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A highly popular method for examining the stability of a data clustering is to split the data into two parts, cluster the observations in Part A, assign the objects in Part B to their nearest centroid in Part A, and then independently cluster the Part B objects. One then examines how close the two partitions are (say, by the Rand measure). Another proposal is to split the data into k parts, and see how their centroids cluster. By means of synthetic data analyses, we demonstrate that these approaches fail to identify the appropriate number of clusters, particularly as sample size becomes large and the variables exhibit higher correlations.
Narcolepsy is a rare but disabling neurological disorder involving disruption of the sleep-wake cycle that is often under- or misdiagnosed (Barateau L, et al. J Sleep Res. 2022;31(4):e13631). It is characterized by a classical tetrad of excessive daytime sleepiness (EDS), cataplexy, hypnagogic hallucinations, and sleep paralysis. Narcolepsy is divided into 3 types: Narcolepsy Type 1 (NT1); Narcolepsy Type 2 (NT2); and Secondary Narcolepsy. The pathophysiology remains unclear but is primarily associated with loss of hypocretin (orexin) neurons involving autoimmune and genetic risk factors, particularly for NT1.
Objectives
To review the currently available therapies for the treatment of narcolepsy.
Methods
The extant literature was reviewed and discussed in the context of clinical relevance.
Results
Treatment historically has included medications developed for the treatment of other conditions such as psychostimulants (methylphenidate, modafinil/armodafinil, pemoline) and antidepressants (SSRIs,TCAs). These agents are also associated with limiting side effects in practice. In more recent years a variety of specific treatments have been approved that act on diverse pathways. Pitolisant, a histamine H3 receptor inverse agonist, is approved for the treatment of EDS or cataplexy in adult patients with narcolepsy (and children> 6 years in European Union) (Keam SJ.Paediatr Drugs. 2023;25(4):483-488). Solriamfetol, a dopamine and norepinephrine reuptake inhibitor (DNRI) is indicated to improve wakefulness in adult patients with EDS associated with narcolepsy or obstructive sleep apnea (OSA) (Winter Y, et al. Sleep Med. 2023;103:138-143). Sodium oxybate (SXB), a GABAB receptor agonist, is approved for the treatment of cataplexy associated with narcolepsy and (EDS) in patients 7 years or older (Bogan RK, et al. CNS Drugs. 2023;37(4):323-335). Current research focuses on on-peptide hypocretin receptor-2 agonists (Saitoh T, Sakurai T. Peptides. 2023;167:171051).
Conclusions
Despite limited understanding of the pathophysiology of narcolepsy there have been substantial advances in the pharmacotherapy, including medications now approved for children. Early diagnosis and treatment are associated with better outcomes. In view of the chronic and disabling morbidity associated with narcolepsy further research and better access to appopriate medications is necessary.
Adequate nutrition is necessary during childhood and early adolescence for adequate growth and development. Hence, the objective of the study was to assess the association between dietary intake and blood levels of minerals (calcium, iron, zinc, and selenium) and vitamins (folate, vitamin B12, vitamin A, and vitamin D) in urban school going children aged 6–16 years in India, in a multicentric cross-sectional study. Participants were enrolled from randomly selected schools in ten cities. Three-day food intake data was collected using a 24-h dietary recall method. The intake was dichotomised into adequate and inadequate. Blood samples were collected to assess levels of micronutrients. From April 2019 to February 2020, 2428 participants (50⋅2 % females) were recruited from 60 schools. Inadequate intake for calcium was in 93⋅4 % (246⋅5 ± 149⋅4 mg), iron 86⋅5 % (7⋅6 ± 3⋅0 mg), zinc 84⋅0 % (3⋅9 ± 2⋅4 mg), selenium 30⋅2 % (11⋅3 ± 9⋅7 mcg), folate 73⋅8 % (93⋅6 ± 55⋅4 mcg), vitamin B12 94⋅4 % (0⋅2 ± 0⋅4 mcg), vitamin A 96⋅0 % (101⋅7 ± 94⋅1 mcg), and vitamin D 100⋅0 % (0⋅4 ± 0⋅6 mcg). Controlling for sex and socioeconomic status, the odds of biochemical deficiency with inadequate intake for iron [AOR = 1⋅37 (95 % CI 1⋅07–1⋅76)], zinc [AOR = 5⋅14 (95 % CI 2⋅24–11⋅78)], selenium [AOR = 3⋅63 (95 % CI 2⋅70–4⋅89)], folate [AOR = 1⋅59 (95 % CI 1⋅25–2⋅03)], and vitamin B12 [AOR = 1⋅62 (95 %CI 1⋅07–2⋅45)]. Since there is a significant association between the inadequate intake and biochemical deficiencies of iron, zinc, selenium, folate, and vitamin B12, regular surveillance for adequacy of micronutrient intake must be undertaken to identify children at risk of deficiency, for timely intervention.
