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AIMS: This study aimed to compare the head dose of a cardiologist to scrub and scout nurses during cardiac angiography. DESIGN: A correlational longitudinal quantitative design was used to examine the relationship between the variable of occupational dose to the medical operator when compared with the dose to the scrub and scout nurses. METHODS: A quantitative analysis was performed on data collected during coronary angiograms (N = 612) for one cardiologist and 22 nurses performing either the scrub or scout role between May 2015 and February 2017. Analysis was based on log-transformed dose levels and reported as geometric means and associated 95% confidence intervals. RESULTS: It was found that scrub nurses received on average 41% more head dose than the cardiologist during diagnostic procedures and 52% higher doses during interventional cases. CONCLUSION: Nurses working in fluoroscopic cardiovascular procedures should be provided with appropriate training and protective equipment, notably lead skull caps, to minimize their occupational radiation exposure. IMPACT: There is a notable lack of research evaluating the occupational head and eye exposure to nurses involved in fluoroscopic procedures. This study found that during diagnostic coronary angiograms, the scrub nurses received 41% more occupational head dose than the cardiologist and 52% higher head doses during interventional cases. Radial access resulted in higher doses to scrub nurses than femoral artery access. It is advisable that staff wear protective lead glasses and skull caps and use appropriately positioned ceiling mounted lead shields to minimize the risk of adverse effects of occupational exposure to ionizing radiation.
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Angiografía , Cateterismo Cardíaco , Cardiólogos , Personal de Enfermería , Exposición Profesional , Adulto , Femenino , Humanos , Masculino , Persona de Mediana EdadRESUMEN
OBJECTIVE: Poverty is related to increased grief-related mental health problems, leading some to suggest bereavement counseling should be tailored to income. However, information about accessibility and effectiveness of such counseling programs serving low-income households is scarce. This longitudinal study therefore investigated the association between poverty and complicated grief (CG), and the effectiveness of a community-based bereavement counseling program in serving low-income households. METHODS: Two hundred eighty-eight participants (75% female) were enrolled. Loss-related and demographic variables were assessed at baseline. Regression analyses were used to investigate household income as a predictor of CG, and examine bereavement counseling effectiveness by comparing CG symptom change across three household income categories across three time-points: baseline (T1), T1 + 12 months (T2), and T1 + 18 months (T3). RESULTS: Of all participants, 35.8% reported below poverty-threshold income, twice the general population's rate. Multiple regression analysis indicated poverty-threshold income was a predictor of CG symptoms over and above demographic and loss-related characteristics. Three-way interaction analysis detected a significant treatment effect for study condition across time, but no differences in treatment effects across income. CONCLUSION: Lower household income was associated with higher CG symptoms. Since income did not predict differential treatment response, community-based bereavement counseling appeared no less efficacious for members of low-income households. Clinical or methodological significance of this article: While previous research has indicated low income may be a risk factor for mental health problems after bereavement, and it has therefore been suggested bereavement counseling should be tailored to income, no study to date has investigated the need for such tailoring. This controlled, longitudinal treatment study fills this gap in knowledge. Main findings are that low income is a key predictor of complicated grief symptoms. The study also shows that the effectiveness of one-to-one bereavement counseling does not appear to differ according to income level.
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Aflicción , Servicios Comunitarios de Salud Mental/métodos , Consejo/métodos , Evaluación de Resultado en la Atención de Salud , Pobreza/psicología , Adulto , Anciano , Femenino , Pesar , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana EdadRESUMEN
Fluoroscopy is a method used to provide real time x-ray imaging of the body during medical procedures to assist with medical diagnosis and treatment. Recent technological advances have seen an increase in the number of fluoroscopic examinations being performed. Nurses are an integral part of the team conducting fluoroscopic investigations and are often located close to the patient resulting in an occupational exposure to radiation. The purpose of this review was to examine recent literature which investigates occupational exposure received by nursing staff during cardiovascular fluoroscopic procedures. Articles published between 2011 and 2017 have been searched and comprehensively reviewed on the referenced medical search engines. Twenty-four relevant studies were identified among which seventeen investigated nursing dose comparative to operator dose. Seven researched the effectiveness of interventions in reducing occupational exposure to nursing staff. While doctors remain at the highest risk of exposure during procedures, evidence suggests that nursing staff may be at risk of exceeding recommended dose limits in some circumstances. There is also evidence of inconsistent use of personal protection such as lead glasses and skull caps by nursing staff to minimize radiation exposure. Conclusions: The review has highlighted a lack of published literature focussing on dose to nurses. There is a need for future research in this area to inform nursing staff of factors which may contribute to high occupational doses and of methods for minimizing the risk of exposure, particularly regarding the importance of utilizing radiation protective equipment.
