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1.
Food Res Int ; 191: 114724, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-39059920

RESUMEN

Plant-based cheese analogs have emerged as a novel global market trend driven by sustainability concerns for our planet. This study examines eleven soft ripened plant-based cheese analogs produced in Europe, primarily with bloomy rinds and cashew nuts as the main ingredient. First, we focused on exploring the macronutrients and salt content stated on the labels, as well a detailed fatty acid analysis of the samples. Compared to dairy cheeses, plant-based cheeses share similarities in lipid content, but their fatty acid profiles diverge significantly, with higher ratio of mono- and polyunsaturated fatty acids such as oleic and linoleic acids. We also investigated the microbiota of these analog products, employing a culture-dependent and -independent approaches. We identified a variety of microorganisms in the plant-based cheeses, with Lactococcus lactis and Leuconostoc mesenteroides being the dominant bacterial species, and Geotrichum candidum and Penicillium camemberti the dominant fungal species. Most of the species characterized are similar to those present in dairy cheeses, suggesting that they have been inoculated as culture starters to contribute to the sensorial acceptance of plant-based cheeses. However, we also identify several species that are possibly intrinsic to plant matrices or originate from the production environment, such as Pediococcus pentosaceus and Enterococcus spp. This coexistence of typical dairy-associated organisms with plant associated species highlights the potential microbial dynamics inherent in the production of plant-based cheese. These findings will contribute to a better understanding of plant-based cheese alternatives, enable the development of sustainable products, and pave the way for future research exploring the use of plant-based substrates in the production of cheese analogues.


Asunto(s)
Queso , Microbiología de Alimentos , Queso/microbiología , Queso/análisis , Europa (Continente) , Valor Nutritivo , Ácidos Grasos/análisis , Bacterias/clasificación
2.
Food Res Int ; 189: 114490, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-38876584

RESUMEN

Fermentation is resurgent around the world as people seek healthier, more sustainable, and tasty food options. This study explores the microbial ecology of miso, a traditional Japanese fermented paste, made with novel regional substrates to develop new plant-based foods. Eight novel miso varieties were developed using different protein-rich substrates: yellow peas, Gotland lentils, and fava beans (each with two treatments: standard and nixtamalisation), as well as rye bread and soybeans. The misos were produced at Noma, a restaurant in Copenhagen, Denmark. Samples were analysed with biological and technical triplicates at the beginning and end of fermentation. We also incorporated in this study six samples of novel misos produced following the same recipe at Inua, a former affiliate restaurant of Noma in Tokyo, Japan. To analyse microbial community structure and diversity, metabarcoding (16S and ITS) and shotgun metagenomic analyses were performed. The misos contain a greater range of microbes than is currently described for miso in the literature. The composition of the novel yellow pea misos was notably similar to the traditional soybean ones, suggesting they are a good alternative, which supports our culinary collaborators' sensory conclusions. For bacteria, we found that overall substrate had the strongest effect, followed by time, treatment (nixtamalisation), and geography. For fungi, there was a slightly stronger effect of geography and a mild effect of substrate, and no significant effects for treatment or time. Based on an analysis of metagenome-assembled genomes (MAGs), strains of Staphylococccus epidermidis differentiated according to substrate. Carotenoid biosynthesis genes in these MAGs appeared in strains from Japan but not from Denmark, suggesting a possible gene-level geographical effect. The benign and possibly functional presence of S. epidermidis in these misos, a species typically associated with the human skin microbiome, suggests possible adaptation to the miso niche, and the flow of microbes between bodies and foods in certain fermentation as more common than is currently recognised. This study improves our understanding of miso ecology, highlights the potential for developing novel misos using diverse local ingredients, and suggests how fermentation innovation can contribute to studies of microbial ecology and evolution.


