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1.
  • Wang, Haidong, et al. (author)
  • Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015 : a systematic analysis for the Global Burden of Disease Study 2015
  • 2016
  • In: The Lancet. - 0140-6736 .- 1474-547X. ; 388:10053, s. 1459-1544
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: Improving survival and extending the longevity of life for all populations requires timely, robust evidence on local mortality levels and trends. The Global Burden of Disease 2015 Study (GBD 2015) provides a comprehensive assessment of all-cause and cause-specific mortality for 249 causes in 195 countries and territories from 1980 to 2015. These results informed an in-depth investigation of observed and expected mortality patterns based on sociodemographic measures.METHODS: We estimated all-cause mortality by age, sex, geography, and year using an improved analytical approach originally developed for GBD 2013 and GBD 2010. Improvements included refinements to the estimation of child and adult mortality and corresponding uncertainty, parameter selection for under-5 mortality synthesis by spatiotemporal Gaussian process regression, and sibling history data processing. We also expanded the database of vital registration, survey, and census data to 14 294 geography-year datapoints. For GBD 2015, eight causes, including Ebola virus disease, were added to the previous GBD cause list for mortality. We used six modelling approaches to assess cause-specific mortality, with the Cause of Death Ensemble Model (CODEm) generating estimates for most causes. We used a series of novel analyses to systematically quantify the drivers of trends in mortality across geographies. First, we assessed observed and expected levels and trends of cause-specific mortality as they relate to the Socio-demographic Index (SDI), a summary indicator derived from measures of income per capita, educational attainment, and fertility. Second, we examined factors affecting total mortality patterns through a series of counterfactual scenarios, testing the magnitude by which population growth, population age structures, and epidemiological changes contributed to shifts in mortality. Finally, we attributed changes in life expectancy to changes in cause of death. We documented each step of the GBD 2015 estimation processes, as well as data sources, in accordance with Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER).FINDINGS: Globally, life expectancy from birth increased from 61·7 years (95% uncertainty interval 61·4-61·9) in 1980 to 71·8 years (71·5-72·2) in 2015. Several countries in sub-Saharan Africa had very large gains in life expectancy from 2005 to 2015, rebounding from an era of exceedingly high loss of life due to HIV/AIDS. At the same time, many geographies saw life expectancy stagnate or decline, particularly for men and in countries with rising mortality from war or interpersonal violence. From 2005 to 2015, male life expectancy in Syria dropped by 11·3 years (3·7-17·4), to 62·6 years (56·5-70·2). Total deaths increased by 4·1% (2·6-5·6) from 2005 to 2015, rising to 55·8 million (54·9 million to 56·6 million) in 2015, but age-standardised death rates fell by 17·0% (15·8-18·1) during this time, underscoring changes in population growth and shifts in global age structures. The result was similar for non-communicable diseases (NCDs), with total deaths from these causes increasing by 14·1% (12·6-16·0) to 39·8 million (39·2 million to 40·5 million) in 2015, whereas age-standardised rates decreased by 13·1% (11·9-14·3). Globally, this mortality pattern emerged for several NCDs, including several types of cancer, ischaemic heart disease, cirrhosis, and Alzheimer's disease and other dementias. By contrast, both total deaths and age-standardised death rates due to communicable, maternal, neonatal, and nutritional conditions significantly declined from 2005 to 2015, gains largely attributable to decreases in mortality rates due to HIV/AIDS (42·1%, 39·1-44·6), malaria (43·1%, 34·7-51·8), neonatal preterm birth complications (29·8%, 24·8-34·9), and maternal disorders (29·1%, 19·3-37·1). Progress was slower for several causes, such as lower respiratory infections and nutritional deficiencies, whereas deaths increased for others, including dengue and drug use disorders. Age-standardised death rates due to injuries significantly declined from 2005 to 2015, yet interpersonal violence and war claimed increasingly more lives in some regions, particularly in the Middle East. In 2015, rotaviral enteritis (rotavirus) was the leading cause of under-5 deaths due to diarrhoea (146 000 deaths, 118 000-183 000) and pneumococcal pneumonia was the leading cause of under-5 deaths due to lower respiratory infections (393 000 deaths, 228 000-532 000), although pathogen-specific mortality varied by region. Globally, the effects of population growth, ageing, and changes in age-standardised death rates substantially differed by cause. Our analyses on the expected associations between cause-specific mortality and SDI show the regular shifts in cause of death composition and population age structure with rising SDI. Country patterns of premature mortality (measured as years of life lost [YLLs]) and how they differ from the level expected on the basis of SDI alone revealed distinct but highly heterogeneous patterns by region and country or territory. Ischaemic heart disease, stroke, and diabetes were among the leading causes of YLLs in most regions, but in many cases, intraregional results sharply diverged for ratios of observed and expected YLLs based on SDI. Communicable, maternal, neonatal, and nutritional diseases caused the most YLLs throughout sub-Saharan Africa, with observed YLLs far exceeding expected YLLs for countries in which malaria or HIV/AIDS remained the leading causes of early death.INTERPRETATION: At the global scale, age-specific mortality has steadily improved over the past 35 years; this pattern of general progress continued in the past decade. Progress has been faster in most countries than expected on the basis of development measured by the SDI. Against this background of progress, some countries have seen falls in life expectancy, and age-standardised death rates for some causes are increasing. Despite progress in reducing age-standardised death rates, population growth and ageing mean that the number of deaths from most non-communicable causes are increasing in most countries, putting increased demands on health systems.
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2.
  • Forouzanfar, Mohammad H, et al. (author)
  • Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990-2013 : a systematic analysis for the Global Burden of Disease Study 2013.
  • 2015
  • In: The Lancet. - 0140-6736 .- 1474-547X. ; 386:10010, s. 2287-2323
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: The Global Burden of Disease, Injuries, and Risk Factor study 2013 (GBD 2013) is the first of a series of annual updates of the GBD. Risk factor quantification, particularly of modifiable risk factors, can help to identify emerging threats to population health and opportunities for prevention. The GBD 2013 provides a timely opportunity to update the comparative risk assessment with new data for exposure, relative risks, and evidence on the appropriate counterfactual risk distribution.METHODS: Attributable deaths, years of life lost, years lived with disability, and disability-adjusted life-years (DALYs) have been estimated for 79 risks or clusters of risks using the GBD 2010 methods. Risk-outcome pairs meeting explicit evidence criteria were assessed for 188 countries for the period 1990-2013 by age and sex using three inputs: risk exposure, relative risks, and the theoretical minimum risk exposure level (TMREL). Risks are organised into a hierarchy with blocks of behavioural, environmental and occupational, and metabolic risks at the first level of the hierarchy. The next level in the hierarchy includes nine clusters of related risks and two individual risks, with more detail provided at levels 3 and 4 of the hierarchy. Compared with GBD 2010, six new risk factors have been added: handwashing practices, occupational exposure to trichloroethylene, childhood wasting, childhood stunting, unsafe sex, and low glomerular filtration rate. For most risks, data for exposure were synthesised with a Bayesian meta-regression method, DisMod-MR 2.0, or spatial-temporal Gaussian process regression. Relative risks were based on meta-regressions of published cohort and intervention studies. Attributable burden for clusters of risks and all risks combined took into account evidence on the mediation of some risks such as high body-mass index (BMI) through other risks such as high systolic blood pressure and high cholesterol.FINDINGS: All risks combined account for 57·2% (95% uncertainty interval [UI] 55·8-58·5) of deaths and 41·6% (40·1-43·0) of DALYs. Risks quantified account for 87·9% (86·5-89·3) of cardiovascular disease DALYs, ranging to a low of 0% for neonatal disorders and neglected tropical diseases and malaria. In terms of global DALYs in 2013, six risks or clusters of risks each caused more than 5% of DALYs: dietary risks accounting for 11·3 million deaths and 241·4 million DALYs, high systolic blood pressure for 10·4 million deaths and 208·1 million DALYs, child and maternal malnutrition for 1·7 million deaths and 176·9 million DALYs, tobacco smoke for 6·1 million deaths and 143·5 million DALYs, air pollution for 5·5 million deaths and 141·5 million DALYs, and high BMI for 4·4 million deaths and 134·0 million DALYs. Risk factor patterns vary across regions and countries and with time. In sub-Saharan Africa, the leading risk factors are child and maternal malnutrition, unsafe sex, and unsafe water, sanitation, and handwashing. In women, in nearly all countries in the Americas, north Africa, and the Middle East, and in many other high-income countries, high BMI is the leading risk factor, with high systolic blood pressure as the leading risk in most of Central and Eastern Europe and south and east Asia. For men, high systolic blood pressure or tobacco use are the leading risks in nearly all high-income countries, in north Africa and the Middle East, Europe, and Asia. For men and women, unsafe sex is the leading risk in a corridor from Kenya to South Africa.INTERPRETATION: Behavioural, environmental and occupational, and metabolic risks can explain half of global mortality and more than one-third of global DALYs providing many opportunities for prevention. Of the larger risks, the attributable burden of high BMI has increased in the past 23 years. In view of the prominence of behavioural risk factors, behavioural and social science research on interventions for these risks should be strengthened. Many prevention and primary care policy options are available now to act on key risks.FUNDING: Bill & Melinda Gates Foundation.
