Low-Dose CT Examinations in Crohn's Disease: Impact on Image Quality, Diagnostic Performance, and Radiation Dose
Department of Radiology, Massachusetts General Hospital, Boston, 02114, USA. American Journal of Roentgenology
(Impact Factor: 2.73).
07/2010; 195(1):78-88. DOI: 10.2214/AJR.09.3420
The objective of this study was to evaluate the image quality and diagnostic performance of simulated low-dose MDCT examinations in patients with Crohn's disease.
Thirty-five MDCT examinations from 25 patients (14 males and 11 females; age range, 16-86 years) with known or suspected Crohn's disease were retrospectively evaluated. The MDCT images (5 mm thickness) were modified by artificially introducing noise using volume CT noise simulation software to simulate low-dose MDCT data acquired with noise indexes (NIs) of 18-35. The 175 MDCT image data sets generated were then randomized and reviewed by two readers to assess the subjective image quality and diagnostic accuracy for confidently detecting Crohn's disease findings on a 5-point scale (1, definitely absent; 5, definitely present). The image quality, diagnostic performance, and radiation dose from the original MDCT examinations served as a reference standard for comparison.
The simulated low-dose CT images with elevated NIs of 18-25 yielded optimal image quality and concordant diagnostic accuracy with standard-dose scans with a mean baseline volume CT dose index of 16 +/- 3.34 (SD) mGy (image quality score, 4-4.9 vs 4.95, respectively; p = 0.4). Images simulating NIs of 30-35 were considered degraded because of excessive image noise and presented lower diagnostic performance (range of image quality score, 3-3.6; weighted kappa = 0.25-0.37; p < 0.001). Diagnostic performance and reader confidence for the determination of Crohn's disease manifestations in cases in which the reference standard was positive were higher at NIs of < or = 25 compared with NI of 30 (reader confidence score, 4.5 vs 3.6, respectively; p < 0.05) and an NI of 35 (3.2, p < 0.05). Compared with the standard-dose examination, a 31-64% reduction in radiation dose was estimated for NI levels of 18-25, which corresponds to image noise of 19-27 HU in subcutaneous fat.
Processed MDCT images with the introduction of noise to simulate low-dose MDCT examinations with NI levels of 18-25 allows substantial dose reduction for CT examinations in Crohn's disease without compromising diagnostic information.
Available from: Patrick D Mc Laughlin
- "Emerging iterative reconstruction algorithms are typically noise efficient and computationally fast, and studies to date have mostly found images with good low-contrast detail, preserved image quality, and have facilitated dose reductions of between 20 and 60% in a variety of phantom      and in vivo adult     studies . Iterative reconstruction will be particularly useful in low-dose CT of the urinary tract where image noise is typically high. "
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ABSTRACT: Objective. To critically evaluate the current literature in an effort to establish the current role of radiologic imaging, advances in computed tomography (CT) and standard film radiography in the diagnosis, and characterization of urinary tract calculi. Conclusion. CT has a valuable role when utilized prudently during surveillance of patients following endourological therapy. In this paper, we outline the basic principles relating to the effects of exposure to ionizing radiation as a result of CT scanning. We discuss the current developments in low-dose CT technology, which have resulted in significant reductions in CT radiation doses (to approximately one-third of what they were a decade ago) while preserving image quality. Finally, we will discuss an important recent development now commercially available on the latest generation of CT scanners, namely, dual energy imaging, which is showing promise in urinary tract imaging as a means of characterizing the composition of urinary tract calculi.
Advances in Urology 08/2012; 2012:606754. DOI:10.1155/2012/606754
Available from: Fergus Shanahan
- "In patients with IBD where CT findings are most commonly limited to the small and large bowel, a larger amount of image noise has been found to be diagnostically acceptable. In a single series, elevating the noise index to 18–25 yielded a 31–64% reduction in radiation dose while preserving diagnostic accuracy . "
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ABSTRACT: Patient awareness and concern regarding the potential health risks from ionizing radiation have peaked recently (Coakley et al., 2011) following widespread press and media coverage of the projected cancer risks from the increasing use of computed tomography (CT) (Berrington et al., 2007). The typical young and educated patient with inflammatory bowel disease (IBD) may in particular be conscious of his/her exposure to ionising radiation as a result of diagnostic imaging. Cumulative effective doses (CEDs) in patients with IBD have been reported as being high and are rising, primarily due to the more widespread and repeated use of CT (Desmond et al., 2008). Radiologists, technologists, and referring physicians have a responsibility to firstly counsel their patients accurately regarding the actual risks of ionizing radiation exposure; secondly to limit the use of those imaging modalities which involve ionising radiation to clinical situations where they are likely to change management; thirdly to ensure that a diagnostic quality imaging examination is acquired with lowest possible radiation exposure. In this paper, we synopsize available evidence related to radiation exposure and risk and we report advances in low-dose CT technology and examine the role for alternative imaging modalities such as ultrasonography or magnetic resonance imaging which avoid radiation exposure.
04/2012; 2012:790279. DOI:10.5402/2012/790279
Available from: ajronline.org
American Journal of Roentgenology 02/2002; 178(1):87-91. DOI:10.2214/ajr.178.1.1780087 · 2.73 Impact Factor
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