Now showing items 1-20 of 1083

    • Letter re: Comparison of acetabular and femoral morphologies on hip, pelvic, and lumbar radiographs (Yun et al.)

      Snaith, Beverly; Flintham, K. (2018)
      We read with interest the recent article by Yun et al. [1] comparing acetabular and hip measurements across pelvis, hip and lumbar spine radiographs. The authors assert that lumbar radiographs can be utilised in place of routine pelvis radiographs for these measurements. The example lumbar spine radiograph (figure 2) appears to be an abdominal image, with a contrast urogram. Indeed, standard texts [2,3] confirm that the anteroposterior lumbar spine radiograph should not include any coverage of the hips as appropriate collimation should limit the anatomy to T12 superiorly, lower sacrum inferiorly and the sacroiliac joints laterally, which would exclude the hip joints. Thus assessing any hip measurements on an appropriately collimated lumbar spine radiograph should not be possible. This is further compounded by the description of the centring point within their study (iliac crest), which varies from the internationally recognised standard of lower costal margin/L3 [2,3].
    • Medication-related risk factors and its association with repeated hospital admissions in frail elderly: A case control study

      Cheong, V-Lin; Sowter, J.; Scally, Andy J.; Hamilton, N.; Ali, A.; Silcock, J. (2019)
      Repeated hospital admissions are prevalent in older people. The role of medication in repeated hospital admissions has not been widely studied. The hypothesis that medication-related risk factors for initial hospital admissions were also associated with repeated hospital admissions was generated. To examine the association between medication-related risk factors and repeated hospital admissions in older people living with frailty. A retrospective case-control study was carried out with 200 patients aged ≥75 years with unplanned medical admissions into a large teaching hospital in England between January and December 2015. Demographic, clinical, and medication-related data were obtained from review of discharge summaries. Statistical comparisons were made between patients with 3 or more hospital admissions during the study period (cases) and those with 2 or fewer admissions (controls). Regressions were performed to establish independent predictors of repeated hospital admissions. Participants had a mean age of 83.8 years (SD 5.68) and 65.5% were female. There were 561 admission episodes across the sample, with the main reasons for admissions recorded as respiratory problems (25%) and falls (17%). Univariate logistic regression revealed five medication-related risks to be associated with repeated hospital admissions: Hyper-polypharmacy (defined as taking ≥10 medications) (OR 2.50, p < 0.005); prescription of potentially inappropriate medications (PIMs) (OR 1.89; p < 0.05); prescription of a diuretic (OR 1.87; p < 0.05); number of high risk medication (OR 1.29; p < 0.05) and the number of 'when required' medication (OR 1.20; p < 0.05). However, the effects of these risk factors became insignificant when comorbid disease was adjusted for in a multivariable model. Medication-related risk factors may play an important role in future repeated admission risk prediction models. The modifiable nature of medication-related risks factors highlights a real opportunity to improve health outcomes.
    • Caregiver influences on 'living well' for people with dementia: Findings from the IDEAL study.

      Quinn, Catherine; Nelis, S.M.; Martyr, A.; Morris, R.G.; Victor, C.; Clare, L. (2019-05)
      Objectives: The capability to ‘live well’ in people with dementia can be influenced by many factors, including those related to the experiences of their informal caregiver. How caregivers experience their own role can affect not only their well-being but also the way they provide care and hence the experience of the person with dementia. The aim of this study is to identify the potential impact of the caregiver’s perception of the caregiving experience on how people with mild to moderate dementia self-rate their QoL, well-being and satisfaction with life. Method: This study utilised time-point 1 data from 1283 informal caregiver and the 1283 people with dementia whom they provide care from the IDEAL cohort study. Multivariate modelling was used to investigate the associations between measures related to the caregiver’s perception of the caregiving experience (caregiving stress, perceived social restrictions, caregiving competence, positive aspects of caregiving, and coping) and the self-ratings of QoL, satisfaction with life, and well-being by the person with dementia. Results: Lower QoL ratings by the person with dementia were associated with high caregiver stress (−1.98; 95% CI: −2.89, −1.07), high perceived social restrictions (−2.04; 95% CI: −2.94, −1.14) and low caregiving competence (−2.01; 95% CI: −2.95, −1.06). Similar associations were found for satisfaction with life and wellbeing. Positive aspects of caregiving and coping were not associated with outcomes for the person with dementia. Conclusion: The findings indicate that how the caregiver experiences caregiving can affect the person with dementia. This finding reinforces the importance of providing support to caregivers.
    • The relationship between perceived functional difficulties and the ability to live well with mild-to-moderate dementia: Findings from the IDEAL programme.

