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1.
Comput Methods Biomech Biomed Engin ; 27(5): 651-679, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37068041

RESUMO

The purpose of this article is to investigate the optimal control of nonlinear fractional order chaotic models of diabetes mellitus, human immunodeficiency virus, migraine and Parkinson's diseases using genetic algorithms and particle swarm optimization. Mathematical chaotic models of nonlinear fractional order type of the above diseases were presented. Then optimal control for each of the models and numerical simulation was done using genetic algorithm and particle swarm optimization algorithm. The results of the genetic algorithm method are excellent. All the results obtained for the particle swarm optimization method show that this method is also very successful and the results are very close to the genetic algorithm method. Very low values of MSE and RMSE errors indicate that the simulation is effective and efficient. Also, Lie symmetry was calculated for the proposed models and the results were presented.


Assuntos
Diabetes Mellitus , Doença de Parkinson , Humanos , HIV , Algoritmos , Modelos Teóricos , Simulação por Computador
2.
Phys Rev Lett ; 130(3): 034001, 2023 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-36763387

RESUMO

The presence of submicrometer structures at liquid-fluid interfaces modifies the properties of many science and technological systems by lowering the interfacial tension, creating tangential Marangoni stresses, and/or inducing surface viscoelasticity. Here we experimentally study the break-up of a liquid filament of a silica nanoparticle dispersion in a background oil phase that contains surfactant assemblies. Although self-similar power-law pinch-off is well documented for threads of Newtonian fluids, we report that when a viscoelastic layer is formed in situ at the interface, the pinch-off dynamics follows an exponential decay. Recently, such exponential neck thinning was found theoretically when surface viscous effects were taken into account. We introduce a simple approach to calculate the effective relaxation time of viscoelastic interfaces and estimate the thickness of the interfacial layer and the viscoelastic properties of liquid-fluid interfaces, where the direct measurement of interfacial rheology is not possible.

3.
Nat Commun ; 13(1): 4162, 2022 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-35851272

RESUMO

Printing a structured network of functionalized droplets in a liquid medium enables engineering collectives of living cells for functional purposes and promises enormous applications in processes ranging from energy storage to tissue engineering. Current approaches are limited to drop-by-drop printing or face limitations in reproducing the sophisticated internal features of a structured material and its interactions with the surrounding media. Here, we report a simple approach for creating stable liquid filaments of silica nanoparticle dispersions and use them as inks to print all-in-liquid materials that consist of a network of droplets. Silica nanoparticles stabilize liquid filaments at Weber numbers two orders of magnitude smaller than previously reported in liquid-liquid systems by rapidly producing a concentrated emulsion zone at the oil-water interface. We experimentally demonstrate the printed aqueous phase is emulsified in-situ; consequently, a 3D structure is achieved with flexible walls consisting of layered emulsions. The tube-like printed features have a spongy texture resembling miniaturized versions of "tube sponges" found in the oceans. A scaling analysis based on the interplay between hydrodynamics and emulsification kinetics reveals that filaments are formed when emulsions are generated and remain at the interface during the printing period. Stabilized filaments are utilized for printing liquid-based fluidic channels.


Assuntos
Nanopartículas , Dióxido de Silício , Emulsões/química , Tinta , Nanopartículas/química , Água/química
4.
Sci Rep ; 11(1): 15404, 2021 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-34321592

RESUMO

This work develops a robust classifier for a COVID-19 pre-screening model from crowdsourced cough sound data. The crowdsourced cough recordings contain a variable number of coughs, with some input sound files more informative than the others. Accurate detection of COVID-19 from the sound datasets requires overcoming two main challenges (i) the variable number of coughs in each recording and (ii) the low number of COVID-positive cases compared to healthy coughs in the data. We use two open datasets of crowdsourced cough recordings and segment each cough recording into non-overlapping coughs. The segmentation enriches the original data without oversampling by splitting the original cough sound files into non-overlapping segments. Splitting the sound files enables us to increase the samples of the minority class (COVID-19) without changing the feature distribution of the COVID-19 samples resulted from applying oversampling techniques. Each cough sound segment is transformed into six image representations for further analyses. We conduct extensive experiments with shallow machine learning, Convolutional Neural Network (CNN), and pre-trained CNN models. The results of our models were compared to other recently published papers that apply machine learning to cough sound data for COVID-19 detection. Our method demonstrated a high performance using an ensemble model on the testing dataset with area under receiver operating characteristics curve = 0.77, precision = 0.80, recall = 0.71, F1 measure = 0.75, and Kappa = 0.53. The results show an improvement in the prediction accuracy of our COVID-19 pre-screening model compared to the other models.