Asunto(s)
Bacterias , Fermentación , Microbiología de Alimentos , Bacterias/clasificación , Bacterias/genética , Bacterias/metabolismo , Gusto , Alimentos Fermentados/microbiología , Microbiota , Japón , Metagenómica
3.
J Spec Oper Med ; 23(2): 107-109, 2023 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-37084414

RESUMEN

In contrast to shallow water (hypoxic) blackout and swimming-induced pulmonary edema (SIPE), acute electrolyte disturbance secondary to acute respiratory alkalosis is not considered a common Combat Swimmer injury but has the potential to be life-threatening. We present the case of a 28-year-old Special Operations Dive Candidate who presented to the Emergency Department after a near-drowning incident with altered mental status, generalized weakness, respiratory distress, and tetany. He was found to have severe symptomatic hypophosphatemia (1.00mg/dL) and mild hypocalcemia secondary to intentional hyperventilation between subsurface "cross-overs," causing subsequent acute respiratory alkalosis. This is a unique presentation of a common electrolyte abnormality in a highly specialized population that is self-limiting when caused by acute respiratory alkalosis but poses a significant danger to Combat Swimmers if rescue personnel are not able to respond quickly.


Asunto(s)
Alcalosis Respiratoria , Hipofosfatemia , Tetania , Masculino , Humanos , Adulto , Alcalosis Respiratoria/etiología , Alcalosis Respiratoria/complicaciones , Tetania/complicaciones , Hipofosfatemia/complicaciones , Hiperventilación/complicaciones , Agua
4.
J Spec Oper Med ; 23(2): 114-117, 2023 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-36951633

RESUMEN

Prolonged Casualty Care (PCC) has become an essential component to Special Operations Forces (SOF) pre-mission training. However, it has not regularly been required in recent combat operations with the availability of medical evacuation (MEDEVAC) support. Poor weather conditions at an austere SOF outpost created an emergency unreachable by aeromedical evacuation. Herein, we report a case of an emergency bilateral above-the-knee amputation procedure performed by three Special Forces Medical Sergeants (18D(a), 18D(b), and 18D(c)) and supporting Army medics with minimal telemedicine consult and guidance.


Asunto(s)
Medicina Militar , Personal Militar , Humanos , Afganistán , Medicina Militar/educación , Personal Militar/educación , Amputación Quirúrgica
5.
J Spec Oper Med ; 21(4): 108-111, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34969139

RESUMEN

Tuberculosis (TB) causes approximately 2 million deaths annually worldwide, with 2 billion persons estimated to be actively infected with TB. While rates of active TB disease in the US military are low, military service in TB-endemic countries remains an uncommon, but important source of infection. United States Special Operations Forces (USSOF) and enablers often operate in TB-endemic countries and, as an inherent risk of their mission sets, are more likely to have high-risk exposure to TB disease. Military medical authorities have provided excellent diagnostic guidance; the Centers for Disease Control and Prevention (CDC) recently updated preferred regimens for the treatment of latent TB infection (LTBI). This review serves as a refresher and update to the management of LTBI in USSOF to optimize medical readiness through targeted testing and short treatment regimens.


Asunto(s)
Tuberculosis Latente , Personal Militar , Tuberculosis , Centers for Disease Control and Prevention, U.S. , Humanos , Tuberculosis Latente/diagnóstico , Tuberculosis Latente/tratamiento farmacológico , Tuberculosis Latente/epidemiología , Tuberculosis/diagnóstico , Tuberculosis/tratamiento farmacológico , Tuberculosis/epidemiología , Estados Unidos/epidemiología
6.
J Ethnobiol Ethnomed ; 13(1): 13, 2017 Feb 08.
Artículo en Inglés | MEDLINE | ID: mdl-28178988

