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1.
Digit Health ; 10: 20552076231225168, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38303970

RESUMO

Objective: In Germany, only a few standardized evaluation tools for assessing the usability of mobile Health apps exist so far. This study aimed to translate and validate the English patient version for standalone apps of the mHealth App Usability Questionnaire (MAUQ) into a German version. Methods: Following scientific guidelines for translation and cross-cultural adaptation, the patient version for standalone apps was forward and back-translated from English into German by an expert panel. In total, 53 participants who were recruited as part of the beta testing process of the recently developed mHealth app HerzFit, answered the questions of the German version of the MAUQ (GER-MAUQ) and the System Usability Scale. Subsequently, a descriptive as well as a psychometric analysis was performed to test validity and reliability. Results: After conducting three cognitive interviews, five items were modified. The values for Cronbach alpha for the entire questionnaire and the three subscales (0.966, 0.814, 0.910, and 0.909) indicate strong internal consistency. The correlation analysis revealed that the scores of the GER-MAUQ, the subscales and the SUS were strongly correlated with each other. The correlation coefficient of the SUS and the GER-MAUQ overall score was r = 0.854, P < 0.001 and the coefficients of the subscales and the SUS were r = 0.642, P < 0.001; r = 0.866, P < 0.001 and r = 0.643, P < 0.001. Conclusions: We have developed a novel German version of the MAUQ and demonstrated it as a reliable and valid measurement tool for assessing the usability of standalone mHealth apps from the patients' perspective. The GER-MAUQ allows a new form of standardized assessment of usability of mHealth apps for patients with cardiovascular disease in Germany. Further research with a larger sample and other samples is recommended.

2.
Z Evid Fortbild Qual Gesundhwes ; 182-183: 125-129, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37806814

RESUMO

INTRODUCTION: In the past decade, a legal framework was created in Germany that promotes intense collaboration at the interface between primary and secondary care. This overview article distinguishes between the effects of two complementary programs aimed at improving ambulatory care in Baden-Wuerttemberg: (1) general practitioner-centered care (GPCC), which strengthens the role of general practitioners, and (2) collaborative cardiology care (CCC), which coordinates primary and cardiology care. METHODS: The overview article presents two already published studies that assess the impact of the programs on hospitalizations in patients with chronic heart failure (CHF) based on claims data from 2016. The hospitalization rate of patients enrolled in GPCC (N=75,096) and CCC (N=13,404) were compared with corresponding control groups (N=65,618 and N=8,776 respectively). RESULTS: The hospitalization rate in GPCC was lower than in the control group (risk ratio 0.97; 95% CI: 0.95-0.99, P=0.0024). GPCC patients with CHF that received specialist cardiology care as part of CCC had significantly lower hospitalization rates than those receiving standard cardiology care (risk ratio 0.92; 0.88-0.97, P=0.0014). DISCUSSION: This overwiew study shows that reforming medical care and compensation at the interface between general practice and specialist care can lead to fewer hospital admissions in patients with CHF. CONCLUSION: Overall, this article underlines the importance of collaboration between primary care physicians and specialists for patients with CHF that are receiving ambulatory care.


Assuntos
Insuficiência Cardíaca , Atenção Secundária à Saúde , Humanos , Medicina de Família e Comunidade , Alemanha , Insuficiência Cardíaca/terapia , Hospitalização
3.
Healthcare (Basel) ; 11(15)2023 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-37570423

RESUMO

The Communication and Tracing App HIV (COMTRAC-HIV) project aims to develop a mobile health application for integrated care of HIV patients due to the low availability of those apps in Germany. This study addressed organizational conditions and necessary app functionalities, especially for the care of late diagnosed individuals (late presenters) and those using pre-exposure prophylaxis. We followed a human-centered design approach and interviewed HIV experts in Germany to describe the context of use of the app. The interviews were paraphrased and analyzed with a qualitative content analysis. To define the context of use, user group profiles were defined and tasks derived, which will represent the functionalities of the app. A total of eight experts were included in the study. The results show that the app should include a symptom diary for entering symptoms, side effects, and their intensity. It offers chat/video call functionality for communication with an HIV expert, appointment organization, and sharing findings. The app should also provide medication overview and reminders for medications and appointments. This qualitative study is a first step towards the development of an app for HIV individuals in Germany. Further research includes involving patients in the initial app design and test design usability.