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Procedimientos Quirúrgicos Cardiovasculares/enfermería , Fluoroscopía/normas , Personal de Enfermería/estadística & datos numéricos , Exposición Profesional/prevención & control , Exposición a la Radiación/prevención & control , Traumatismos por Radiación/prevención & control , Protección Radiológica/métodos , Procedimientos Quirúrgicos Cardiovasculares/efectos adversos , Humanos , Exposición Profesional/efectos adversos , Dosis de Radiación , Exposición a la Radiación/efectos adversos , Traumatismos por Radiación/etiologíaRESUMEN
This controlled, longitudinal investigation tested the effectiveness of a bereavement counselling model for adults on reducing complicated grief (CG) symptoms. Participants (N = 344; 79% female; mean age: 49.3 years) were adult residents of Scotland who were bereaved of a close relation or partner, experiencing elevated levels of CG, and/or risks of developing CG. It was hypothesized that participants who received intervention would experience a greater decline in CG levels immediately following the intervention compared to the control participants, but the difference would diminish at follow-up (due to relapse). Data were collected via postal questionnaire at 3 time points: baseline (T), post-intervention (T + 12 months), and follow-up (T + 18 months). CG, post-traumatic stress, and general psychological distress were assessed at all time points. Multilevel analyses controlling for relevant covariates were conducted to examine group differences in symptom levels over time. A stepwise, serial gatekeeping procedure was used to correct for multiple hypothesis testing. A main finding was that, contrary to expectations, counselling intervention and control group participants experienced a similar reduction in CG symptoms at postmeasure. However, intervention participants demonstrated a greater reduction in symptom levels at follow-up (M = 53.64; d = .33) compared to the control group (M = 62.00). Results suggest community-based bereavement counselling may have long-term beneficial effects. Further longitudinal treatment effect investigations with extensive study intervals are needed.
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Aflicción , Servicios Comunitarios de Salud Mental/métodos , Consejo/métodos , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Escocia , Encuestas y CuestionariosRESUMEN
Standardized, evidence-based risk assessment is an important component in providing effective bereavement care. E-health intake assessments have been offered alongside or instead of in-person assessments, although evidence concerning the equivalence of assessment results is lacking. This article examines differences between a semistructured intake assessment for grief intervention conducted over the telephone (n = 330) and in-person (n = 115). Differences in scores and clinical implications were evaluated. Although composite assessment scores were lower in the telephone condition, further examination revealed this occurred in the semistructured assessment of risk of complications, not the structured grief symptom assessment. Implications for care provision are discussed.
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Pesar , Entrevista Psicológica , Telemedicina , Intervención Médica Temprana , Femenino , Humanos , Masculino , Evaluación de Resultado en la Atención de Salud , Factores de RiesgoRESUMEN
The number and complexity of transcatheter procedures continue to increase, raising concerns regarding radiation exposure to patients and staff. Procedures such as transaortic valve implantations (TAVI) have led to cardiologists adopting higher dose techniques, such as digital subtraction angiography (DSA). This study compared the estimated patient and occupational eye dose during coronary angiography (CA), percutaneous coronary intervention (PCI), TAVI workups (TWU), TAVI, endovascular aneurysm repairs (EVAR), and other peripheral diagnostic (VD) and interventional (VI) vascular procedures. A quantitative analysis was performed on patient dose during 299 endovascular and 1498 cardiac procedures. Occupational dose was measured for the cardiologists (n = 24), vascular surgeons (n = 3), scrub (n = 32) and circulator nurses (n = 35). TAVI and EVAR were associated with the highest average dose for all staff, and significantly higher patient dose area product, probably attributable to the use of DSA. Scrub nurses were exposed to higher average doses than the operator and scout nurse during CA, VD and VI. Circulating nurses had the highest average levels of exposure during TAVI. This study has demonstrated that EVAR and TAVI have similar levels of occupational and patient dose, with a notable increase in circulator dose during TAVI. The use of DSA during cardiac procedures is associated with an increase in patient and staff dose, and cardiologists should evaluate whether DSA is necessary. Scrub nurses may be exposed to higher levels of occupational dose than the operator.