      Martyr, A.; Nelis, S.M.; Quinn, Catherine; Rusted, J.M.; Morris, R.G.; Clare, L. (2019)
      Objectives: The objectives of the study are to investigate how different levels of functional ability relate to quality of life, well‐being, and satisfaction with life, conceptualised as reflecting capability to “live well” in people with dementia. Methods/design: Participants were 1496 people with mild‐to‐moderate dementia and 1188 informants who completed baseline assessments in the Improving the experience of Dementia and Enhancing Active Life (IDEAL) cohort study. Total selfrated and informant‐rated scores on the Functional Activities Questionnaire were split into six ability levels to monitor how poorer functioning impacts the ability to live well. We also investigated the potential influence of sociodemographic and diagnostic variables, depression, cognition, and carer stress. Results: Multivariate multiple regression models found that people with dementia who had the greatest functional impairment according to self‐ratings and informant ratings had poorer living well scores than those with the least functional impairment. Sociodemographic and diagnostic factors and cognition had little impact on effect sizes. For self‐ratings, depression attenuated the relationship between functional ability and living well, whereas carer stress attenuated informant ratings. Conclusions: People with dementia with the least functional impairments had greater capability to live well than those with the most functional impairment. Even subtle perceived difficulties in functional ability had a detrimental effect on the ability of people with dementia to live well. Depression in people with dementia and carer stress in informants influenced these associations, and therefore, these factors should be routinely included in future research studies and clinical assessments.
    • Compassionate communities: design and preliminary results of the experience of Vic (Barcelona, Spain) caring city

      Gómez-Batiste, X.; Mateu, S.; Serra-Jofre, S.; Molas, M.; Mir-Roca, S.; Amblàs, J.; Costa, X.; Lasmarías, C.; Serrarols, M.; Solà-Serrabou, A.; Calle, C.; Kellehear, Allan (2018)
      Background: A program of Compassionate City or Community (CC) has been designed and developed in the City of Vic (43,964 habitants, Barcelona, Spain), based on The Compassionate City Charter and other public health literature and experiments, with the joint leadership of the City Council and the Chair of Palliative Care at the University of Vic, and as an expansion of a comprehensive and integrated system of palliative care. Methods: The program started with an assessment of needs of the city as identified by 48 social organizations with a foundational workshop and a semi-structured survey. After this assessment, the mission, vision, values and aims were agreed. The main aims consisted in promoting changes in social and cultural attitudes toward the end of life (EoL) and providing integrated care for people with advanced chronic conditions and social needs such as loneliness, poverty, low access to services at home, or conflict. The selected slogan was “Living with meaning, dignity, and support the end of life”. Results: The program for the first year has included 19 activities (cultural, training, informative, and mixed) and followed by 1,260 attendants, and the training activities were followed by 147 people. Local and regional sponsors are funding the initiative. After a year, a quantitative and qualitative evaluation was performed, showing high participation and satisfaction of the attendants and organizations. In the second year, the care for particular vulnerable people defined as targets (EoL and social factors described before) will start with volunteers with more organizations to join the project. Conclusions: The key identified factors for the initial success are: the strong joint leadership between social department of the Council and the University; clear aims and targets; high participation rates; the limited size of the geographical context; which allowed high participation and recognition; and the commitment to evaluate results.
    • Assessing community readiness for early intervention programmes to promote social and emotional health in children

