Predicting pediatric kidney disease progression-are 3 variables all you need?

Accurate estimation of chronic kidney disease (CKD) progression risk is vital for clinical decision-making. Existing risk equations lack validation in pediatric CKD populations. Ng et al. developed new risk equations using the CKD in Children and European Study Consortium for Chronic Kidney Disorders Affecting Pediatric Patients cohorts. The elementary model, incorporating estimated glomerular filtration rate, urine protein-creatinine ratio, and diagnosis, exhibited excellent discrimination and calibration at external validation. External validation of enriched models is pending. The equations have the potential to aid pediatric CKD centers in patient counseling and care planning.

Multi-institutional dosimetric and geometric commissioning of image-guided small animal irradiators.

PURPOSE: To compare the dosimetric and geometric properties of a commercial x-ray based image-guided small animal irradiation system, installed at three institutions and to establish a complete and broadly accessible commissioning procedure. METHODS: The system consists of a 225 kVp x-ray tube with fixed field size collimators ranging from 1 to 44 mm equivalent diameter. The x-ray tube is mounted opposite a flat-panel imaging detector, on a C-arm gantry with 360° coplanar rotation. Each institution performed a full commissioning of their system, including half-value layer, absolute dosimetry, relative dosimetry (profiles, percent depth dose, and relative output factors), and characterization of the system geometry and mechanical flex of the x-ray tube and detector. Dosimetric measurements were made using Farmer-type ionization chambers, small volume air and liquid ionization chambers, and radiochromic film. The results between the three institutions were compared. RESULTS: At 225 kVp, with 0.3 mm Cu added filtration, the first half value layer ranged from 0.9 to 1.0 mm Cu. The dose-rate in-air for a 40 × 40 mm(2) field size, at a source-to-axis distance of 30 cm, ranged from 3.5 to 3.9 Gy/min between the three institutions. For field sizes between 2.5 mm diameter and 40 × 40 mm(2), the differences between percent depth dose curves up to depths of 3.5 cm were between 1% and 4% on average, with the maximum difference being 7%. The profiles agreed very well for fields >5 mm diameter. The relative output factors differed by up to 6% for fields larger than 10 mm diameter, but differed by up to 49% for fields ≤5 mm diameter. The mechanical characteristics of the system (source-to-axis and source-to-detector distances) were consistent between all three institutions. There were substantial differences in the flex of each system. CONCLUSIONS: With the exception of the half-value layer, and mechanical properties, there were significant differences between the dosimetric and geometric properties of the three systems. This underscores the need for careful commissioning of each individual system for use in radiobiological experiments.

Assessment of residual active chlorine in sodium hypochlorite solutions after dissolution of porcine incisor pulpal tissue.

BACKGROUND: In previous studies, surfactant-containing Hypochlor brands of sodium hypochlorite showed better tissue solubilizing abilities than Milton; differences not explained by original active chlorine content or presence of surfactant. It was postulated that exhaustion of active chlorine content could explain differences. This study aimed to assess whether Milton's poorer performance was due to exhaustion of active chlorine. Parallel experiments assessed the influence of titration methods, and the presence of chlorates, on active chlorine measurements. METHODS: Time required to dissolve one or groups of 10 samples of porcine incisor pulp samples in Milton was determined. Residual active chlorine was assessed by thermometric titration. Iodometric and thermometric titration was carried out on samples of Milton. Chlorate content was also measured. RESULTS: Dissolution of single and 10 pulp samples caused a mean loss of 1% and 3% respectively of active chlorine, not being proportional to tissue dissolved. Thermometric ammonium ion titration resulted in 10% lower values than iodometric titration. Chlorate accounted for much of this difference. CONCLUSIONS: Depletion of active chlorine is not the reason for differences in tissue dissolving capabilities of Milton. Thermometric ammonium ion titration gives more accurate measurement of active chlorine content than iodometric titration.

Carbon monoxide poisoning: Novel magnetic resonance imaging pattern in the acute setting.

The presentation of carbon monoxide (CO) poisoning is non-specific and highly variable. The diagnosis is made when a compatible history and examination occur in a patient with elevated carboxyhaemoglobin levels. The severity of intoxication is difficult to assess accurately based on laboratory markers alone. Magnetic resonance imaging (MRI) has been shown to have superior sensitivity to computed tomography for the detection of abnormalities post CO poisoning. We report a novel imaging pattern on MRI undertaken in the acute setting in a patient with CO intoxication. We also discuss the management and follow up of patients with CO poisoning.

