82 research outputs found
Investigation of error detection capabilities of phantom, EPID and MLC log file based IMRT QA methods
A patient specific quality assurance (QA) should detect errors that originate anywhere in the treatment planning process. However, the increasing complexity of treatment plans has increased the need for improvements in the accuracy of the patient specific pretreatment verification process. This has led to the utilization of higher resolution QA methods such as the electronic portal imaging device (EPID) as well as MLC log files and it is important to know the types of errors that can be detected with these methods. In this study, we will compare the ability of three QA methods (Delta 4 ®, MU-EPID, Dynalog QA) to detect specific errors. Multileaf collimator (MLC) errors, gantry angle, and dose errors were introduced into five volumetric modulated arc therapy (VMAT) plans for a total of 30 plans containing errors. The original plans (without errors) were measured five times with each method to set a threshold for detectability using two standard deviations from the mean and receiver operating characteristic (ROC) derived limits. Gamma passing percentages as well as percentage error of planning target volume (PTV) were used for passing determination. When applying the standard 95% pass rate at 3%/3 mm gamma analysis errors were detected at a rate of 47, 70, and 27% for the Delta 4 , MU-EPID and Dynalog QA respectively. When using thresholds set at 2 standard deviations from our base line measurements errors were detected at a rate of 60, 30, and 47% for the Delta 4 , MU-EPID and Dynalog QA respectively. When using ROC derived thresholds errors were detected at a rate of 60, 27, and 47% for the Delta 4 , MU-EPID and Dynalog QA respectively. When using dose to the PTV and the Dynalog method 11 of the 15 small MLC errors were detected while none were caught using gamma analysis. A combination of the EPID and Dynalog QA methods (scaling Dynalog doses using EPID images) matches the detection capabilities of the Delta 4 by adding additional comparison metrics. These additional metrics are vital in relating the QA measurement to the dose received by the patient which is ultimately what is being confirmed
Diagnostic examination of the child with urolithiasis or nephrocalcinosis
Urolithiasis and nephrocalcinosis are more frequent in children then currently anticipated, but still remain under- or misdiagnosed in a significant proportion of patients, since symptoms and signs may be subtle or misleading. All children with colicky abdominal pain or macroscopic hematuria should be examined thoroughly for urolithiasis. Also, other, more general, abdominal manifestations can be the first symptoms of renal stones. The patients and their family histories, as well as physical examination, are important initial steps for diagnostic evaluation. Thereafter, diagnostic imaging should be aimed at the location of calculi but also at identification of urinary tract anomalies or acute obstruction due to stone disease. This can often be accomplished by ultrasound examination alone, but sometimes radiological methods such as plain abdominal films or more sensitive non-enhanced computed tomography are necessary. Since metabolic causes are frequent in children, diagnostic evaluation should be meticulous so that metabolic disorders that cause recurrent urolithiasis or even renal failure, such as the primary hyperoxalurias and others, can be ruled out. The stone is not the disease itself; it is only one serious sign! Therefore, thorough and early diagnostic examination is mandatory for every infant and child with the first stone event, or with nephrocalcinosis
Groundwater discharge to the western Antarctic coastal ocean
Submarine groundwater discharge (SGD) measurements have been limited along the Antarctic coast, although groundwater discharge is becoming recognized as an important process in the Antarctic. Quantifying this meltwater path-way is important for hydrologic budgets, ice mass balances and solute delivery to the coastal ocean. Here, we estimate the combined discharge of subglacial and submarine groundwater to the Antarctic coastal ocean. SGD, including subglacial and submarine groundwater, is quantified along the WAP at the Marr Glacier terminus using the activities of naturally occurring radium isotopes (223Ra, 224Ra). Estimated SGD fluxes from a 224Ra mass balance ranged from (0.41 ± 0.14)×104 and (8.2 ± 2.3)×104m3 d−1. Using a salinity mass balance, we estimate SGD contributes up to 32% of the total freshwater to the coastal environment near Palmer Station. This study suggests that a large portion of the melting glacier may be infiltrating into the bedrock and being discharged to coastal waters along the WAP. Meltwater infiltrating as groundwater at glacier termini is an import-ant solute delivery mechanism to the nearshore environment that can influence biological productivity. More importantly, quantifying this meltwater pathway may be worthy of attention when predicting future impacts of climate change on retreat of tidewater glaciers
ACE (I/D) polymorphism and response to treatment in coronary artery disease: a comprehensive database and meta-analysis involving study quality evaluation