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Aneurisma de la Aorta Abdominal , Implantación de Prótesis Vascular , Procedimientos Endovasculares , Personal de Enfermería , Exposición Profesional , Intervención Coronaria Percutánea , Humanos , Procedimientos Endovasculares/efectos adversos , Aneurisma de la Aorta Abdominal/etiología , Dosis de Radiación , Exposición Profesional/efectos adversosRESUMEN
X-ray guided procedures are being performed by an increasing variety of medical specialties. Due to improvements in vascular transcatheter therapies, there is an increasing overlap of imaged anatomy between medical specialties. There is concern that non-radiology fluoroscopic operators may not have sufficient training to be well informed of the potential implications of radiation exposure and mitigation strategies to reduce dose. This was a prospective, observational, single center study to compare occupational and patient dose levels when imaging different anatomical regions during fluoroscopically guided cardiac and endovascular procedures. Occupational radiation dose was measured at the level of the temple of 24 cardiologists and 3 vascular surgeons (n = 1369), 32 scrub nurses (n = 1307) and 35 circulating nurses (n = 885). The patient dose was recorded for procedures (n = 1792) performed in three angiography suites. Abdominal imaging during endovascular aneurysm repair (EVAR) procedures was associated with a comparatively high average patient, operator and scrub nurse dose despite additional table-mounted lead shields. Air kerma was relatively high for procedures performed in the chest, and chest + pelvis. Higher dose area product and staff eye dose were recorded during procedures of the chest + pelvis due to the use of digital subtraction angiography to evaluate access route prior to/during transaortic valve implantation. Scrub nurses were exposed to higher average radiation levels than the operator during some procedures. Staff should be cognizant of the potentially higher radiation burden to patients and exposed personnel during EVAR procedures and cardiac procedures using digital subtraction angiography.
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Aneurisma de la Aorta Abdominal , Implantación de Prótesis Vascular , Procedimientos Endovasculares , Humanos , Procedimientos Endovasculares/métodos , Aneurisma de la Aorta Abdominal/cirugía , Estudios Prospectivos , Dosis de Radiación , Angiografía de Substracción DigitalRESUMEN
OBJECTIVE: The reduction in circulating low-density lipoprotein cholesterol (LDL-c) is the primary aim of lipid-lowering therapies as a method of atherosclerotic cardiovascular disease risk reduction. Inclisiran is a new and potent lipid-lowering drug that is shown to be effective in reducing LDL-c in randomised controlled trials, however, real-world data of its use are not yet known. We sought to analyse the early effects of this drug in a tertiary centre lipid and cardiovascular risk clinic. METHODS: We performed a retrospective analysis of the first 80 patients who received a single dose of inclisiran at our lipid clinic between 1 December 2021 and 1 September 2022. Data were collected using electronic healthcare records. Baseline blood tests were taken prior to start of treatment and were repeated at 2 months follow-up. Data on adverse events were also recorded. RESULTS: At 2 months after treatment initiation, mean baseline LDL-c fell from 3.5±1.1 mmol/L by 48.6% to 1.8±1.0 mmol/L and total cholesterol from 5.7±1.3 mmol/L by 33.3% to 3.8±1.1 mmol/L (both p<0.0001). Mean high-density lipoprotein-c rose by 7.7% to 1.4±0.4 mmol/L (p=0.02) and median triglycerides fell by 31.3% to 1.1 mmol/L (IQR 0.9-2) (p=0.001). Adverse events (injection site reaction, fatigue and headache) were recorded in three patients and all had self-resolved by time of follow-up. CONCLUSION: Inclisiran use in line with National Institute for Health and Care Excellence guidelines led to significant lowering of LDL-c at 2 months, with efficacy similar to that reported in trials with good tolerability.
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Enfermedades Cardiovasculares , Humanos , LDL-Colesterol , Estudios Retrospectivos , Enfermedades Cardiovasculares/inducido químicamente , Hipolipemiantes/uso terapéuticoRESUMEN
The aim of this study is to investigate the effectiveness of dose reducing software (ClarityIQ) on patient and staff dose during fluoroscopically guided cardiac procedures. Dose measurements were collected in a room without dose reducing software (n = 157) and compared with similar procedures performed in two rooms with the software (n = 1141). Procedures included diagnostic coronary angiography, percutaneous coronary intervention, deployment of cardiac closure devices (for occlusion of atrial septal defect, patent foramen ovale, and atrial appendage) and insertion of permanent pacemakers. The dose reducing software was found to be effective in reducing patient and staff dose by approximately 50%. This study has added to the limited literature reporting on the capability of dose reducing software to decrease radiation exposure during the implantation of cardiac closure devices, as well as demonstrating a reduction in dose to the cardiologist and nursing staff. Administrators should ensure timely upgrades to angiographic equipment to safeguard patients and staff against the potentially adverse effects of radiation exposure. Regardless of the use of dose reducing software, the mean occupational dose during closure devices was in descending order scout > scrub > cardiologist. Scrub nurse dose was found to be higher than the cardiologist during closure devices (0.98/0.26 µSv) and diagnostic coronary angiograms (1.51/0.82 µSv). Nursing staff should be aware that their levels of radiation dose during some cardiac procedures may come close to or even exceed that of the cardiologist.