4.
Int J Integr Care ; 23(2): 22, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37275630

RESUMO

Objective: To evaluate a novel healthcare programme for the treatment of patients with hip and knee osteoarthritis in southern Germany in terms of clinical and health economic outcomes. The study is based on claims data from 2014 to 2017. Methods: We conducted a retrospective comparative cohort study of 9768 patients with hip and knee osteoarthritis, of whom 9231 were enrolled in a collaborative ambulatory orthopaedic care programme (intervention group), and 537 patients received usual orthopaedic care (control group). Key features of the programme are coordinated care, morbidity-adapted reimbursement and extended consultation times. Multivariable analysis was performed to determine effects on health utilisation outcomes. The economic analysis considered annual costs per patient from a healthcare payer perspective, stratified by healthcare service sector. Besides multivariable regression analyses, bootstrapping was used to estimate confidence intervals for predicted mean costs by group. Results: Musculoskeletal-disease-related hospitalisation was much less likely among intervention group patients than control group patients [odds ratio (OR): 0.079; 95% CI: 0.062-0.099]. The number of physiotherapy prescriptions per patient was significantly lower in the intervention group (RR: 0.814; 95% CI: 0.721-0.919), while the likelihood of participation in exercise programmes over one year was significantly higher (OR: 3.126; 95% CI: 1.604-6.094). Enrolment in the programme was associated with significantly higher ambulatory costs (€1048 vs. €925), but costs for inpatient care, including hospital stays, were significantly lower (€1003 vs. €1497 and €928 vs. €1300 respectively). Overall annual cost-savings were €195 per patient. Conclusions: Collaborative ambulatory orthopaedic care was associated with reduced hospitalisation in patients with hip and knee osteoarthritis. Health costs for programme participants were lower overall, despite higher costs for ambulatory care.

6.
BMJ Open ; 12(8): e062657, 2022 08 08.
Artigo em Inglês | MEDLINE | ID: mdl-35940832

RESUMO

OBJECTIVES: To compare opioid prescription rates between patients enrolled in coordinated ambulatory care and patients receiving usual care. DESIGN: In this retrospective cohort study, we analysed claims data for insured patients with non-specific/specific back pain or osteoarthritis of hip or knee from 2014 to 2017. SETTING: The study was based on administrative data provided by the statutory health insurance fund 'Allgemeine Ortskrankenkasse', in the state of Baden-Wurttemberg, Germany. PARTICIPANTS: The intervention group consisted of patients enrolled in a coordinated ambulatory healthcare model; the control group included patients receiving usual care. Outcomes were overall strong and weak opioid prescriptions. Generalised linear regression models were used to analyse the effect of the intervention. RESULTS: Overall, 46 001 (non-specific 18 787/specific 27 214) patients with back pain and 19 366 patients with osteoarthritis belonged to the intervention group, and 7038 (2803/4235) and 963 patients to the control group, respectively. No significant difference in opioid prescriptions existed between the groups. However, the chance of being prescribed strong opioids was significantly lower in the intervention group (non-specific back pain: Odds Ratio (OR) 0.735, 95% Confidential Interval (CI) 0.563 to 0.960; specific back pain: OR 0.702, 95% CI 0.577 to 0.852; osteoarthritis: OR 0.644, 95% CI 0.464 to 0.892). The chance of being prescribed weak opioids was significantly higher in patients with specific back pain (OR 1.243, 95% CI 1.032 to 1.497) and osteoarthritis (OR 1.493, 95% CI 1.037 to 2.149) in the intervention group. CONCLUSION: Coordinated ambulatory healthcare appears to be associated with a lower prescription rate for strong opioids in patients with chronic musculoskeletal disorders. TRIAL REGISTRATION NUMBER: German Clinical Trials Register (DRKS00017548).