RESUMEN

BACKGROUND: Domestication is an important and contested concept. Insects are used as food worldwide, and while some have been described as domesticated and even 'semi-domesticated', the assumptions and implications of this designation are not clear. The purpose of this paper is to explore these aspects of insect domestication, and broader debates in domestication studies, through the case of edible wasps in central rural Japan. METHODS: Both authors conducted ethnographic fieldwork with communities in central rural Japan. Fieldwork comprised participant observation, semi-structured interviews, quantitative surveys and a review of resources including the personal and public records of wasp collectors. RESULTS: The practice of keeping wasps in hive boxes has historical roots and has changed significantly within living memory. Current attempts to further develop the practice involve collectors' great efforts to keep new queens during their hibernation. Collectors have also tried, still without success, to keep wasps living within a human-made enclosure for their entire life cycle. These and other practices are costly in both time and money for collectors, who emphasise enjoyment as their primary motivation. At the same time, they also engage in practices such as pesticide use that they recognise as damaging to wasp ecology. CONCLUSIONS: These practices can be understood to some extent in domesticatory terms, and in terms of care. We develop a framework for understanding domesticatory practices of insect care, discuss how this case contributes to ongoing debates within domestication studies, and recommend further research to be pursued.


Asunto(s)
Domesticación , Alimentos , Avispas , Animales , Humanos , Entrevistas como Asunto , Japón , Larva , Estadios del Ciclo de Vida , Población Rural , Encuestas y Cuestionarios , Avispas/fisiología
7.
J Endod ; 42(10): 1490-5, 2016 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-27663615

RESUMEN

INTRODUCTION: Root canal disinfection and the establishment of an intracanal microenvironment conducive to the proliferation/differentiation of stem cells play a significant role in regenerative endodontics. This study was designed to (1) investigate the antimicrobial efficacy of triple antibiotic-containing nanofibers against a dual-species biofilm and (2) evaluate the ability of dental pulp stem cells (DPSCs) to adhere to and proliferate on dentin upon nanofiber exposure. METHODS: Seven-day-old dual-species biofilm established on dentin specimens was exposed for 3 days to the following: saline (control), antibiotic-free nanofibers (control), and triple antibiotic-containing nanofibers or a saturated triple antibiotic paste (TAP) solution (50 mg/mL in phosphate buffer solution). Bacterial viability was assessed using the LIVE/DEAD assay (Molecular Probes, Inc, Eugene, OR) and confocal laser scanning microscopy. For cytocompatibility studies, dentin specimens after nanofiber or TAP (1 g/mL in phosphate buffer solution) exposure were evaluated for cell adhesion and spreading by actin-phalloidin staining. DPSC proliferation was assessed on days 1, 3, and 7. Statistics were performed, and significance was set at the 5% level. RESULTS: Confocal laser scanning microscopy showed significant bacterial death upon antibiotic-containing nanofiber exposure, differing significantly (P < .05) from antibiotic-free fibers and the control (saline). DPSCs showed enhanced adhesion/spreading on dentin specimens treated with antibiotic-containing nanofibers when compared with its TAP counterparts. The DPSC proliferation rate was similar on days 1 and 3 in antibiotic-free nanofibers, triple antibiotic-containing nanofibers, and TAP-treated dentin. Proliferation was higher (9-fold) on dentin treated with antibiotic-containing nanofibers on day 7 compared with TAP. CONCLUSIONS: Triple antibiotic-containing polymer nanofibers led to significant bacterial death, whereas they did not affect DPSC attachment and proliferation on dentin.


Asunto(s)
Antibacterianos/administración & dosificación , Biopelículas/efectos de los fármacos , Sistemas de Liberación de Medicamentos/métodos , Nanofibras/administración & dosificación , Polímeros/administración & dosificación , Antibacterianos/química , Bacterias/citología , Bacterias/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Pulpa Dental/citología , Pulpa Dental/efectos de los fármacos , Pulpa Dental/microbiología , Dentina/microbiología , Desinfección/métodos , Humanos , Nanofibras/química , Tratamiento del Conducto Radicular/métodos , Células Madre/citología , Células Madre/efectos de los fármacos , Células Madre/microbiología
8.
Clin Oral Investig ; 20(2): 387-93, 2016 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-26319981