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3.
  • Naghavi, Mohsen, et al. (author)
  • Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013
  • 2015
  • In: The Lancet. - 1474-547X .- 0140-6736. ; 385:9963, s. 117-171
  • Journal article (peer-reviewed)abstract
    • Background Up-to-date evidence on levels and trends for age-sex-specifi c all-cause and cause-specifi c mortality is essential for the formation of global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013) we estimated yearly deaths for 188 countries between 1990, and 2013. We used the results to assess whether there is epidemiological convergence across countries. Methods We estimated age-sex-specifi c all-cause mortality using the GBD 2010 methods with some refinements to improve accuracy applied to an updated database of vital registration, survey, and census data. We generally estimated cause of death as in the GBD 2010. Key improvements included the addition of more recent vital registration data for 72 countries, an updated verbal autopsy literature review, two new and detailed data systems for China, and more detail for Mexico, UK, Turkey, and Russia. We improved statistical models for garbage code redistribution. We used six different modelling strategies across the 240 causes; cause of death ensemble modelling (CODEm) was the dominant strategy for causes with sufficient information. Trends for Alzheimer's disease and other dementias were informed by meta-regression of prevalence studies. For pathogen-specifi c causes of diarrhoea and lower respiratory infections we used a counterfactual approach. We computed two measures of convergence (inequality) across countries: the average relative difference across all pairs of countries (Gini coefficient) and the average absolute difference across countries. To summarise broad findings, we used multiple decrement life-tables to decompose probabilities of death from birth to exact age 15 years, from exact age 15 years to exact age 50 years, and from exact age 50 years to exact age 75 years, and life expectancy at birth into major causes. For all quantities reported, we computed 95% uncertainty intervals (UIs). We constrained cause-specific fractions within each age-sex-country-year group to sum to all-cause mortality based on draws from the uncertainty distributions. Findings Global life expectancy for both sexes increased from 65.3 years (UI 65.0-65.6) in 1990, to 71.5 years (UI 71.0-71.9) in 2013, while the number of deaths increased from 47.5 million (UI 46.8-48.2) to 54.9 million (UI 53.6-56.3) over the same interval. Global progress masked variation by age and sex: for children, average absolute diff erences between countries decreased but relative diff erences increased. For women aged 25-39 years and older than 75 years and for men aged 20-49 years and 65 years and older, both absolute and relative diff erences increased. Decomposition of global and regional life expectancy showed the prominent role of reductions in age-standardised death rates for cardiovascular diseases and cancers in high-income regions, and reductions in child deaths from diarrhoea, lower respiratory infections, and neonatal causes in low-income regions. HIV/AIDS reduced life expectancy in southern sub-Saharan Africa. For most communicable causes of death both numbers of deaths and age-standardised death rates fell whereas for most non-communicable causes, demographic shifts have increased numbers of deaths but decreased age-standardised death rates. Global deaths from injury increased by 10.7%, from 4.3 million deaths in 1990 to 4.8 million in 2013; but age-standardised rates declined over the same period by 21%. For some causes of more than 100 000 deaths per year in 2013, age-standardised death rates increased between 1990 and 2013, including HIV/AIDS, pancreatic cancer, atrial fibrillation and flutter, drug use disorders, diabetes, chronic kidney disease, and sickle-cell anaemias. Diarrhoeal diseases, lower respiratory infections, neonatal causes, and malaria are still in the top five causes of death in children younger than 5 years. The most important pathogens are rotavirus for diarrhoea and pneumococcus for lower respiratory infections. Country-specific probabilities of death over three phases of life were substantially varied between and within regions. Interpretation For most countries, the general pattern of reductions in age-sex specifi c mortality has been associated with a progressive shift towards a larger share of the remaining deaths caused by non-communicable disease and injuries. Assessing epidemiological convergence across countries depends on whether an absolute or relative measure of inequality is used. Nevertheless, age-standardised death rates for seven substantial causes are increasing, suggesting the potential for reversals in some countries. Important gaps exist in the empirical data for cause of death estimates for some countries; for example, no national data for India are available for the past decade.
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4.
  • Vos, Theo, et al. (author)
  • Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013
  • 2015
  • In: The Lancet. - 1474-547X .- 0140-6736. ; 386:9995, s. 743-800
  • Journal article (peer-reviewed)abstract
    • Background Up-to-date evidence about levels and trends in disease and injury incidence, prevalence, and years lived with disability (YLDs) is an essential input into global, regional, and national health policies. In the Global Burden of Disease Study 2013 (GBD 2013), we estimated these quantities for acute and chronic diseases and injuries for 188 countries between 1990 and 2013. Methods Estimates were calculated for disease and injury incidence, prevalence, and YLDs using GBD 2010 methods with some important refinements. Results for incidence of acute disorders and prevalence of chronic disorders are new additions to the analysis. Key improvements include expansion to the cause and sequelae list, updated systematic reviews, use of detailed injury codes, improvements to the Bayesian meta-regression method (DisMod-MR), and use of severity splits for various causes. An index of data representativeness, showing data availability, was calculated for each cause and impairment during three periods globally and at the country level for 2013. In total, 35 620 distinct sources of data were used and documented to calculated estimates for 301 diseases and injuries and 2337 sequelae. The comorbidity simulation provides estimates for the number of sequelae, concurrently, by individuals by country, year, age, and sex. Disability weights were updated with the addition of new population-based survey data from four countries. Findings Disease and injury were highly prevalent; only a small fraction of individuals had no sequelae. Comorbidity rose substantially with age and in absolute terms from 1990 to 2013. Incidence of acute sequelae were predominantly infectious diseases and short-term injuries, with over 2 billion cases of upper respiratory infections and diarrhoeal disease episodes in 2013, with the notable exception of tooth pain due to permanent caries with more than 200 million incident cases in 2013. Conversely, leading chronic sequelae were largely attributable to non-communicable diseases, with prevalence estimates for asymptomatic permanent caries and tension-type headache of 2.4 billion and 1.6 billion, respectively. The distribution of the number of sequelae in populations varied widely across regions, with an expected relation between age and disease prevalence. YLDs for both sexes increased from 537.6 million in 1990 to 764.8 million in 2013 due to population growth and ageing, whereas the age-standardised rate decreased little from 114.87 per 1000 people to 110.31 per 1000 people between 1990 and 2013. Leading causes of YLDs included low back pain and major depressive disorder among the top ten causes of YLDs in every country. YLD rates per person, by major cause groups, indicated the main drivers of increases were due to musculoskeletal, mental, and substance use disorders, neurological disorders, and chronic respiratory diseases; however HIV/AIDS was a notable driver of increasing YLDs in sub-Saharan Africa. Also, the proportion of disability-adjusted life years due to YLDs increased globally from 21.1% in 1990 to 31.2% in 2013. Interpretation Ageing of the world's population is leading to a substantial increase in the numbers of individuals with sequelae of diseases and injuries. Rates of YLDs are declining much more slowly than mortality rates. The non-fatal dimensions of disease and injury will require more and more attention from health systems. The transition to non-fatal outcomes as the dominant source of burden of disease is occurring rapidly outside of sub-Saharan Africa. Our results can guide future health initiatives through examination of epidemiological trends and a better understanding of variation across countries.
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5.
  • Kassebaum, Nicholas J., et al. (author)
  • Global, regional, and national disability-adjusted life-years (DALYs) for 315 diseases and injuries and healthy life expectancy (HALE), 1990-2015 : a systematic analysis for the Global Burden of Disease Study 2015
  • 2016
  • In: The Lancet. - 0140-6736 .- 1474-547X. ; 388:10053, s. 1603-1658
  • Journal article (peer-reviewed)abstract
    • Background Healthy life expectancy (HALE) and disability-adjusted life-years (DALYs) provide summary measures of health across geographies and time that can inform assessments of epidemiological patterns and health system performance, help to prioritise investments in research and development, and monitor progress toward the Sustainable Development Goals (SDGs). We aimed to provide updated HALE and DALYs for geographies worldwide and evaluate how disease burden changes with development. Methods We used results from the Global Burden of Diseases, Injuries, and Risk Factors Study 2015 (GBD 2015) for all-cause mortality, cause-specific mortality, and non-fatal disease burden to derive HALE and DALYs by sex for 195 countries and territories from 1990 to 2015. We calculated DALYs by summing years of life lost (YLLs) and years of life lived with disability (YLDs) for each geography, age group, sex, and year. We estimated HALE using the Sullivan method, which draws from age-specific death rates and YLDs per capita. We then assessed how observed levels of DALYs and HALE differed from expected trends calculated with the Socio-demographic Index (SDI), a composite indicator constructed from measures of income per capita, average years of schooling, and total fertility rate. Findings Total global DALYs remained largely unchanged from 1990 to 2015, with decreases in communicable, neonatal, maternal, and nutritional (Group 1) disease DALYs off set by increased DALYs due to non-communicable diseases (NCDs). Much of this epidemiological transition was caused by changes in population growth and ageing, but it was accelerated by widespread improvements in SDI that also correlated strongly with the increasing importance of NCDs. Both total DALYs and age-standardised DALY rates due to most Group 1 causes significantly decreased by 2015, and although total burden climbed for the majority of NCDs, age-standardised DALY rates due to NCDs declined. Nonetheless, age-standardised DALY rates due to several high-burden NCDs (including osteoarthritis, drug use disorders, depression, diabetes, congenital birth defects, and skin, oral, and sense organ diseases) either increased or remained unchanged, leading to increases in their relative ranking in many geographies. From 2005 to 2015, HALE at birth increased by an average of 2.9 years (95% uncertainty interval 2.9-3.0) for men and 3.5 years (3.4-3.7) for women, while HALE at age 65 years improved by 0.85 years (0.78-0.92) and 1.2 years (1.1-1.3), respectively. Rising SDI was associated with consistently higher HALE and a somewhat smaller proportion of life spent with functional health loss; however, rising SDI was related to increases in total disability. Many countries and territories in central America and eastern sub-Saharan Africa had increasingly lower rates of disease burden than expected given their SDI. At the same time, a subset of geographies recorded a growing gap between observed and expected levels of DALYs, a trend driven mainly by rising burden due to war, interpersonal violence, and various NCDs. Interpretation Health is improving globally, but this means more populations are spending more time with functional health loss, an absolute expansion of morbidity. The proportion of life spent in ill health decreases somewhat with increasing SDI, a relative compression of morbidity, which supports continued efforts to elevate personal income, improve education, and limit fertility. Our analysis of DALYs and HALE and their relationship to SDI represents a robust framework on which to benchmark geography-specific health performance and SDG progress. Country-specific drivers of disease burden, particularly for causes with higher-than-expected DALYs, should inform financial and research investments, prevention efforts, health policies, and health system improvement initiatives for all countries along the development continuum.