      Islam, Shahid; Small, Neil A.; Bryant, M.; Bridges, S.; Hancock, N.; Dickerson, J. (2019-06)
      Evidence for early intervention and prevention-based approaches for im-proving social and emotional health in young children is robust. However, rates of participation in programmes are low. We explored the dynamics which affect levels of community readiness to address the issues of social and emotional health for preg-nant women, young children (0-4 years) and their mothers.Setting:A deprived inner‐city housing estate in the north of England. The estate falls within the catchment area of a project that has been awarded long-term funding to address social and emotional health during pregnancy and early childhood.Methods:We interviewed key respondents using the Community Readiness Model. This approach applies a mixed methodology, incorporating readiness scores and qualitative data. A mean community readiness score was calculated enabling the placement of the community in one of nine possible stages of readiness. Interview transcripts were analysed using a qualitative framework approach to generate con-textual information to augment the numerical scores.Results:An overall score consistent with vague awareness was achieved, indicating a low level of community readiness for social and emotional health interventions. This score suggests that there will be a low likelihood of participation in programmes that address these issues.Conclusion:Gauging community readiness offers a way of predicting how willing and prepared a community is to address an issue. Modifying implementation plans so that they first address community readiness may improve participation rates.
    • Diet and physical activity in pregnancy: a study exploring women's beliefs and behaviours

      Chana, R.; Haith-Cooper, Melanie (2019-05-02)
      Being obese or gaining excessive weight during pregnancy can increase health risks for mother and baby. Adopting a healthy diet and increasing physical activity reduces these risks and has long-term health benefits for women. Despite this, women do not always maintain a healthy lifestyle during pregnancy. Aim To explore the factors that encouraged and prevented a diverse group of women to maintain a healthy lifestyle during pregnancy. Methods A total of 12 women participated in semi-structured qualitative interviews, underpinned by the theory of planned behaviour. Interviews were audio recorded, transcribed verbatim then subject to deductive thematic analysis. Findings Four themes emerged: women's knowledge of a healthy lifestyle, sociocultural influences, physical health and health professional support. These influenced women's intentions and actual behaviours during pregnancy. Conclusions Enhanced health professional advice may motivate women to adopt a healthy lifestyle during pregnancy. This could be through new means such as health technology.
    • Caregivers' beliefs about dementia: findings from the IDEAL study

      Quinn, Catherine; Jones, I.R.; Martyr, A.; Nelis, S.M.; Morris, R.G.; Clare, L.; IDEAL Study Team (2019)
      Objective: Informal caregivers of people with dementia develop their own beliefs about the condition, referred to as Dementia Representations (DRs), as they try to make sense of the changes they are observing. The first aim of this study was to provide a profile of the types of DRs held by caregivers. The second aim was to examine the impact of caregivers’ DRs on their well-being, satisfaction with life (SwL) and caregiving stress. Methods: Participants were 1264 informal caregivers of people in the mild-to-moderate stages of dementia from time-point 1 of the IDEAL cohort study. Measures: DRs were measured using questionnaire items covering: Identity, Cause, Control, and Timeline. Results: Almost half (49.2%) of caregivers used a diagnostic term to describe the person’s condition, although 93.4% of caregivers stated they were aware of the diagnosis. Higher well-being, SwL, and lower caregiving stress were associated with the use of an identity term relating to specific symptoms of dementia, attributing the cause to ageing or not knowing the cause, and believing the condition would stay the same. Lower well-being, SwL, and higher caregiving stress were associated with believing there was little that could be done to control the effects of the condition. Conclusion: Healthcare professionals should assess and gain an understanding of caregivers’ DRs in order to provide more tailored information and support.
    • The inclusion of delirium in version 2 of the National Early Warning Score will substantially increase the alerts for escalating levels of care: findings from a retrospective database study of emergency medical admissions in two hospitals