Assuntos
COVID-19/diagnóstico , Tosse/classificação , COVID-19/epidemiologia , Tosse/virologia , Aprendizado Profundo , Humanos , Aprendizado de Máquina , Programas de Rastreamento/métodos , Redes Neurais de Computação , Curva ROC , SARS-CoV-2/isolamento & purificação , Sensibilidade e Especificidade , Som , Espectrografia do Som/métodos , Tomografia Computadorizada por Raios X/métodos
5.
Curr Oncol ; 26(4): 234-239, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31548802

RESUMO

Background: Expert groups have recommended incorporation of a geriatric assessment into clinical practice for older patients starting oncologic therapy. However, that practice is not standard primarily because of resource limitations. In the present study, we evaluated the effect on treatment decisions by oncologists in the community oncology setting of a brief geriatric assessment tool that estimates risk of toxicity. Methods: This prospective longitudinal study in 5 community oncology practices in British Columbia involved patients 70 years of age and older starting a new cytotoxic chemotherapy regimen. Clinical personnel completed a brief validated geriatric assessment tool-the Cancer and Aging Research Group chemotherapy toxicity tool (carg-tt)-that estimates the risk of grade 3 or greater toxicity in older patients. Physicians were asked if the carg-tt changed their treatment plan or prompted extra supports. Patients were followed to assess the incidence of toxicity during treatment. Results: The study enrolled 199 patients between July 2016 and February 2018. Mean age was 77 years. Treatment was palliative in 61.4% of the group. Compared with physician judgment, the carg-tt predicted higher rates of toxicity. In 5 patients, treatment was changed based on the carg-tt. In 38.5% of the patients, data from the tool prompted extra supports. Within the first 3 cycles of treatment, 21.3% of patients had experienced grade 3 or greater toxicity. Conclusions: This study demonstrates that use of a brief geriatric assessment tool is possible in a broad community oncology practice. The tool modified the oncologist's supportive care plan for a significant number of older patients undertaking cytotoxic chemotherapy.


Assuntos
Antineoplásicos/efeitos adversos , Avaliação Geriátrica/métodos , Neoplasias/tratamento farmacológico , Idoso , Idoso de 80 Anos ou mais , Antineoplásicos/uso terapêutico , Colúmbia Britânica , Tomada de Decisão Clínica , Feminino , Humanos , Estudos Longitudinais , Masculino , Cuidados Paliativos/estatística & dados numéricos , Estudos Prospectivos , Medição de Risco
6.
Trop Biomed ; 35(1): 82-90, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33601780

RESUMO

Dogs can act as reservoirs, carriers, and transmitters of several zoonotic intestinal parasites that can cause serious health problems for humans. The aim of this study was to determine the prevalence of intestinal parasites in dogs in Kermanshah Province, west of Iran. Faecal samples were collected from domestic and stray dogs from 30 rural areas of Kermanshah province from August 2014 to April 2015 and were analyzed by formalin-ether sedimentation, sucrose otation technique and the modied Ziehl-Neelsen method. Out of 301 dogs examined, 230 (76.4%) were infected with at least one parasite. The incidence on the different types of intestinal parasitic species recovered from domestic and stray dogs are as follows: Toxocara leonina (20.8% and 27.6%), T. canis (7.5% and 9.4%), Taenia spp. (9.2% and 9.4%), hookworm spp. (18.3% and 33.7%), Capillaria spp. (0.8 and 1.7%), Dicrocoelium dendriticum (0.8% and 3.3%), Fasciola spp. (0.8% and 2.2%), Acanthocephal spp. (3.3% and 5.5%), Trichuris vulpis (0.8% and 1.7%), Dipylidium caninum (4.2% and 3.3%), Physaloptera spp. (6.7% and 6.6%), Cryptosporidium spp.(21.7% and 25.4%), Eimeria spp. (35.0% and 34.3%), Giardia spp. (6.7% and 12.7%), Cystoisospora spp. (7.5% and 5.5%), Blastocystis spp. (18.3% and 20.4%) and Sarcocystis spp. (6.7% and 7.2%), respectively. Signicant difference in infection rates was observed between domestic and stray dogs (P>0.05). Hookworm and Eimeria spp. were the most common intestinal helminth and protozoa detected with 83 (27.6%) out of 301 and 104 (34.6%), out of 301, respectively. There was no significant difference in prevalence and distribution of intestinal parasites between male and female dogs (P>0.05). The wide range of zoonotic parasites indicated that people residing in rural areas in Kermanshah province are at risk of exposure to these pathogens. In this respect, appropriate implementation of control programs by public health authorities and veterinarians should be taken into account.