Characterization of image quality and image-guidance performance of a preclinical microirradiator.

PURPOSE: To assess image quality and image-guidance capabilities of a cone-beam CT based small-animal image-guided irradiation unit (micro-IGRT). METHODS: A micro-IGRT system has been developed in collaboration with the authors' laboratory as a means to study the radiobiological effects of conformal radiation dose distributions in small animals. The system, the X-Rad 225Cx, consists of a 225 kVp x-ray tube and a flat-panel amorphous silicon detector mounted on a rotational C-arm gantry and is capable of both fluoroscopic x-ray and cone-beam CT imaging, as well as image-guided placement of the radiation beams. Image quality (voxel noise, modulation transfer, CT number accuracy, and geometric accuracy characteristics) was assessed using water cylinder and micro-CT test phantoms. Image guidance was tested by analyzing the dose delivered to radiochromic films fixed to BB's through the end-to-end process of imaging, targeting the center of the BB, and irradiation of the film/BB in order to compare the offset between the center of the field and the center of the BB. Image quality and geometric studies were repeated over a 5-7 month period to assess stability. RESULTS: CT numbers reported were found to be linear (R2 0.998) and the noise for images of homogeneous water phantom was 30 HU at imaging doses of approximately 1 cGy (to water). The presampled MTF at 50% and 10% reached 0.64 and 1.35 mm(-1), respectively. Targeting accuracy by means of film irradiations was shown to have a mean displacement error of [deltax, deltay, deltaz] = [-0.12, -0.05, -0.02] mm, with standard deviations of [0.02, 0.20, 0.17] mm. The system has proven to be stable over time, with both the image quality and image-guidance performance being reproducible for the duration of the studies. CONCLUSIONS: The micro-IGRT unit provides soft-tissue imaging of small-animal anatomy at acceptable imaging doses (< or =1 cGy). The geometric accuracy and targeting systems permit dose placement with submillimeter accuracy and precision. The system has proven itself to be stable over 2 yr of routine laboratory use (>1800 irradiations) and provides a platform for the exploration of targeted radiation effects in small-animal models.

Sci-Sat AM(1): Imaging-03: On-line dynamic contrast enhanced cone-beam CT for measuring.

We propose a novel on-line functional imaging method with which tumor microenvironment can be quantified at the treatment unit. It is an X-ray contrast enhanced method based the (kv) cone beam CT (CBCT) platform and it promises to provide a surrogate measurement of tumor perfusion. The method was tested with 6 rabbits implanted with VX2 tumor. The technique involves a baseline CBCT followed by a contrast enhanced CBCT synchronized with contrast injection. The scan time for each CBCT is approximately 2 minutes during which a set of projections are acquired. The conventional reconstruction approach of contrast enhanced CBCT will give a single volumetric image with no temporal signature. On the other hand, the proposed technique makes use of a mathematical expression to parameterize the wash-in and wash-out behavior of contrast uptake in each voxel. Based on the projection data, the new method uses non-linear optimization to solve for the parameters describing the dynamic characteristics of injected contrast with which tumor perfusion can be derived. In our rabbit study, dynamic contrast enhanced images were reconstructed with the CBCT projections by the proposed method. Results show that the estimated contrast enhancement with the proposed CBCT method is in excellent agreement with the measured enhancement by CT. The proposed CBCT method is sensitive for detecting changes in the tumor microenvironment as a result of radiation treatment.

Bayesian modelling of shared gene function.

MOTIVATION: Biological assays are often carried out on tissues that contain many cell lineages and active pathways. Microarray data produced using such material therefore reflect superimpositions of biological processes. Analysing such data for shared gene function by means of well-matched assays may help to provide a better focus on specific cell types and processes. The identification of genes that behave similarly in different biological systems also has the potential to reveal new insights into preserved biological mechanisms. RESULTS: In this article, we propose a hierarchical Bayesian model allowing integrated analysis of several microarray data sets for shared gene function. Each gene is associated with an indicator variable that selects whether binary class labels are predicted from expression values or by a classifier which is common to all genes. Each indicator selects the component models for all involved data sets simultaneously. A quantitative measure of shared gene function is obtained by inferring a probability measure over these indicators. Through experiments on synthetic data, we illustrate potential advantages of this Bayesian approach over a standard method. A shared analysis of matched microarray experiments covering (a) a cycle of mouse mammary gland development and (b) the process of in vitro endothelial cell apoptosis is proposed as a biological gold standard. Several useful sanity checks are introduced during data analysis, and we confirm the prior biological belief that shared apoptosis events occur in both systems. We conclude that a Bayesian analysis for shared gene function has the potential to reveal new biological insights, unobtainable by other means. AVAILABILITY: An online supplement and MatLab code are available at http://www.sykacek.net/research.html#mcabf

Stochastic Liouville equation treatment of the electron paramagnetic resonance line shape of an S-state ion in solution.