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Foramen Oval Permeable , Marcapaso Artificial , Cateterismo Cardíaco , Angiografía Coronaria , Foramen Oval Permeable/terapia , Humanos , Programas InformáticosRESUMEN
BACKGROUND: Exposure to radiation during fluoroscopically guided cardiac procedures is a cause for concern for both the patient and staff. AIMS: This study sought to compare the occupational and patient radiation dose during femoral and radially accessed invasive coronary angiography (CA). METHODS AND RESULTS: Occupational dose (µSv) was measured at the left temple of the cardiologist (n = 17), scrub (n = 27), and circulator nurse (n = 27) during 761 femoral and 671 radially accessed diagnostic coronary angiograms and percutaneous coronary intervention (PCI) procedures. Patient dose parameters of dose area product (DAP) (Gy.cm2) and air kerma (AK) (Gy) were also measured. Coronary angiography performed via the radial artery is associated with greater mean dose to the cardiologist, with the exception of procedures including only PCI. Results demonstrated that scrub nurses are exposed to higher mean doses than the cardiologist when using femoral access and similar doses during radial cases. Both AK and DAP were associated with a higher average dose for femoral PCI than radial, with DAP being significantly higher. CONCLUSIONS: Awareness of factors that increase the dose to staff and patients is vital to inform and improve practice. This study has demonstrated that access route during diagnostic CA and PCI influences both patient and staff dose. Radiation dose to in-room staff other than the fluoroscopic operator should be a focus of future research. In addition, all staff present during X-ray guided procedures should be provided with radiation education and adopt dose minimization strategies to reduce occupational exposures.
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Cardiólogos , Intervención Coronaria Percutánea , Angiografía Coronaria/efectos adversos , Arteria Femoral , Humanos , Intervención Coronaria Percutánea/efectos adversos , Arteria Radial , Dosis de RadiaciónRESUMEN
There is a paucity of literature comparing patient and staff dose during coronary angiography (CA), implantable cardiac devices, permanent pacemakers (PPM) and electrophysiology (EP) procedures and little noting dose to staff other than cardiologists. This study sought to compare patient and occupational dose during a range of fluoroscopically guided cardiac procedures. Radiation dose levels for the patients (n = 1651), cardiologists (n = 24), scrub (n = 32) and scout nurses (n = 35) were measured in a prospective single-centre study between February 2017 and August 2019. A comparison of dose during CA, device implantation, PPM insertion and EP studies was performed. Three angiographic units were used, with dosimeters worn on the temple of staff. Results indicated that occupational dose during PPM was significantly higher than other procedures. The cardiologist had the highest mean dose during biventricular implantable cardioverter-defibrillators; levels were approximately five times that of 'normal' pacemaker insertions. Transcatheter aortic valve implantations (TAVI) were associated with relatively high mean doses for both staff and patients and had a statistically significant higher (>2 times) mean patient dose area product than all other categories. TAVI workups were also related to higher mean cardiologist and scrub nurse dose. It was observed that the mean scrub nurse dose can exceed that of the cardiologist. The highest mean dose for Scout nurses were recorded during EP studies. Given the significantly higher temple dose associated with PPM insertion, cardiologists should consider utilizing ceiling mounted lead shields, lead glasses and/or skull caps where possible. Efforts should also be made to minimize the use of DSA during TAVI and TAVI workups to reduce cardiologist, nurse and patient dose.