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6.
  • Wang, Haidong, et al. (author)
  • Estimates of global, regional, and national incidence, prevalence, and mortality of HIV, 1980-2015 : the Global Burden of Disease Study 2015.
  • 2016
  • In: The lancet. HIV. - : Elsevier. - 2352-3018. ; 3:8, s. e361-e387
  • Journal article (peer-reviewed)abstract
    • BACKGROUND: Timely assessment of the burden of HIV/AIDS is essential for policy setting and programme evaluation. In this report from the Global Burden of Disease Study 2015 (GBD 2015), we provide national estimates of levels and trends of HIV/AIDS incidence, prevalence, coverage of antiretroviral therapy (ART), and mortality for 195 countries and territories from 1980 to 2015.METHODS: For countries without high-quality vital registration data, we estimated prevalence and incidence with data from antenatal care clinics and population-based seroprevalence surveys, and with assumptions by age and sex on initial CD4 distribution at infection, CD4 progression rates (probability of progression from higher to lower CD4 cell-count category), on and off antiretroviral therapy (ART) mortality, and mortality from all other causes. Our estimation strategy links the GBD 2015 assessment of all-cause mortality and estimation of incidence and prevalence so that for each draw from the uncertainty distribution all assumptions used in each step are internally consistent. We estimated incidence, prevalence, and death with GBD versions of the Estimation and Projection Package (EPP) and Spectrum software originally developed by the Joint United Nations Programme on HIV/AIDS (UNAIDS). We used an open-source version of EPP and recoded Spectrum for speed, and used updated assumptions from systematic reviews of the literature and GBD demographic data. For countries with high-quality vital registration data, we developed the cohort incidence bias adjustment model to estimate HIV incidence and prevalence largely from the number of deaths caused by HIV recorded in cause-of-death statistics. We corrected these statistics for garbage coding and HIV misclassification.FINDINGS: Global HIV incidence reached its peak in 1997, at 3·3 million new infections (95% uncertainty interval [UI] 3·1-3·4 million). Annual incidence has stayed relatively constant at about 2·6 million per year (range 2·5-2·8 million) since 2005, after a period of fast decline between 1997 and 2005. The number of people living with HIV/AIDS has been steadily increasing and reached 38·8 million (95% UI 37·6-40·4 million) in 2015. At the same time, HIV/AIDS mortality has been declining at a steady pace, from a peak of 1·8 million deaths (95% UI 1·7-1·9 million) in 2005, to 1·2 million deaths (1·1-1·3 million) in 2015. We recorded substantial heterogeneity in the levels and trends of HIV/AIDS across countries. Although many countries have experienced decreases in HIV/AIDS mortality and in annual new infections, other countries have had slowdowns or increases in rates of change in annual new infections.INTERPRETATION: Scale-up of ART and prevention of mother-to-child transmission has been one of the great successes of global health in the past two decades. However, in the past decade, progress in reducing new infections has been slow, development assistance for health devoted to HIV has stagnated, and resources for health in low-income countries have grown slowly. Achievement of the new ambitious goals for HIV enshrined in Sustainable Development Goal 3 and the 90-90-90 UNAIDS targets will be challenging, and will need continued efforts from governments and international agencies in the next 15 years to end AIDS by 2030.
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7.
  • Barber, R. M., et al. (author)
  • Healthcare access and quality index based on mortality from causes amenable to personal health care in 195 countries and territories, 1990-2015 : A novel analysis from the global burden of disease study 2015
  • 2017
  • In: The Lancet. - : Lancet Publishing Group. - 0140-6736 .- 1474-547X. ; 390:10091, s. 231-266
  • Journal article (peer-reviewed)abstract
    • Background National levels of personal health-care access and quality can be approximated by measuring mortality rates from causes that should not be fatal in the presence of effective medical care (ie, amenable mortality). Previous analyses of mortality amenable to health care only focused on high-income countries and faced several methodological challenges. In the present analysis, we use the highly standardised cause of death and risk factor estimates generated through the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) to improve and expand the quantification of personal health-care access and quality for 195 countries and territories from 1990 to 2015. Methods We mapped the most widely used list of causes amenable to personal health care developed by Nolte and McKee to 32 GBD causes. We accounted for variations in cause of death certification and misclassifications through the extensive data standardisation processes and redistribution algorithms developed for GBD. To isolate the effects of personal health-care access and quality, we risk-standardised cause-specific mortality rates for each geography-year by removing the joint effects of local environmental and behavioural risks, and adding back the global levels of risk exposure as estimated for GBD 2015. We employed principal component analysis to create a single, interpretable summary measure-the Healthcare Quality and Access (HAQ) Index-on a scale of 0 to 100. The HAQ Index showed strong convergence validity as compared with other health-system indicators, including health expenditure per capita (r=0·88), an index of 11 universal health coverage interventions (r=0·83), and human resources for health per 1000 (r=0·77). We used free disposal hull analysis with bootstrapping to produce a frontier based on the relationship between the HAQ Index and the Socio-demographic Index (SDI), a measure of overall development consisting of income per capita, average years of education, and total fertility rates. This frontier allowed us to better quantify the maximum levels of personal health-care access and quality achieved across the development spectrum, and pinpoint geographies where gaps between observed and potential levels have narrowed or widened over time. Findings Between 1990 and 2015, nearly all countries and territories saw their HAQ Index values improve; nonetheless, the difference between the highest and lowest observed HAQ Index was larger in 2015 than in 1990, ranging from 28·6 to 94·6. Of 195 geographies, 167 had statistically significant increases in HAQ Index levels since 1990, with South Korea, Turkey, Peru, China, and the Maldives recording among the largest gains by 2015. Performance on the HAQ Index and individual causes showed distinct patterns by region and level of development, yet substantial heterogeneities emerged for several causes, including cancers in highest-SDI countries; chronic kidney disease, diabetes, diarrhoeal diseases, and lower respiratory infections among middle-SDI countries; and measles and tetanus among lowest-SDI countries. While the global HAQ Index average rose from 40·7 (95% uncertainty interval, 39·0-42·8) in 1990 to 53·7 (52·2-55·4) in 2015, far less progress occurred in narrowing the gap between observed HAQ Index values and maximum levels achieved; at the global level, the difference between the observed and frontier HAQ Index only decreased from 21·2 in 1990 to 20·1 in 2015. If every country and territory had achieved the highest observed HAQ Index by their corresponding level of SDI, the global average would have been 73·8 in 2015. Several countries, particularly in eastern and western sub-Saharan Africa, reached HAQ Index values similar to or beyond their development levels, whereas others, namely in southern sub-Saharan Africa, the Middle East, and south Asia, lagged behind what geographies of similar development attained between 1990 and 2015. Interpretation This novel extension of the GBD Study shows the untapped potential for personal health-care access and quality improvement across the development spectrum. Amid substantive advances in personal health care at the national level, heterogeneous patterns for individual causes in given countries or territories suggest that few places have consistently achieved optimal health-care access and quality across health-system functions and therapeutic areas. This is especially evident in middle-SDI countries, many of which have recently undergone or are currently experiencing epidemiological transitions. The HAQ Index, if paired with other measures of health-system characteristics such as intervention coverage, could provide a robust avenue for tracking progress on universal health coverage and identifying local priorities for strengthening personal health-care quality and access throughout the world. Copyright © The Author(s). Published by Elsevier Ltd.
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8.
