1,513 research outputs found
Designing 21st Century Standard Ware: The Cultural Heritage of Leach and the Potential Applications of Digital Technologies
No full textThis practice-based research investigates the potential applications of digital manufacturing technologies in the design and production of hand-made tableware at the Leach Pottery. The methodology for the research establishes an approach grounded in my previous experience as a maker that is informed by an open, experimental, emergent, and responsive framework based on Naturalistic Inquiry.
A critical contextual review describes the cultural heritage of Leach which, for the purposes of the research, is developed through the Leach Pottery as a significant site, the historical production of the iconic Leach Standard Ware and the contemporary production of Leach Tableware. This is followed by an examination of Potter’s Tools in the Leach production environment, and a review of makers’ digital ceramic practice.
The contextual review is followed by an explication of ‘standards’ presented through visual lineages of Standard Ware and Leach Tableware to define ‘standard’ at a design (macro) level, followed by an examination of how ‘standard’ operates at a making (micro level) level. This chapter presents new knowledge in relation to defining the visual field of Leach Pottery tableware production and its standards of design.
A chapter focussed on practice presents the outcomes and analysis of my engagement with digital manufacturing technologies which resulted in the development of new tools to support Leach Tableware production and the interrogation of Leach forms, in different mediums, which led to the creation of Digital-Analogue Leach forms. The practice culminated in the design and development of new 21st century Standard Ware: a range of 9 forms, called Echo of Leach, that were developed by myself using digital and analogue methods: the designs were realised by myself, the Leach Studio, and a further four makers. The outcomes of the research were presented in a three month exhibition at the Leach Pottery in 2013.
The conclusions of the research draw on the key points raised in the analysis of the practice and relate these to the approaches to making pottery that are highlighted in the cultural heritage of Leach in the contextual review. These are also discussed in relation to ways in which these findings could be taken forward into development of knowledge about Standard Ware, especially in a broader studio pottery context
A novel approach to evaluate spatial resolution of MRI clinical images for optimization and standardization of breast screening protocols
No full textPURPOSE: Stringent quality assurance is required in MRI breast screening to ensure that different scanners and imaging protocols reach similar diagnostic performance. The authors propose a methodology, based on power spectrum analysis (PSA), to evaluate spatial resolution in clinical images. To demonstrate this approach, the authors have retrospectively compared two MRI sequences commonly employed in breast screening. METHODS: In a novel approach to PSA, spatial frequency response curves (SFRCs) were extracted from the images. The SFRC characterizes spatial resolution describing the spatial frequency content of an image over a range of frequencies. Verification of the SFRCs was performed on MRI images of Eurospin agarose gel tubes acquired with different resolution settings. SFRCs of volunteer and patient images obtained with two clinical MRI sequences were then compared. The two sequences differed primarily in k-space coverage pattern, which was either radial (RAD) or linear (LIN). RESULTS: The computed SFRCs were able to demonstrate the differences between RAD and LIN sequences in relatively small groups of subjects. The curves showed a similar pattern of decay in both volunteer and patient images, indicating that the spatial frequency response is mainly determined by the imaging protocol and not by intersubject anatomical differences. The LIN protocol produced images with increased sharpness; this was reflected in the corresponding SFRCs, which showed a higher content of spatial frequencies associated with image details. CONCLUSIONS: The SFRC can provide an objective assessment of the presence of spatial details in the image and represent a useful quality assurance tool in the evaluation of different breast screening protocols. With a reference image, a comparative analysis of the SFRCs could ensure that equivalent image quality is achieved across different scanners and sites
Slice Encoding for Metal Artefact Correction in magnetic resonance imaging examinations for radiotherapy planning
No full textAbstractBackground and purposeMagnetic resonance (MR) and computed tomography (CT) images are degraded in the presence of metallic implants. We investigate whether SEMAC (Slice Encoding for Metal Artifact Correction) MR is advantageous for radiotherapy (RT) planning.MethodsConventional and SEMAC MR protocols were compared (1.5T). A spine fixation device suspended in gelatine, two patients with spine fixation devices and six patients with bilateral hip replacements were scanned with both conventional and SEMAC protocols. In spine patients the visibility of the spinal canal and spinal cord was assessed; in prostate patients, the visibility of the prostate, pelvic structures and the pelvic girdle.ResultsThe signal loss volume surrounding the spine fixation device was reduced by approximately 20% when the SEMAC protocol was employed, and registration errors were reduced. For spine patients, the spinal canal was completely visible only using the SEMAC protocol. In hip replacement patients, metal artifacts were local; the signal loss extended to the internal surface of the acetabulum in eight implants with conventional protocols, but only in four using SEMAC.ConclusionsSEMAC MR contributes towards correct co-registration of MR and CT images for RT planning, and is particularly relevant when the TV or OARs are close to implants
Pre-natal exposures and breast tissue composition: findings from a British pre-birth cohort of young women and a systematic review.