The objectives of this research were (1) to study different factors affecting milk total bacterial count (TBC) and (2) to estimate the economic value associated with TBC in Holstein dairy herds in Iran. The relationships between bulk tank TBC and farm management and economic factors were examined on 56 randomly selected intensive dairy farms. Herd management factors associated with bulk tank TBC were determined using mixed linear models. The median bulk tank TBC for the sample herds was 299 (range 81–1185) × 103 cfu/ml. The average economic premium opportunity from bulk tank TBC was US$ 1.32 per ton of milk ranging from US$ 0.02 per ton of milk for herds applying wet tissue procedures as teat cleaning material and washing the water troughs three times per day to US$ 5.20 per ton of milk for herds with dirty barns. Results showed that the following management factors were associated with low TBC and high economic value: frequency of cleaning water troughs, teat cleaning material, the frequency of milk delivery to the processor, bedding material, herd size, education level of workers, udder washing material, material of milking parlor wall, frequency of disinfection of the calving area, presence of veterinarian, water quality control, having a hospital pen and barn hygiene. In conclusion, our findings highlight the need to pay more attention to farm management issues, particularly farm hygiene practices to reduce milk TBC and so reduce the economic burden of TBC in dairy herds in Iran.
There are no conclusive findings about the possible protective role of religion on students’ mental health during the COVID-19 pandemic. Therefore, more research is needed.
Objectives
The purpose of this study was to assess the relationship between the level of emotional distress and religiosity among students from 7 different countries during the COVID-19 pandemic.
Methods
Data were collected by an online cross-sectional survey that was distributed amongst Polish (N = 1196), Bengali (N = 1537), Indian (N = 483), Mexican (N = 231), Egyptian (N = 565), Philippine (N = 2062), and Pakistani (N = 506) students (N = 6642) from 12th April to 1st June 2021. The respondents were asked several questions regarding their religiosity which was measured by The Duke University Religion Index (DUREL), the emotional distress was measured by the Depression, Anxiety, and Stress Scale-21 (DASS-21).
Results
Egypt with Islam as the dominant religion showed the greatest temple attendance (organizational religious activity: M=5.27±1.36) and spirituality (intrinsic religiosity: M=5.27±1.36), p<0.0001. On another hand, Egyptian students had the lowest emotional distress measured in all categories DASS-21 (depression: M=4.87±10.17, anxiety: M=4.78±10.13, stress: M=20.76±11.46). Two countries with the dominant Christian religion achieved the highest score for private religious activities (non-organizational religious activity; Mexico: M=3.94±0.94, Poland: M=3.63±1.20; p<0.0001) and experienced a moderate level of depressive symptoms, anxiety, and stress. Students from Mexico presented the lowest attendance to church (M=2.46±1,39) and spirituality (M=6.68± 3.41) and had the second highest level of depressive symptoms (M=19.13±13.03) and stress (M=20.27±1.98). Philippines students had the highest DASS-21 score (depression: M=22.77±12.58, anxiety: M=16.07±10.77, stress: M=4.87±10.08) and their level of religiosity reached average values in the whole group. The performed regression analysis confirmed the importance of the 3 dimensions (organizational religious activity, non-organizational religious activity, intrinsic religiosity) of religiosity for the well-being of students, except for the relationship between anxiety and private religious activities. The result was as presented for depression: R2=0.0398, F(3.664)=91.764, p<0.0001, SE of E: 12.88; anxiety: R2=0.0124, F(3.664)=27.683, p<0.0001, SE of E: 10,62; stress: R2= 0.0350, F(3.664)=80.363, p<0.0001, SE of E: 12.30.