  • Barber, R. M., et al. (author)
  • Healthcare Access and Quality Index based on mortality from causes amenable to personal health care in 195 countries and territories, 1990-2015: a novel analysis from the Global Burden of Disease Study 2015
  • 2017
  • In: Lancet. - : Elsevier BV. - 0140-6736. ; 390:10091, s. 231-266
  • Journal article (peer-reviewed)abstract
    • Background National levels of personal health-care access and quality can be approximated by measuring mortality rates from causes that should not be fatal in the presence of effective medical care (ie, amenable mortality). Previous analyses of mortality amenable to health care only focused on high-income countries and faced several methodological challenges. In the present analysis, we use the highly standardised cause of death and risk factor estimates generated through the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) to improve and expand the quantification of personal health-care access and quality for 195 countries and territories from 1990 to 2015. Methods We mapped the most widely used list of causes amenable to personal health care developed by Nolte and McKee to 32 GBD causes. We accounted for variations in cause of death certification and misclassifications through the extensive data standardisation processes and redistribution algorithms developed for GBD. To isolate the effects of personal health-care access and quality, we risk-standardised cause-specific mortality rates for each geography-year by removing the joint effects of local environmental and behavioural risks, and adding back the global levels of risk exposure as estimated for GBD 2015. We employed principal component analysis to create a single, interpretable summary measure-the Healthcare Quality and Access (HAQ) Index-on a scale of 0 to 100. The HAQ Index showed strong convergence validity as compared with other health-system indicators, including health expenditure per capita (r= 0.88), an index of 11 universal health coverage interventions (r= 0.83), and human resources for health per 1000 (r= 0.77). We used free disposal hull analysis with bootstrapping to produce a frontier based on the relationship between the HAQ Index and the Socio-demographic Index (SDI), a measure of overall development consisting of income per capita, average years of education, and total fertility rates. This frontier allowed us to better quantify the maximum levels of personal health-care access and quality achieved across the development spectrum, and pinpoint geographies where gaps between observed and potential levels have narrowed or widened over time. Findings Between 1990 and 2015, nearly all countries and territories saw their HAQ Index values improve; nonetheless, the difference between the highest and lowest observed HAQ Index was larger in 2015 than in 1990, ranging from 28.6 to 94.6. Of 195 geographies, 167 had statistically significant increases in HAQ Index levels since 1990, with South Korea, Turkey, Peru, China, and the Maldives recording among the largest gains by 2015. Performance on the HAQ Index and individual causes showed distinct patterns by region and level of development, yet substantial heterogeneities emerged for several causes, including cancers in highest-SDI countries; chronic kidney disease, diabetes, diarrhoeal diseases, and lower respiratory infections among middle-SDI countries; and measles and tetanus among lowest-SDI countries. While the global HAQ Index average rose from 40.7 (95% uncertainty interval, 39.0-42.8) in 1990 to 53.7 (52.2-55.4) in 2015, far less progress occurred in narrowing the gap between observed HAQ Index values and maximum levels achieved; at the global level, the difference between the observed and frontier HAQ Index only decreased from 21.2 in 1990 to 20.1 in 2015. If every country and territory had achieved the highest observed HAQ Index by their corresponding level of SDI, the global average would have been 73.8 in 2015. Several countries, particularly in eastern and western sub-Saharan Africa, reached HAQ Index values similar to or beyond their development levels, whereas others, namely in southern sub-Saharan Africa, the Middle East, and south Asia, lagged behind what geographies of similar development attained between 1990 and 2015. Interpretation This novel extension of the GBD Study shows the untapped potential for personal health-care access and quality improvement across the development spectrum. Amid substantive advances in personal health care at the national level, heterogeneous patterns for individual causes in given countries or territories suggest that few places have consistently achieved optimal health-care access and quality across health-system functions and therapeutic areas. This is especially evident in middle-SDI countries, many of which have recently undergone or are currently experiencing epidemiological transitions. The HAQ Index, if paired with other measures of health-systemcharacteristics such as intervention coverage, could provide a robust avenue for tracking progress on universal health coverage and identifying local priorities for strengthening personal health-care quality and access throughout the world. Copyright (C) The Author(s). Published by Elsevier Ltd.
  •  
9.
  • Golnabi, Amir H., et al. (author)
  • 3-D Microwave Tomography Using the Soft Prior Regularization Technique: Evaluation in Anatomically Realistic MRI-Derived Numerical Breast Phantoms
  • 2019
  • In: IEEE Transactions on Biomedical Engineering. - 0018-9294 .- 1558-2531. ; 66:9, s. 2566-2575
  • Journal article (peer-reviewed)abstract
    • Objective: Fusion of magnetic resonance imaging (MRI) breast images with microwave tomography is accomplished through a soft prior technique, which incorporates spatial information (from MRI), i. e., accurate boundary location of different regions of interest, into the regularization process of the microwave image reconstruction algorithm. Methods: Numerical experiments were completed on a set of three-dimensional (3-D) breast geometries derived from MR breast data with different parenchymal densities, as well as a simulated tumor to evaluate the performance over a range of breast shapes, sizes, and property distributions. Results: When the soft prior regularization technique was applied, both permittivity and conductivity relative root mean square error values decreased by more than 87% across all breast densities, except in two cases where the error decrease was only 55% and 78%. In addition, the incorporation of structural priors increased contrast between tumor and fibroglandular tissue by 59% in permittivity and 192% in conductivity. Conclusion: This study confirmed that the soft prior algorithm is robust in 3-D and can function successfully across a range of complex geometries and tissue property distributions. Significance: This study demonstrates that our microwave tomography is capable of recovering accurate tissue property distributions when spatial information from MRI is incorporated through soft prior regularization.
  •  
10.
  • Henriksson, Tommy, 1978- (author)
  • CONTRIBUTION TO QUANTITATIVE MICROWAVE IMAGING TECHNIQUES FOR BIOMEDICAL APPLICATIONS
  • 2009
  • Doctoral thesis (other academic/artistic)abstract
    • This dissertation presents a contribution to quantitative microwave imaging for breast tumor detection. The study made in the frame of a joint supervision Ph.D. thesis between University Paris-SUD 11 (France) and Mälardalen University (Sweden), has been conducted through two experimental microwave imaging setups, the existing 2.45 GHz planar camera (France) and the multi-frequency flexible robotic system, (Sweden), under development. In this context a 2D scalar flexible numerical tool based on a Newton-Kantorovich (NK) scheme, has been developed. Quantitative microwave imaging is a three dimensional vectorial nonlinear inverse scattering problem, where the complex permittivity of an object is reconstructed from the measured scattered field, produced by the object. The NK scheme is used in order to deal with the nonlinearity and the ill-posed nature of this problem. A TM polarization and a two dimensional medium configuration have been considered in order to avoid its vectorial aspect. The solution is found iteratively by minimizing the square norm of the error with respect to the scattered field data. Consequently, the convergence of such iterative process requires, at least two conditions. First, an efficient calibration of the experimental system has to be associated to the minimization of model errors. Second, the mean square difference of the scattered field introduced by the presence of the tumor has to be large enough, according to the sensitivity of the imaging system. The existing planar camera associated to a flexible 2D scalar NK code, are considered as an experimental platform for quantitative breast imaging. A preliminary numerical study shows that the multi-view planar system is quite efficient for realistic breast tumor phantoms, according to its characteristics (frequency, planar geometry and water as a coupling medium), as long as realistic noisy data are considered. Furthermore, a multi-incidence planar system, more appropriate in term of antenna-array arrangement, is proposed and its concept is numerically validated. On the other hand, an experimental work which includes a new fluid-mixture for the realization of a narrow band cylindrical breast phantom, a deep investigation in the calibration process and model error minimization, is presented. This conducts to the first quantitative reconstruction of a realistic breast phantom by using multi-view data from the planar camera. Next, both the qualitative and quantitative reconstruction of 3D inclusions into the cylindrical breast phantom, by using data from all the retina, are shown and discussed. Finally, the extended work towards the flexible robotic system is presented.
  •  
11.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • A discrete dipole approximation solver based on the COCG-FFT algorithm and its application to microwave breast imaging
  • 2019
  • In: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2019
  • Journal article (peer-reviewed)abstract
    • We introduce the discrete dipole approximation (DDA) for efficiently calculating the two-dimensional electric field distribution for our microwave tomographic breast imaging system. For iterative inverse problems such as microwave tomography, the forward field computation is the time limiting step. In this paper, the two-dimensional algorithm is derived and formulated such that the iterative conjugate orthogonal conjugate gradient (COCG) method can be used for efficiently solving the forward problem. We have also optimized the matrix-vector multiplication step by formulating the problem such that the nondiagonal portion of the matrix used to compute the dipole moments is block-Toeplitz. The computation costs for multiplying the block matrices times a vector can be dramatically accelerated by expanding each Toeplitz matrix to a circulant matrix for which the convolution theorem is applied for fast computation utilizing the fast Fourier transform (FFT). The results demonstrate that this formulation is accurate and efficient. In this work, the computation times for the direct solvers, the iterative solver (COCG), and the iterative solver using the fast Fourier transform (COCG-FFT) are compared with the best performance achieved using the iterative solver (COCG-FFT) in C++. Utilizing this formulation provides a computationally efficient building block for developing a low cost and fast breast imaging system to serve under-resourced populations.