No full textBACKGROUND: Breast density, the amount of fibroglandular tissue in the adult breast for a women's age and body mass index, is a strong biomarker of susceptibility to breast cancer, which may, like breast cancer risk itself, be influenced by events early in life. In the present study, we investigated the association between pre-natal exposures and breast tissue composition. METHODS: A sample of 500 young, nulliparous women (aged approximately 21 years) from a U.K. pre-birth cohort underwent a magnetic resonance imaging examination of their breasts to estimate percent water, a measure of the relative amount of fibroglandular tissue equivalent to mammographic percent density. Information on pre-natal exposures was collected throughout the mothers' pregnancy and shortly after delivery. Regression models were used to investigate associations between percent water and pre-natal exposures. Mediation analysis, and a systematic review and meta-analysis of the published literature, were also conducted. RESULTS: Adjusted percent water in young women was positively associated with maternal height (p for linear trend [p t] = 0.005), maternal mammographic density in middle age (p t = 0.018) and the participant's birth size (p t < 0.001 for birthweight). A 1-SD increment in weight (473 g), length (2.3 cm), head circumference (1.2 cm) and Ponderal Index (4.1 g/cm3) at birth were associated with 3 % (95 % CI 2-5 %), 2 % (95 % CI 0-3 %), 3 % (95 % CI 1-4 %) and 1 % (95 % CI 0-3 %), respectively, increases in mean adjusted percent water. The effect of maternal height on the participants' percent water was partly mediated through birth size, but there was little evidence that the effect of birthweight was primarily mediated via adult body size. The meta-analysis supported the study findings, with breast density being positively associated with birth size. CONCLUSIONS: These findings provide strong evidence of pre-natal influences on breast tissue composition. The positive association between birth size and relative amount of fibroglandular tissue indicates that breast density and breast cancer risk may share a common pre-natal origin
A generalized framework unifying image registration and respiratory motion models and incorporating image reconstruction, for partial image data or full images
No full textSurrogate-driven respiratory motion models relate the motion of the internal anatomy to easily acquired respiratory surrogate signals, such as the motion of the skin surface. They are usually built by first using image registration to determine the motion from a number of dynamic images, and then fitting a correspondence model relating the motion to the surrogate signals. In this paper we present a generalized framework that unifies the image registration and correspondence model fitting into a single optimization. This allows the use of 'partial' imaging data, such as individual slices, projections, or k-space data, where it would not be possible to determine the motion from an individual frame of data. Motion compensated image reconstruction can also be incorporated using an iterative approach, so that both the motion and a motion-free image can be estimated from the partial image data. The framework has been applied to real 4DCT, Cine CT, multi-slice CT, and multi-slice MR data, as well as simulated datasets from a computer phantom. This includes the use of a super-resolution reconstruction method for the multi-slice MR data. Good results were obtained for all datasets, including quantitative results for the 4DCT and phantom datasets where the ground truth motion was known or could be estimated
Evaluation of diffusion models in breast cancer
No full textPURPOSE: The purpose of this study is to investigate whether the microvascular pseudodiffusion effects resulting with non-monoexponential behavior are present in breast cancer, taking into account tumor spatial heterogeneity. Additionally, methodological factors affecting the signal in low and high diffusion-sensitizing gradient ranges were explored in phantom studies. METHODS: The effect of eddy currents and accuracy of b-value determination using a multiple b-value diffusion-weighted MR imaging sequence were investigated in test objects. Diffusion model selection and noise were then investigated in volunteers (n = 5) and breast tumor patients (n = 21) using the Bayesian information criterion. RESULTS: 54.3% of lesion voxels were best fitted by a monoexponential, 26.2% by a stretched-exponential, and 19.5% by a biexponential intravoxel incoherent motion (IVIM) model. High correlation (0.92) was observed between diffusion coefficients calculated using mono- and stretched-exponential models and moderate (0.59) between monoexponential and IVIM (medians: 0.96/0.84/0.72 × 10(-3) mm(2)/s, respectively). Distortion due to eddy currents depended on the