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Desfibriladores Implantables , Exposición Profesional , Angiografía Coronaria , Electrofisiología , Humanos , Estudios Prospectivos , Dosis de RadiaciónRESUMEN
PURPOSE: Cardiologists often perform angiography of the common femoral artery (CFA) access site to evaluate whether the anatomy is suitable for deployment of a vascular closure device or to assess whether iatrogenic vessel damage has occurred. The choice of acquisition mode has radiation dose implications. The objective of this study was to investigate the influence of the selected type of CFA x-ray imaging mode (fluoro save, cine acquisition and digital subtraction angiography (DSA)) and tube angle on patient and staff dose during coronary angiography. MATERIALS AND METHODS: Assessment of image quality for the different modes was performed to determine whether lower dose modes provide images of sufficient clinical quality to be routinely employed. Radiation dose levels for the patients (n=782), cardiologists (n=17), scrub nurses (n=27) and scout nurses (n=32) were measured in a prospective single-centre study between February 2017 and August 2019. Three Philips angiographic units and DoseAware dose monitoring systems were used. RESULTS: Among the acquisition modes, fluoro save provided acceptable diagnostic quality for visualizing femoral access points and diagnosing pathology in 99% of cases. Average patient dose area product (DAP) was 83.95, 742.50, and 3363.41mGy2 and average patient air kerma (AK) was 0.87, 8.44, and 18.61mGy for fluoro save, cine, and DSA acquisitions, respectively. The use of higher dose imaging modes, imaging in the contralateral view and utilizing steeper TA was associated with a higher patient dose. Due to staff dose being highly correlated with DAP and AK, it was difficult to observe any association between staff dose and CFA imaging mode. However, this does not discount a potential increase in occupational dose due to the use of cine angiography or digital subtraction angiography during CFA imaging. CONCLUSION: DSA of the CFA should be avoided during transfemoral coronary angiography unless critical to diagnostic analysis. It is recommended that fluoroscopic operators consider utilizing lower dose modes in the ipsilateral orientation ≤32° TA to reduce the risk of patient and staff radiation exposure.
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This study aimed to evaluate the effect of nurse and doctor height on occupational dose to the temple during fluoroscopically guided cardiovascular procedures. Additionally, an evaluation of the relationship between doctor height and table height was performed. Staff exposed during fluoroscopic procedures may be at elevated risk of cardiovascular damage or oncogenesis and have demonstrated a higher incidence of subscapular cataracts. The heads of taller staff may be exposed to reduced levels of radiation due to the increased distance from the area of highest intensity X-ray scatter. Limited research has been performed investigating height as a predictor of head dose to nursing staff. The level of radiation dose at the level of the temple to the doctor (n = 25), scrub (n = 28), and scout nurse (n = 29) was measured in a prospective single-center, observational study using Philips DoseAware badges. Procedural characteristics were recorded for vascular and cardiac cases performed in three dedicated angiography suites. Data were also collected to investigate relationships between doctor height and table height. Data were collected for 1585 cardiac and 294 vascular procedures. Staff height was a statistically significant predictor of temple dose for doctors, scrub, and scout nurses when considering the full data sample. The log temple dose demonstrated an inverse relationship to staff height during cardiac procedures, but a positive relationship for scrub and scout nurses during vascular studies. This observational study has demonstrated that taller staff are exposed to less cranial exposure dose during fluoroscopically guided cardiac examinations but has revealed a positive correlation between height and temple dose during vascular procedures. It was also determined that doctor height was correlated with average procedural table height and that vascular access point influences the choice of table elevation.
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Procedimientos Endovasculares/efectos adversos , Exposición a la Radiación/efectos adversos , Traumatismos por Radiación/etiología , Angiografía/efectos adversos , Femenino , Fluoroscopía/efectos adversos , Cabeza/efectos de la radiación , Humanos , Masculino , Personal de Enfermería , Exposición Profesional/efectos adversos , Estudios Prospectivos , Dosis de Radiación , Protección Radiológica/métodos , Radiografía Intervencional/efectos adversos , Rayos X/efectos adversosRESUMEN
OBJECTIVE: This study assessed the validity of the Indicator of Bereavement Adaptation Cruse Scotland (IBACS). Designed for use in clinical and non-clinical settings, the IBACS measures severity of grief symptoms and risk of developing complications. METHOD: N = 196 (44 male, 152 female) help-seeking, bereaved Scottish adults participated at two timepoints: T1 (baseline) and T2 (after 18 months). Four validated assessment instruments were administered: CORE-R, ICG-R, IES-R, SCL-90-R. Discriminative ability was assessed using ROC curve analysis. Concurrent validity was tested through correlation analysis at T1. Predictive validity was assessed using correlation analyses and ROC curve analysis. Optimal IBACS cutoff values were obtained by calculating a maximal Youden index J in ROC curve analysis. Clinical implications were compared across instruments. RESULTS: ROC curve analysis results (AUC = .84, p < .01, 95% CI between .77 and .90) indicated the IBACS is a good diagnostic instrument for assessing complicated grief. Positive correlations (p < .01, 2-tailed) with all four instruments at T1 demonstrated the IBACS' concurrent validity, strongest with complicated grief measures (r = .82). Predictive validity was shown to be fair in T2 ROC curve analysis results (n = 67, AUC = .78, 95% CI between .65 and .92; p < .01). Predictive validity was also supported by stable positive correlations between IBACS and other instruments at T2. Clinical indications were found not to differ across instruments. CONCLUSIONS: The IBACS offers effective grief symptom and risk assessment for use by non-clinicians. Indications are sufficient to support intake assessment for a stepped model of bereavement intervention.
