance in patients with claudication due to PAD. CLINICALTRIALSGOV IDENTIFIER NCT01131013:

Evaluation of Acuros XB algorithm based on RTOG 0813 dosimetric criteria for SBRT lung treatment with RapidArc.

The Radiation Therapy Oncology Group (RTOG) 0813 protocol requires the use of dose calculation algorithms with tissue heterogeneity corrections to compute dose on stereotactic body radiation therapy (SBRT) non-small cell lung cancer (NSCLC) plans. A new photon dose calculation algorithm called Acuros XB (AXB) has recently been implemented in the Eclipse treatment planning system (TPS). The main purpose of this study was to compare the dosimetric results of AXB with that of anisotropic analytical algorithm (AAA) for RTOG 0813 parameters. Additionally, phantom study was done to evaluate the dose prediction accuracy of AXB and AAA beyond low-density medium of different thicknesses by comparing the calculated results with the measurements. For the RTOG dosimetric study, 14 clinically approved SBRT NSCLC cases were included. The planning target volume (PTV) ranged from 3.2-43.0 cc. RapidArc treatment plans were generated in the Eclipse TPS following RTOG 0813 dosimetric criteria, and treatment plans were calculated using AAA with heterogeneity correction (AAA plans). All the AAA plans were then recalculated using AXB with heterogeneity correction (AXB plans) for identical beam parameters and same number of monitor units. The AAA and AXB plans were compared for following RTOG 0813 parameters: ratio of prescription isodose volume to PTV (R100%), ratio of 50% prescription isodose volume to PTV (R50%), maximal dose 2 cm from the PTV in any direction as a percentage of prescription dose (D2cm), and the percentage of ipsilateral lung receiving dose equal to or larger than 20 Gy (V20). The phantom study showed that the results of AXB had better agreement with the measurements, and the difference ranged from -1.7% to 2.8%. The AAA results showed larger disagreement with the measurements, with differences from 4.1% to 12.5% for field size 5 × 5cm2 and from 1.4% to 6.8% for field size 10 × 10 cm2. The results from the RTOG SBRT lung cases showed that, on average, the AXB plans produced lower values for R100%, R50%, and D2cm by 4.96%, 1.15%, and 1.60%, respectively, but higher V20 of ipsilateral lung by 1.09% when compared with AAA plans. In the set of AAA plans, minor deviation was seen for R100% (six cases), R50% (nine cases), D2cm (four cases), and V20 (one case). Similarly, the AXB plans also showed minor deviation for R100% (one case), R50% (eight cases), D2cm (three cases), and V20 (one case). The dosimetric results presented in the current study show that both the AXB and AAA can meet the RTOG 0813 dosimetric criteria.

Total Ischemic Event Reduction With Rivaroxaban After Peripheral Arterial Revascularization in the VOYAGER PAD Trial.

BACKGROUND: Patients with peripheral artery disease (PAD) undergoing lower extremity revascularization (LER) are at high risk of major adverse limb and cardiovascular events. The VOYAGER PAD (Efficacy and Safety of Rivaroxaban in Reducing the Risk of Major Thrombotic Vascular Events in Subjects With Symptomatic Peripheral Artery Disease Undergoing Peripheral Revascularization Procedures of the Lower Extremities) trial demonstrated that rivaroxaban 2.5 mg twice daily reduced first events by 15%. The benefit of rivaroxaban on total (first and subsequent) events in this population is unknown. OBJECTIVES: This study sought to evaluate the total burden of vascular events in patients with PAD after LER and the efficacy of low-dose rivaroxaban on total events. METHODS: VOYAGER PAD randomized patients with PAD undergoing LER to rivaroxaban 2.5 mg twice daily plus aspirin or aspirin alone. The primary endpoint was time to first event of acute limb ischemia, major amputation of a vascular cause, myocardial infarction, ischemic stroke, or cardiovascular death. The current analysis considered all events (first and subsequent) for components of the primary endpoint as well as additional vascular events including peripheral revascularizations and venous thromboembolism. HRs were estimated by marginal proportional hazards models. RESULTS: Among 6,564 randomized events, there were 4,714 total first and subsequent vascular events including 1,614 primary endpoint events and 3,100 other vascular events. Rivaroxaban reduced total primary endpoint events (HR: 0.86; 95% CI: 0.75-0.98; P = 0.02) and total vascular events (HR: 0.86; 95% CI: 0.79-0.95; P = 0.003). An estimated 4.4 primary and 12.5 vascular events per 100 participants were avoided with rivaroxaban over 3 years. CONCLUSIONS: Patients with symptomatic PAD who are undergoing LER have a high total event burden that is significantly reduced with rivaroxaban. Total event reduction may be a useful metric to quantify the efficacy of rivaroxaban in this setting. (Efficacy and Safety of Rivaroxaban in Reducing the Risk of Major Thrombotic Vascular Events in Subjects With Symptomatic Peripheral Artery Disease Undergoing Peripheral Revascularization Procedures of the Lower Extremities [VOYAGER PAD]; NCT02504216).