      Mohammad, Mohammad A.; Faisal, Muhammad; Richardson, D.; Scally, Andy J.; Howes, R.; Beatson, K.; Irwin, S.; Speed, K. (2019-03-01)
      Background The National Early Warning Score (NEWS) is being replaced with NEWS2 which adds 3 points for new confusion or delirium. We estimated the impact of adding delirium on the number of medium/high level alerts that are triggers to escalate care. Methods Analysis of emergency medical admissions in two acute hospitals (York Hospital (YH) and Northern Lincolnshire and Goole NHS Foundation Trust hospitals (NH)) in England. Twenty per cent were randomly assigned to have delirium. Results The number of emergency admissions (YH: 35584; NH: 35795), mortality (YH: 5.7%; NH: 5.5%), index NEWS (YH: 2.5; NH: 2.1) and numbers of NEWS recorded (YH: 879193; NH: 884072) were similar in each hospital. The mean number of patients with medium level alerts per day increased from 55.3 (NEWS) to 69.5 (NEWS2), a 25.7% increase in YH and 64.1 (NEWS) to 77.4 (NEWS2), a 20.7% increase in NH. The mean number of patients with high level alerts per day increased from 27.3 (NEWS) to 34.4 (NEWS2), a 26.0% increase in YH and 29.9 (NEWS) to 37.7 (NEWS2), a 26.1% increase in NH. Conclusions The addition of delirium in NEWS2 will have a substantial increase in medium and high level alerts in hospitalised emergency medical patients. Rigorous evaluation of NEWS2 is required before widespread implementation because the extent to which staff can cope with this increase without adverse consequences remains unknown.
    • Development and validation of a novel computer-aided score to predict the risk of in-hospital mortality for acutely ill medical admissions in two acute hospitals using their first electronically recorded blood test results and vital signs: a cross-sectional study

      Faisal, Muhammad; Scally, Andy J.; Jackson, N.; Richardson, D.; Beatson, K.; Howes, R.; Speed, K.; Menon, M.; Daws, J.; Dyson, J.; Marsh, C.; Mohammad, Mohammad A. (2018-12)
      Objectives There are no established mortality risk equations specifically for emergency medical patients who are admitted to a general hospital ward. Such risk equations may be useful in supporting the clinical decision-making process. We aim to develop and externally validate a computer-aided risk of mortality (CARM) score by combining the first electronically recorded vital signs and blood test results for emergency medical admissions. Design Logistic regression model development and external validation study. Setting Two acute hospitals (Northern Lincolnshire and Goole NHS Foundation Trust Hospital (NH)—model development data; York Hospital (YH)—external validation data). Participants Adult (aged ≥16 years) medical admissions discharged over a 24-month period with electronic National Early Warning Score(s) and blood test results recorded on admission. Results The risk of in-hospital mortality following emergency medical admission was 5.7% (NH: 1766/30 996) and 6.5% (YH: 1703/26 247). The C-statistic for the CARM score in NH was 0.87 (95% CI 0.86 to 0.88) and was similar in an external hospital setting YH (0.86, 95% CI 0.85 to 0.87) and the calibration slope included 1 (0.97, 95% CI 0.94 to 1.00). Conclusions We have developed a novel, externally validated CARM score with good performance characteristics for estimating the risk of in-hospital mortality following an emergency medical admission using the patient’s first, electronically recorded, vital signs and blood test results. Since the CARM score places no additional data collection burden on clinicians and is readily automated, it may now be carefully introduced and evaluated in hospitals with sufficient informatics infrastructure.
    • Understanding and applying practitioner and patient views on the implementation of a novel automated Computer-Aided Risk Score (CARS) predicting the risk of death following emergency medical admission to hospital: qualitative study