direction of the diffusion gradient and displacement varied between 1 and 6 mm for high b-value images. Shift in the apparent diffusion coefficient due to intrinsic field gradients was compensated for by averaging diffusion data obtained from opposite directions. CONCLUSIONS: Pseudodiffusion and intravoxel heterogeneity effects were not observed in approximately half of breast cancer and normal tissue voxels. This result indicates that stretched and IVIM models should be utilized in regional analysis rather than global tumor assessment. Cross terms between diffusion-sensitization gradients and other imaging or susceptibility-related gradients are relevant in clinical protocols, supporting the use of geometric averaging of diffusion-weighted images acquired with diffusion-sensitization gradients in opposite directions
Breast MRI segmentation for density estimation: Do different methods give the same results and how much do differences matter?
No full textPURPOSE: To compare two methods of automatic breast segmentation with each other and with manual segmentation in a large subject cohort. To discuss the factors involved in selecting the most appropriate algorithm for automatic segmentation and, in particular, to investigate the appropriateness of overlap measures (e.g., Dice and Jaccard coefficients) as the primary determinant in algorithm selection. METHODS: Two methods of breast segmentation were applied to the task of calculating MRI breast density in 200 subjects drawn from the Avon Longitudinal Study of Parents and Children, a large cohort study with an MRI component. A semiautomated, bias-corrected, fuzzy C-means (BC-FCM) method was combined with morphological operations to segment the overall breast volume from in-phase Dixon images. The method makes use of novel, problem-specific insights. The resulting segmentation mask was then applied to the corresponding Dixon water and fat images, which were combined to give Dixon MRI density values. Contemporaneously acquired T1 - and T2 -weighted image datasets were analyzed using a novel and fully automated algorithm involving image filtering, landmark identification, and explicit location of the pectoral muscle boundary. Within the region found, fat-water discrimination was performed using an Expectation Maximization-Markov Random Field technique, yielding a second independent estimate of MRI density. RESULTS: Images are presented for two individual women, demonstrating how the difficulty of the problem is highly subject-specific. Dice and Jaccard coefficients comparing the semiautomated BC-FCM method, operating on Dixon source data, with expert manual segmentation are presented. The corresponding results for the method based on T1 - and T2 -weighted data are slightly lower in the individual cases shown, but scatter plots and interclass correlations for the cohort as a whole show that both methods do an excellent job in segmenting and classifying breast tissue. CONCLUSIONS: Epidemiological results demonstrate that both methods of automated segmentation are suitable for the chosen application and that it is important to consider a range of factors when choosing a segmentation algorithm, rather than focus narrowly on a single metric such as the Dice coefficient
Leach and EP (extraction procedure) toxicity tests on grouted waste from Tank 106-AN
No full textPacific Northwest Laboratory is conducting laboratory experiments to produce leach rate data for various waste species that will be contained in grout at Hanford. In the work reported here, grout made from Tank 106-AN liquid waste was used to produce empirical leach rate data for several radionuclides ({sup 60}Co, {sup 90}Sr, {99}Tc, {129}I, {137}Cs, and {sup 241}Am), stable major components (NO{sub 3}{sup {minus}}, NO{sub 2}{sup {minus}}, F, Cl, and Na), and trace metals (Cr, Mo, and Ni). Two types of tests were used to produce leach rate data: an intermittent replacement leach test (ANS 16.1 leach test) and a static leach test. Measured effective diffusivities of key species are as follows: 4 to 6 {times} 10{sup {minus}8} cm{sup 2}/sec for {sup 99}Tc, 3 to 7 {times} 10{sup {minus}8} cm{sup 2}/sec for {sup 129}I, 4 to 6 {times} 10{sup {minus}9} cm{sup 2}/sec for nitrate, and 6 to 7 {times} 10{sup {minus}9} cm{sup 2}/sec for nitrite. The leach indices of all species studied are above (more favorable than) the waste form criteria. The leach indices for {sup 99}Tc and {sup 129}I are 7.4 {plus minus} 1.2 and 7.6 {plus minus} 0.4, respectively, and are being further investigated in continuing studies of double-shell slurry feed grouts. An Extraction Procedure (EP) toxicity test was also conducted and the grouted water is considered nontoxic per this test protocol. 19 refs., 9 figs., 8 tabs
Growth Trajectories, Breast Size, and Breast-Tissue Composition in a British Prebirth Cohort of Young Women.
