Publications by authors named "Bridgen P"

Purpose: To determine the expected range of NMR relaxation times (T and T) in the neonatal brain at 7 T.

Methods: Data were acquired in a total of 40 examinations on infants in natural sleep. The cohort included 34 unique subjects with postmenstrual age range between 33 and 52 weeks and contained a mix of healthy individuals and those with clinical concerns.

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Purpose: This work proposes a "hybrid" RF pulse design method for parallel transmit (pTx) systems to simultaneously control flip angle and root-mean-squared ( ). These pulses are generally only designed for flip angle, however, this can lead to uncontrolled , which then leads to variable magnetization transfer (MT) effects. We demonstrate the hybrid design approach for quantitative imaging where both flip angle and are important.

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Background And Aims: Histopathological diagnosis is the gold standard in many acquired inflammatory, infiltrative and amyloid based peripheral nerve diseases and a sensory nerve biopsy of sural or superficial peroneal nerve is favoured where a biopsy is deemed necessary. The ability to determine nerve pathology by high-resolution imaging techniques resolving anatomy and imaging characteristics might improve diagnosis and obviate the need for biopsy in some. The sural nerve is anatomically variable and occasionally adjacent vessels can be sent for analysis in error.

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Purpose: This study leverages externally generated Pilot Tone (PT) signals to perform motion-corrected brain MRI for sequences with arbitrary k-space sampling and image contrast.

Theory And Methods: PT signals are promising external motion sensors due to their cost-effectiveness, easy workflow, and consistent performance across contrasts and sampling patterns. However, they lack robust calibration pipelines.

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Introduction: Ultra-high field MR imaging offers marked gains in signal-to-noise ratio, spatial resolution, and contrast which translate to improved pathological and anatomical sensitivity. These benefits are particularly relevant for the neonatal brain which is rapidly developing and sensitive to injury. However, experience of imaging neonates at 7T has been limited due to regulatory, safety, and practical considerations.

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Purpose: The MP2RAGE sequence is typically optimized for either T -weighted uniform image (UNI) or gray matter-dominant fluid and white matter suppression (FLAWS) contrast images. Here, the purpose was to optimize an MP2RAGE protocol at 7 Tesla to provide UNI and FLAWS images simultaneously in a clinically applicable acquisition time at <0.7 mm isotropic resolution.

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Purpose: To develop a fully data-driven retrospective intrascan motion-correction framework for volumetric brain MRI at ultrahigh field (7 Tesla) that includes modeling of pose-dependent changes in polarizing magnetic (B ) fields.

Theory And Methods: Tissue susceptibility induces spatially varying B distributions in the head, which change with pose. A physics-inspired B model has been deployed to model the B variations in the head and was validated in vivo.

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Purpose: This work proposes a novel RF pulse design for parallel transmit (pTx) systems to obtain uniform saturation of semisolid magnetization for magnetization transfer (MT) contrast in the presence of transmit field inhomogeneities. The semisolid magnetization is usually modeled as being purely longitudinal, with the applied field saturating but not rotating its magnetization; thus, standard pTx pulse design methods do not apply.

Theory And Methods: Pulse design for saturation homogeneity (PUSH) optimizes pTx RF pulses by considering uniformity of root-mean squared , , which relates to the rate of semisolid saturation.

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A national survey was conducted in 2011-2013 to assess serum concentrations of brominated flame retardants (BFRs) and perfluorinated alkyl substances (PFASs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 geographic regions, 2 ethnic groups (Māori/non-Māori) and sex. Eligible participants (n = 734; response rate of contacted individuals = 37%) donated up to 30 mL of blood, after which serum was pooled (49 pools for BFRs, 63 pools for PFASs) according to demographic strata.

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A national survey was conducted in 2011-2013 to assess serum concentrations of persistent organic pollutants (POPs) in adult New Zealanders. Participants were randomly selected from the 2010 Electoral Roll within 64 demographic strata according to 4 age groups, 4 regions, 2 ethnic groups (Māori/non-Māori) and gender. Eligible subjects (n=734) donated up to 30ml of blood, after which serum was pooled (n=49) according to demographic strata prior to analysis by GC-HRMS.

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The Antarctic Treaty permits the discharge of wastewater into Antarctic marine waters providing that conditions exist for initial dilution and rapid dispersal. We investigated the dilution and dispersal of macerated wastewater around Australia's Davis Station in East Antarctica and examined sediments for evidence of contaminants. Methods used to examine hydrodynamic conditions included current meters, dye release experiments and measurement of sewage-associated microbial markers and surfactants in the water column.

