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    X-ray phase-contrast computed tomography for soft tissue Imaging at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron
    (MDPI, 2021-04-30) Arhatari, BD; Stevenson, AW; Abbey, B; Nesterets, YI; Maksimenko, A; Hall, CJ; Thompson, D; Mayo, SC; Fiala, T; Quiney, HM; Taba, ST; Lewis, SJ; Brennan, PC; Dimmock, M; Häusermann, D; Gureyev, TE
    The Imaging and Medical Beamline (IMBL) is a superconducting multipole wiggler-based beamline at the 3 GeV Australian Synchrotron operated by the Australian Nuclear Science and Technology Organisation (ANSTO). The beamline delivers hard X-rays in the 25–120 keV energy range and offers the potential for a range of biomedical X-ray applications, including radiotherapy and medical imaging experiments. One of the imaging modalities available at IMBL is propagation-based X-ray phase-contrast computed tomography (PCT). PCT produces superior results when imaging low-density materials such as soft tissue (e.g., breast mastectomies) and has the potential to be developed into a valuable medical imaging tool. We anticipate that PCT will be utilized for medical breast imaging in the near future with the advantage that it could provide better contrast than conventional X-ray absorption imaging. The unique properties of synchrotron X-ray sources such as high coherence, energy tunability, and high brightness are particularly well-suited for generating PCT data using very short exposure times on the order of less than 1 min. The coherence of synchrotron radiation allows for phase-contrast imaging with superior sensitivity to small differences in soft-tissue density. Here we also compare the results of PCT using two different detectors, as these unique source characteristics need to be complemented with a highly efficient detector. Moreover, the application of phase retrieval for PCT image reconstruction enables the use of noisier images, potentially significantly reducing the total dose received by patients during acquisition. This work is part of ongoing research into innovative tomographic methods aimed at the introduction of 3D X-ray medical imaging at the IMBL to improve the detection and diagnosis of breast cancer. Major progress in this area at the IMBL includes the characterization of a large number of mastectomy samples, both normal and cancerous, which have been scanned at clinically acceptable radiation dose levels and evaluated by expert radiologists with respect to both image quality and cancer diagnosis. © 2021 The Authors, Licensee MDPI, Basel, Switzerland. Open Access Creative Commons Attribution (CC BY).
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    Optimisation of PET data processing for a single injection experiment with [11C]Raclopride using a simulations based approach
    (Society of Nuclear Medicine, 2014-11-05) Wimberley, CA; Angelis, GI; Boisson, F; Callaghan, PD; Fischer, K; Pichler, BJ; Meikle, SR; Grégoire, MC; Reilhac, A
    Objectives Positron emission tomography (PET) with [11C]Raclopride is an important tool for studying dopamine D2 receptor expression in vivo. [11C]Raclopride PET binding experiments conducted using the Partial Saturation Approach (PSA) (a simple, single injection experiment, Delforge 1995) allow the estimation of receptor density (Bavail) and the in vivo affinity 1/(KD). To achieve accurate and stable parameter estimates, and the ability to detect small changes in these parameters, the impact of the data processing chain should be investigated and optimised. Methods Two groups of PET scans were generated for a Partial Saturation Approach (PSA) experiment using Monte Carlo simulation software with a biological phenomenon inferred between the groups. The kinetic parameters Bavail and KD were estimated and the impact of spatial smoothing, temporal denoising and image resolution recovery on the statistical detectability of change in the estimates was investigated. Results Before optimisation, the inferred Bavail difference between the two groups was underestimated by 42% and detected in 66% of cases (at p<0.05), while a false decrease of KD by 13% was detected in more than 11% of cases. After optimisation, the calculated Bavail difference was underestimated by only 3.7% and detected in 89% of cases, while a false slight increase of KD by 3.7 % was detected in only 2% of cases. Conclusions The use of Monte Carlo generated PET scans allowed the optimisation of the data processing chain in order to reliably estimate and detect changes in the parameters Bavail and KD.