Assuntos
Analgésicos Opioides , Osteoartrite , Analgésicos Opioides/uso terapêutico , Dor nas Costas/tratamento farmacológico , Atenção à Saúde , Humanos , Osteoartrite/tratamento farmacológico , Prescrições , Estudos Retrospectivos
7.
BMC Musculoskelet Disord ; 23(1): 740, 2022 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-35922853

RESUMO

BACKGROUND: In 2014, the novel orthopedic care program was established by the AOK health insurance fund in southern Germany to improve ambulatory care for patients with musculoskeletal disorders. The program offers extended consultation times, structured collaboration between general practitioners and specialists, as well as a renewed focus on guideline-recommended therapies and patient empowerment. The aim of this study was to assess the impact of the program on health service utilization in patients with hip and knee osteoarthritis (OA). METHODS: This retrospective cohort study, which is based on claims data, evaluated health service utilization in patients with hip and knee OA from 2014 to 2017. The intervention group comprised OA patients enrolled in collaborative ambulatory orthopedic care, and the control group received usual care. The outcomes were participation in exercise interventions, prescription of physical therapy, OA-related hospitalization, and endoprosthetic surgery rates. Generalized linear regression models were used to analyze the effect of the intervention. RESULTS: Claims data for 24,170 patients were analyzed. Data for the 23,042 patients in the intervention group were compared with data for the 1,128 patients in the control group. Participation in exercise interventions (Odds Ratio (OR): 1.781; 95% Confidence Interval (CI): 1.230-2.577; p = 0.0022), and overall prescriptions of physical therapy (Rate Ratio (RR): 1.126; 95% CI: 1.025-1.236; p = 0.0128) were significantly higher in the intervention group. The intervention group had a significantly lower risk of OA -related hospitalization (OR: 0.375; 95% CI: 0.290-0.485; p < 0.0001). Endoprosthetic surgery of the knee was performed in 53.8% of hospitalized patients in the intervention group vs. 57.5% in the control group; 27.7% of hospitalized patients underwent endoprosthetic surgery of the hip in the intervention group versus 37.0% in the control group. CONCLUSIONS: In patients with hip and knee OA, collaborative ambulatory orthopedic care is associated with a lower risk of OA-related hospitalization, higher participation in exercise interventions, and more frequently prescribed physical therapy.


Assuntos
Osteoartrite do Quadril , Osteoartrite do Joelho , Assistência Ambulatorial , Estudos de Coortes , Humanos , Osteoartrite do Quadril/reabilitação , Osteoartrite do Quadril/cirurgia , Osteoartrite do Joelho/reabilitação , Osteoartrite do Joelho/cirurgia , Estudos Retrospectivos
8.
Z Evid Fortbild Qual Gesundhwes ; 173: 40-48, 2022 Sep.
Artigo em Alemão | MEDLINE | ID: mdl-35780042

RESUMO

BACKGROUND: At the onset of the COVID-19 pandemic general practitioners complained about feeling uninformed and lacking a sufficient flow of information from the local health authorities. Secure instant messaging describes a digital, chat-based form of communication enabling ambulatory care providers to connect in real-time and share information across medial sectors. KomPan, a proof-of-concept study, established a secure instant messaging structure in two model regions in Germany to improve communication between general practitioners and local health authorities via an additional communication pathway. This paper presents results of a qualitative user survey. METHODS: We recruited general practitioners (n = 43) and staff of local health authorities (n=10) in two Hessian model regions for using the secure instant messaging (SIM) app of the Famedly GmbH, starting in December 2020 (2nd COVID-19 wave). We asked participants to share their usage experiences after a usage time of multiple months. In guided telephone interviews, we primarily asked how communication between the two user groups had changed while using secure instant messaging. The interviews were transcribed verbatim and analysed using thematic analysis. RESULTS: We conducted ten interviews with general practitioners and two with staff of the participating local health authorities. Using our SIM-based platform promoted professional exchange between general practitioners. In contrast, the app had little impact on communication between local health authorities and general practitioners. Opposing expectations and usage patterns of the two user groups, among other reasons, probably led to a reduced direct trans-sectoral communication via secure instant messaging. CONCLUSION: Establishing local chat groups for general practitioners was welcomed, especially during the pandemic situation, to improve professional exchange while experiencing challenging working conditions. To use secure instant messaging effectively for trans-sectoral communication a more comprehensive approach seems to be needed, such as digitalisation of institutional communication structures and improved networks of local healthcare providers.