7.
Trop Biomed ; 35(1): 91-99, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33601781

RESUMO

Echinococcus granulosus, the etiologic agent of echinococcosis, is one of the most important zoonotic helminthes worldwide. Knowledge of E. granulosus species and genotypes has important implications for epidemiology, control, and prevention of diseases as well as future vaccine and drug designs. There are many molecular methods developed to define genotypes of E. granulosus, among them high resolution melting (HRM) analysis, as a new approach, is a single step and closed tube method. It is appropriate for fast screening of large number of isolates. This technique is an accurate, user friendly, cost-effective, fast and simple method, which does not need post-PCR processes. Between March and lst august 2016, of 726 sheep examined in abattoirs in Razavi Khorasan province, Northeast Iran, 109 harboured cystic echincoccosis lesions (liver samples= 65 and lung samples= 44) which were collected for analysis. Total genomic DNA was extracted from each sample and amplified for the presence of polymorphism in the mitochondrial cox1 gene of Echinococcus granulosus using a high resolution melting curve (HRM) method. A total of 109 hydatid cyst samples analyzed by PCR high-resolution melting (qPCR-HRM) curve of the cox1 gene, all isolates were identified as G1 genotype (sheep strain). G1 is the predominant genotype in sheep in northeast of Iran. The high incidence of the G1 genotype (known to be the predominant E. granulosus genotype infecting humans globally) in sheep has considerable implications for hydatid disease control programs in this area.

8.
Iran J Ped Hematol Oncol ; 6(1): 64-9, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27222704

RESUMO

BACKGROUND: Iron-deficiency anemia is a widespread public health problem with major consequences for human health especially, children. However, in a fraction of patients an underlying cause is never found during routine investigation. Recent studies have suggested an association between Helicobacter pylori (H. Pylori) infection and iron-deficiency anemia. CASE PRESENTATION: Here is reported four school aged children (two male, two female) with refractory severe iron-deficiency anemia associated H. Pylori gastritis. Mean age of the patients was 13.62 years old and they were admitted with chief complaints of abdominal, chest pain weakness, headache and respiratory distress. Mean hemoglobin level in patients was 6.2 g/dl with persistence to iron therapy. After the diagnosis and therapy of H. pylori infection, clinical complaints, hemoglobin level and iron profiles were being normal and they gained weight. CONCLUSION: This study suggests screening of H. pylori infection and appropriate treatment in any case of refractory moderate to severe iron-deficiency anemia, especially with clinical manifestations of gastrointestinal tract in children.

9.
Iran J Ped Hematol Oncol ; 5(3): 145-8, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26705453

RESUMO

BACKGROUND: Thalassemia patients that are conventionally treated by a regular transfusion regimen are exposed to blood born viral infections.The aim of this study was to investigate the seroprevalence of hepatitis B virus (HBV), hepatitis C virus (HCV), and human Immunodeficiency virus (HIV) among all multitransfused thalassemia patients in west north of Iran. MATERIAL AND METHODS: A retrospective study was conducted in February 2014, on 32 patients in Urmia, suffering from transfusion dependent thalassemia were admitted to Motahari and Emam Khomeini hospitals. Patients' medical records were studied for HBs antigen and seropositivity for HCV, and HIV antibodies. RESULTS: Out of 32transfusion dependent thalassemia patients aged between 5-17years, 18 (56.25%) and14 (43.75%) were male and female, respectively. All of them were found seronegative for HBs antigen, HCV, and HIV antibodies. CONCLUSION: It seems that screening of blood products is efficient in Urmia, capital of West Azarbaijan, Iran for prevention of blood born viral infections.