  •  
12.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Application of the discrete dipole approximation in microwave breast imaging
  • 2019
  • In: Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019. ; , s. 0868-0868
  • Conference paper (peer-reviewed)abstract
    • In this work, we propose the two-dimensional discrete dipole approximation (2D DDA) to calculate the electric field distributions in the microwave imaging system. The motive is to develop a significantly fast reconstruction algorithm. To accomplish this, the 2D DDA on a uniform grid in the forward model zone is used, which enables computational times be significantly reduced compared to common algorithms.
  •  
13.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Application of two-dimensional discrete dipole approximation in simulating electric field of a microwave breast imaging system
  • 2019
  • In: IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology. - 2469-7249. ; 3:2, s. 80-87
  • Journal article (peer-reviewed)abstract
    • © 2016 IEEE. The 2-D electric field distribution of the microwave imaging system is numerically simulated for a simplified breast tumour model. The proposed two-dimensional discrete dipole approximation (DDA) has the potential to improve computational speed compared to other numerical methods while retaining comparable accuracy. We have modeled the field distributions in COMSOL Multiphysics as baseline results to benchmark the DDA simulations. We have also investigated the adequate sampling size and the effect of inclusion size and property contrast on solution accuracy. In this way, we can utilize the 2-D DDA as an alternative, fast, and reliable forward solver for microwave tomography. From a mathematical perspective, the derivation of the 2-D DDA and its application to microwave imaging is new and not previously implemented. The simulation results and the measurements show that the 2-D DDA is a well-grounded forward solver for the specified microwave breast imaging system.
  •  
14.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Comparison of Two Forward Models For Electric Field of Microwave Imaging Systems
  • 2017
  • In: 2017 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538632840 ; 2017-January, s. 969-970
  • Conference paper (peer-reviewed)abstract
    • We propose an alternative numerical method, discrete dipole approximation (DDA), to model the two dimensional electric field of forward solution. Our observations show that discrete dipole approximation can be used as a fast and reliable numerical method on the forward solution of the microwave imaging systems. Two dimensional electric field of the microwave imaging systems has been modelled in finite element method with help of COMSOL Multiphysics as well. The numerical experiments obtained from COMSOL Multiphysics agree well with the discrete dipole approximation approach.
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15.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Discrete Dipole Approximation-Based Microwave Tomography for Fast Breast Cancer Imaging
  • 2021
  • In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 69:5, s. 2741-2752
  • Journal article (peer-reviewed)abstract
    • This article describes a fast microwave tomography reconstruction algorithm based on the 2-D discrete dipole approximation (DDA). Synthetic data from a finite-element-based solver and experimental data from a microwave imaging system are used to reconstruct images and to validate the algorithm. The microwave measurement system consists of 16 monopole antennas immersed in a tank filled with lossy coupling liquid and a vector network analyzer. The low-profile antennas and lossy nature of the system make the DDA an ideal forward solver in image reconstructions. The results show that the algorithm can readily reconstruct a 2-D plane of a cylindrical phantom. The proposed forward solver combined with the nodal adjoint method for computing the Jacobian matrix enables the algorithm to reconstruct an image within 6 s. This implementation provides significant time savings and reduced memory requirements and is a dramatic improvement over previous implementations.
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16.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Expansion of the nodal-adjoint method for simple and efficient computation of the 2d tomographic imaging jacobian matrix
  • 2021
  • In: Sensors. - : MDPI AG. - 1424-8220. ; 21:3, s. 1-16
  • Journal article (other academic/artistic)abstract
    • This paper focuses on the construction of the Jacobian matrix required in tomographic reconstruction algorithms. In microwave tomography, computing the forward solutions during the iterative reconstruction process impacts the accuracy and computational efficiency. Towards this end, we have applied the discrete dipole approximation for the forward solutions with significant time savings. However, while we have discovered that the imaging problem configuration can dramatically impact the computation time required for the forward solver, it can be equally beneficial in constructing the Jacobian matrix calculated in iterative image reconstruction algorithms. Key to this implementation, we propose to use the same simulation grid for both the forward and imaging domain discretizations for the discrete dipole approximation solutions and report in detail the theoretical aspects for this localization. In this way, the computational cost of the nodal adjoint method decreases by several orders of magnitude. Our investigations show that this expansion is a significant enhancement compared to previous implementations and results in a rapid calculation of the Jacobian matrix with a high level of accuracy. The discrete dipole approximation and the newly efficient Jacobian matrices are effectively implemented to produce quantitative images of the simplified breast phantom from the microwave imaging system.
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17.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Fast Jacobian Matrix Formulation for Microwave Tomography Applications
  • 2021
  • In: 15th European Conference on Antennas and Propagation, EuCAP 2021.
  • Conference paper (peer-reviewed)abstract
    • We have developed a new technique for computing the Jacobian matrix for microwave tomography systems which is orders of magnitude faster than conventional approaches. It exploits concepts from the nodal adjoint method and previous observations that rows of the matrix can be plotted over the imaging domain to produce sensitivity maps associated with specific transmit/receive antenna pairs. It also requires that the forward solutions and parameter reconstruction distributions be represented on the same grid or mesh. In this way, it computes full rows of the matrix simultaneously via a simple vector-vector multiplication of the forward solutions associated with sources broadcasting from both the designated transmit and receive antennas times a scalar constant. The time savings is substantial and is viable for both 2D and 3D applications.
  •  
18.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Integrating the discrete dipole approximation forward solver with a microwave tomography algorithm
  • 2018
  • In: 2018 IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538671023 - 9781538671023 ; , s. 2295-2296
  • Conference paper (peer-reviewed)abstract
    • The discrete dipole approximation (DDA) has been suggested as a viable alternative method for computing the forward solutions during the iterative reconstruction process used in microwave tomography. While efficient algorithms such as finite difference time domain and finite elements have been successfully used by multiple groups, the forward solution time remains the time-limiting step. The DDA has been shown to be accurate and efficient as a forward solver. However, the configuration of the imaging scenario can have a significant impact on its efficiency. We examine two possible forward solution set-ups and describe the benefits with respect to implementing the DDA.
  •  
19.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • On the electric field of microwave imaging systems using discrete dipole approximation
  • 2018
  • In: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018. - 9781538657959
  • Conference paper (peer-reviewed)abstract
    • The two dimensional electric field for our microwave imaging system consisting of 16 low profile monopole antennas is modelled via the discrete dipole approximation (DDA). We have used two dimensional electromagnetic waves in frequency domain in COMSOL Multiphysics to assess the level of reliability of the proposed two dimensional numerical solver, the 2-D DDA. Our observations show that the DDA is mainly dependent on the applied resolution on the imaging domain while physical properties in the media also contribute to the overall error.
  •  
20.
  • Hosseinzadegan, Samar, 1987, et al. (author)
  • Optimization of a microwave tomography algorithm using the DDA as a fast forward solver
  • 2019
  • In: 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019 - Proceedings. ; , s. 1683-1684
  • Conference paper (peer-reviewed)abstract
    • © 2019 IEEE. The forward model directly impacts the computation time of an iterative image reconstruction algorithm for microwave tomography. Therefore, there is a need to decrease the computation time without sacrificing accuracy. To accomplish this, the discrete dipole approximation (DDA) is used to improve time efficiency. Although the DDA is an accurate and efficient forward solver, the optimization of its implementation can have a significant impact on its time efficiency. We propose a possible forward solution set-up to benefit in computation time efficiency. Optimizing the DDA implementation can decrease the computation time for a microwave tomography algorithm significantly, and thus produces images closer to real time.
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21.
  •  
22.
  • Mattsson, Viktor (author)
  • Data-Driven Methods for Microwave Sensor Devices in Musculoskeletal Diagnostics
  • 2024
  • Doctoral thesis (other academic/artistic)abstract
    • Microwave sensors can be used within medicine as they use non-ionizing radiation, are often low cost, and can be designed for a specific purpose. The application of microwave sensors for diagnostics and monitoring can be improved using appropriate data analysis. The multi-layered structure of the human body makes the measurements on people complex. A tremendous effort is required to create an analytical model of the body. In this context a data-driven approach, building a model that learns from previous measurements, is more suitable to analyze the data. This thesis aims to address statistical and data-driven approaches based on microwave sensor data for biomedical applications.A significant part of this thesis deals with microwave sensors for assessing muscle quality. It details the progress from initial clinical campaign to the creation of a machine learning algorithm to assess the local body composition. Such a device would be suitable for screening age-related muscle disorders like sarcopenia and muscle atrophy. Statistical analysis following the initial clinical campaign revealed no significant differences in the microwave data. Therefore, new sensor designs were evaluated. The most promising sensor was used in a small clinical campaign where it was able to detect a change in muscle size for one patient with multiple measurements over time. Successive measurements followed on tissue emulating phantoms and volunteers. For data analysis a machine learning algorithm was designed to predict the skin, fat, and muscle properties. This changes the aim from assessing muscle quality to assessing local body composition. For phantom data the algorithm was accurate for skin and fat and for volunteer data for fat and muscle. Crucially, the algorithm also performed better with more data available, meaning that results should improve if more data is collected.Microwave sensors have also been employed to assess bone. The first of two applications was to monitor the bone healing progression post surgery treating craniosynostosis. No substantial conclusions could be drawn from the statistical analysis most likely due to measurement uncertainties. The second application used a purpose-built setup for controlled measurements in ex vivo bone samples submerged in liquid, to simulate an in vivo environment. The purpose was to estimate the dielectric properties of bone. The derived bone properties were lower than expected, probably due to air trapped inside the sample.
