Monocrystalline diamond detector for online monitoring during synchrotron microbeam radiotherapy.

Microbeam radiation therapy (MRT) is a radiotherapy technique combining spatial fractionation of the dose distribution on a micrometric scale, X-rays in the 50-500 keV range and dose rates up to 16 × 103 Gy s-1. Nowadays, in vivo dosimetry remains a challenge due to the ultra-high radiation fluxes involved and the need for high-spatial-resolution detectors. The aim here was to develop a striped diamond portal detector enabling online microbeam monitoring during synchrotron MRT treatments. The detector, a 550 µm bulk monocrystalline diamond, is an eight-strip device, of height 3 mm, width 178 µm and with 60 µm spaced strips, surrounded by a guard ring. An eight-channel ASIC circuit for charge integration and digitization has been designed and tested. Characterization tests were performed at the ID17 biomedical beamline of the European Synchrotron Radiation Facility (ESRF). The detector measured direct and attenuated microbeams as well as interbeam fluxes with a precision level of 1%. Tests on phantoms (RW3 and anthropomorphic head phantoms) were performed and compared with simulations. Synchrotron radiation measurements were performed on an RW3 phantom for strips facing a microbeam and for strips facing an interbeam area. A 2% difference between experiments and simulations was found. In more complex geometries, a preliminary study showed that the absolute differences between simulated and recorded transmitted beams were within 2%. Obtained results showed the feasibility of performing MRT portal monitoring using a microstriped diamond detector. Online dosimetric measurements are currently ongoing during clinical veterinary trials at ESRF, and the next 153-strip detector prototype, covering the entire irradiation field, is being finalized at our institution.

Future temperature-related excess mortality under climate change and population aging scenarios in Canada.

OBJECTIVE: Climate change is expected to increase global temperatures. How temperature-related mortality risk will change is not completely understood, and how future demographic changes will affect temperature-related mortality needs to be clarified. We evaluate temperature-related mortality across Canada until 2099, accounting for age groups and scenarios of population growth. METHODS: We used daily counts of non-accidental mortality for 2000 to 2015 for all 111 health regions across Canada, incorporating in the study both urban and rural areas. A two-part time series analysis was used to estimate associations between mean daily temperatures and mortality. First, current and future daily mean temperature time series simulations were developed from Coupled Model Inter-Comparison Project 6 (CMIP6) climate model ensembles from past and projected climate change scenarios under Shared Socioeconomic Pathways (SSPs). Next, excess mortality due to heat and cold and the net difference were projected to 2099, also accounting for different regional and population aging scenarios. RESULTS: For 2000 to 2015, we identified 3,343,311 non-accidental deaths. On average, a net increase of 17.31% (95% eCI: 13.99, 20.62) in temperature-related excess mortality under a higher greenhouse gas emission scenario is expected for Canada in 2090-2099, which represents a greater burden than a scenario that assumed strong levels of greenhouse gas mitigation policies (net increase of 3.29%; 95% eCI: 1.41, 5.17). The highest net increase was observed among people aged 65 and over, and the largest increases in both net and heat- and cold-related mortality were observed in population scenarios that incorporated the highest rates of aging. CONCLUSION: Canada may expect net increases in temperature-related mortality under a higher emissions climate change scenario, compared to one assuming sustainable development. Urgent action is needed to mitigate future climate change impacts.