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The external effects of oil on wildlife can be obvious and acute. Internal effects are more difficult to detect and can occur without any external signs. To quantify internal effects from oil ingestion by wildlife during an oil spill, baseline levels of ubiquitous hydrocarbon fractions, like polycyclic aromatic hydrocarbons (PAHs), need to be established.

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A nation-wide passive air sampling campaign recorded concentrations of persistent organic pollutants in Australia's atmosphere in 2012. XAD-based passive air samplers were deployed for one year at 15 sampling sites located in remote/background, agricultural and semi-urban and urban areas across the continent. Concentrations of 47 polychlorinated biphenyls ranged from 0.

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Aim: To estimate average infant daily intake of chlorinated persistent organic pollutants (POPs) through the consumption of breast milk in New Zealand.

Method: Breast milk of 39 first-time mothers aged 20-30 years was collected during 2007-2010 and analysed for persistent organic pollutants including dioxin-like compounds and organochlorine pesticides. The quantity of POPs consumed by infants assuming exclusive breast feeding was estimated by calculating the Estimated Daily Intake (EDI) expressed as amount consumed through breast milk per kilogram of body weight per day.

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This article gives an overview of a range of persistent organic pollutant chemical levels in shellfish (Batissa violacea and Anadara antiquata) species and eel (Gymnothorax flavimarginatus) from Fiji. As there is limited data in published literature to date, this paper reports first data on a range of persistent organic pollutants and highlights the more prominent POP chemicals present in marine biota in Fiji. A significant number of POP chemicals were detected (e.

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Breast milk samples of 39 first time mothers aged 20-30 were collected in 2007-2010 from rural and urban areas of New Zealand, following the fourth World Health Organization coordinated survey protocol. Samples were individually analysed for persistent organic pollutants (POPs) including dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs). The lipid adjusted concentrations of PCDD/Fs (mean toxic equivalent (TEQ): 3.

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Polychlorinated biphenyls (PCBs) and organochlorine (OC) pesticide levels were determined in blubber samples collected from stranded and incidentally by-caught Hector's (Cephalorhynchus hectori hectori) and Maui's (Cephalorhynchus hectori maui) dolphins from New Zealand waters between 1997 and 2009. PCBs (45 congeners) and a range of OC pesticides including dieldrin, hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT), along with its metabolites DDE and DDD were determined. OC pesticides dieldrin, p,p'-DDE, p,p'-DDD and p,p'-DDT were present at the highest concentrations.

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This article investigates the development and interaction of the views of medical professionals and health officials on elderly care between 1946 and the early 1970s. It examines how the cultural and political context in which new ideas on the treatment of elderly people emerged in the early post-war period affected policy development in this area. The article argues that, in combination, the political and financial imperatives of health officials and the cultural prejudices of many in the medical profession created a situation in which progressive ideas about geriatric medicine and home care were used, not to improve the overall standard of care for elderly people, but to restrict their access to long-term medical and nursing care.

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Homogeneous human lymphoblastoid interferon with an apparent molecular size of 18,500 daltons was characterized by its amino acid composition. Analysis of the amino terminal sequence by Edman degradation indicates that the sequence is unique.

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One component of human lymphoblastoid interferon obtained from Namalwa cultures induced by Newcastle disease virus has been purified to a specific activity of 2.5 x 10(8) interferon units per mg of protein (protein content based on amino acid analysis). A single polypeptide species with an apparent molecular weight of 18,500 comigrating with the antiviral activity was observed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis.

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The human lymphoblastoid cell line, Namalwa, can be cultured in serum-free media to cell densities of 3 to 4 x 10(6) cells per ml. These cultures produce up to 10 000 units of interferon per ml when induced with Newcastle disease virus, strain B1. Maximum accumulation of interferon was obtained at approx.

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A stable and predictable production system is described for pilot plant quantities (milligram) of human lymphoid interferon, using suspension culture of an African Burkitt's lymphoma derived cell line Namalva with induction by Newcastle disease virus, B-1 strain. Cell cultures were grown in impeller-driven 50-liter fermentors with dilution of the postinduction culture using serum-free medium. High levels of dissolved oxygen were necessary for optimum cell growth.

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