Conclusions
The higher commitment to organizational religious activity, non-organizational religious activity, and intrinsic religiositywas correlated with the lower level of depressive symptoms, stress, and anxiety among students during the COVID-19 pandemic, but taking into account factors related to religiosity explains the level of emotional well-being to a small extent.
TDuring COVID-19 pandemic, it was noticed that it was students who were mostly affected by the changes that aroused because of the pandemic. The interesting part is whether students’ well-being could be associated with their fields of study as well as coping strategies.
Objectives
In this study, we aimed to assess 1) the mental health of students from nine countries with a particular focus on depression, anxiety, and stress levels and their fields of study, 2) the major coping strategies of students after one year of the COVID-19 pandemic.
Methods
We conducted an anonymous online cross-sectional survey on 12th April – 1st June 2021 that was distributed among the students from Poland, Mexico, Egypt, India, Pakistan, China, Vietnam, Philippines, and Bangladesh. To measure the emotional distress, we used the Depression, Anxiety, and Stress Scale-21 (DASS-21), and to identify the major coping strategies of students - the Brief-COPE.
Results
We gathered 7219 responses from students studying five major studies: medical studies (N=2821), social sciences (N=1471), technical sciences (N=891), artistic/humanistic studies (N=1094), sciences (N=942). The greatest intensity of depression (M=18.29±13.83; moderate intensity), anxiety (M=13.13±11.37; moderate intensity ), and stress (M=17.86±12.94; mild intensity) was observed among sciences students. Medical students presented the lowest intensity of all three components - depression (M=13.31±12.45; mild intensity), anxiety (M=10.37±10.57; moderate intensity), and stress (M=13.65±11.94; mild intensity). Students of all fields primarily used acceptance and self-distraction as their coping mechanisms, while the least commonly used were self-blame, denial, and substance use. The group of coping mechanisms the most frequently used was ‘emotional focus’. Medical students statistically less often used avoidant coping strategies compared to other fields of study. Substance use was only one coping mechanism that did not statistically differ between students of different fields of study. Behavioral disengagement presented the highest correlation with depression (r=0.54), anxiety (r=0.48), and stress (r=0.47) while religion presented the lowest positive correlation with depression (r=0.07), anxiety (r=0.14), and stress (r=0.11).
Conclusions
1) The greatest intensity of depression, anxiety, and stress was observed among sciences students, while the lowest intensity of those components was found among students studying medicine.
2) Not using avoidant coping strategies might be associated with lower intensity of all DASS components among students.
3) Behavioral disengagement might be strongly associated with greater intensity of depression, anxiety, and stress among students.
4) There was no coping mechanism that provided the alleviation of emotional distress in all the fields of studies of students.
Burnout in the medical profession has garnered a lot of attention over the recent years. While it is reported across all specialties and all stages of medical education; resident physicians in particular are at high risk for burnout throughout their years of training.
Objectives
This study aimed at evaluating the prevalence and correlates of burnout among resident physicians in Alberta.
Methods
Through a descriptive cross-sectional study design, a self-administered questionnaire was used to gather data from resident physicians at two medical schools in Alberta, Canada. Maslach Burnout Inventory was used as an assessment tool. Chi-squared and multivariate binary logistic regression analyses were used.
Results
Overall burnout prevalence among residents was 58.2%. Working more than 80 hours/week (OR= 16.437; 95% CI: 2.059 – 131.225), being dissatisfied (OR= 22.28; 95% CI: 1.75– 283.278) or being neither satisfied nor dissatisfied with a career in medicine [(OR= 23.81; 95% CI: 4.89 – 115.86) were significantly associated with high depersonalization. Dissatisfaction with efficiency and resources (OR= 10.83; CI: 1.66- 70.32) or being neither satisfied nor dissatisfied with a career in medicine (OR= 5.14; CI: 1.33- 19.94)] were significantly associated with high emotional exhaustion. Working more than 80 hours/week (OR= 5.36; CI: 1.08- 26.42) and feeling that the residency program is somewhat having enough strategies aimed at resident well-being in place (OR= 3.70; CI: 1.10- 12.46) were significantly associated with high work exhaustion and interpersonal disengagement. Young age of the residents (≤ 30 years) (OR= 0.044; CI: 0.004- 0.445) was significantly associated with low professional fulfillment.