Assuntos
COVID-19 , Aplicativos Móveis , Médicos de Atenção Primária , COVID-19/prevenção & controle , Comunicação , Alemanha , Humanos , Pandemias/prevenção & controle
9.
BMC Med Educ ; 22(1): 508, 2022 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-35765057

RESUMO

BACKGROUND: The COVID-19 pandemic has made it more difficult to maintain high quality in medical education. As online formats are often considered unsuitable, interactive workshops and seminars have particularly often been postponed or cancelled. To meet the challenge, we converted an existing interactive undergraduate elective on safety culture into an online event. In this article, we describe the conceptualization and evaluation of the elective. METHODS: The learning objectives of the safety culture elective remained unchanged, but the teaching methods were thoroughly revised and adapted to suit an online setting. The online elective was offered as a synchronous two-day course in winter semester 2020/21 during the "second wave" of the COVID-19 pandemic in Germany. At the end of each day, participating students evaluated the elective by completing an online survey. Items were rated on a six-point Likert scale. We used SPSS for data analysis. RESULTS: Twenty medical undergraduates completed the elective and rated it extremely positively (1.1 ± 0.2). Students regard safety culture as very important and felt the learning objectives had been achieved. Moreover, they were very satisfied with the design and content of the elective, and especially with interactive elements like role-play. Around 55% of participants would recommend continuing to offer the online elective after the pandemic. CONCLUSIONS: It makes sense to offer undergraduate medical students online elective courses on safety culture, especially during a pandemic. The elective described here can serve as a best practice example of how to teach safety culture to undergraduates, especially when physical presence is unfeasible. Electives requiring a high degree of interaction can also function well online.


Assuntos
COVID-19 , Estudantes de Medicina , Humanos , Aprendizagem , Pandemias/prevenção & controle , Gestão da Segurança
10.
Artigo em Inglês | MEDLINE | ID: mdl-36612434

RESUMO

The coronavirus (COVID-19) has presented Germany with major challenges and has led to concerns about patient safety. We conducted an observational, population-based, nationwide, repeated cross-sectional survey on patient safety in Germany in 2019, 2020, and 2021. Each of the three samples consisted of 1000 randomly recruited adults. Self-reported data via computer-assisted telephone interviews were taken from TK Monitor of Patient Safety. Perceptions, experience, and knowledge relating to patient safety were assessed. The majority of respondents considered medical treatment to involve risks to patient safety. This proportion decreased during the pandemic. The majority also had a high degree of self-efficacy regarding the prevention of medical errors, whereby the percentage that felt well informed with regard to patient safety rose throughout the pandemic. The proportion of persons that suspected they had in the past experienced an error in their treatment remained steady at one third as well as the reported errors. In 2020, 65% of respondents thought health communication with service providers (e.g., extent and comprehensibility of information) remained unchanged during the pandemic, while 35% reported that medical appointments had been cancelled or postponed. This study is the first to assess patient safety from a general population perspective during the coronavirus pandemic in Germany. COVID-19 had a positive impact on perceived patient safety but no impact on suspected and reported errors. Self-efficacy with regard to medical error prevention steadily increased in the general population, and people considered themselves well informed.