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Pesar , Psicometría/métodos , Adulto , Área Bajo la Curva , Aflicción , Femenino , Humanos , Entrevistas como Asunto , Masculino , Persona de Mediana Edad , Curva ROC , Factores de Riesgo , Trastornos por Estrés Postraumático/patologíaRESUMEN
Aspects of the socioeconomic costs of bereavement in Scotland were estimated using 3 sets of data. Spousal bereavement was associated with increased mortality and longer hospital stays, with additional annual cost of around £20 million. Cost of bereavement coded consultations in primary care was estimated at around £2.0 million annually. In addition, bereaved people were significantly less likely to be employed in the year of and 2 years after bereavement than non-bereaved matched controls, but there were no significant differences in income between bereaved people and matched controls before and after bereavement.
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Aflicción , Empleo , Atención Primaria de Salud , Esposos , Adulto , Anciano , Costos y Análisis de Costo , Empleo/economía , Empleo/psicología , Femenino , Mal Uso de los Servicios de Salud/economía , Humanos , Tiempo de Internación/economía , Masculino , Persona de Mediana Edad , Evaluación de Necesidades , Atención Primaria de Salud/economía , Atención Primaria de Salud/estadística & datos numéricos , Escocia , Factores Socioeconómicos , Esposos/psicología , Esposos/estadística & datos numéricos , Factores de TiempoRESUMEN
INTRODUCTION: A novel realistic 3D virtual reality (VR) application has been developed to allow medical imaging students at Queensland University of Technology to practice radiographic techniques independently outside the usual radiography laboratory. METHODS: A flexible agile development methodology was used to create the software rapidly and effectively. A 3D gaming environment and realistic models were used to engender presence in the software while tutor-determined gold standards enabled students to compare their performance and learn in a problem-based learning pedagogy. RESULTS: Students reported high levels of satisfaction and perceived value and the software enabled up to 40 concurrent users to prepare for clinical practice. Student feedback also indicated that they found 3D to be of limited value in the desktop version compared to the usual 2D approach. A randomised comparison between groups receiving software-based and traditional practice measured performance in a formative role play with real equipment. The results of this work indicated superior performance with the equipment for the VR trained students (P = 0.0366) and confirmed the value of VR for enhancing 3D equipment-based problem-solving skills. CONCLUSIONS: Students practising projection techniques virtually performed better at role play assessments than students practising in a traditional radiography laboratory only. The application particularly helped with 3D equipment configuration, suggesting that teaching 3D problem solving is an ideal use of such medical equipment simulators. Ongoing development work aims to establish the role of VR software in preparing students for clinical practice with a range of medical imaging equipment.
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We analyze generalization in XCSF and introduce three improvements. We begin by showing that the types of generalizations evolved by XCSF can be influenced by the input range. To explain these results we present a theoretical analysis of the convergence of classifier weights in XCSF which highlights a broader issue. In XCSF, because of the mathematical properties of the Widrow-Hoff update, the convergence of classifier weights in a given subspace can be slow when the spread of the eigenvalues of the autocorrelation matrix associated with each classifier is large. As a major consequence, the system's accuracy pressure may act before classifier weights are adequately updated, so that XCSF may evolve piecewise constant approximations, instead of the intended, and more efficient, piecewise linear ones. We propose three different ways to update classifier weights in XCSF so as to increase the generalization capabilities of XCSF: one based on a condition-based normalization of the inputs, one based on linear least squares, and one based on the recursive version of linear least squares. Through a series of experiments we show that while all three approaches significantly improve XCSF, least squares approaches appear to be best performing and most robust. Finally we show how XCSF can be extended to include polynomial approximations.