      Dyson, J.; Marsh, C.; Jackson, N.; Richardson, D.; Faisal, Muhammad; Scally, Andy J.; Mohammad, Mohammad A. (2019-04)
      Objectives The Computer-Aided Risk Score (CARS) estimates the risk of death following emergency admission to medical wards using routinely collected vital signs and blood test data. Our aim was to elicit the views of healthcare practitioners (staff) and service users and carers (SU/C) on (1) the potential value, unintended consequences and concerns associated with CARS and practitioner views on (2) the issues to consider before embedding CARS into routine practice. Setting This study was conducted in two National Health Service (NHS) hospital trusts in the North of England. Both had in-house information technology (IT) development teams, mature IT infrastructure with electronic National Early Warning Score (NEWS) and were capable of integrating NEWS with blood test results. The study focused on emergency medical and elderly admissions units. There were 60 and 39 acute medical/elderly admissions beds at the two NHS hospital trusts. Participants We conducted eight focus groups with 45 healthcare practitioners and two with 11 SU/Cs in two NHS acute hospitals. Results Staff and SU/Cs recognised the potential of CARS but were clear that the score should not replace or undermine clinical judgments. Staff recognised that CARS could enhance clinical decision-making/judgments and aid communication with patients. They wanted to understand the components of CARS and be reassured about its accuracy but were concerned about the impact on intensive care and blood tests. Conclusion Risk scores are widely used in healthcare, but their development and implementation do not usually involve input from practitioners and SU/Cs. We contributed to the development of CARS by eliciting views of staff and SU/Cs who provided important, often complex, insights to support the development and implementation of CARS to ensure successful implementation in routine clinical practice.
    • Computer-aided National Early Warning Score to predict the risk of sepsis following emergency medical admission to hospital: a model development and external validation study

      Faisal, Muhammad; Richardson, D.; Scally, Andy J.; Howes, R.; Beatson, K.; Speed, K.; Mohammad, Mohammad A. (2019-04-08)
      Background: In English hospitals, the patient’s vital signs are monitored and summarised into a National Early Warning Score (NEWS). NEWS is more accurate than the quick sepsis related organ failure assessment (qSOFA) score at identifying patients with sepsis. We investigate the extent to which the accuracy of the NEWS is enhanced by developing computer-aided NEWS (cNEWS) models. We compared three cNEWS models (M0=NEWS alone; M1=M0 + age + sex; M2=M1 + subcomponents of NEWS + diastolic blood pressure) to predict the risk of sepsis. Methods: All adult emergency medical admissions discharged over 24-months from two acute hospitals (YH–York Hospital for model development; NH–Northern Lincolnshire and Goole Hospital for external model validation). We used a validated Canadian method for defining sepsis from administrative hospital data. Findings: The prevalence of sepsis was lower in YH (4.5%=1596/35807) than NH (8.5%=2983/35161). The c-statistic increased across models (YH: M0: 0.705, M1:0.763, M2:0.777; NH:M0: 0.708, M1:0.777, M2:0.791). At NEWS 5+, sensitivity increased (YH: 47.24% vs 50.56% vs 52.69%; NH: 37.91% vs 43.35% vs 48.07%)., the positive likelihood ratio increased (YH: 2.77 vs 2.99 vs 3.06; NH: 3.18 vs 3.32 vs 3.45) and the positive predictive value increased (YH: 11.44% vs 12.24% vs 12.49%; NH: 22.75% vs 23.55% vs 24.21%). Interpretation: From the three cNEWS models, Model M2 is the most accurate. Since it places no additional data collection burden on clinicians and can be automated, it may now be carefully introduced and evaluated in hospitals with sufficient informatics infrastructure.
    • How much image noise can be added in cardiac x-ray imaging without loss in perceived image quality?