<p>Abstract</p> <p>Background</p> <p>The role of angiotensin-converting enzyme (<it>ACE</it>) gene insertion/deletion (<it>I/D</it>) polymorphism in modifying the response to treatment modalities in coronary artery disease is controversial.</p> <p>Methods</p> <p>PubMed was searched and a database of 58 studies with detailed information regarding <it>ACE I/D </it>polymorphism and response to treatment in coronary artery disease was created. Eligible studies were synthesized using meta-analysis methods, including cumulative meta-analysis. Heterogeneity and study quality issues were explored.</p> <p>Results</p> <p>Forty studies involved invasive treatments (coronary angioplasty or coronary artery by-pass grafting) and 18 used conservative treatment options (including anti-hypertensive drugs, lipid lowering therapy and cardiac rehabilitation procedures). Clinical outcomes were investigated by 11 studies, while 47 studies focused on surrogate endpoints. The most studied outcome was the restenosis following coronary angioplasty (34 studies). Heterogeneity among studies (p < 0.01) was revealed and the risk of restenosis following balloon angioplasty was significant under an additive model: the random effects odds ratio was 1.42 (95% confidence interval:1.07–1.91). Cumulative meta-analysis showed a trend of association as information accumulates. The results were affected by population origin and study quality criteria. The meta-analyses for the risk of restenosis following stent angioplasty or after angioplasty and treatment with angiotensin-converting enzyme inhibitors produced non-significant results. The allele contrast random effects odds ratios with the 95% confidence intervals were 1.04(0.92–1.16) and 1.10(0.81–1.48), respectively. Regarding the effect of <it>ACE I/D </it>polymorphism on the response to treatment for the rest outcomes (coronary events, endothelial dysfunction, left ventricular remodeling, progression/regression of atherosclerosis), individual studies showed significance; however, results were discrepant and inconsistent.</p> <p>Conclusion</p> <p>In view of available evidence, genetic testing of <it>ACE I/D </it>polymorphism prior to clinical decision making is not currently justified. The relation between <it>ACE </it>genetic variation and response to treatment in CAD remains an unresolved issue. The results of long-term and properly designed prospective studies hold the promise for pharmacogenetically tailored therapy in CAD.</p
Nitric oxide and cyclic nucleotides: Their roles in junction dynamics and spermatogenesis
Spermatogenesis is a highly complicated process in which functional spermatozoa (haploid, 1n) are generated from primitive mitotic spermatogonia (diploid, 2n). This process involves the differentiation and transformation of several types of germ cells as spermatocytes and spermatids undergo meiosis and differentiation. Due to its sophistication and complexity, testis possesses intrinsic mechanisms to modulate and regulate different stages of germ cell development under the intimate and indirect cooperation with Sertoli and Leydig cells, respectively. Furthermore, developing germ cells must translocate from the basal to the apical (adluminal) compartment of the seminiferous epithelium. Thus, extensive junction restructuring must occur to assist germ cell movement. Within the seminiferous tubules, three principal types of junctions are found namely anchoring junctions, tight junctions, and gap junctions. Other less studied junctions are desmosome-like junctions and hemidesmosome junctions. With these varieties of junction types, testes are using different regulators to monitor junction turnover. Among the uncountable junction modulators, nitric oxide (NO) is a prominent candidate due to its versatility and extensive downstream network. NO is synthesized by nitric oxide synthase (NOS). Three traditional NOS, specified as endothelial NOS (eNOS), inducible NOS (iNOS), and neuronal NOS (nNOS), and one testis-specific nNOS (TnNOS) are found in the testis. For these, eNOS and iNOS were recently shown to have putative junction regulation properties. More important, these two NOSs likely rely on the downstream soluble guanylyl cyclase/cGMP/protein kinase G signaling pathway to regulate the structural components at the tight junctions and adherens junctions in the testes. Apart from the involvement in junction regulation, NOS/NO also participates in controlling the levels of cytokines and hormones in the testes. On the other hand, NO is playing a unique role in modulating germ cell viability and development, and indirectly acting on some aspects of male infertility and testicular pathological conditions. Thus, NOS/NO bears an irreplaceable role in maintaining the homeostasis of the microenvironment in the seminiferous epithelium via its different downstream signaling pathways
The orotate transporter oroP from Lactococcus lactis can be used both as a very efficient, food-grade selection and counter-selection marker for strain construction in many different organisms
The orotate transporter encoded by oroP from Lactococcus lactis is required for orotate utilization and is functional in both Gram-positive and Gram-negative bacteria
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Oral History Interview with Ira T. DeFoor, May 24, 1983
Interview with college instructor Ira T. DeFoor from Denton, Texas. In the interview, DeFoor discusses his experiences from when he was the equipment manager for the football team during the desegregation of athletics at North Texas State College in 1956
NAD(P)H oxidase P22phox gene A640G and C242T polymorphisms and aerobic power in coronary artery disease.
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