RESUMEN

OBJECTIVES: This study sought to investigate, in vitro, the effects of a recently developed triple antibiotic paste (TAP)-mimic polymer nanofibrous scaffold against Porphyromonas gingivalis-infected dentin biofilm. MATERIALS AND METHODS: Dentin specimens (4 × 4 × 1 mm(3)) were prepared from human canines. The specimens were sterilized, inoculated with P. gingivalis (ATCC 33277), and incubated for 1 week to allow for biofilm formation. Infected dentin specimens were exposed for 3 days to the following treatments: antibiotic-free polydioxanone scaffold (PDS, control), PDS + 25 wt% TAP [25 mg of each antibiotic (metronidazole, ciprofloxacin, and minocycline) per mL of the PDS polymer solution], or a saturated TAP-based solution (50 mg of each antibiotic per mL of saline solution). In order to serve as the negative control, infected dentin specimens were left untreated (bacteria only). To determine the antimicrobial efficacy of the TAP-mimic scaffold, a colony-forming unit (CFU) per milliliter (n = 10/group) measurement was performed. Furthermore, additional specimens (n = 2/group) were prepared to qualitatively study biofilm inhibition via scanning electron microscopy (SEM). Statistics were performed, and significance was set at the 5% level. RESULTS: Both the TAP-mimic scaffold and the positive control (TAP solution) led to complete bacterial elimination, differing statistically (p < 0.05) from the negative control group (bacteria only). No statistical differences were observed for CFU per milliliter data between antibiotic-free scaffolds (2.7 log10 CFU/mL) and the negative control (5.9 log10 CFU/mL). CONCLUSIONS: The obtained data revealed significant antimicrobial properties of the novel PDS-based TAP-mimic scaffold against an established P. gingivalis-infected dentin biofilm. CLINICAL RELEVANCE: Collectively, the data suggest that the proposed nanofibrous scaffold might be used as an alternative to the advocated clinical gold standard (i.e., TAP) for intracanal disinfection prior to regenerative endodontics.


Asunto(s)
Antibacterianos/farmacología , Biopelículas/efectos de los fármacos , Dentina/efectos de los fármacos , Dentina/microbiología , Porphyromonas gingivalis/efectos de los fármacos , Ciprofloxacina/farmacología , Combinación de Medicamentos , Humanos , Técnicas In Vitro , Metronidazol/farmacología , Minociclina/farmacología , Nanofibras , Polidioxanona , Polímeros
9.
IEEE Trans Med Imaging ; 35(2): 685-98, 2016 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-26469126

RESUMEN

We propose a new algorithm, called line integral alternating minimization (LIAM), for dual-energy X-ray CT image reconstruction. Instead of obtaining component images by minimizing the discrepancy between the data and the mean estimates, LIAM allows for a tunable discrepancy between the basis material projections and the basis sinograms. A parameter is introduced that controls the size of this discrepancy, and with this parameter the new algorithm can continuously go from a two-step approach to the joint estimation approach. LIAM alternates between iteratively updating the line integrals of the component images and reconstruction of the component images using an image iterative deblurring algorithm. An edge-preserving penalty function can be incorporated in the iterative deblurring step to decrease the roughness in component images. Images from both simulated and experimentally acquired sinograms from a clinical scanner were reconstructed by LIAM while varying the regularization parameters to identify good choices. The results from the dual-energy alternating minimization algorithm applied to the same data were used for comparison. Using a small fraction of the computation time of dual-energy alternating minimization, LIAM achieves better accuracy of the component images in the presence of Poisson noise for simulated data reconstruction and achieves the same level of accuracy for real data reconstruction.


Asunto(s)
Algoritmos , Intensificación de Imagen Radiográfica/métodos , Tomografía Computarizada por Rayos X/métodos , Absorciometría de Fotón , Humanos , Modelos Biológicos , Fantasmas de Imagen
10.
Med Phys ; 42(6): 2908-14, 2015 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-26127044