      Gislason-Lee, Amber J.; Kumcu, A.; Kengyelics, S.M.; Brettle, D.S.; Treadgold, L.A.; Sivananthan, M.; Davies, A.G. (2015-10)
      Cardiologists use x-ray image sequences of the moving heart acquired in real-time to diagnose and treat cardiac patients. The amount of radiation used is proportional to image quality; however, exposure to radiation is damaging to patients and personnel. The amount by which radiation dose can be reduced without compromising patient care was determined. For five patient image sequences, increments of computer-generated quantum noise (white + colored) were added to the images, frame by frame using pixel-to-pixel addition, to simulate corresponding increments of dose reduction. The noise adding software was calibrated for settings used in cardiac procedures, and validated using standard objective and subjective image quality measurements. The degraded images were viewed next to corresponding original (not degraded) images in a two-alternativeforced- choice staircase psychophysics experiment. Seven cardiologists and five radiographers selected their preferred image based on visualization of the coronary arteries. The point of subjective equality, i.e., level of degradation where the observer could not perceive a difference between the original and degraded images, was calculated; for all patients the median was 33% 15% dose reduction. This demonstrates that a 33% 15% increase in image noise is feasible without being perceived, indicating potential for 33% 15% dose reduction without compromising patient care.
    • Selecting stimuli parameters for video quality studies based on perceptual similarity distances

      Kumcu, A.; Platisa, L.; Chen, H.; Gislason-Lee, Amber J.; Davies, A.G.; Schelkens, P.; Taeymans, Y.; Philips, W. (2015-03)
      This work presents a methodology to optimize the selection of multiple parameter levels of an image acquisition, degradation, or post-processing process applied to stimuli intended to be used in a subjective image or video quality assessment (QA) study. It is known that processing parameters (e.g. compression bit-rate) or techni- cal quality measures (e.g. peak signal-to-noise ratio, PSNR) are often non-linearly related to human quality judgment, and the model of either relationship may not be known in advance. Using these approaches to select parameter levels may lead to an inaccurate estimate of the relationship between the parameter and subjective quality judgments – the system’s quality model. To overcome this, we propose a method for modeling the rela- tionship between parameter levels and perceived quality distances using a paired comparison parameter selection procedure in which subjects judge the perceived similarity in quality. Our goal is to enable the selection of evenly sampled parameter levels within the considered quality range for use in a subjective QA study. This approach is tested on two applications: (1) selection of compression levels for laparoscopic surgery video QA study, and (2) selection of dose levels for an interventional X-ray QA study. Subjective scores, obtained from the follow-up single stimulus QA experiments conducted with expert subjects who evaluated the selected bit-rates and dose levels, were roughly equidistant in the perceptual quality space - as intended. These results suggest that a similarity judgment task can help select parameter values corresponding to desired subjective quality levels.
    • Machine vision image quality measurement in cardiac x-ray imaging

      Kengyelics, S.M.; Gislason-Lee, Amber J.; Keeble, C.; Magee, D.; Davies, A.G. (2015-03)
      The purpose of this work is to report on a machine vision approach for the automated measurement of x-ray image contrast of coronary arteries lled with iodine contrast media during interventional cardiac procedures. A machine vision algorithm was developed that creates a binary mask of the principal vessels of the coronary artery tree by thresholding a standard deviation map of the direction image of the cardiac scene derived using a Frangi lter. Using the mask, average contrast is calculated by tting a Gaussian model to the greyscale pro le orthogonal to the vessel centre line at a number of points along the vessel. The algorithm was applied to sections of single image frames from 30 left and 30 right coronary artery image sequences from di erent patients. Manual measurements of average contrast were also performed on the same images. A Bland-Altman analysis indicates good agreement between the two methods with 95% con dence intervals -0.046 to +0.048 with a mean bias of 0.001. The machine vision algorithm has the potential of providing real-time context sensitive information so that radiographic imaging control parameters could be adjusted on the basis of clinically relevant image content.
    • Context sensitive cardiac x-ray imaging: a machine vision approach to x-ray dose control