Conclusions
Burnout is a serious occupational phenomenon that can degenerate to other conditions or disrupts one’s professional performance. Significant correlates were associated with high rates of burnout. Leaders of medical schools and policy makers need to acknowledge, design, and implement various strategies capable of providing continuous effective mental health support to improve the psychological health of the medical resident across Canada.
Specialty on-call clinicians cover large areas and complex workloads. This study aimed to assess clinical communication using the mixed-reality HoloLens 2 device within a simulated on-call scenario.
Method
This study was structured as a randomised, within-participant, controlled study. Thirty ENT trainees used either the HoloLens 2 or a traditional telephone to communicate a clinical case to a consultant. The quality of the clinical communication was scored objectively and subjectively.
Results
Clinical communication using the HoloLens 2 scored statistically higher than telephone (n = 30) (11.9 of 15 vs 10.2 of 15; p = 0.001). Subjectively, consultants judged more communication episodes to be inadequate when using the telephone (7 of 30) versus the HoloLens 2 (0 of 30) (p = 0.01). Qualitative feedback indicates that the HoloLens 2 was easy to use and would add value during an on-call scenario with remote consultant supervision.
Conclusion
This study demonstrated the benefit that mixed-reality devices, such as the HoloLens 2 can bring to clinical communication through increasing the accuracy of communication and confidence of the users.
Dementia’s prevalence increases due to population aging, it has become a major public health concern.
Objectives
To estimate the incidence of dementia and to describe the socio-demographic and clinical profile of patients attended in the psychiatry department of Gabes (Southern of Tunisia).
Methods
It was a retrospective descriptive study including all the patients who attended for the first time in the psychiatry department of Gabes, from the 1st January, 2010 to December 31, 2018, and who were diagnosed with dementia according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). Socio-demographic and clinical data were assessed. The Mini Mental State Examination (MMSE) was used as a neuropsychological examination.
Results
We included 98 patients. The mean annual hospital incidence of dementia was 2.38%. The mean age was 76.5 ± 9.8 years. Patients were married (68%), illiterate (68%) and jobless (42.9%). A family history of dementia was noted in 39.8% of patients. The common cardiovascular comorbidity was high blood pressure (41.8%). Among our patients, 30 (30.6%) were smokers. The mean age of onset of dementia was 73 ± 11 years. The mean duration of untreated dementia was 3 years [3 months to 11 years]. First symptoms were mainly memory disorders (57.3 %) and behavioral disorders (17.3%) The mean MMSE score was 14 ± 4.8. Alzheimer’s disease was the most frequent etiology of dementia (80 cases, 82.7%).
Conclusions
Our study shows a high incidence of dementia and made it possible to draw up a socio-demographic and clinical profile of dementia patients.
Greenland glaciers exhibit variable seasonal velocity signals that may reflect differences in subglacial hydrology. Here, we conduct a first GrIS-wide glacier classification based on seasonal velocity patterns derived from 2017 Sentinel-1 radar data. Our classification focuses on two distinct seasonal ice velocity patterns, with the first (type-2 from Moon and others, 2014) showing periods of both speedup and slowdown during the melt season, and the second (type-3) instead showing a longer period of slowdown from elevated velocities in the winter and spring. We analyze 221 glaciers in 2017 and show that 48 exhibit type-2 behavior, and 72 exhibit type-3 behavior. We extend the classification to 2018 and 2019 and find that while the glaciers meeting each criterion vary year to year, type-2 is consistently more common in the northern regions and type-3 is more common in the south. Our results highlight the varied impact of meltwater on subglacial drainage systems and glacier flow in Greenland.