RESUMEN

PURPOSE: To provide a noninvasive technique to measure the intensity profile of the fan beam in a computed tomography (CT) scanner that is cost effective and easily implemented without the need to access proprietary scanner information or service modes. METHODS: The fabrication of an inexpensive aperture is described, which is used to expose radiochromic film in a rotating CT gantry. A series of exposures is made, each of which is digitized on a personal computer document scanner, and the resulting data set is analyzed to produce a self-consistent calibration of relative radiation exposure. The bow tie profiles were analyzed to determine the precision of the process and were compared to two other measurement techniques, direct measurements from CT gantry detectors and a dynamic dosimeter. RESULTS: The radiochromic film method presented here can measure radiation exposures with a precision of ∼ 6% root-mean-square relative error. The intensity profiles have a maximum 25% root-mean-square relative error compared with existing techniques. CONCLUSIONS: The proposed radiochromic film method for measuring bow tie profiles is an inexpensive (∼$100 USD + film costs), noninvasive method to measure the fan beam intensity profile in CT scanners.


Asunto(s)
Dosimetría por Película/métodos , Tomografía Computarizada por Rayos X/instrumentación , Rotación
11.
Med Phys ; 41(10): 101915, 2014 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-25281967

RESUMEN

PURPOSE: Several areas of computed tomography (CT) research require knowledge about the intensity profile of the x-ray fan beam that is introduced by a bow tie filter. This information is considered proprietary by CT manufacturers, so noninvasive measurement methods are required. One method using real-time dosimeters has been proposed in the literature. A commercially available dosimeter was used to apply that method, and analysis techniques were developed to extract fan beam profiles from measurements. METHODS: A real-time ion chamber was placed near the periphery of an empty CT gantry and the dose rate versus time waveform was recorded as the x-ray source rotated about the isocenter. In contrast to previously proposed analysis methods that assumed a pointlike detector, the finite-size ion chamber received varying amounts of coverage by the collimated x-ray beam during rotation, precluding a simple relationship between the source intensity as a function of fan beam angle and measured intensity. A two-parameter model for measurement intensity was developed that included both effective collimation width and source-to-detector distance, which then was iteratively solved to minimize the error between duplicate measurements at corresponding fan beam angles, allowing determination of the fan beam profile from measured dose-rate waveforms. Measurements were performed on five different scanner systems while varying parameters such as collimation, kVp, and bow tie filters. On one system, direct measurements of the bow tie profile were collected for comparison with the real-time dosimeter technique. RESULTS: The data analysis method for a finite-size detector was found to produce a fan beam profile estimate with a relative error between duplicate measurement intensities of <5%. It was robust over a wide range of collimation widths (e.g., 1-40 mm), producing fan beam profiles that agreed with a relative error of 1%-5%. Comparison with a direct measurement technique on one system produced agreement with a relative error of 2%-6%. Fan beam profiles were found to differ for different filter types on a given system and between different vendors. CONCLUSIONS: A commercially available real-time dosimeter probe was found to be a convenient and accurate instrument for measuring fan beam profiles. An analysis method was developed that could handle a wide range of collimation widths by explicitly considering the finite width of the ion chamber. Relative errors in the profiles were found to be less than 5%. Measurements of five different clinical scanners demonstrate the variation in bow tie designs, indicating that generic bow tie models will not be adequate for CT system research.


Asunto(s)
Radiometría/instrumentación , Radiometría/métodos , Tomógrafos Computarizados por Rayos X , Algoritmos , Modelos Teóricos , Tomografía Computarizada por Rayos X , Rayos X
12.
Med Phys ; 40(12): 121914, 2013 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-24320525