  •  
23.
  • Mattsson, Viktor, et al. (author)
  • Machine Learning Powered Microwave Device for Local Body Composition Assessment
  • 2023
  • In: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; , s. 1-1
  • Journal article (peer-reviewed)abstract
    • In this paper a standalone microwave device is evaluated for its ability to assess local body composition with the ultimate goal to assess muscle quality. Data have been collected from volunteers who were measured on their thigh using the microwave device and ultrasound. A machine learning algorithm with three stages is designed that utilizes the stacked nature of the tissues in the thigh to predict skin and fat thickness and the cross-sectional area of the rectus femoris muscle. The input to the algorithm is the signal response from the microwave sensor and also the prediction from the previous layers. The ultrasound measurements are used as the ground truth labels for each tissue to train the machine learning models. The measurements were performed with two sensors, where usage of the combined data from both sensors produced the best results for fat and muscle, 0.57 and 0.63 in R 2 score, respectively. In the drop analysis, a step where a select proportion of the data is temporarily removed, the identified models showed increased scores with a larger amount of data available indicating the learning of the models improves with more data. Although the results are encouraging more data is ultimately needed to further study the algorithm.
  •  
24.
  • Mattsson, Viktor, et al. (author)
  • MAS : Standalone Microwave Resonator to Assess Muscle Quality
  • 2021
  • In: Sensors. - : MDPI. - 1424-8220. ; 21:16
  • Journal article (peer-reviewed)abstract
    • Microwave-based sensing for tissue analysis is recently gaining interest due to advantages such as non-ionizing radiation and non-invasiveness. We have developed a set of transmission sensors for microwave-based real-time sensing to quantify muscle mass and quality. In connection, we verified the sensors by 3D simulations, tested them in a laboratory on a homogeneous three-layer tissue model, and collected pilot clinical data in 20 patients and 25 healthy volunteers. This report focuses on initial sensor designs for the Muscle Analyzer System (MAS), their simulation, laboratory trials and clinical trials followed by developing three new sensors and their performance comparison. In the clinical studies, correlation studies were done to compare MAS performance with other clinical standards, specifically the skeletal muscle index, for muscle mass quantification. The results showed limited signal penetration depth for the Split Ring Resonator (SRR) sensor. New sensors were designed incorporating Substrate Integrated Waveguides (SIW) and a bandstop filter to overcome this problem. The sensors were validated through 3D simulations in which they showed increased penetration depth through tissue when compared to the SRR. The second-generation sensors offer higher penetration depth which will improve clinical data collection and validation. The bandstop filter is fabricated and studied in a group of volunteers, showing more reliable data that warrants further continuation of this development.
  •  
25.
  •  
26.
  • Mattsson, Viktor, et al. (author)
  • Muscle Analyzer System : Exploring Correlation Between Novel Microwave Resonator and Ultrasound-based Tissue Information in the Thigh
  • 2022
  • In: 2022 16TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - : Institute of Electrical and Electronics Engineers (IEEE). - 9788831299046
  • Conference paper (peer-reviewed)abstract
    • A microwave sensor to safely measure quality of muscle tissue for diagnosis and screening of diseases and medical conditions characterized by fat infiltration in muscle is presented. Fat infiltration in muscle may be seen by a lower dielectric constant of muscle at microwave frequencies corresponding to the large contrast between fat and muscle tissues. A planar resonator based on a bandstop filter and optimized to noninvasively interrogate muscle in the thigh on tissue quality is proposed. Currently, a study based on clinical trials is carried out, and, here, we present a preliminary correlation between skin and fat thicknesses and rectus femoris cross sectional area (CSA) measured with ultrasound and the proposed sensor's resonance frequency. CST simulations based on the ultrasound information guide the analysis. We see that although there are signs of a potential correlation between CSA and resonance, skin and fat variability is still an issue to overcome.
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27.
  •  
28.
  • Meaney, Paul M, 1960, et al. (author)
  • A 4-channel, vector network analyzer microwave imaging prototype based on software defined radio technology
  • 2019
  • In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 90:4
  • Journal article (peer-reviewed)abstract
    • We have implemented a prototype 4-channel transmission-based, microwave measurement system built on innovative software defined radio (SDR) technology. The system utilizes the B210 USRP SDR developed by Ettus Research that operates over a 70 MHz-6 GHz bandwidth. While B210 units are capable of being synchronized with each other via coherent reference signals, they are somewhat unreliable in this configuration and the manufacturer recommends using N200 or N210 models instead. For our system, N-series SDRs were less suitable because they are not amenable to RF shielding required for the cross-channel isolation necessary for an integrated microwave imaging system. Consequently, we have configured an external reference that overcame these limitations in a compact and robust package. Our design exploits the rapidly evolving technology being developed for the telecommunications environment for test and measurement tasks with the higher performance specifications required in medical microwave imaging applications. In a larger channel configuration, the approach is expected to provide performance comparable to commercial vector network analyzers at a fraction of the cost and in a more compact footprint.
  •  
29.
  • Meaney, Paul M, 1960, et al. (author)
  • A Transmission-Based Dielectric Property Probe for Clinical Applications
  • 2018
  • In: Sensors. - : MDPI AG. - 1424-8220. ; 18:10
  • Journal article (peer-reviewed)abstract
    • We have developed a transmission-based, open-ended coaxial dielectric probe that can be used in clinical situations and overcomes many of the limitations related to the typical reflection-based dielectric probes. The approach utilizes the low profile, open-ended coaxial cables enabling clinicians to still probe relatively compact spaces. The sensing depth can be extended to as large as 1.5 to 2 cm compared with the more typical range of 0.3 mm for conventional probes and is dramatically less affected by measurement technique variability including poor sample contact and cable bending. As a precursor to an actual clinical implementation, we study the technique in a range of homogeneous liquids with substantially varying dielectric properties. The initial results demonstrate good agreement between the transmission-based probe and commercial, reflection-based probes and pave the way for more substantial clinical implementation.
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30.
  • Meaney, Paul M, 1960, et al. (author)
  • Comments on "Investigation of Histology Region Dielectric Measurements of Heterogeneous Tissues"
  • 2020
  • In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 68:1, s. 615-616
  • Journal article (peer-reviewed)abstract
    • In the article, "Investigation of histology region in dielectric measurements of heterogeneous tissues," by Porter and O'Halloran, the authors utilize a flexible phantom in a layered material dielectric property analysis to quantify the effective sensing volume of a coaxial dielectric probe. Ostensibly, this test has been used by others to characterize the region for which percent variation in the material composition in front of the probe corresponds to percent variation in the computed effective dielectric properties. By employing a compressible material, the authors fail to isolate features that are attributable solely to the probe, itself, and inadvertently incorporate confounding characteristics associated with the compressible nature of the material. The net effect is to exaggerate the probe's sensing volume, which undermines the conclusions drawn from the subsequent tissue dielectric property studies. © 2019 IEEE.
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31.
  • Meaney, Paul M, 1960, et al. (author)
  • Conformal mesh and two-step tomographic imaging of the Supelec breast phantom
  • 2017
  • In: 2016 IEEE Conference on Antenna Measurements and Applications, CAMA 2016, Syracuse, United States, 23-27 October 2016.
  • Conference paper (peer-reviewed)abstract
    • The realistic breast phantom developed by the French team at Supelec provides an excellent opportunity to explore various measurement systems and associated algorithms. In this case there is a known ground truth for the geometry of the segmented regions for direct comparison of images with actual sizes, shapes and locations of the different features. It also allows for testing utilizing a range of dielectric materials for both the adipose and fibroglandular region which can be useful given the disparity of published property values. For this experiment, we are exploring our tomographic imaging algorithm with a log transformation in the context of restricting the imaging zone strictly to that space occupied by the phantom. In this case, the 2-dimensional perimeter of the breast was approximated by a simple ellipse which was extracted from the original image. All images were recovered without the assistance of a priori information and also included our 2-step imaging scheme. Simple parameter tests were performed to assess the limitations of the technique, especially when the imaging zone was not accurately determined. The final results were also analyzed by examination of histograms of the field residuals to assess whether the algorithm is robust and unbiased.
  •  
32.
