Browsing by Author "Warmerdam, N. C."
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- Optimisation of chest computed tomography using a phantom: impact of mAs and reconstruction techniques on image qualityPublication . Reis, Cláudia; Faquir, T.; Harsaker, V.; Hogg, Peter; Kristoffersen, L.; van Rein, I. L.; Stancombe, K.; Warmerdam, N. C.; Wergeland, C.Purpose: To verify if the mAs and reconstruction techniques affect the visualization of relevant structures in lung Computed Tomography (CT) using a phantom. Methods and Materials: Images were acquired using varying mAs and reconstruction techniques. Image quality (IQ) was analyzed applying two approaches: perceptual, using 5 observers and objective (edge gradient calculation) to verify the sharpness of the structures. Dose was recorded. Wilcoxon Signed Rank test was used to compare the data from the perceptual image analysis. P-values were calculated (Bonferroni-Correction method) to compare reconstruction techniques and mAs. A Kappa Test with linear weighting was performed to calculate the level of agreement between observers.
- Optimisation of chest computed tomography using a phantom: impact of mAs and reconstruction techniques on image qualityPublication . Reis, Cláudia; Faqir, T.; Harsaker, V.; Hogg, Peter; Kristoffersen, L.; van Rein, I. L.; Stancombe, K.; Warmerdam, N. C.; Wergeland, C.Objectives: To verify if the mAs and reconstruction techniques affect the visualisation of relevant structures in lung Computed Tomography (CT) using a phantom. Methods: Images were acquired using various mAs and reconstruction techniques. Image quality (IQ) was analysed applying two approaches: perceptual, using 5 observers and objective (edge gradient calculation) to verify the sharpness of the structures. Dose was recorded. Wilcoxon Signed Rank test was used to compare the data from the perceptual image analysis. P-values were calculated (Bonferroni-Correction method) to compare reconstruction techniques and mAs. A Kappa Test with linear weighting was performed to calculate the level of agreement between observers. Results: The Wilcoxon-Signed-Rank-Test showed no significant difference between the reconstruction techniques tested (p<0.05). In addition, the test showed no significant difference between any of the mAs values with a Bonferroni correction (p = 0.0167). For 10 mAs the observers scored differently, depending on which structures they were looking at. The overall IQ was acceptable and the nodules were well defined. The agreement for visualising the range of anatomical regions (Kappa test linear-weighting) suggests that observer 2 and 3 had a poor agreement level (0-0.366) and observer 1,4 and 5 had moderate agreement (0.5714-0.751). Conclusion: The visual measures of IQ were largely unaffected by reconstruction techniques or mAs values. However, further work is needed for a better understanding of visual and clinical value of reconstruction techniques at lower doses.
- Ultrasound assessment of muscle thickness and muscle crosssectional area: a reliability studyPublication . Nijholt, W.; Aandahl, Ingrid J.; Adajar, G.; Borgen, M. H.; Carreiras, I.; Rab, A.; Totland, H.; Warmerdam, N. C.; van der Wal, S. C. M.; Crofts, G.Purpose: Previous studies showed that ultrasound imaging is reliable when measuring the cross-sectional area (CSA) of a muscle. However, measurements of muscles could be affected by the level of experience of the observer. The aim of this pilot study was to investigate the reliability of observers when measuring the CSA and thickness of the rectus femoris (RF). Methods and Materials: Seven observers assessed eight different images of RF. On each image, the CSA and thickness were measured three times using ImageJ. The measurements were analyzed using IBM SPSS. Intraclass Correlation Coefficient (ICC) and Bland-Altman plots were used to analyze reliability. A Paired Sample T-Test was used to investigate any differences between the first and mean measurement recorded by the observers. Results: No significant differences were found between the first and mean of the repeated measures for CSA and thickness respectively (p = 0.217-0.817, p = 0.337-0.897). Intra-observer reliability shows excellent agreement between measurement one and the mean for each observer (CSA ICC = 0.987-1.000, thickness ICC = 0.996-1.000). High inter-observer reliability was found for both CSA (ICC = 0.938, 95% CI = 0.845-0.985) and thickness (ICC = 0.9774, 95% CI = 0.934-0.994). Agreement between an experienced and inexperienced observer was excellent (ICC = 0.991, 95% CI = 0.959-0.998). Conclusion: This pilot study shows that there is a high level of inter- and intraobserver reliability among the observers in measuring the CSA and thickness of the RF. It also shows that experience in ultrasound measurements is not a factor in reliability.