RESUMEN

PURPOSE: Accurate patient-specific photon cross-section information is needed to support more accurate model-based dose calculation for low energy photon-emitting modalities in medicine such as brachytherapy and kilovoltage x-ray imaging procedures. A postprocessing dual-energy CT (pDECT) technique for noninvasive in vivo estimation of photon linear attenuation coefficients has been experimentally implemented on a commercial CT scanner and its accuracy assessed in idealized phantom geometries. METHODS: Eight test materials of known composition and density were used to compare pDECT-estimated linear attenuation coefficients to NIST reference values over an energy range from 10 keV to 1 MeV. As statistical image reconstruction (SIR) has been shown to reconstruct images with less random and systematic error than conventional filtered backprojection (FBP), the pDECT technique was implemented with both an in-house polyenergetic SIR algorithm, alternating minimization (AM), as well as a conventional FBP reconstruction algorithm. Improvement from increased spectral separation was also investigated by filtering the high-energy beam with an additional 0.5 mm of tin. The law of propagated uncertainty was employed to assess the sensitivity of the pDECT process to errors in reconstructed images. RESULTS: Mean pDECT-estimated linear attenuation coefficients for the eight test materials agreed within 1% of NIST reference values for energies from 1 MeV down to 30 keV, with mean errors rising to between 3% and 6% at 10 keV, indicating that the method is unbiased when measurement and calibration phantom geometries are matched. Reconstruction with FBP and AM algorithms conferred similar mean pDECT accuracy. However, single-voxel pDECT estimates reconstructed on a 1 × 1 × 3 mm(3) grid are shown to be highly sensitive to reconstructed image uncertainty; in some cases pDECT attenuation coefficient estimates exhibited standard deviations on the order of 20% around the mean. Reconstruction with the statistical AM algorithm led to standard deviations roughly 40% to 60% less than FBP reconstruction. Additional tin filtration of the high energy beam exhibits similar pDECT estimation accuracy as the unfiltered beam, even when scanning with only 25% of the dose. Using the law of propagated uncertainty, low Z materials are found to be more sensitive to image reconstruction errors than high Z materials. Furthermore, it is estimated that reconstructed CT image uncertainty must be limited to less than 0.25% to achieve a target linear-attenuation coefficient estimation uncertainty of 3% at 28 keV. CONCLUSIONS: That pDECT supports mean linear attenuation coefficient measurement accuracies of 1% of reference values for energies greater than 30 keV is encouraging. However, the sensitivity of the pDECT measurements to noise and systematic errors in reconstructed CT images warrants further investigation in more complex phantom geometries. The investigated statistical reconstruction algorithm, AM, reduced random measurement uncertainty relative to FBP owing to improved noise performance. These early results also support efforts to increase DE spectral separation, which can further reduce the pDECT sensitivity to measurement uncertainty.


Asunto(s)
Algoritmos , Procesamiento de Imagen Asistido por Computador/métodos , Fotones , Tomografía Computarizada por Rayos X/instrumentación , Calibración , Incertidumbre
13.
Phys Med ; 29(5): 500-12, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23343747

RESUMEN

PURPOSE: To present a framework for characterizing the data needed to implement a polyenergetic model-based statistical reconstruction algorithm, Alternating Minimization (AM), on a commercial fan-beam CT scanner and a novel method for assessing the accuracy of the commissioned data model. METHODS: The X-ray spectra for three tube potentials on the Philips Brilliance CT scanner were estimated by fitting a semi-empirical X-ray spectrum model to transmission measurements. Spectral variations due to the bowtie filter were computationally modeled. Eight homogeneous cylinders of PMMA, Teflon and water with varying diameters were scanned at each energy. Central-axis scatter was measured for each cylinder using a beam-stop technique. AM reconstruction with a single-basis object-model matched to the scanned cylinder's composition allows assessment of the accuracy of the AM algorithm's polyenergetic data model. Filtered-backprojection (FBP) was also performed to compare consistency metrics such as uniformity and object-size dependence. RESULTS: The spectrum model fit measured transmission curves with residual root-mean-square-error of 1.20%-1.34% for the three scanning energies. The estimated spectrum and scatter data supported polyenergetic AM reconstruction of the test cylinders to within 0.5% of expected in the matched object-model reconstruction test. In comparison to FBP, polyenergetic AM exhibited better uniformity and less object-size dependence. CONCLUSIONS: Reconstruction using a matched object-model illustrate that the polyenergetic AM algorithm's data model was commissioned to within 0.5% of an expected ground truth. These results support ongoing and future research with polyenergetic AM reconstruction of commercial fan-beam CT data for quantitative CT applications.


