Browsing by Subject "image quality"

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    Evaluation of a Hybrid Iterative Reconstruction technique "iDose" for CT Dose Reduction and Image Quality
    (Office of the Vice Chancellor for Research, 2014-04-11) Liang, Yun
    Purpose: To investigate the use of a commercial designed hybrid iterative reconstruction technique iDose (by Philips Medical Systems) for CT radiation dose reduction and its effect on image quality. Methods: A catphan®504 phantom was scanned using a 64-slice CT (Ingenuity, Philips Medical Systems) with two different tube voltages (100 kVp, and 120 kVp) at three different doses, a reference dose (CTDIvol) of 42 mGy and two reduced doses of about 50% and 75% of the reference. Images were reconstructed with standard filtered-back-projection (FBP) and with iDose algorithms. Six different iDose levels were employed. Quantitative evaluation of spatial resolution, image noise, noise power spectrum (NPS), and low-contrast detectability were carried out. Results: For any given dose level, there was a static noise reduction with increased iDose level over the FBP. To match the “standard” noise resulted from the FBP at the “reference dose”, a minimum iDose level of 4 and 6 was required for 50% and 75% dose reduction respectively. NPS showed moderate shift towards the lower frequency as the iDose level increased. The NPS shift was consistent with the observed subtle change of noise texture. This shift also correlated with the change in low-contrast detectability among images with the same noise level, the higher the iDose level that was used in image reconstruction, the lower the low-contrast detectability. Conclusions: The iDose algorithm clearly demonstrates effectiveness in noise suppression over the FBP. The low-contrast detectability depends on noise but also on NPS, which is shifted by iDose algorithm. At very low-dose levels, greater iDose levels would be needed to reduce the image noise but may not improve the low-contrast detectability. This findings indicate that for any given specific clinical task, the lowest dose limit achievable is determined by an “optimal” iDose level ascertaining the noise reduction as well as maintaining desired low-contrast detectability.
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    Image Quality: It Really Does Matter
    (2013-11) Edwards, Paul C.
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    Use of a Knowledge-based Iterative Reconstruction Technique, IMR, to Improve Image Quality and Lower Radiation Dose
    (Anderson, 2019) Hameed, Tariq A.; Radiology and Imaging Sciences, School of Medicine
    Use of IMR in Clinical Practice IMR is used in a variety of ways in our practice. Since our department has already reduced radiation dose as part of standard practice, we use IMR to improve the image quality at a given radiation dose. [...]we use IMR for CT angiography (CTA) examinations that require high contrast and high spatial resolution; in these cases, IMR is useful to reduce section thickness and lower noise (Case 5). Because IMR images are virtually noise free, they appear different from iDose4 images. [...]in the initial stages, reviewing images side-by-side with both reconstruction techniques may help to achieve familiarity with the new technique. The dissection flap (red arrow) is also more sharply delineated from the surrounding true and false lumen on the IMR image (C). [...]using the same CT examination, but 2 different processing techniques, it is apparent that with IMR, there is better contrast resolution between the lesion and the surrounding parenchyma, improving the sensitivity for lesion detection and providing better visualization of the abnormality, compared to iDose4.