  • Meaney, Paul M, 1960, et al. (author)
  • Electrical Characterization of Glycerin: Water Mixtures: Implications for Use as a Coupling Medium in Microwave Tomography
  • 2017
  • In: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 65:5, s. 1471-1478
  • Journal article (peer-reviewed)abstract
    • We examine the broadband behavior of complex electrical properties of glycerin and water mixtures over the frequency range of 0.1-25.0 GHz, especially as they relate to using these liquids as coupling media for microwave tomographic imaging. Their combination is unique in that they are mutually miscible over the full range of concentrations, which allows them to be tailored to dielectric property matching for biological tissues. While the resultant mixture properties are partially driven by differences in the inherent low-frequency permittivity of each constituent, relaxation frequency shifts play a disproportionately larger role in increasing the permittivity dispersion while also dramatically increasing the effective conductivity over the frequency range of 1-3 GHz. For the full range of mixture ratios, the relaxation frequency shifts from 17.5 GHz for 0% glycerin to less than 0.1 GHz for 100% glycerin. Of particular interest is the fact that the conductivity stays above 1.0 S/m over the 1-3-GHz range for glycerin mixture ratios (70%-90% glycerin) we use for microwave breast tomography. The high level of attenuation is critical for suppressing unwanted multipath signals. This paper presents a full characterization of these liquids along with a discussion of their benefits and limitations in the context of microwave tomography.
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33.
  • Meaney, Paul M, 1960, et al. (author)
  • Examination of the phase and log magnitude measurement projections and the implications for tomographic image reconstruction behavior
  • 2017
  • In: 2017 1st IEEE MTT-S International Microwave Bio Conference, IMBioC 2017. - 9781538617137
  • Conference paper (peer-reviewed)abstract
    • We examine the log magnitude and phase projections of simple circular objects in a 2D microwave tomography setting. Because of the inherent insight visible with these log transformed quantities, we can explore the forward and associated inverse scattering characteristics. For these situations, it is clear that the reconstructions for the cases where the target properties are higher than that of the background take more iterations and the convergence behavior is more uneven. Interestingly this corresponds to the situation where the composite pattern from the antenna/target combination produces a crudely focused beam with corresponding side nulls and lobes. We speculate that these features are somewhat confounding and ultimately prove more challenging for the reconstruction algorithm than for when the target properties are less than the background.
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34.
  • Meaney, Paul M, 1960, et al. (author)
  • Examination of the sensitivity matrix during the iterative reconstruction process for microwave tomography
  • 2018
  • In: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018.
  • Conference paper (peer-reviewed)abstract
    • We have reconstructed microwave tomographic images utilizing a Gauss-Newton scheme with a log transformation. While the recovered images are quite good, we have analyzed the behavior of the associated Jacobian, or sensitivity, matrix with respect to how it evolves during the reconstruction process. We found that in general the highest sensitivities are along the periphery of the imaging zone confirming the fact that most algorithms operate best for features nearest the outside. Interestingly, our log transformed algorithm appears to evolve during the reconstruction process to increase its internal sensitivity once the major exterior ones have been resolved. These results provide useful insight into a key driver of the reconstruction process and provide useful tools for assessing different system design criteria.
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35.
  • Meaney, Paul M., et al. (author)
  • Microwave Vertebrae Strength Probe Development: Robust and Fast Phase Unwrapping Technique
  • 2024
  • In: IEEE JOURNAL OF ELECTROMAGNETICS RF AND MICROWAVES IN MEDICINE AND BIOLOGY. - : Institute of Electrical and Electronics Engineers (IEEE). - 2469-7257 .- 2469-7249. ; 8:1, s. 78-83
  • Journal article (peer-reviewed)abstract
    • We have developed a new transmission-based, open-ended coaxial probe for assessing vertebrae strength during spinal fusion surgery. The approach exploits the fact that the probes are within the far field of each other implying that the phase varies linearly with respect to propagation distance. Determining the absolute phase is critical for recovering the associated tissue dielectric properties from which bone strength will be determined. Unfortunately, unwanted multi-path signals corrupt the signals at the lower end of the operating frequency range from which our conventional unwrapping strategy depends. Our new approach requires only three measurements within the prime frequency range and can be determined robustly with a minimum of computations. This will be vital to developing a commercial device since the signal levels will be extremely low power requiring longer than usual data acquisition times, which will be mitigated by measuring the data at only a few frequencies. Fast and efficient operation will be critical for clinical success.
  •  
36.
  • Meaney, Paul M, 1960, et al. (author)
  • Quasi- Open-Ended Coaxial Dielectric Probe Array for Skin Burn Characterization
  • 2019
  • In: 2019 13th European Conference On Antennas And Propagation (EUCAP). - : IEEE. - 9788890701887
  • Conference paper (peer-reviewed)abstract
    • We have developed a planar probe for measuring dielectric properties. It exploits modern circuit board fabrication technologies that effectively construct a quasi-coaxial structure running perpendicular to the board. The feed line is a printed coplanar waveguide which comes in from the side on the top plane. The opening to the bottom behaves exactly like an open-ended coaxial probe. The initial results are comparable to the existing coaxial probes. The geometry of these probes allows them to be fabricated in an array utilizing standard, multi-layer circuit fabrication technology. These probe arrays may prove extremely useful in applications such as tumor margin detection for resected tissue, skin cancer screening and characterizing burns.
  •  
37.
  • Meaney, Paul M, 1960, et al. (author)
  • Transmission-Based Dielectric Probes for Surgical Applications
  • 2019
  • In: 13th European Conference on Antennas and Propagation, EuCAP 2019.
  • Conference paper (peer-reviewed)abstract
    • We have developed a new type of transmission-based dielectric probe that is idea for certain surgical applications - most notably spinal fusion surgery. It utilizes small-diameter open-ended coaxial cables, but exploits the fact that for the vertebrae surgery, the surgeon has access to both sides of the bone. While the space separation needs to be small (<2 cm), it is sufficiently large to get a signal across. The mathematics is dramatically simplified since it operates in the far field for which a number of simplifications can be employed. The penetration depth is effectively the full span between the two probes which is dramatically larger than that for open-ended coaxial reflection-based probes. Because it operates in the transmission mode, the effects from cable bending and such are minimal and subsequently lends itself to hand held operation which will be critical for a surgical setting.
  •  
38.
  • Meaney, Paul M, 1960, et al. (author)
  • Two-step reconstruction process for microwave tomography without a priori information
  • 2016
  • In: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016. - 2164-3342. - 9788890701863 ; , s. Arti no 7481674-
  • Conference paper (peer-reviewed)abstract
    • While our log transform reconstruction algorithm provides significant advantages over competing algorithms because of its ability to converge to a unique, global solution without utilizing a priori information, the process still requires a modest amount of regularization which naturally tends to smooth the image and sometimes blur important features. We have integrated this overall technique with a novel 2-step reconstruction to produce significantly improved images with respect to feature definition without inducing unwanted artifacts. The critical challenge in this scenario is determining the regularization parameter for the Euclidean distance penalty term in the second step. In this case, because the algorithm is quite fast, the regularization term is computed using a simple linear search. Initial phantom experiment results indicate that targets as small as 5mm diameter are detectable and that the algorithm behaves as an efficient estimator according to standard parameter estimation metrics for a wide range of targets. Results also suggest that there are equally significant improvements in reconstructions from actual patient exams. © 2016 European Association of Antennas and Propagation.
  •  
39.
  • Meaney, Paul M, 1960, et al. (author)
  • Visualization of the effects of multipath signals in complementary imaging and dielectric probing scenarios
  • 2018
  • In: 2018 IEEE Conference on Antenna Measurements and Applications, CAMA 2018. - 9781538657959
  • Conference paper (peer-reviewed)abstract
    • Distinguishing the effects of multipath signals from desired ones is often a challenging proposition. In this paper, we present two examples where multipath signals have impacted the desired signals. In each case, solutions were found to either further attenuate the unwanted signals to irrelevant levels or to understand their behavior as a means of developing ways to avoid such problems. These examples are reasonably representative of challenges encountered by all systems and are illustrative of the challenges they present.
  •  
40.
  • Meaney, Paul M, 1960, et al. (author)
  • y Two-step inversion with a logarithmic transformation for microwave breast imaging
  • 2017
  • In: Medical Physics. - : Wiley. - 2473-4209 .- 0094-2405. ; 44:8, s. 4239-4251
  • Journal article (peer-reviewed)abstract
    • Purpose: The authors have developed a new two-step microwave tomographic image reconstruction process specifically designed to incorporate logarithmic transformed microwave imaging algorithms as a means of significantly improving spatial resolution and target property recovery. Log transform eliminates the need for a priori information, but spatial filtering often integrated as part of the regularization required to stabilize image recovery, generally smooths image features and reduces object definition. The new implementation begins with this smoothed image as the first step, but then utilizes it as the starting estimate for a second step which continues the iterative process with a standard weighted Euclidean distance regularization. The penalty term of the latter restricts the new image to a multi-dimensional location close to the original but allows the algorithm to optimize the image without excessive smoothing. Methods: The overall approach is based on a Gauss-Newton iterative scheme which incorporates a log transformation as a way of making the reconstruction more linear. It has been shown to be robust and not require a priori information as a condition for convergence, but does produce somewhat smoothed images as a result of associated regularization. The new two-step process utilizes the previous technique to generate a smoothed initial estimate and then uses the same reconstruction process with a weighted Euclidean distance penalty term. A simple and repeatable method has been implemented to determine the weighting factor without significant computational burden. The reconstructions are assessed according to conventional parameter estimation metrics. Results: We apply the approach to phantom experiments using large, high contrast canonical shapes followed by a set of images recovered from an actual patient exam. The image improvements are substantial in regards to improved property recovery and feature delineation without inducing unwanted artifacts. Analysis of the residual vector after the reconstruction process further emphasizes that the minimization criterion is efficient with minimal biases. Conclusions: The outcome is a novel synergism of an established stable reconstruction algorithm with a conventional regularization technique. It maintains the ability to recover high quality microwave tomographic images without the bias of a priori information while substantially improving image quality. The results are confirmed on both phantom experiments and patient exams.