10.
Iran J Ped Hematol Oncol ; 5(4): 206-10, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26985353

RESUMO

BACKGROUND: Iron overload is the main transfusion related side effects in patients with transfusion dependent hemoglobinopathies. Severe iron deposition in tissues leads to organ dysfunction. Many organs can be affected such as heart, liver, and endocrine organs. Cardiac failure and liver fibrosis are the consequent of Iron overload in transfusion dependent hemoglobinopathy. Magnetic Resonance Imaging (MRI) is a safe, noninvasive, and accurate method for the assessment of iron deposition in different tissues. This study assessed iron levels in liver and heart of the patients with transfusion dependent hemoglobinopathies. MATERIALS AND METHODS: The studied population consisted of 12 patients (7 male and 5 female) with transfusion dependent hemoglobinopathies, aged between 10-18 years old. Then, Cardiac and liver T2*- weighted magnetic resonance imaging (MRI) were obtained. RESULTS: In current study, 1patient (8.33%) had severe, 2 patients (16.66%) had moderate and 2(16.66%) had mild cardiac iron deposition. Out of 12 patients, 1 had severe iron deposition in liver (8.33%), 5(41.66%) and 4(33.33%) had moderate and mild hepatic iron deposition, respectively. Differences between Hepatic and cardiac iron levels were not significant between males and females (p>0.05). CONCLUSION: Since cardiac and liver iron levels were higher than normal in most of the study group, checking ferritin level and liver function test and also echocardiography in shorter intervals (each 3 months) in involved group is suggested instead of checking routinely in 6 month intervals in patients with transfusion dependent hemoglobinopathies.

11.
Iran J Ped Hematol Oncol ; 4(2): 68-71, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25002928

RESUMO

BACKGROUND: Patients with thalassemia major and intermedia are susceptible to osteopenia and osteoporosis. The mechanism of osteoporosis in these patients is multifactorial. Transfusion related iron overload in endocrine organs leads to impaired growth hormone secretion, diabetes mellitus, hypothyroidism, hypoparathyroidism, lack of sex steroids and vitamin D deficiency that contribute to impairment in achieving an adequate bone mass .The aim of this study was assessment of frequency of bone loss in patients with thalassemia major and intermedia in Urmia City of West Azerbaijan, Iran. MATERIALS AND METHODS: In this cross sectional descriptive study,10 patients (lower than 18 y/o)with transfusion dependent thalassemia attending to Motahari and Emam Khomeini hospitals in Urmia city of Iran were enrolled and scanned for Bone Mineral Density (BMD) starting at around 10 years old. RESULTS: Tenatients (6 male and 4 female) with transfusion dependent thalassemia (ß-thalassemia major and intermedia) aged 13to 17 years in Urmia city of Iran were enrolled. Mean age of patients was 15.1±.37year old. Among them, 8 patients (80%)had low BMD and2 of them (20%) had normal BMD in lumbar spine. Only 30% of patients had low BMD in the neck of femur. CONCLUSION: We should perform annual BMD in patients with thalassemia major and intermedia and hemoglobin H disease in age of higher than 8 year old and treat low BMD with administration of bisphosphonate, calcium and vitamin D supplements. Medical consultation with a rheumatologist and /or an endocrinologist should be performed in these patients. Changing lifestyle with mild daily exercise, adequate calcium containing foods, avoiding heavy activities, stop smoking, iron chelation therapy in adequate dosage, early diagnosis and treatment of endocrine insufficiency and regular blood transfusions can help to achieve an optimal bone density in these patients.