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    Impact of pasteurization on the self-assembly of human milk lipids during digestion
    (Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology, 2022-05) Binte Abu Bakar, SY; Salim, M; Clulow, AJ; Hawley, A; Pelle, J; Geddes, DT; Nicholas, KR; Boyd, BJ
    Human milk is critical for the survival and development of infants. This source of nutrition contains components that protect against infections while stimulating immune maturation. In cases where the mother's own milk is unavailable, pasteurized donor milk is the preferred option. Although pasteurization has been shown to have minimal impact on the lipid and FA composition before digestion, no correlation has been made between the impact of pasteurization on the FFA composition and the self-assembly of lipids during digestion, which could act as delivery mechanisms for poorly water-soluble components. Pooled nonpasteurized and pasteurized human milk from a single donor was used in this study. The evolving FFA composition during digestion was determined using GC coupled to a flame ionization detector. In vitro digestion coupled to small-angle X-ray scattering was utilized to investigate the influence of different calcium levels, fat content, and the presence of bile salts on the extent of digestion and structural behavior of human milk lipids. Almost complete digestion was achieved when bile salts were added to the systems containing high calcium to milk fat ratio, with similar structural behavior of lipids during digestion of both types of human milk being apparent. In contrast, differences in the colloidal structures were formed during digestion in the absence of bile salt because of a greater amount of FFAs being released from the nonpasteurized than pasteurized milks. This difference in FFAs released from both types of human milk could result in varying nutritional implications for infants. © 2022 The Authors. This is an open access article under the CC BY licence
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    Phase behaviour and aggregate structures of the surface-active ionic liquid [BMIm][AOT] in water
    (Elsevier B.V., 2023-12-15) Zhang, YX; Marlow, JB; Wood, K; Wang, J; Warr, GG; Li, H; Atkin, R
    Hypothesis: The surface-active ionic liquid, 1-butyl-3-methylimidazolium 1,4-bis-2-ethylhexylsulfosuccinate ([BMIm][AOT]), has a sponge-like bulk nanostructure consisting of percolating polar and apolar domains formed by the ion charge groups and alkyl chains, respectively. We hypothesise that added water will swell the polar domains and change the liquid nanostructure. Experiments: Small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and polarizing optical microscopy (POM) were used to investigate the nanostructure of [BMIm][AOT] as a function of water content. Differential scanning calorimetry (DSC) was employed to probe the thermal transitions of [BMIm][AOT]-water mixtures and the mobility of water molecules. Findings: SAXS, SANS and POM show that at lower water contents, [BMIm][AOT]-water mixtures have a sponge-like nanostructure similar to the pure SAIL, at medium water contents a lamellar phase forms, and at high water contents vesicles form. DSC results reveal that water molecules are supercooled in the lamellar phase. For the first time, results reveal a series of transitions from inverse sponge, to lamellar then to vesicles, for [BMIm][AOT] upon dilution with water. © 2023 Elsevier Inc.
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    Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) study on the structure of sodium caseinate in dispersions and at the oil-water interface: effect of calcium ions
    (Elsevier B. V., 2022-04) Cheng, LR; Ye, AQ; Yang, Z; Gilbert, EP; Knott, RB; de Campo, L; Storer, B; Hemar, Y; Singh, H
    The structure of sodium caseinate particles, as affected by the presence of calcium ions (Ca2+), in aqueous solution and in oil (toluene)-in-water emulsions, was investigated by small-angle X-ray and neutron scattering (SAXS and SANS). SAXS analyses indicated that the sodium caseinate dispersed in water as small particles with electrostatic interactions, which has a radius of gyration (Rg) of ~5 nm and an effective radius (Reff) of ~ 10 nm with an assuming spherical shape. In the presence of Ca2+, the caseinate particles aggregated as large particles with a hydrodynamic diameter > 100 nm as determined by dynamic light scattering. The networks within the large particles were self-assembled from the small Ca2+-cross-linked particles (Rg ~ 6.5–8.0 nm), as probed by SAXS. The fractal-like dimension increased from 2.5 to 3.4 with increasing protein and CaCl2 concentrations, suggesting a denser structure. The integrity of the caseinate particles at the oil-water interface was enhanced by Ca2+ cross-linking, as observed by transmission electron microscopy. The oilsingle bondwater interface stabilised by Ca2+-cross-linked caseinate particles was ~ 30 nm thick, six times thicker than that stabilised by sodium caseinate (~ 5 nm) as analysed by SANS with contrast variation technique. Quantifying the structure of sodium caseinate in an aqueous solution and at the oil-water interface provides valuable insights for designing new casein-based functional materials. © 2022 Elsevier Ltd