No full textMammographic percent density, the proportion of fibroglandular tissue in the breast, is a strong risk factor for breast cancer, but its determinants in young women are unknown. We examined associations of magnetic resonance imaging (MRI) breast-tissue composition at age 21 years with prospectively collected measurements of body size and composition from birth to early adulthood and markers of puberty (all standardized) in a sample of 500 nulliparous women from a prebirth cohort of children born in Avon, United Kingdom, in 1991-1992 and followed up to 2011-2014. Linear models were fitted to estimate relative change in MRI percent water, which is equivalent to mammographic percent density, associated with a 1-standard-deviation increase in the exposure of interest. In mutually adjusted analyses, MRI percent water was positively associated with birth weight (relative change (RC) = 1.03, 95% confidence interval (CI): 1.00, 1.06) and pubertal height growth (RC = 1.07, 95% CI: 1.02, 1.13) but inversely associated with pubertal weight growth (RC = 0.86, 95% CI: 0.84, 0.89) and changes in dual-energy x-ray absorptiometry percent body fat mass (e.g., for change between ages 11 years and 13.5 years, RC = 0.96, 95% CI: 0.93, 0.99). Ages at thelarche and menarche were positively associated with MRI percent water, but these associations did not persist upon adjustment for height and weight growth. These findings support the hypothesis that growth trajectories influence breast-tissue composition in young women, whereas puberty plays no independent role
Leach tests on grouts made with actual and trace metal-spiked synthetic phosphate/sulfate waste
No full textPacific Northwest Laboratory conducted experiments to produce empirical leach rate data for phosphate-sulfate waste (PSW) grout. Effective diffusivities were measured for various radionuclides ({sup 90}Sr, {sup 99}Tc, {sup 14}C, {sup 129}I, {sup 137}Cs, {sup 60}Co, {sup 54}Mn, and U), stable major components (NO{sub 3}{sup {minus}}, SO{sub 4}{sup 2{minus}}, H{sub 3}BO{sub 3}, K and Na) and the trace constituents Ag, As, Cd, Hg, Pb, and Se. Two types of leach tests were used on samples of actual PSW grout and synthetic PSW grout: the American Nuclear Society (ANS) 16.1 intermittent replacement leach test and a static leach test. Grout produced from both synthetic and real PSW showed low leach rates for the trace metal constituents and most of the waste radionuclides. Many of the spiked trace metals and radionuclides were not detected in any leachates. None of the effluents contained measurable quantities of {sup 137}Cs, {sup 60}Co, {sup 54}Mn, {sup 109}Cd, {sup 51}Cr, {sup 210}Pb, {sup 203}Hg, or As. For those trace species with detectable leach rates, {sup 125}I appeared to have the greatest leach rate, followed by {sup 99}Tc, {sup 75}Se, and finally U, {sup 14}C, and {sup 110m}Ag. Leach rates for nitrate are between those for I and Tc, but there is much scatter in the nitrate data because of the very low nitrate inventory. 32 refs., 6 figs., 15 tabs
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