Roads affect wildlife in a variety of negative ways. Road ecology studies have mostly concentrated on areas in the northern hemisphere despite the potentially greater impact of roads on biodiversity in tropical habitats. Here, we examine 4 years (January 2016–December 2019) of opportunistic observations of mammalian roadkill along a road intersecting Jozani-Chwaka Bay National Park, Unguja, Zanzibar. In particular, we assess the impact of collisions on the population of an endemic primate, the Endangered Zanzibar red colobus Piliocolobus kirkii. Primates accounted for the majority of roadkill in this dataset. Monthly rainfall was not associated with roadkill frequency for mammals generally, nor for the Zanzibar red colobus. No single age–sex class of colobus was found dead more often than expected given their occurrence in the local population. The overall effect of roadkill on colobus populations in habitats fragmented by roads is unknown given the lack of accurate, long-term life history data for this species. Our findings suggest that mortality from collisions with vehicles in some groups of colobus is within the range of mortality rates other primates experience under natural predation. Unlike natural predators, however, vehicles do not kill selectively, so their impact on populations may differ. Although a comparison with historical accounts suggests that the installation of speedbumps along the road near the Park's entrance has led to a significant decrease in colobus roadkill, further actions to mitigate the impact of the road could bring substantial conservation benefits.
Former lakes and wetlands can provide valuable insights to the late Pleistocene environments encountered by the first humans to enter the Levant from Africa. Fluvial incision along Wadi Gharandal in hyperarid southern Jordan has exposed remnants of a small riverine wetland that accumulated as a sedimentary sequence up to ~20 m thick. We conducted a chronometric and sedimentological study of this wetland, including 10 optically stimulated luminescence dates. The wetland sequence accumulated during the period ~125 to 70 ka in response to a positive water balance coupled with a (possibly coseismic) landslide that dammed the outlet. The valley fill was dissected when the dam was incised shortly after ~36 ± 3 ka. Comparison of our ages with regional palaeoclimate indicates that the Gharandal oasis developed during the relatively humid Marine Isotope Stage 5. A minimum age of 74 ± 7 ka for two Levallois flakes collected from stratified sediments suggests that the oasis was visited by humans during the critical 130–90 ka time window of human migration out of Africa. Gharandal joins a growing network of freshwater sites that enabled humans to cross areas of the Levant and Arabia along corridors of human dispersal.
A reformulation of the Social Brain Theory of schizophrenia is proposed that contends that schizophrenia is a novel human phenomenon that arose following the establishment of large permanent human settlements and the abandonment of the hunter-gatherer way of life. It is contended that the blurring of the demarcation between ingroup and outgroup membership and living in close proximity to strangers is a stressor that leads to perturbation in the development of the social brain in vulnerable individuals leading to the syndrome of schizophrenia. Contrary to previous authors who have considered schizophrenia to be an inherently human condition that has existed throughout human history we suggest that schizophrenia is a relatively recent phenomenon and that the vulnerability to it remained hidden amongst hunter-gatherers. Hence, we contend that schizophrenia is the result of a mismatch between the post-Neolithic human social environment and the design of the social brain. The importance of the distinction between ingroup and outgroup membershipin human evolutionary history lies at the heart of inter-group conflict, violence and xenophobia. This formulation explains a range of epidemiological findings on schizophrenia related to the risk of migration and urbanisation. The present hypothesis can therefore, account for a range of disparate findings regarding schizophrenia that have thus far defied explanation by other extant theories. However, as this formulation claims to have identified the ultimate causation of schizophrenia the hypothesis does not specify the proximate mechanisms that lead to it. We conclude with a number of testable and refutable predictions.
This chapter reviews the most researched psychotherapeutic interventions for individuals with cognitive impairment (CI) and common symptoms targeted by these interventions. Elements of assessment and psychotherapy modifications to consider when working with individuals with dementia are also discussed. Assessment components might include clarification of medical symptom overlap, collateral information, assessment instruments developed for individuals with cognitive difficulties, and incorporating consultation with other specialties. In general, clinicians should consider using simplified skills, increasing the number and frequency of sessions, shortening sessions, reducing group size, and providing more guidance during skill instruction and practice when working with individuals with cognitive impairments. Despite their promise and recommendations for their use, nonpharmacological therapies for individuals with dementia have a small research base and warrant continued development and evaluation.