Assuntos
COVID-19 , Adulto , Humanos , COVID-19/epidemiologia , Estudos Transversais , Pandemias , SARS-CoV-2 , Segurança do Paciente , Alemanha/epidemiologia
11.
Gesundheitswesen ; 83(S 02): S97-S101, 2021 Nov.
Artigo em Alemão | MEDLINE | ID: mdl-34695867

RESUMO

AIM OF THE STUDY: The evaluation of complex interventions such as different forms of healthcare are methodologically challenging. The aim of this study was to use generalized estimating equations (GEE) to investigate how quality differences between family practitioner-based healthcare (HZV) and standard care develop over time. METHODS: A longitudinal secondary data analysis for 2011-2018 was conducted using routine data from the AOK Baden Wuerttemberg health insurer. A dynamic cohort of insured persons that fulfilled the inclusion criteria were included in the analysis at the beginning of each year of observation, so the size and composition of the cohorts varied from year to year. Quality differences between HZV and standard care were investigated, whereby an autoregressive covariance structure (AR1) was assumed for multiple measurements. Under observation were a group variable for healthcare type, a variable for year of observation, and any interaction between the two. The resulting estimates provided information on the relationship between the two groups at the beginning of the observation period, and on how the groups developed both individually and in relation to one another over time. RESULTS: The GEE were used exemplarily on the quality indicator prescription of potentially inappropriate medication (PIM) in elderly insured patients. At the beginning of the observation period, the chance of PIM in those over 65 years of age (year 2018; N=628,523) was significantly lower in the HZV group than in the group receiving standard care (odds ratio 0.978; 95% confidence interval: 0.968-0.987). The chance of a PIM in the following seven years declined in both groups, but faster in the HZV group than the group receiving standard care. CONCLUSION: A secondary data-based trend analysis with GEE of quality differences in comparison groups over time has considerable potential in the evaluation of new and existing forms of healthcare.


Assuntos
Atenção à Saúde , Instalações de Saúde , Idoso , Alemanha/epidemiologia , Humanos , Prescrição Inadequada
12.
Z Evid Fortbild Qual Gesundhwes ; 165: 13-20, 2021 Oct.
Artigo em Alemão | MEDLINE | ID: mdl-34412979

RESUMO

INTRODUCTION: The growing number of people with multimorbidity and polypharmacy in Germany has led to increasing complexity in health care and risks to patient safety. A high priority should therefore be placed on identifying and preventing avoidable adverse events. The patient perspective plays an important role in improving patient safety. In this study, we conducted a representative, population-based survey of knowledge, perceptions and experiences of patient safety, especially of subjectively experienced errors in health care. Our aim was, in particular, to assess patient safety from the patients' point of view, and to analyze differences in assessments of risk and preventability between persons that felt well or poorly informed about patient safety topics. METHODS: In 2019, computer-assisted telephone interviews were conducted nationwide as part of the "TK-Monitor Patient Safety" project. Recruitment was carried out by using multistage selection and forming a stratified random sample. Adults (18 years and older) with sufficient knowledge of German were included. The survey was conducted using a structured guideline containing 21 questions concerning perceptions and experiences of patient safety, and 12 questions on sociodemographic factors. The results were analyzed both descriptively and using inferential statistical methods. RESULTS: Of a total of 1,000 respondents (51% female), approx. half (52%) were gainfully employed, and 57% rated their state of health as "very good" or "good". The patients regarded data protection, medication errors, hospital infections and diagnostic (un)certainty as of major relevance to patient safety. Overall, 55% of the respondents rated their knowledge of patient safety as "very good" or "good". The results showed that subjective knowledge was negatively associated with important outcome parameters such as having experience of medication errors or suspecting errors had been made in a medical examination or treatment. Patients that considered themselves well-informed also reckoned they could contribute towards increasing safety in health care. DISCUSSION: The respondents considered diagnostic uncertainty to be one of the greatest risks to their person. This shows that they recognized a need for further information and felt this need was inadequately satisfied in the German research landscape. With regard to the correlation between subjective knowledge and outcome parameters, it is also necessary to analyze whether the respondents' subjective knowledge reflects their actual knowledge, as this would be necessary for preventive measures to be effective. This question will be the subject of further studies. CONCLUSION: The patient perspective is an important addition to the study of the safety of medical care in Germany. Factors influencing subjective knowledge should be investigated. Furthermore, regular surveys would be desirable in order to gain greater insight into the topic.