C-reactive protein as a risk factor for coronary heart disease: a systematic review and meta-analyses for the U.S. Preventive Services Task Force.

BACKGROUND: C-reactive protein (CRP) may help to refine global risk assessment for coronary heart disease (CHD), particularly among persons who are at intermediate risk on the basis of traditional risk factors alone. PURPOSE: To assist the U.S. Preventive Services Task Force (USPSTF) in determining whether CRP should be incorporated into guidelines for CHD risk assessment. DATA SOURCES: MEDLINE search of English-language articles (1966 to November 2007), supplemented by reference lists of reviews, pertinent studies, editorials, and Web sites and by expert suggestions. STUDY SELECTION: Prospective cohort, case-cohort, and nested case-control studies relevant to the independent predictive ability of CRP when used in intermediate-risk persons. DATA EXTRACTION: Included studies were reviewed according to predefined criteria, and the quality of each study was rated. DATA SYNTHESIS: The validity of the body of evidence and the net benefit or harm of using CRP for CHD risk assessment were evaluated. The combined magnitude of effect was determined by meta-analysis. The body of evidence is of good quality, consistency, and applicability. For good studies that adjusted for all Framingham risk variables, the summary estimate of relative risk for incident CHD was 1.58 (95% CI, 1.37 to 1.83) for CRP levels greater than 3.0 mg/L compared with levels less than 1.0 mg/L. Analyses from 4 large cohorts were consistent in finding evidence that including CRP improves risk stratification among initially intermediate-risk persons. C-reactive protein has desirable test characteristics, and good data exist on the prevalence of elevated CRP levels in intermediate-risk persons. Limited evidence links changes in CRP level to primary prevention of CHD events. LIMITATIONS: Study methods for measuring Framingham risk variables and other covariates varied. Ethnic and racial minority populations were poorly represented in most studies, limiting generalizability. Few studies directly assessed the effect of CRP on risk reclassification in intermediate-risk persons. CONCLUSION: Strong evidence indicates that CRP is associated with CHD events. Moderate, consistent evidence suggests that adding CRP to risk prediction models among initially intermediate-risk persons improves risk stratification. However, sufficient evidence that reducing CRP levels prevents CHD events is lacking.

Emerging risk factors for coronary heart disease: a summary of systematic reviews conducted for the U.S. Preventive Services Task Force.

BACKGROUND: Traditional risk factors do not explain all of the risk for incident coronary heart disease (CHD) events. Various new or emerging risk factors have the potential to improve global risk assessment for CHD. PURPOSE: To summarize the results of 9 systematic reviews of novel risk factors to help the U.S. Preventive Services Task Force (USPSTF) evaluate the factors' clinical usefulness. DATA SOURCES: Results from a MEDLINE search for English-language articles published from 1966 to September 2008, using the Medical Subject Heading terms cohort studies and cardiovascular diseases in combination with terms for each risk factor. STUDY SELECTION: Studies were included if the participants had no baseline cardiovascular disease and the investigators adjusted for at least 6 Framingham risk factors. DATA EXTRACTION: Study quality was evaluated by using USPSTF criteria and overall quality of evidence for each risk factor by using a modified version of the Grading of Recommendations, Assessment, Development, and Evaluation framework. Each factor's potential clinical value was evaluated by using a set of criteria that emphasized the importance of the effect of that factor on the reclassification of intermediate-risk persons. DATA SYNTHESIS: 9 systematic reviews were conducted. C-reactive protein (CRP) was the best candidate for use in screening and the most rigorously studied, but evidence that changes in CRP level lead to primary prevention of CHD events is inconclusive. The other evaluated risk factors were coronary artery calcium score as measured by electron-beam computed tomography, lipoprotein(a) level, homocysteine level, leukocyte count, fasting blood glucose, periodontal disease, ankle-brachial index, and carotid intima-media thickness. The availability and validity of the evidence varied considerably across the risk factors in terms of aggregate quality, consistency of findings, and applicability to intermediate-risk persons in the general population. For most risk factors, no studies assessed their usefulness for reclassifying intermediate-risk persons. LIMITATIONS: Because of lack of access to original data, no firm conclusions could be drawn about differences in risk prediction among racial and ethnic groups. The review did not emphasize within-cohort comparisons of multiple risk factors. CONCLUSION: The current evidence does not support the routine use of any of the 9 risk factors for further risk stratification of intermediate-risk persons.