Introduction: Email and text messaging holds the potential to not only contact patients after emergency department (ED) care for clinically important communications such as appointment reminders, but also to solicit feedback for quality improvement and/or participation in research. A necessary first step though is the collection of electronic contact information, but little is known about current practice in Ontario EDs. In this study, we sought to characterize current collection, consent and use of patient email and texting to communicate with ED patients at academic and community hospitals across Ontario. Methods: We developed a questionnaire, with a blend of multiple choice and open-ended questions, targeted at ED registration administrators. The questions focused on if and how EDs collect, store and consent for patient emails, how and what they utilize those emails for and if they text patients. The questionnaire was administered both online and by phone. Participants were recruited through snowball sampling, including facilitated dissemination of the questionnaire via an existing listserv of the Patient Registration Network of Ontario (PRNO). Results: Twenty-two respondents (41% response rate) completed the questionnaire. Seven of the 22 institutions were academic health centres (32%). Nine institutions (41%) collected patient email addresses in the ED and none collected or used text message technology. In all 9, registration staff were tasked with asking, consenting, collecting and storing patient details within their hospital admissions, discharge and transfer system (ADT). For sites with email address collection, respondents estimated 40-60% of ED patients shared an email address. Seven of 9 institutions had a verbal consent process, while 2 used implied consent. Only 2 institutions used email to send patients post-discharge feedback questionnaires and four used email to facilitate access to patient portals. Four institutions were looking at using text messages to direct patients at triage, sometime in the future. Conclusion: Engagement in optimized care and feedback requires communication which is quickly shifting to electronic format. Collection of electronic contact information continues to be slow and uneven in Ontario. There is an immediate need for clearer guidance to accelerate collection, storage, consent and use of email and text messaging technology.
Based on hierarchies of filter lengths, the large eddy decomposition and the related subgrid stresses are recognized to represent generalized central moments for the study and modelling of the different modes composing turbulence. In particular, the subgrid stresses and the subgrid dissipation are shown to be alternative observables for quantitatively assessing the scale-dependent properties of momentum flux (subgrid stresses) and the energy exchange between the large and small scales (subgrid dissipation). In this work we present a theoretical framework for the study of the subgrid stress and dissipation. Starting from an alternative decomposition of the turbulent stresses, a new formalism for their approximation and understanding is proposed which is based on a tensorial turbulent viscosity. The derived formalism highlights that every decomposition of the turbulent stresses is naturally approximated by a general form of turbulent viscosity tensor based on velocity increments which is then recognized to be a peculiar property of small-scale stresses in turbulence. The analysis in a turbulent channel shows the rich physics of the small-scale stresses which is unveiled by the tensorial formalism and usually missed in scalar approaches. To further exploit the formalism, we also show how it can be used to derive new modelling approaches. The proposed models are based on the second- and third-order inertial properties of the grid element. The basic idea is that the structure of the integration volume for filtering (either implicit or explicit) impacts the anisotropy and inhomogeneity of the filtered-out motions and, hence, this information could be leveraged to improve the prediction of the main unknown features of small-scale turbulence. The formalism provides also a rigorous definition of characteristic lengths for the turbulent stresses, which can be computed in every type of computational elements, thus overcoming the rather elusive definition of filter length commonly employed in more classical models. A preliminary analysis in a turbulent channel shows reasonable results. In order to solve numerical stability issues, a tensorial dynamic procedure for the evolution of the model constants is also developed. The generality of the procedure is such that it can be employed also in more conventional closures.
The purpose of this study is the verification of intensity modulated radiation therapy (IMRT) head neck treatment planning with one-dimensional and two-dimensional (2D) dosimeters using imaging and radiation oncology core (IROC) Houston head & neck (H&N) phantom.