The current approaches used for the analysis of electron paramagnetic resonance spectra of Gd3+ complexes suffer from a number of drawbacks. Even the elaborate model of [Rast et al., J. Chem. Phys. 113, 8724 (2000)] where the electron spin relaxation is explained by the modulation of the zero-field splitting (ZFS), by molecular tumbling (the so called static contribution), and deformations (transient contribution), is only readily applicable within the validity range of the Redfield theory [Advances in Magnetic Resonance, edited by J.-S. Waugh (Academic, New York, 1965), Vol. 1, p. 1], that is, when the ZFS is small compared to the Zeeman energy and the rotational and vibrational modulations are fast compared to the relaxation time. Spin labels (nitroxides and transition metal complexes) have been studied for years in systems that violate these conditions. The theoretical framework commonly used in such studies is the stochastic Liouville equation (SLE). The authors shall show how the physical model of Rast et al. can be cast into the SLE formalism, paying special attention to the specific problems introduced by the [Uhlenbeck and Ornstein, Phys. Rev. 36, 823 (1930)] process used to model the transient ZFS. The resulting equations are very general and valid for arbitrary correlation times, magnetic field strength, electron spin S, or symmetry. The authors demonstrate the equivalence of the SLE approach with the Redfield approximation for two well-known Gd3+ complexes.

Variable temperature and EPR frequency study of two aqueous Gd(III) complexes with unprecedented sharp lines.

We present an EPR study of two Gd(III) complexes in aqueous solution at multiple temperatures and EPR frequencies. These two complexes, [Gd(TPATCN)] and [Gd(DOTAM)(H(2)O)](3+), display remarkably sharp lines (i.e. slow transverse electron spin relaxation) in comparison with all complexes studied in the past, especially at X-band ( approximately 9.08 GHz). These unprecedented spectra even show, for the first time in solution, a distinct influence of hyperfine coupling to two magnetically active Gd isotopes ((155)Gd 14.8%, I = 3/2, gamma = -0.8273 x 10(7) s(-1) T(-1) and (157)Gd, 15.65%, I = 3/2, -1.0792 x 10(7) s(-1) T(-1)). The hyperfine coupling splitting in [Gd(TPATCN)] was determined accurately for a (157)Gd-enriched complex, and the value A((157)Gd)/gmu(B) = 5.67 G seems to be a good estimation for most chelates of interest. Consequently, we can safely assert that neglecting the Gd isotopes in line shape studies is not a significant source of error as long as the apparent peak-to-peak width is greater than 10-20 G. This is generally the case, except at very high EPR frequencies (>150 GHz). Analyzing the spectra within the physical model of Rast et al. we find that the slow electron spin relaxation is due to a nearly zero static ZFS. We discuss some structural features that might explain this interesting electron structure.

Dissolution of porcine incisor pulps in sodium hypochlorite solutions of varying compositions and concentrations.

BACKGROUND: The solubility of dental pulp tissue in sodium hypochlorite has been extensively investigated but results have been inconsistent; due most likely to variations in experimental design, the volume and/or rate of replenishment of the solutions used and the nature of the tissues assessed. Traditionally, the sodium hypochlorite solutions used for endodontic irrigation in Australia have been either Milton or commercial bleach, with Milton being the most common. Recently, a range of Therapeutic Goods Administration (TGA) approved proprietary sodium hypochlorite solutions, which contain surfactant, has become available. Some domestic chlorine bleaches now also contain surfactants. The purpose of this study was to perform new solubility assessments, comparing Milton with new TGA approved products, Hypochlor 1% and Hypochlor 4% forte, and with a domestic bleach containing surfactant (White King). METHODS: Ten randomly assigned pulp samples of porcine dental pulp of approximately equal dimensions were immersed in the above solutions, as well as representative concentrations of sodium hydroxide. Time to complete dissolution was measured and assessed statistically. RESULTS: White King 4% showed the shortest dissolution time, closely followed by Hypochlor 4% forte. White King 1% and Hypochlor 1% each took around three times as long to completely dissolve the samples of pulp as their respective 4% concentrations, while Milton took nearly 10 times as long. The sodium hydroxide solutions showed no noticeable dissolution of the pulp samples. CONCLUSIONS: The composition and content of sodium hypochlorite solutions had a profound effect on the ability of these solutions to dissolve pulp tissue in vitro. Greater concentrations provided more rapid dissolution of tissue. One per cent solutions with added surfactant and which contained higher concentrations of sodium hydroxide were significantly more effective in dissolution of pulp tissue than Milton.