RéSUMé: OBJECTIF: Les changements climatiques devraient accroître les températures mondiales. La façon dont le risque de mortalité lié à la température évoluera n'est pas entièrement comprise, et la façon dont les changements démographiques futurs influeront sur la mortalité liée à la température doit être clarifiée. Nous étudions la mortalité liée à la température au Canada jusqu'en 2099, en tenant compte des groupes d'âge et des scénarios de croissance démographique. MéTHODES: Nous avons utilisé les nombres quotidiens de mortalité non accidentelle pour 2000 à 2015 pour toutes les 111 régions socio sanitaires du Canada, en intégrant dans l'étude des régions urbaines et rurales. Une analyse en séries chronologiques en deux parties a été utilisée pour estimer les associations entre les températures quotidiennes moyennes et la mortalité. Premièrement, des simulations de séries chronologiques de températures moyennes quotidiennes actuelles et futures ont été élaborées à partir d'ensembles de modèles climatiques du Projet de comparaison croisée 6 (CMIP6) du modèle couplé à partir de scénarios de changements climatiques passés et projetés dans le cadre de voies socioéconomiques partagées (SSP). Ensuite, la surmortalité due à la chaleur et au froid et la différence nette ont été projetées jusqu'en 2099, ce qui tient également compte de différents scénarios régionaux et de vieillissement de la population. RéSULTATS: De 2000 à 2015, nous avons recensé 3 343 311 décès non accidentels. En moyenne, une augmentation nette de 17,31% (eCI à 95%: 13,99, 20,62) de la mortalité excessive liée à la température dans le cadre d'un scénario d'émissions de gaz à effet de serre plus élevées est prévue pour le Canada en 2090­2099, ce qui représente un fardeau plus lourd qu'un scénario qui suppose des niveaux élevés de politiques d'atténuation des émissions de gaz (augmentation nette de 3,29%; eCI à 95%: 1,41, 5,17). La plus forte augmentation nette a été observée chez les personnes de 65 ans ou plus, et les plus fortes augmentations de la mortalité nette, de mortalité liée à la chaleur et au froid ont été observées dans les scénarios de population qui comprenaient les taux de vieillissement les plus élevés. CONCLUSION: Le Canada pourrait s'attendre à des augmentations nettes de la mortalité liée à la température dans le cadre d'un scénario de changement climatique à émissions plus élevées, comparativement à un scénario de développement durable. Des mesures urgentes sont nécessaires pour atténuer les répercussions futures des changements climatiques.

A high sensitivity Cherenkov detector for prompt gamma timing and time imaging.

We recently proposed a new approach for the real-time monitoring of particle therapy treatments with the goal of achieving high sensitivities on the particle range measurement already at limited counting statistics. This method extends the Prompt Gamma (PG) timing technique to obtain the PG vertex distribution from the exclusive measurement of particle Time-Of-Flight (TOF). It was previously shown, through Monte Carlo simulation, that an original data reconstruction algorithm (Prompt Gamma Time Imaging) allows to combine the response of multiple detectors placed around the target. The sensitivity of this technique depends on both the system time resolution and the beam intensity. At reduced intensities (Single Proton Regime-SPR), a millimetric proton range sensitivity can be achieved, provided the overall PG plus proton TOF can be measured with a 235 ps (FWHM) time resolution. At nominal beam intensities, a sensitivity of a few mm can still be obtained by increasing the number of incident protons included in the monitoring procedure. In this work we focus on the experimental feasibility of PGTI in SPR through the development of a multi-channel, Cherenkov-based PG detector with a targeted time resolution of 235 ps (FWHM): the TOF Imaging ARrAy (TIARA). Since PG emission is a rare phenomenon, TIARA design is led by the concomitant optimisation of its detection efficiency and Signal to Noise Ratio (SNR). The PG module that we developed is composed of a small PbF[Formula: see text] crystal coupled to a silicon photoMultiplier to provide the time stamp of the PG. This module is currently read in time coincidence with a diamond-based beam monitor placed upstream the target/patient to measure the proton time of arrival. TIARA will be eventually composed of 30 identical modules uniformly arranged around the target. The absence of a collimation system and the use of Cherenkov radiators are both crucial to increase the detection efficiency and the SNR, respectively. A first prototype of the TIARA block detector was tested with 63 MeV protons delivered from a cyclotron: a time resolution of 276 ps (FWHM) was obtained, resulting in a proton range sensitivity of 4 mm at 2[Formula: see text] with the acquisition of only 600 PGs. A second prototype was also evaluated with 148 MeV protons delivered from a synchro-cyclotron obtaining a time resolution below 167 ps (FWHM) for the gamma detector. Moreover, using two identical PG modules, it was shown that a uniform sensitivity on the PG profiles would be achievable by combining the response of gamma detectors uniformly distributed around the target. This work provides the experimental proof-of-concept for the development of a high sensitivity detector that can be used to monitor particle therapy treatments and potentially act in real-time if the irradiation does not comply to treatment plan.

A time-of-flight-based reconstruction for real-time prompt-gamma imaging in proton therapy.