Method
The image of the H&N phantom was obtained by computed tomography scan which was then transferred to Pinnacle@3 treatment planning system (TPS) for treatment planning. The contouring of the target volumes and critical organ were done manually and dose constraints were set for each organ according to IROC prescription. The plan was optimised by adoptive convolution algorithm to meet the IROC criteria and collapse cone convolution algorithm calculated the delivered doses for treatment. Varian Clinac 2110 was used to deliver the treatment plan to the phantom, the process of irradiation and measurement were repeated three times for reproducibility and reliability. The treatment plan was verified by measuring the doses from thermoluminescent dosimeters (TLDs) and GafChromic external beam therapy 2 films. The agreement between the planned and delivered doses were checked by calculating the percentage dose differences, analysing their isodose line profiles and 2D gamma maps.
Results
The average percent dose difference of 1·8% was obtained between computed doses by TPS and measured doses from TLDs, however these differences were found to be higher for organ at risk. The film dose profile was well in agreement with the planned dose distribution with distance to agreement of 1·5 mm. The gamma analysis of the computed and recorded doses passed the criteria of 3%/3 mm with passing percentages of >96%, which shows successful authentication of delivered doses for IMRT.
Conclusion
IMRT pre-treatment validation can be done with IROC anthropomorphic phantoms, which is essential for the delivery of modulated radiotherapies. It was concluded that films and TLDs can be used as quality assurance tools for IMRT.
To verify dose delivery and quality assurance of volumetric-modulated arc therapy (VMAT) for head and neck (H&N) cancer.
Method
The Imaging and Radiation Oncology Core Houston (IROC-H) H&N phantom with thermoluminescent dosimeters (TLDs) and films, were imaged with computed tomography scan and the reconstructed image was transferred to pinnacle treatment planning system (TPS). On TPS, the planning target volume (PTV), secondary target volume (STV) and organ at risk (OAR) were delineated manually and a treatment plan was made. The dose constraints were determined for the concerned organs according to IROC-H prescription. The treatment plan was optimised using adoptive convolution algorithm to improve dose homogeneity and conformity. The dose calculation was performed using C.C Convolution algorithm and a Varian True Beam linear accelerator was used to deliver the treatment plan to the H&N phantom. The delivered radiation dose to the phantom was measured through TLDs and GafChromic external beam radiotherapy 2 (EBT2) films. The dosimetric performance of the VMAT delivery was studied by analysing percent dose difference, isodose line profile and gamma analysis of the TPS-computed dose and linac-delivered doses.
Result
The percent dose difference of 3.8% was observed between the planned and measured doses of TLDs and a 1.5-mm distance to agreement (DTA) was observed by comparing isodose line profiles. Passed the gamma criteria of 3%/3 mm was with good percentages.
Conclusion
The dosimetric performance of VMAT delivery for a challenging H&N radiotherapy can be verified using TLDs and films embedded in an anthropomorphic H&N phantom.
Direct numerical simulations of turbulent suspension flows are carried out with the force-coupling method in plane Couette and pressure-driven channel configurations. Dilute to moderately concentrated suspensions of neutrally buoyant finite-size spherical particles are considered when the Reynolds number is slightly above the laminar–turbulent transition. Tests performed with synthetic streaks, in both turbulent channel and Couette flows, show clearly that particles trigger the instability in channel flow whereas the plane Couette flow becomes laminar. Moreover, we have shown that particles have a pronounced impact on pressure-driven flow through a detailed temporal and spatial analysis whereas they have no significant impact on the plane Couette flow configuration. The substantial difference between the two flow configurations is related to the spatial preferential distribution of particles in the large-scale rolls (inactive motion) in Couette flow, whereas they are accumulated in the ejection (active motion) regions in pressure-driven flow. Through investigation of particle modification in two distinct flow configurations, we were able to show the specific response of turbulent structures and the modulation of the fundamental mechanisms composing the regeneration cycle in the buffer layer of the near-wall turbulence. Especially for pressure-driven flow, the particles enhance the lift-up and let it act continuously whereas the particles do not significantly alter the streak breakdown process. The reinforcement of the streamwise vortices is attributed to the vorticity stretching term by the wavy streaks. The smaller and more numerous wavy streaks enhance the vorticity stretching and consequently strengthen the circulation of large-scale streamwise vortices in suspension flow.