Soliton solutions to the einstein equations in five dimensions.

We present a new class of solutions in odd dimensions to Einstein's equations containing either a positive or a negative cosmological constant. These solutions resemble the even-dimensional Eguchi-Hanson-(anti)-de Sitter [(A)dS] metrics, with the added feature of having Lorentzian signatures. They provide an affirmative answer to the open question as to whether or not there exist solutions with a negative cosmological constant that asymptotically approach AdS5/gamma but have less energy than AdS5/gamma. We present evidence that these solutions are the lowest-energy states within their asymptotic class.

On the philosophy of optimizing contrast agents. An analysis of 1H NMRD profiles and ESR lineshapes of the Gd(III)complex MS-325+HSA.

A generalization of the modified SBM theory is developed in closed analytical form. The theory is applied to describe the paramagnetically enhanced water proton spin-lattice relaxation rates of the aqueous-systems containing a gadolinium(S=7/2) complex(MS-325) in the presence or absence of human serum albumin (HSA). MS-325 binds to HSA: in the absence of the protein the reorientational time, tauR, is short, but when HSA is added tauR becomes much longer. In this way, the effect of reorientational motion, static (Delta s), and transient (Delta t) zero-field splitting (ZFS) interactions on both the water proton relaxivity and the Gd ESR lineshapes are investigated. Two dynamic models of electron spin relaxation are presented, characterized by transient and static ZFS-interactions. X-, Q-, and W-bands ESR spectra of MS-325+HSA are analyzed in order to describe the effect on the electron spin system upon binding to a macromolecule. A computer program based on this theory is developed which calculates solvent water proton T1 NMRD profiles and the corresponding X-, Q-, U-, and W-bands ESR lineshapes.

A survey of sodium hypochlorite use by general dental practitioners and endodontists in Australia.

BACKGROUND: Sodium hypochlorite is used commonly as an endodontic irrigant, but there are no published reports that provide details of its use. This survey sought to determine the percentage of Australian dentists who practiced endodontics, whether they used sodium hypochlorite for irrigation, and the manner of dilution, storage and dispensing sodium hypochlorite used by both dentists and endodontists. METHODS: All Australian endodontists and a stratified random sample of 200 general dentists in Australia were surveyed to address the issues identified above. RESULTS: Almost 98 per cent of dentists surveyed performed endodontic treatment. Among endodontists, nearly 94 per cent used sodium hypochlorite for irrigation compared with just under 75 per cent of general dentists. Sodium hypochlorite use by general dentists was more common in Victoria and South Australia than in other States. An infant sanitizer (Milton or Johnson's Antibacterial Solution) was used by just over 92 per cent of general practitioners and by more than 67 per cent of endodontists. All other respondents used domestic bleach. One hundred and sixty four of the respondents (80 per cent of endodontists and over 90 per cent of general dentists) used a 1 per cent w/v solution. Ten practitioners used a 4 per cent w/v solution, five used a 2 per cent w/v solution and four used a 1.5 per cent w/v solution. Eighty per cent of the practitioners who diluted their sodium hypochlorite before use, used demineralized water for this purpose. The remainder used tap water. Only four practitioners stored sodium hypochlorite in a manner which risked light exposure and loss of available chlorine content. CONCLUSIONS: Sodium hypochlorite is commonly used as an endodontic irrigant and Australian dentists generally stored the material correctly.

Mass, action, and entropy of Taub-Bolt-de Sitter spacetimes.

We apply a recent proposal for defining conserved mass in asymptotically de Sitter spacetimes to the class of Taub-Bolt-de Sitter spacetimes. We compute the action, entropy, and conserved mass of these spacetimes, and find that in certain instances the mass and entropy can exceed that of pure de Sitter spacetime, in violation of recent suggestive conjectures to the contrary.

Development of biocompatible oxygen-permeable films holding paramagnetic carbon particles: evaluation of their performance and stability in EPR oximetry.