We propose a novel prompt-gamma (PG) imaging modality for real-time monitoring in proton therapy: PG time imaging (PGTI). By measuring the time-of-flight (TOF) between a beam monitor and a PG detector, our goal is to reconstruct the PG vertex distribution in 3D. In this paper, a dedicated, non-iterative reconstruction strategy is proposed (PGTI reconstruction). Here, it was resolved under a 1D approximation to measure a proton range shift along the beam direction. In order to show the potential of PGTI in the transverse plane, a second method, based on the calculation of the centre of gravity (COG) of the TIARA pixel detectors' counts was also explored. The feasibility of PGTI was evaluated in two different scenarios. Under the assumption of a 100 ps (rms) time resolution (achievable in single proton regime), MC simulations showed that a millimetric proton range shift is detectable at 2σwith 108incident protons in simplified simulation settings. With the same proton statistics, a potential 2 mm sensitivity (at 2σwith 108incident protons) to beam displacements in the transverse plane was found using the COG method. This level of precision would allow to act in real-time if the treatment does not conform to the treatment plan. A worst case scenario of a 1 ns (rms) TOF resolution was also considered to demonstrate that a degraded timing information can be compensated by increasing the acquisition statistics: in this case, a 2 mm range shift would be detectable at 2σwith 109incident protons. By showing the feasibility of a time-based algorithm for the reconstruction of the PG vertex distribution for a simplified anatomy, this work poses a theoretical basis for the future development of a PG imaging detector based on the measurement of particle TOF.

A Study of the Radiation Tolerance of CVD Diamond to 70 MeV Protons, Fast Neutrons and 200 MeV Pions.

We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 µm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43±0.14) × 1016 neutrons/cm2, and (6.5±1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron-hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)× 10-18 cm2/(p µm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)× 10-18 cm2/(n µm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)× 10-18 cm2/(π µm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.

Socioeconomic disparities in life and health expectancy among the household population in Canada.

BACKGROUND: Life expectancy (LE) and health expectancy have increased throughout much of the world. However, these gains have not been shared equally across all population groups. Socioeconomic disparities exist, though varied methodologies and data sources have made it difficult to ascertain changes over time in Canada. DATA AND METHODS: The 1996 and 2011 Canadian Census Health and Environment Cohorts, with a five-year mortality follow-up, were used to estimate the LE of the household population at ages 25 and 65, according to individual-level education and income. Health status was measured by the Health Utilities Index Mark 3 instrument in two national population health surveys and was used to adjust LE to estimate health-adjusted life expectancy (HALE). Disparities in LE and HALE, and differences between cohorts, were examined. RESULTS: LE, HALE and the ratio of HALE to LE were greater at higher levels of education or income. A stepwise gradient was also observed by level of education within and across income quintiles, with people in the lowest combined education and income categories at the greatest disadvantage. Disparities were wider in the 2011 cohort compared with the 1996 cohort, but not necessarily to the same extent for both sexes or at different ages. DISCUSSION: In Canada, education-related and income-related disparities in life and health expectancy persist and may be wider than they were in the past. This underscores the importance of ongoing data development for routine monitoring of trends in mortality and morbidity, which can, in turn, inform policy development and planning to advance health equity.

Health-adjusted life expectancy in Canada.

BACKGROUND: Over the past century, life expectancy at birth in Canada has risen substantially. However, these gains in the quantity of life say little about gains in the quality of life. DATA AND METHODS: Health-adjusted life expectancy (HALE), an indicator of quality of life, was estimated for the household and institutional populations combined every four years from 1994/1995 to 2015. Health status was measured by the Health Utilities Index Mark 3 instrument in two national population health surveys, and was used to adjust life expectancy. The percentage of the population living in health-related institutions was estimated based on the Census of Population. Attribute-deleted HALE was calculated to determine how various aspects of health status contributed to the differences between life expectancy and HALE. RESULTS: HALE has increased in Canada. Greater gains among males have narrowed the gap between males and females. The ratio of HALE to life expectancy changed little for males, and a marginal improvement was observed for females aged 65 or older. Mobility problems and pain, the latter mainly among females, accounted for an increased share of the burden of ill health over time. Exclusion of the institutional population significantly increased the estimates of HALE and yielded higher ratios of HALE to life expectancy. DISCUSSION: Although people are living longer, the share of years spent in good functional health has remained fairly constant. Data for both the household and institutional populations are necessary for a complete picture of health expectancy in Canada.

Health-promoting factors and good health among Canadians in mid- to late life.