Assuntos
Segurança do Paciente , Polimedicação , Adulto , Feminino , Alemanha , Humanos , Masculino , Inquéritos e Questionários
13.
Z Evid Fortbild Qual Gesundhwes ; 161: 57-62, 2021 Apr.
Artigo em Alemão | MEDLINE | ID: mdl-33640287

RESUMO

INTRODUCTION: The World Health Organization has called for more importance to be attached to the subject of patient safety in medical studies. However, teaching staff are unsure when the right time is to include this topic in existing medical school curricula. The aim of this article is to present the learning objectives, design and evaluation of a two-day elective on patient safety offered in the preclinical phase of medical studies at the Faculty of Medicine, University of Frankfurt am Main. To the best of our knowledge, no existing elective on safety culture has been provided at such an early stage of medical studies in Germany. METHODS: After defining learning objectives and teaching methods, the safety culture elective was offered in the winter term 2019/20. Based on a questionnaire, a quantitative and qualitative evaluation of the students' acceptance of the elective was carried out. We also sought to investigate whether group role-play was considered an effective means of communicating the teaching content. Acceptance and rejection of the elective were evaluated on a six-point Likert scale. RESULTS: The resulting elective, consisting of topical input via film, an introductory speech, role-play and discussions, is presented. Nineteen students in the preclinical phase of their medical studies took part. Overall, the quantitative and qualitative evaluation delivered positive results (1.2±0.5), and the topic was perceived to very important. The students considered the didactic implementation and the learning objectives to be very good, and they became acquainted with different sources of error. DISCUSSION: The preclinical elective would appear to be suitable for demonstrating the importance of medical safety to medical students and teaching them how to deal with the topic constructively. It can be viewed as a best-practice example for the development of comparable learning formats at medical faculties. CONCLUSION: The results show that the preclinical phase is a suitable time to illustrate the importance of the subject of patient safety during medical studies.


Assuntos
Educação de Graduação em Medicina , Estudantes de Medicina , Currículo , Atenção à Saúde , Alemanha , Humanos , Gestão da Segurança
14.
BMC Fam Pract ; 21(1): 53, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32183738

RESUMO

BACKGROUND: Experienced and anticipated regret influence physicians' decision-making. In medicine, diagnostic decisions and diagnostic errors can have a severe impact on both patients and physicians. Little empirical research exists on regret experienced by physicians when they make diagnostic decisions in primary care that later prove inappropriate or incorrect. The aim of this study was to explore the experience of regret following diagnostic decisions in primary care. METHODS: In this qualitative study, we used an online questionnaire on a sample of German primary care physicians. We asked participants to report on cases in which the final diagnosis differed from their original opinion, and in which treatment was at the very least delayed, possibly resulting in harm to the patient. We asked about original and final diagnoses, illness trajectories, and the reactions of other physicians, patients and relatives. We used thematic analysis to assess the data, supported by MAXQDA 11 and Microsoft Excel 2016. RESULTS: 29 GPs described one case each (14 female/15 male patients, aged 1.5-80 years, response rate < 1%). In 26 of 29 cases, the final diagnosis was more serious than the original diagnosis. In two cases, the diagnoses were equally serious, and in one case less serious. Clinical trajectories and the reactions of patients and relatives differed widely. Although only one third of cases involved preventable harm to patients, the vast majority (27 of 29) of physicians expressed deep feelings of regret. CONCLUSION: Even if harm to patients is unavoidable, regret following diagnostic decisions can be devastating for clinicians, making them 'second victims'. Procedures and tools are needed to analyse cases involving undesirable diagnostic events, so that 'true' diagnostic errors, in which harm could have been prevented, can be distinguished from others. Further studies should also explore how physicians can be supported in dealing with such events in order to prevent them from practicing defensive medicine.