The utilization of intravascular lithotripsy to facilitate transcarotid artery revascularization.

Carotid artery disease and stroke account for the second cause of mortality in worldwide. Recently, transcarotid artery stenting (TCAR) has emerged as a treatment modality that carries a very low stroke rate. However, there are limitations to TCAR, such as heavily calcified plaques that might preclude optimal stent expansion. We describe a successful transcarotid artery stenting with flow reversal performed in an independent and active nonagenarian with focal, circumferentially calcified carotid artery plaque, for which intravascular lithotripsy was utilized.

Performing a myocardial biopsy in a cardiac transplant patient with a persistent left superior vena cava.

The life expectancy of patients with congenital heart disease is increasing. Thus, as the prevalence of adults with congenital heart disease increases, invasive cardiologists will have more exposure to these patients and will benefit from expertise in the anatomy of congenital heart defects. We present a case of performing right heart catheterization and myocardial biopsy in a cardiac transplant patient with a history of multiple congenital defects including a persistent left superior vena cava.

Finding Common Ground between Adaptive Management and Evidence-Based Approaches to Biodiversity Conservation.

Adaptive management (AM) and evidence-based conservation (EBC) have emerged as major decision-making frameworks for conservation management. AM deals with complexity and the importance of local context in making conservation decisions under conditions of high variability, uncertainty, and rapid environmental and social change. EBC seeks for generality from empirical data and aims to develop and enhance best practice. The goal of this review is to explore opportunities for finding common ground between AM and EBC. We propose a framework for distinguishing the subset of conservation problems that are amenable to an evidence-based approach, based on levels of uncertainty, complexity, and social agreement. We then suggest ways for combining multiple lines of evidence and developing greater opportunities for iteration and co-learning in EBC.

Seasonal and temperature-related movement of Colorado River cutthroat trout in a low-elevation, Rocky Mountain stream.

Mobile species will migrate considerable distances to find habitats suitable for meeting life history requirements, and stream-dwelling salmonids are no exception. In April-October 2014, we used radio-telemetry to examine habitat use and movement of 36 Colorado River cutthroat trout Oncorhynchus clarkii pleuriticus (CRCT) in a 14.9-km fragment of Milk Creek, a relatively low-elevation stream in the Rocky Mountains (Colorado). We also used a network of data loggers to track stream temperature across time and space. Our objectives were to (1) characterize distribution and movement of CRCT, (2) evaluate seasonal differences in distribution and movement of CRCT, and (3) explore the relationship between stream temperature and distribution and movement of CRCT. During the course of our study, median range of CRCT was 4.81 km (range = 0.14-10.94) and median total movement was 5.94 km (range = 0.14-26.02). Median location of CRCT was significantly further upstream in summer than in spring, whereas range and movement of CRCT were greater in spring than in summer. Twenty-six of the 27 CRCT tracked through mid-June displayed a potamodromous (freshwater migratory) life history, migrating 1.8-8.0 km upstream during the spring spawning season. Four of the seven CRCT tracked through July migrated >1.4 km in summer. CRCT selected relatively cool reaches during summer months, and early-summer movement was positively correlated with mean stream temperature. Study fish occupied stream segments in spring and fall that were thermally unsuitable, if not lethal, to the species in summer. Although transmitter loss limited the scope of inference, our findings suggest that preferred habitat is a moving target in Milk Creek, and that CRCT move to occupy that target. Because mobile organisms move among complementary habitats and exploit seasonally-unsuitable reaches, we recommend that spatial and temporal variability be accounted for in delineations of distributional boundaries.

Comparison of Primary Care Physician Reimbursement Rates in the United States.

With a growing shortage of physicians, particularly primary care physicians, the issue of adequate pay in Hawai'i is increasingly important. Anecdotal reports of low pay in Hawai'i have rarely been substantiated. Data from FAIR Health, a company that tracks private insurance reimbursement rates, is compared across the United States (US) for the CPT code 99213. In addition, FAIR Health and Medicare rates are compared for cities with both similar and disparate cost of living to Hawai'i. Hawai'i is in the second lowest quintile for payment in the US for private insurances, and providers are reimbursed significantly lower than in cities with similar cost of living by both Medicare and private insurances. Methods for increasing payment to physicians in Hawai'i are essential to recruiting the necessary workforce. Revising payment methodologies that increase pay for services in areas of unmet need, revising Medicare Geographic Price Cost Indices to better balance pay in areas of need, and making use of the 10% Medicare Bonus Program for physicians working in Health Professions Shortage Areas are first steps to creating a sustainable plan for physician payment in the future.

