ABSTRACT
OBJECTIVE: The purpose of this study was to assess the potential for iterative reconstruction algorithms to be used to reduce patient radiation dose for computed tomography pulmonary angiography examinations while maintaining diagnostic image quality. MATERIALS AND METHODS: This two-stage study first considered current computed tomography pulmonary angiography image quality through an audit of current practice. Secondly, an experimental design was adopted using an anthropomorphic phantom with the addition of contrast-enhanced tubes to mimic pulmonary arteries. The radiation dose was reduced by incrementally reducing the milliampere seconds value from the standard institutional protocol, and subjective and objective (contrast-to-noise ratio [CNR] and signal-to-noise ratio [SNR]) quality measures were recorded for each exposure and reconstruction. RESULTS: A sample of 10 patients met the inclusion criteria for the audit, and a mean CNR of 44.2 and an SNR of 47.9 were established as baseline quality. A clear positive correlation was identified between the number of iterations and objective quality measures (CNR [r = 0.78, P < .001] and SNR [r = 0.78, P < .001]). No relationship was identified between the subjective measures and either radiation exposure (milliampere seconds) or the number of iterations. Findings suggest that a potential reduction in effective dose of 1.46 mSv (57.0%) is possible with no associated loss of image quality with the use of iterative reconstruction. CONCLUSION: Findings suggest that the potential dose reduction may be as great as 57%; however, further work is required to confirm this in a patient population.
ABSTRACT
Nonresponse bias in survey research can result in misleading or inaccurate findings and assessment of nonresponse bias is advocated to determine response sample representativeness. Four methods of assessing nonresponse bias (analysis of known characteristics of a population, subsampling of nonresponders, wave analysis, and linear extrapolation) were applied to the results of a postal survey of U.K. hospital organizations. The purpose was to establish whether validated methods for assessing nonresponse bias at the individual level can be successfully applied to an organizational level survey. The aim of the initial survey was to investigate trends in the implementation of radiographer abnormality detection schemes, and a response rate of 63.7% (325/510) was achieved. This study identified conflicting trends in the outcomes of analysis of nonresponse bias between the different methods applied and we were unable to validate the continuum of resistance theory as applied to organizational survey data. Further work is required to ensure established nonresponse bias analysis approaches can be successfully applied to organizational survey data. Until then, it is suggested that a combination of methods should be used to enhance the rigor of survey analysis.