      Kengyelics, S.M.; Gislason-Lee, Amber J.; Keeble, C.; Magee, D.R.; Davies, A.G. (2015-09)
      Modern cardiac x-ray imaging systems regulate their radiation output based on the thickness of the patient to maintain an acceptable signal at the input of the x-ray detector. This approach does not account for the context of the examination or the content of the image displayed. We have developed a machine vision algorithm that detects iodine-filled blood vessels and fits an idealized vessel model with the key parameters of contrast, diameter, and linear attenuation coefficient. The spatio-temporal distribution of the linear attenuation coefficient samples, when appropriately arranged, can be described by a simple linear relationship, despite the complexity of scene information. The algorithm was tested on static anthropomorphic chest phantom images under different radiographic factors and 60 dynamic clinical image sequences. It was found to be robust and sensitive to changes in vessel contrast resulting from variations in system parameters. The machine vision algorithm has the potential of extracting real-time context sensitive information that may be used for augmenting existing dose control strategies.
    • Methods for the analysis of ordinal response data in medical image quality assessment

      Keeble, C.; Baxter, P.D.; Gislason-Lee, Amber J.; Treadgold, L.A.; Davies, A.G. (2016-04)
      The assessment of image quality in medical imaging often requires observers to rate images for some metric or detectability task. These subjective results are used in optimization, radiation dose reduction or system comparison studies and may be compared to objective measures from a computer vision algorithm performing the same task. One popular scoring approach is to use a Likert scale, then assign consecutive numbers to the categories. The mean of these response values is then taken and used for comparison with the objective or second subjective response. Agreement is often assessed using correlation coefficients. We highlight a number of weaknesses in this common approach, including inappropriate analyses of ordinal data and the inability to properly account for correlations caused by repeated images or observers. We suggest alternative data collection and analysis techniques such as amendments to the scale and multilevel proportional odds models. We detail the suitability of each approach depending upon the data structure and demonstrate each method using a medical imaging example. Whilst others have raised some of these issues, we evaluated the entire study from data collection to analysis, suggested sources for software and further reading, and provided a checklist plus flowchart for use with any ordinal data. We hope that raised awareness of the limitations of the current approaches will encourage greater method consideration and the utilization of a more appropriate analysis. More accurate comparisons between measures in medical imaging will lead to a more robust contribution to the imaging literature and ultimately improved patient care.
    • How much image noise can be added in cardiac x-ray imaging without loss in perceived image quality?

      Gislason-Lee, Amber J.; Kumcu, A.; Kengyelics, S.M.; Rhodes, L.A.; Davies, A.G. (2015-03)
      Dynamic X-ray imaging systems are used for interventional cardiac procedures to treat coronary heart disease. X-ray settings are controlled automatically by specially-designed X-ray dose control mechanisms whose role is to ensure an adequate level of image quality is maintained with an acceptable radiation dose to the patient. Current commonplace dose control designs quantify image quality by performing a simple technical measurement directly from the image. However, the utility of cardiac X-ray images is in their interpretation by a cardiologist during an interventional procedure, rather than in a technical measurement. With the long term goal of devising a clinically-relevant image quality metric for an intelligent dose control system, we aim to investigate the relationship of image noise with clinical professionals’ perception of dynamic image sequences. Computer-generated noise was added, in incremental amounts, to angiograms of five different patients selected to represent the range of adult cardiac patient sizes. A two alternative forced choice staircase experiment was used to determine the amount of noise which can be added to a patient image sequences without changing image quality as perceived by clinical professionals. Twenty-five viewing sessions (five for each patient) were completed by thirteen observers. Results demonstrated scope to increase the noise of cardiac X-ray images by up to 21% ± 8% before it is noticeable by clinical professionals. This indicates a potential for 21% radiation dose reduction since X-ray image noise and radiation dose are directly related; this would be beneficial to both patients and personnel.
    • Technical Note: Impact on detective quantum efficiency of edge angle determination method by International Electrotechnical Commission methodology for cardiac x-ray image detectors