Asunto(s)
Algoritmos , Procesamiento de Imagen Asistido por Computador/métodos , Estadística como Asunto/métodos , Tomografía Computarizada por Rayos X/instrumentación , Radioterapia Guiada por Imagen , Incertidumbre
14.
Med Phys ; 38(3): 1444-58, 2011 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-21520856

RESUMEN

PURPOSE: In comparison with conventional filtered backprojection (FBP) algorithms for x-ray computed tomography (CT) image reconstruction, statistical algorithms directly incorporate the random nature of the data and do not assume CT data are linear, noiseless functions of the attenuation line integral. Thus, it has been hypothesized that statistical image reconstruction may support a more favorable tradeoff than FBP between image noise and spatial resolution in dose-limited applications. The purpose of this study is to evaluate the noise-resolution tradeoff for the alternating minimization (AM) algorithm regularized using a nonquadratic penalty function. METHODS: Idealized monoenergetic CT projection data with Poisson noise were simulated for two phantoms with inserts of varying contrast (7%-238%) and distance from the field-of-view (FOV) center (2-6.5 cm). Images were reconstructed for the simulated projection data by the FBP algorithm and two penalty function parameter values of the penalized AM algorithm. Each algorithm was run with a range of smoothing strengths to allow quantification of the noise-resolution tradeoff curve. Image noise is quantified as the standard deviation in the water background around each contrast insert. Modulation transfer functions (MTFs) were calculated from six-parameter model fits to oversampled edge-spread functions defined by the circular contrast-insert edges as a metric of local resolution. The integral of the MTF up to 0.5 1p/mm was adopted as a single-parameter measure of local spatial resolution. RESULTS: The penalized AM algorithm noise-resolution tradeoff curve was always more favorable than that of the FBP algorithm. While resolution and noise are found to vary as a function of distance from the FOV center differently for the two algorithms, the ratio of noises when matching the resolution metric is relatively uniform over the image. The ratio of AM-to-FBP image variances, a predictor of dose-reduction potential, was strongly dependent on the shape of the AM's nonquadratic penalty function and was also strongly influenced by the contrast of the insert for which resolution is quantified. Dose-reduction potential, reported here as the fraction (%) of FBP dose necessary for AM to reconstruct an image with comparable noise and resolution, for one penalty parameter value of the AM algorithm was found to vary from 70% to 50% for low-contrast and high-contrast structures, respectively, and from 70% to 10% for the second AM penalty parameter value. However, the second penalty, AM-700, was found to suffer from poor low-contrast resolution when matching the high-contrast resolution metric with FBP. CONCLUSIONS: The results of this simulation study imply that penalized AM has the potential to reconstruct images with similar noise and resolution using a fraction (10%-70%) of the FBP dose. However, this dose-reduction potential depends strongly on the AM penalty parameter and the contrast magnitude of the structures of interest. In addition, the authors' results imply that the advantage of AM can be maximized by optimizing the nonquadratic penalty function to the specific imaging task of interest. Future work will extend the methods used here to quantify noise and resolution in images reconstructed from real CT data.


Asunto(s)
Algoritmos , Procesamiento de Imagen Asistido por Computador/métodos , Tomografía Computarizada por Rayos X/métodos , Distribución Normal , Fantasmas de Imagen , Dispersión de Radiación
15.
Soc Sci Med ; 69(5): 716-21, 2009 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-19608322

RESUMEN

In this paper we present a dialogue about the seemingly innocuous presence of environmental art in hospital settings as a way of furthering critical perspectives on the therapeutic landscapes concept and its application to medical spaces. We explicitly consider the potential utility of two perspectives, Foucaultian and Lacanian readings, for understanding the relationship between environmental art and the hospital waiting room. We use this paper as a vehicle to demonstrate how such theoretical perspectives can enhance critical scholarship on the therapeutic landscape concept, particularly as it is applied to settings such as health clinics and hospitals. A brief agenda for further critical engagements with the therapeutic nature of health care spaces is put forth in the conclusion.


Asunto(s)
Arte , Arquitectura y Construcción de Hospitales , Diseño Interior y Mobiliario , Ambiente , Estética , Humanos , Filosofía Médica , Psicología
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