Assuntos
Tomada de Decisão Clínica/ética , Diagnóstico Tardio , Erros de Diagnóstico/psicologia , Emoções , Médicos de Atenção Primária/psicologia , Diagnóstico Tardio/ética , Diagnóstico Tardio/prevenção & controle , Diagnóstico Tardio/psicologia , Erros de Diagnóstico/efeitos adversos , Erros de Diagnóstico/estatística & dados numéricos , Humanos , Segurança do Paciente , Sistemas de Apoio Psicossocial , Julgamento Moral Retrospectivo , Percepção Social , Inquéritos e Questionários , Incerteza
15.
Soft Matter ; 15(4): 779-784, 2019 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-30633288

RESUMO

We present a new and accurate method to determine the Poisson's ratio of PDMS, using thermal expansion and an optical surface profilometer. The Poisson's ratio of Sylgard 184 was found to be ν = 0.4950 ± 0.0010 and for Sylgard 182, ν = 0.4974 ± 0.0006. Furthermore, we found that for both PDMS types, the coefficient of thermal expansion depends approximately linearly on the curing temperature. This method can be used for almost any kind of soft polymer that can be cured from a liquid at elevated temperatures.

16.
MAGMA ; 32(4): 437-447, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30649708

RESUMO

OBJECTIVE: The applicability of the balanced steady-state free precession (bSSFP) sequence to the field of MR microscopy was investigated, since the potentially high SNR makes bSSFP attractive. However, particularly at ultra-high magnetic fields, a number of constraints emerge: the frequency sensitivity of the bSSFP signal, the duty cycle of the imaging gradients, and the intrinsic diffusion attenuation of the steady state due to the imaging gradients. MATERIALS AND METHODS: Optimization of the bSSFP sequence was performed on three imaging systems (7 T and 9.4 T) suited for MR microscopy. Since biological samples are often imaged in the very proximity of materials from sample containers/holder or devices such as electrodes, several microscopy phantoms representing such circumstances were fabricated and examined with 3D bSSFP. RESULTS: Artifact-free microscopic bSSFP images could be obtained with voxel sizes down to 16 µm × 16 µm × 78 µm and with an SNR gain of 25% over standard gradient echo images. CONCLUSION: With appropriate choice of phantom materials, optimization of the flip angle to the diffusion-attenuated steady state and protocols considering duty-cycle limitations, bSSFP can be a valuable tool in MR microscopy.


Assuntos
Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Microscopia/métodos , Algoritmos , Artefatos , Simulação por Computador , Aumento da Imagem , Processamento de Imagem Assistida por Computador/métodos , Campos Magnéticos , Imagens de Fantasmas , Reprodutibilidade dos Testes , Razão Sinal-Ruído , Água
17.
Opt Express ; 25(19): 22640-22647, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-29041571

RESUMO

We investigate segmented Bessel beams that are created by placing different ring apertures behind an axicon that is illuminated with a plane wave. We find an analytical estimate to determine the shortest possible beam segment by deriving a scale-invariant analytical model using appropriate dimensionless parameters such as the wavelength and the axicon angle. This is verified using simulations and measurements, which are in good agreement. The size of the ring apertures was varied from small aperture sizes in the Frauhofer diffraction limit to larger aperture sizes in the classical limit.

18.
Opt Express ; 24(15): 17433-52, 2016 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-27464190

RESUMO

We study the spatial intensity distribution and the self-reconstruction of quasi-Bessel beams produced from refractive axicon lenses with edge emitting laser diodes as asymmetric and astigmatic illumination sources. Comparing these to a symmetric mono-mode fiber source, we find that the asymmetry results in a transition of a quasi-Bessel beam into a bow-tie shaped pattern and eventually to a line shaped profile at a larger distance along the optical axis. Furthermore, we analytically estimate and discuss the effects of astigmatism, substrate modes and non-perfect axicons. We find a good agreement between experiment, simulation and analytic considerations. Results include the derivation of a maximal axicon angle related to astigmatism of the illuminating beam, impact of laser diode beam profile imperfections like substrate modes and a longitudinal oscillation of the core intensity and radius caused by a rounded axicon tip.

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