      Gislason-Lee, Amber J.; Tunstall, C.M.; Kengyelics, S.K.; Cowen, A.R.; Davies, A.G. (2015-08)
      Purpose: Cardiac x-ray detectors are used to acquire moving images in real-time for angiography and interventional procedures. Detective quantum efficiency (DQE) is not generally measured on these dynamic detectors; the required “for processing” image data and control of x-ray settings have not been accessible. By 2016, USA hospital physicists will have the ability to measure DQE and will likely utilize the International Electrotechnical Commission (IEC) standard for measuring DQE of dynamic x-ray imaging devices. The current IEC standard requires an image of a tilted tungsten edge test object to obtain modulation transfer function (MTF) for DQE calculation. It specifies the range of edge angles to use; however, it does not specify a preferred method to determine this angle for image analysis. The study aimed to answer the question “will my choice in method impact my results?” Four different established edge angle determination methods were compared to investigate the impact on DQE. Methods: Following the IEC standard, edge and flat field images were acquired on a cardiac flat-panel detector to calculate MTF and noise power spectrum, respectively, to determine DQE. Accuracy of the methods in determining the correct angle was ascertained using a simulated edge image with known angulations. Precision of the methods was ascertained using variability of MTF and DQE, calculated via bootstrapping. Results: Three methods provided near equal angles and the same MTF while the fourth, with an angular difference of 6%, had a MTF lower by 3% at 1.5 mm−1 spatial frequency and 8% at 2.5 mm−1; corresponding DQE differences were 6% at 1.5 mm−1 and 17% at 2.5 mm−1; differences were greater than standard deviations in the measurements. Conclusions: DQE measurements may vary by a significant amount, depending on the method used to determine the edge angle when following the IEC standard methodology for a cardiac x-ray detector. The most accurate and precise methods are recommended for absolute assessments and reproducible measurements, respectively.
    • Dose optimization in cardiac x-ray imaging

      Gislason-Lee, Amber J.; McMillan, C.; Cowen, A.R.; Davies, A.G. (2013-09)
      Purpose: The aim of this research was to optimize x-ray image quality to dose ratios in the cardiac catheterization laboratory. This study examined independently the effects of peak x-ray tube voltage (kVp), copper (Cu), and gadolinium (Gd) x-ray beam filtration on the image quality to radiation dose balance for adult patient sizes. Methods: Image sequences of polymethyl methacrylate (PMMA) phantoms representing two adult patient sizes were captured using a modern flat panel detector based x-ray imaging system. Tin and copper test details were used to simulate iodine-based contrast medium and stents/guide wires respectively, which are used in clinical procedures. Noise measurement for a flat field image and test detail contrast were used to calculate the contrast to noise ratio (CNR). Entrance surface dose (ESD) and effective dose measurements were obtained to calculate the figure of merit (FOM), CNR2/dose. This FOM determined the dose efficiency of x-ray spectra investigated. Images were captured with 0.0, 0.1, 0.25, 0.4, and 0.9 mm Cu filtration and with a range of gadolinium oxysulphide (Gd2O2S) filtration. Results: Optimum x-ray spectra were the same for the tin and copper test details. Lower peak tube voltages were generally favored. For the 20 cm phantom, using 2 Lanex Fast Back Gd2O2S screens as x-ray filtration at 65 kVp provided the highest FOM considering ESD and effective dose. Considering ESD, this FOM was only marginally larger than that from using 0.4 mm Cu at 65 kVp. For the 30 cm phantom, using 0.25 mm copper filtration at 80 kVp was most optimal; considering effective dose the FOM was highest with no filtration at 65 kVp. Conclusions: These settings, adjusted for x-ray tube loading limits and clinically acceptable image quality, should provide a useful option for optimizing patient dose to image quality in cardiac x-ray imaging. The same optimal x-ray beam spectra were found for both the tin and copper details, suggesting that iodine contrast based imaging and visualization of interventional devices could potentially be optimized for dose using similar x-ray beam spectra.