12.
Eur J Trauma Emerg Surg ; 40(1): 51-5, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26815777

RESUMO

PURPOSE: Obesity is a risk factor in treatment outcomes of critically ill patients. This study was conducted to determine the impact of obesity on the likelihood of recovery from traumatic brain injury (TBI) in intensive care unit (ICU) patients. METHODS: We carried out a prospective study on 115 head injury patients who were admitted to the ICU of Poursina Hospital, Rasht, in the one-year period between July 2006 and June 2007. Obese patients (body mass index [BMI] ≥ 30 kg/m(2)) were compared with non-obese patients (BMI < 30 kg/m(2)). Demographic information, acute physiology and chronic health evaluation scores, Injury Severity Scores (ISS), Glasgow Coma Scale scores, and ICU mortality incidences were recorded. RESULTS: Obese patients had significantly higher ICU mortality rates compared to non-obese patients (p = 0.02). Furthermore, we observed a trend towards a higher ICU mortality rate in obese patients with ISS > 25 (p = 0.04). Moreover, obesity was associated with prolonged mechanical ventilation, ICU length of stay (ILOS), and hospital length of stay (HLOS) (p < 0.001). CONCLUSIONS: Obesity was associated with increased ICU mortality and prolonged dependency on mechanical ventilation, ILOS, and HLOS in patients with TBI. However, further prospective studies with larger sample sizes are needed to substantiate these findings.

13.
Scand J Immunol ; 78(5): 478-84, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23980810

RESUMO

Cutaneous leishmaniasis (CL) is a self-healing skin disease which rarely for unknown reason(s) the lesion develops to a non-healing form. It seems that the initial contact of Leishmania parasites with the host innate immune system is an important step in the outcome of the disease. Recent studies suggested that toll-like receptors (TLRs) play a role in Leishmania recognition. In this study, the level of TLR2 and TLR4 was checked in patients with healing form of lesion and compared with that of patients with non-healing form of lesion caused by Leishmania major. Gene expression of TLR2 and TLR4 in peripheral blood-derived macrophages, before and after stimulation with live L. major promastigotes, was evaluated using quantitative real-time reverse transcription PCR and flow cytometry. The results showed that the mean relative gene expression and difference membrane expression of TLR2 in macrophages of patients with healing form of lesion were significantly higher than patients with non-healing form of lesion (P < 0.0001 and P = 0.0034), respectively, and the mean relative gene expression and difference in protein expression of TLR4 in macrophages of patients with healing form of lesion were significantly higher than that of patients with non-healing form of lesion (P = 0.021 and P = 0.002), respectively. The data suggested a possible role for TLR2 and TLR4 in the outcome of CL lesion. Further studies are needed to understand more about the detail role of the immune factors in leishmaniasis.


Assuntos
Leishmaniose Cutânea/imunologia , Macrófagos/imunologia , Receptor 2 Toll-Like/imunologia , Receptor 4 Toll-Like/imunologia , Citometria de Fluxo , Expressão Gênica , Interações Hospedeiro-Parasita/imunologia , Humanos , Leishmania major/imunologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Receptor 2 Toll-Like/genética , Receptor 2 Toll-Like/metabolismo , Receptor 4 Toll-Like/genética , Receptor 4 Toll-Like/metabolismo
14.
East Mediterr Health J ; 19(2): 156-61, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23516826

RESUMO

Studies of risk factors for acute leukaemia are inconclusive. This case-control study was done in West Azerbaijan province, Islamic Republic of Iran, to determine the relationship between birth weight and acute leukaemia in children aged under 15 years. For every patient 2 age- and sex-matched controls were selected from hospital and community populations. Of 130 cases diagnosed over the period 2003-2009,108 (83.1%) had lymphoblastic and 22 (16.9%) myloblastic type. Significantly more of them were male than female (55.4% versus 44.6%). In a multivariate logistic regression model variables significantly associated with acute leukaemia were: birth weight (OR = 2.25), birth order (OR = 2.25), birth place (OR = 7.93), history of chickenpox (OR = 0.46) and mothers' education (OR = 3.23). The risk of acute leukaemia increased significantly with increasing birth weight in the total group and among girls, but not among boys.


Assuntos
Peso ao Nascer , Leucemia/epidemiologia , Doença Aguda , Adolescente , Ordem de Nascimento , Estudos de Casos e Controles , Varicela/epidemiologia , Criança , Pré-Escolar , Escolaridade , Feminino , Humanos , Irã (Geográfico)/epidemiologia , Masculino , Razão de Chances , Fatores de Risco , Distribuição por Sexo , Inquéritos e Questionários
15.
Iran Red Crescent Med J ; 14(5): 276-82, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22829986