Dosimetric evaluation of Acuros XB dose calculation algorithm with measurements in predicting doses beyond different air gap thickness for smaller and larger field sizes.

In this study, dose prediction accuracy of Acuros XB (AXB) dose calculation algorithm beyond air gap thickness (range 2, 4, and 6 cm) in simple inhomogeneous phantoms was investigated. The evaluation of AXB was performed by comparing the doses calculated by AXB with the doses calculated by Anisotropic Analytical Algorithm (AAA) and the measured data for different field sizes (3 × 3, 5 × 5, and 10 × 10 cm(2)) of a 6 MV photon beam. The dose computation was performed within Eclipse treatment planning system, and measurements were acquired with a cylindrical ionization chamber. Central axis depth dose comparisons were done in solid-water material region up to 5 cm distance from air/solid-water interface. The results of AXB had better agreement with measurements at all measured points than that of AAA. The discrepancies between AXB and measured data were seen from - 3.81% to + 0.9%, whereas the AAA differences with measurement from - 3.1% to - 10.9%. The combination of the smallest test field size and the largest air gap produced the highest range (1-5 cm distance from air/solid-water interface) in dose difference (AAA: -4.0% to - 10.6% and AXB: -3.8% to + 0.6%). The AAA computational time was about 8 times faster than that of AXB. In conclusion, AXB is more appropriate to use for dose predictions, especially when low-density heterogeneities are involved.

Dosimetric impact of Acuros XB dose calculation algorithm in prostate cancer treatment using RapidArc.

PURPOSE: The purpose of this study is to assess the dosimetric impact of Acuros XB dose calculation algorithm (AXB), in comparisons with Anisotropic Analytical Algorithm (AAA) calculations in prostate cancer treatment using RapidArc. MATERIALS AND METHODS: A computed tomography (CT) dataset of low-risk prostate cancer patients treated at Arizona Center for Cancer Care was selected and contoured for prostate, seminal vesicles, and organs at risk (OARs)(rectum, bladder, and femur heads). Plans were created for 6 MV photon beam using RapidArc technique in Eclipse treatment planning system. Dose calculations were performed with AAA and AXB for same number of monitor units and identical beam setup. Mean and maximum doses to planning target volume (PTV) and OARs were analyzed. Additionally, minimum dose to PTV and V100 was analyzed. Finally, point-dose difference between planar dose distributions of AAA and AXB plans was investigated. RESULTS: The highest dose difference was up to 0.43% (range: 0.05-0.43%, P> 0.05) for PTV and 1.98% (range: 0.22-1.98%, P> 0.05) for OARs with AAA predicting higher dose than AXB. The V100 values of AAA plans (95 %) and AXB plans (range: 93.1-97.9 %) had an average difference of 0.89 ± 1.47% with no statistical significance (P = 0.25411). The point-dose difference analysis showed that AAA predicted higher dose than AXB at significantly higher percentage (in average 94.15) of total evaluated points. CONCLUSION: The dosimetric results of this study suggest that the AXB can perform the dose computation comparable to AAA in RapidArc prostate cancer treatment plans that are generated by a partial single-arc technique.

Regional insight into savanna hydrogeomorphology from termite mounds.

Global vegetation models predict the spread of woody vegetation in African savannas and grasslands under future climate scenarios, but they operate too broadly to consider hillslope-scale variations in tree-grass distribution. Topographically linked hydrology-soil-vegetation sequences, or catenas, underpin a variety of ecological processes in savannas, including responses to climate change. In this study, we explore the three-dimensional structure of hillslopes and vegetation, using high-resolution airborne LiDAR (Light Detection And Ranging), to understand the long-term effects of mean annual precipitation (MAP) on catena pattern. Our results reveal that the presence and position of hillslope hydrological boundaries, or seeplines, vary as a function of MAP through its long-term influence on clay redistribution. We suggest that changes in climate will differentially alter the structure of savannas through hydrological changes to the seasonally saturated grasslands downslope of seeplines. The mechanisms underlying future woody encroachment are not simply physiological responses to elevated temperatures and CO(2) levels but also involve hydrogeomorphological processes at the hillslope scale.