EPR oximetry using paramagnetic particles relies on the measurement of the EPR linewidth, which is directly related to the pO2. It was previously found that some of the paramagnetic materials with optimal EPR spectroscopic properties in vitro may lose their responsiveness to oxygen in tissues (change of the calibration curve of the EPR linewidth as a function of the pO2). We hypothesized that coating paramagnetic particle materials could improve the stability of response, as well as the biocompatibility. In this study, very thin films holding paramagnetic materials were prepared with different biopolymers (cellulose acetate, cellulose triacetate, cellulose nitrate, silicone, and polyurethane) that already are accepted for clinical applications. Their performance was evaluated in EPR oximetry by measuring the stability of the calibration curves (EPR linewidth as a function of pO2) after a prolonged period in an aqueous environment (1 week in saline) or in vivo (implantation for 3 weeks under the skin of mice). We found that one type of silicone film was able to stabilize the responsiveness of an intrinsically unstable carbon material (a wood char).

Mechanism of oxygen response in carbon-based sensors.

The mechanism of oxygen response in several newly synthesized oxygen-sensitive chars was studied with the use of EPR spectroscopy. The results suggest that the compounds contain two basic types of paramagnetic centers (PC). The change in oxygen concentration leads to a mutual and reversible transformation of PCs in chars, which is reflected in EPR parameters. The adsorbed molecular oxygen progressively disturbs the wave functions of the PCs and so breaks the Heisenberg exchange between them. At high oxygen concentration, the 2D dipole-dipole interaction between PCs at the surface comes into play and determines the EPR lineshape. A suggested model quantitatively describes the evolution of the basic EPR parameters of each PC as a function of oxygen concentration.

Peculiarities in the Water Adsorption and Morphology of Carbon Chars Assessed by NMR.

Proton spin-lattice relaxation and (1)H NMR spectroscopic data are used for studies of the water adsorption and morphology of several newly synthesized carbon-based chars. Two NMR lines have been observed in accordance with a difference between macropore and micropore water in a system with heterogeneous pore structure. The macropores occupy about the half of the char particle volume. In aqueous suspension fast molecular exchange between water in macropores and bulk water leads to an intense NMR line with a single spin-lattice relaxation time T(1), which exhibits a strong particle size effect. This effect has been used for the estimation of T(1) of water molecules in the vicinity of paramagnetic centers at the surface of chars, as well as for macropore size estimation. The kinetics of water vapor adsorption in chars as seen by (1)H NMR indicates that this process begins in micropores, which serve as primary adsorption centers. Water molecules in micropores exhibit specific properties which are characteristic of liquids in a small, restricted space, and they give rise to the observed accumulation as well as saturation effects. Copyright 2001 Academic Press.

The shelf-life of sodium hypochlorite irrigating solutions.

BACKGROUND: Sodium hypochlorite (bleach) solutions are widely used as irrigants in endodontics. Their tendency to deteriorate is worsened by environmental influences which could cause loss of available chlorine content. METHODS: This study measured the loss of available chlorine concentration in a range of sodium hypochlorite solutions under conditions which mimic clinical usage and storage. Domestic bleach, both undiluted and diluted with demineralised water or hard water, was tested, along with Milton, for initial concentration of available chlorine, and then retested after varying periods and modes of storage to measure loss of chlorine concentration. The types of storage were: (1) in closed plastic bottles which were opened daily and agitated; (2) in open plastic bottles; (3) in syringes exposed to sunlight; (4) in syringes kept in the dark; (5) in open stainless steel bowls; (6) in closed stainless steel bowls; and (7) when heated to 50 degrees C. Not all solutions were tested under all storage conditions. RESULTS: Of the solutions opened daily, undiluted domestic bleach was the most stable and Milton was the least stable. Initially, diluted bleach left open deteriorated rapidly but deterioration slowed with time. Solutions in syringes exposed to sunlight showed the most rapid loss of chlorine content. Heated bleach lost nearly 5 per cent of its strength in six hours. Diluted bleach surprisingly, increased its chlorine concentration in open bowls probably due to evaporation of water. Dilution of bleach with hard tap water did not significantly affect shelf-life. Preloading of diluted bleach into syringes appears to be a sound technique if the syringes are stored away from light. CONCLUSIONS: This study reinforces the need for sodium hypochlorite to be stored in closed opaque containers. Constant opening of containers appears to cause greater loss in chlorine concentration of diluted bleach solutions, perhaps because a lower concentration of sodium hydroxide allows the pH to drop more rapidly.