According to results from the Canadian Community Health Survey-Healthy Aging, 76% of Canadians in mid-life (45 to 64) and 56% of seniors reported good health in 2009. This is based on a definition of health composed of: positive self-perceived general and mental health, functional ability, and independence in activities of daily living. Good health existed even in the presence of chronic conditions such as high blood pressure, arthritis and back problems, all of which were common among people aged 45 or older. Eight modifiable factors were associated with good health: smoking status, body mass index, physical activity, diet, sleep, oral health, stress, and social participation. Eighty-four percent of the younger age group and 91% of seniors reported positive tendencies on four or more of these factors. The more factors on which positive tendencies were reported, the greater the likelihood of having good health.

Healthy living among seniors.

OBJECTIVES: This article investigates good health among Canadian seniors in relation to health behaviours and psychosocial factors. DATA SOURCES: Data are from the 2003 Canadian Community Health Survey and the 1994/95 through 2002/03 National Population Health Survey, household components. ANALYTICAL TECHNIQUES: Multiple logistic regression modeling was used to study associations between being in good health and behavioural risk and psychosocial factors in 2003. Proportional hazards modelling and logistic regression were used to examine health-related characteristics and psychosocial factors in relation to maintaining and recovering health. MAIN RESULTS: Seniors who exercised frequently, had a body mass index in the normal range, were high consumers of fruit and vegetables and moderate consumers of alcohol were more likely to be in good health. Low levels of stress and feeling connected to the community were also associated with good health. Healthy behaviours were related to maintaining good health over time, as well as increased likelihood of recovery. These findings persisted when controlling for socio-demographic factors and chronic conditions.

Dependent seniors at home--formal and informal help.

OBJECTIVES: This article documents the number of hours of help that seniors living in private households received from formal and/or informal sources in 1996. DATA SOURCE: Data are from Cycle 11 of the General Social Survey, conducted in 1996. This analysis focuses on 1,089 respondents aged 65 or older who, because of a long-term health problem, required assistance to remain in their homes and who indicated the source of assistance and the amount of help time received. ANALYTICAL TECHNIQUES: Analysis of variance, followed by Tukey's HSD test, was used to examine differences in help time received from each source. Medians are presented using an independent medians test. Linear regression was used to model associations between the amount of help time received from each source and certain characteristics. MAIN RESULTS: In 1996, dependent seniors living in the community received a median of 3 hours of help a week. Most of this assistance came from informal sources. Living arrangements and age were the major influences on hours received from informal sources. Having no surviving children and being disabled in terms of dexterity or mobility/flexibility were associated with increased hours of formal care. For those getting both types of help, increased hours from formal sources did not significantly reduce the hours received from informal sources.

Gender differences in disability-free life expectancy for selected risk factors and chronic conditions in Canada.

This article shows how mortality and morbidity patterns differ for women and men 45 years of age and older. The impact on disability-free life expectancy was calculated for selected risk factors and chronic conditions: low income, low education, abnormal body mass index, lack of physical activity, smoking, cancer, diabetes, and arthritis. For each factor, the expected number of years free of disability was calculated for men and women using multi-state life tables. In terms of disability-free life expectancy, the greatest impacts on affected women were for diabetes (14.1 years), arthritis (8.8 years), and physical inactivity (6.0 years), while for affected men, the greatest impacts were for diabetes (10.5 years), smoking (6.9 years), arthritis (6.5 years), and cancer (6.4 years). The implications of these results are discussed from the perspective of developing programs designed to improve population health status.

Loss and recovery of independence among seniors.

OBJECTIVES: This article identifies risk factors associated with the loss and recovery of independence among the household population aged 65 or older. DATA SOURCES: The data are from the longitudinal component of the first two cycles (1994/95 and 1996/97) of Statistics Canada's National Population Health Survey (NPHS). Supplementary information is from the cross-sectional component of the 1998/99 NPHS. ANALYTICAL TECHNIQUES: Cross-tabulations were used to estimate the proportions of seniors who lost or regained independence between 1994/95 and 1996/97. Logistic regression models were used to explore associations between loss or recovery of independence and demographic, behavioural and socioeconomic variables, as well as chronic conditions. MAIN RESULTS: Age, sex and the effects of stroke were significantly related to the loss and recovery of independence among seniors. Bronchitis/emphysema, diabetes, heart disease, weight, physical activity, education and household income were associated with the loss of independence, but not its recovery. Dependent seniors with back problems, urinary incontinence, or who smoked had low odds of regaining independence.