RESUMO

BACKGROUND: The benzodiazepines are used primarily for anxiolysis, amnesia and sedation. However, recent investigations have shown that some forms of this group of drugs have also direct effect on pain. This study aims to determine the effect of midazolam in reducing the severity of pain in women scheduled for elective cesarean section. METHODS: In a prospective, double blind randomized controlled trial, two groups parallel study, was conducted in Imam Reza/Moatazedi Hospital, an affiliate of Kermanshah University of Medical Sciences. Parturient women who met study inclusion criteria were consecutively assigned into either experimental (n=62) or control groups (n=62). Women in the experimental group received bupivacaine (10 mg) plus intrathecal midazolam (2 mg/ml) (BM) and those in the control group received bupivacaine plus normal saline (BNS). The outcome pain severity was measured by Verbal Numerical Rating Scale. RESULTS: In comparison with the BNS group, mothers in the BM group reported a significant relief in pain (15 min and 120 min) after the surgery. There were no significant differences between the groups regarding the intensity of pain 5, 30, 60 and 240 min after the surgery. The average time until the first dose of additional analgesic, per mother's request was 142.18±55.19 min in the BNS vs 178.06±77.33 min in the BM group. CONCLUSION: Combination of bupivacaine plus intrathecal midazolam was an effective anesthetic technique to provide improvement in pain. The onset of sedation was faster in the BM group compared with the BNS group. The duration of effective analgesia, and the time for regression of sensory analgesia was the same in both groups in our study. However, incidence of nausea and vomiting was higher in the experimental group.

16.
J Anim Sci ; 77(3): 507-15, 1999 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10229345

RESUMO

In Exp. 1, early-weaned Targhee and Polypay crossbred lambs (60 ewes and 66 rams; initial BW 24 +/- 1.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole shelled corn [WSC] or ground and pelleted corn [GC]) in combination with supplemental fiber (none [control]; soybean hulls, SBH [highly digestible]; or peanut hulls, PH [highly indigestible]) on DMI, ADG, feed efficiency, and visceral organ weight. For the total trial, WSC resulted in a 4% increase (P < .01) in ADG vs GC, and supplemental fiber resulted in increased (P < .01) DMI and ADG vs the control diet. Experiment 2 was conducted using 12 Targhee and Polypay crossbred wether lambs (initial BW 25 +/- 7 kg) to determine the effects of corn processing and fiber source in high-concentrate diets on diet digestibility and N retention using the same diets as in Exp. 1. Lambs fed WSC had greater (P < .001) apparent N digestion, true N digestion, and N retention (P < .01) than those fed GC. The apparent digestibilities of DM, OM, and NDF were greater (P < .001) for WSC than for GC diets. Peanut hulls resulted in decreased (P < .01) DM, OM, and NDF apparent digestibilities compared with the control and SBH diets. Starch digestion was not affected (P > .10) by diet. Whole corn resulted in improved DM, OM, NDF, and N digestibility compared with GC. Overall, both the SBH and PH diets resulted in greater DMI and ADG than the control diet, which lacked supplemental fiber.


Assuntos
Ração Animal , Criação de Animais Domésticos/métodos , Fibras na Dieta , Manipulação de Alimentos , Nitrogênio/metabolismo , Ovinos/metabolismo , Zea mays , Animais , Digestão , Feminino , Masculino , Tamanho do Órgão , Ovinos/crescimento & desenvolvimento , Vísceras
17.
Med Phys ; 24(2): 287-97, 1997 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-9048370

RESUMO

System modeling is used to investigate the effect of various system parameters on the image quality in CCD-based x-ray imaging systems. The systems considered consist of a typical phosphor-based scintillating screen coupled to a CCD through lens or fiberoptic taper. Two applications, chest radiography and mammography, are analyzed. For each application typical system characteristics and operating conditions are used to determine the detective quantum efficiency (DQE) as a function of spatial frequency, optical collection efficiency, optical demagnification factor, and electronic noise. The DQE is modeled by extending the analysis for storage phosphor systems. The calculations are done for typical exposure conditions (0.25 mR for chest and 10.0 mR for mammography); however, the exposure effects are also discussed. It was found that a reasonable DQE can be obtained for both applications through each coupling approach; however, the demagnification requirements and electronic noise limitations are more stringent for the digital mammography application.


Assuntos
Mamografia/métodos , Intensificação de Imagem Radiográfica , Radiografia Torácica/métodos , Raios X , Fenômenos Biofísicos , Biofísica , Modelos Teóricos , Tecnologia Radiológica
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