  •  
41.
  • Meaney, Paul, et al. (author)
  • Open-Ended Transmission Coaxial Probes for Sarcopenia Assessment
  • 2022
  • In: Sensors. - : MDPI AG. - 1424-8220. ; 22:3
  • Journal article (peer-reviewed)abstract
    • We developed a handheld, side-by-side transmission-based probe for interrogating tissue to diagnose sarcopenia-a condition largely characterized by muscle loss and replacement by fat. While commercial microwave reflection-based probes exist, they can only be used in a lab for a variety of applications. The penetration depth of these probes is only in the order of 0.3 mm, which does not even traverse the skin layer, and minor motion of the coaxial feedlines can completely dismantle the calibration. Our device builds primarily on the transmission-based concept that allows for substantially greater signal penetration depth operating over a very broad bandwidth. Additional features were integrated to further improve the penetration, optimize the geometry for a more focused planar excitation, and juxtapose the coaxial apertures for more controlled interrogation. The larger coaxial apertures further increased the penetration depth while retaining the broadband performance. Three-dimensional printing technology made it possible for the apertures to be compressed into ellipses for interrogation in a near-planar geometry. Finally, fixed side-by-side positioning provided repeatable and reliable performance. The probes were also not susceptible to multipath signal corruption due to the close proximity of the transmitting and receiving apertures. The new concept worked from 100 MHz to over 8 GHz and could sense property changes as deep as 2-3 cm. While the signal changes due to deeper feature aberrations were more subtle than for signals emanating from the skin and subcutaneous fat layers, the large property contrast between muscle and fat is a sarcopenic indication that helps to distinguish even the deepest objects. This device has the potential to provide needed specificity information about the relevant underlying tissue.
  •  
42.
  • Meaney, Paul, et al. (author)
  • Transmission-Based Vertebrae Strength Probe Development : Far Field Probe Property Extraction and Integrated Machine Vision Distance Validation Experiments
  • 2023
  • In: Sensors. - : MDPI AG. - 1424-8220. ; 23:10
  • Journal article (peer-reviewed)abstract
    • We are developing a transmission-based probe for point-of-care assessment of vertebrae strength needed for fabricating the instrumentation used in supporting the spinal column during spinal fusion surgery. The device is based on a transmission probe whereby thin coaxial probes are inserted into the small canals through the pedicles and into the vertebrae, and a broad band signal is transmitted from one probe to the other across the bone tissue. Simultaneously, a machine vision scheme has been developed to measure the separation distance between the probe tips while they are inserted into the vertebrae. The latter technique includes a small camera mounted to the handle of one probe and associated fiducials printed on the other. Machine vision techniques make it possible to track the location of the fiducial-based probe tip and compare it to the fixed coordinate location of the camera-based probe tip. The combination of the two methods allows for straightforward calculation of tissue characteristics by exploiting the antenna far field approximation. Validation tests of the two concepts are presented as a precursor to clinical prototype development.
  •  
43.
  • Meaney, Paul, et al. (author)
  • Vertebrae Transmission Probe Testing - Preliminary Bone Measurements
  • 2023
  • In: 2023 17th European Conference on Antennas and Propagation, EuCAP. - : IEEE. - 9788831299077 - 9781665475419
  • Conference paper (peer-reviewed)abstract
    • We are developing a new transmission-based probe for assessing vertebrae strength via the differences between the dielectric properties of normal and osteoporotic bone. The probes are simple open-ended coaxial cables that will fit easily into the pedicle canals drilled by the surgeons before implanting screws to secure the supporting instrumentation. If the screws pull because of bone weakness, it can inflict a wide range of complications. In the progression towards actual clinical trials, we have already validated the approach on different liquids with varying dielectric properties. In this study, we assess actual animal bone samples as a precursor to human investigations. We exploit the fact that the trabecular bone is considerably different on opposite sides of the growth plate of long bones such as the femur - somewhat mimicking differences between normal and osteoporotic bone. For these experiments, we show that the properties of the distal and proximal sections are considerably different and present opportunities to exploit them in a diagnostic setting
  •  
44.
  •  
45.
  •  
46.
  • Rubaek, Tonny, 1979, et al. (author)
  • A Contrast Source Inversion Algorithm Formulated Using the Log-Phase Formulation
  • 2011
  • In: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2011
  • Journal article (peer-reviewed)abstract
    • The contrast source inversion (CSI) algorithm was introduced for microwave imaging in 1997 and has since proven to be one of the most successful algorithms for nonlinear microwave tomography. In the CSI algorithm, the nonlinear integral equation, which must be solved to extract the constitutive electromagnetic parameters of the object under test from the microwave measurements, is represented by two linear equations, known as the data and the object equations. In this paper, the data equation in the CSI algorithm is reformulated using the so-called log-phase formulation. In this formulation, the measured data is represented by the change in the logarithm of the amplitude and the change in the unwrapped phase. This formulation has previously been applied for nonlinear tomography within the framework of a Gauss-Newton based algorithm for detection of breast cancer. Here, significant improvements have been observed compared to the more commonly used real-imaginary formulation. The modified CSI algorithm is tested on both simulated data and on a measurement of a breast. It is shown that for imaging setups with large differences in the measured signals, the new formulation of the data equation significantly improves the performance of the CSI algorithm.
  •  
47.
  • Rydholm, Tomas, 1991, et al. (author)
  • A First Evaluation of the Realistic Supelec-Breast Phantom
  • 2017
  • In: IEEE Journal of Electromagnetics, RF and Microwaves in Medicine and Biology. - 2469-7249. ; 1:2, s. 59-65
  • Journal article (peer-reviewed)abstract
    • A microwave tomographic system is used to evaluate the realistic breast phantom developed at the Supelec institute. The system utilizes 16 monopole antennas and a modern vector network analyzer (VNA) to measure the phantoms influence on the S-parameters. An iterative algorithm is then used to solve the inverse problem and reconstruct a 2-D plane transecting the phantom. The reconstructed images are compared to the ones recovered from a cylindrical phantom of equivalent phantom media. The results show that both phantoms are possible to reconstruct, although the interior of the Supelec phantom is more challenging.
  •  
48.
  • Rydholm, Tomas, 1991, et al. (author)
  • Comparing a time-domain and frequency-domain based algorithm in microwave tomography
  • 2018
  • In: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741
  • Conference paper (peer-reviewed)abstract
    • A comparison of two different reconstruction algorithms developed for microwave tomographic imaging has been performed. One of the algorithm is an FDTD algorithm and the other one is an FEM-based one. Simulated S-parameters for a 16-antenna system are generated for a numerical phantom, which are then used to solve the inverse problem. It is shown that both algorithms could use the generated S-parameters to successfully reconstruct the studied phantoms.
  •  
49.
  • Rydholm, Tomas, 1991, et al. (author)
  • Effects of the Plastic of the Realistic GeePS-L2S-Breast Phantom
  • 2018
  • In: Diagnostics. - : MDPI AG. - 2075-4418. ; 8:3
  • Journal article (peer-reviewed)abstract
    • A breast phantom developed at the Supelec Institute was interrogated to study its suitability for microwave tomography measurements. A microwave measurement system based on 16 monopole antennas and a vector network analyzer was used to study how the S-parameters are influenced by insertion of the phantom. The phantom is a 3D-printed structure consisting of plastic shells that can be filled with tissue mimicking liquids. The phantom was filled with different liquids and tested with the measurement system to determine whether the plastic has any effects on the recovered images or not. Measurements of the phantom when it is filled with the same liquid as the surrounding coupling medium are of particular interest. In this case, the phantom plastic has a substantial effects on the measurements which ultimately detracts from the desired images.
  •  
50.
  • Rydholm, Tomas, 1991, et al. (author)
  • Microwave tomographic image improvement by fitting to a Cole-Cole relaxation model
  • 2017
  • In: 2017 11th European Conference on Antennas and Propagation, EUCAP 2017. - 9788890701870 ; , s. 682-684
  • Conference paper (peer-reviewed)abstract
    • We have reconstructed microwave tomographic images of the Supelec breast phantom using our imaging fixture in combination with a multi-channel vector network analyzer. During this study we were able to recover images without the support of a priori information over a broad frequency range - 1100-1900 MHz. We then fitted the spectral values at each pixel within the field of view to a Cole-Cole curve and extracted the coefficients at each location. While the individual images at each frequency provided reasonably representations of the target permittivity and conductivity distributions, the fibroglandular features were generally quite blurred with the surrounding adipose region. However, several of the Cole-Cole coefficient plots provided a higher level of resolution for the inclusions. While there was a noticeably high level of artifacts outside of the breast phantom perimeter, the internal structures are quite representative of the target. This is one of the first Cole-Cole image fittings using broadband measurement data on an actual phantom and sets the stage for higher specificity imaging.
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