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ABSTRACT: PURPOSE/AIM: Studies have shown that commercially available adaptive non-linear post processing image filters can be used to reduce the radiation dose associated with CT. The purpose of our educational exhibit is to describe how image filters can be applied to reduce radiation dose in day to day clinical practice. Technical aspects of installing adaptive filters, workflow concern, network performance issues, and limitations of these filters will be described.
CONTENT ORGANIZATION:
1. Overview of image post processing 2D adaptive filters
2. How to install the 2D adaptive filters?
3. Where to install the image filters in CT image workflow?
4. Technical concerns with the CT image workflow and workload.
5. How to select appropriate filter settings?
6. Limitations of adaptive image filters
SUMMARY
Image post processing filters have become available for improving the image quality of CT scanning performed at lower radiation dose. This education exhibit highlights specific aspects of these adaptive filters with practical and easy to use methods of reducing radiation dose.
RSNA 09, Chicago; 11/2009
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ABSTRACT: PURPOSE: Although image filters have been shown to reduce noise, they also decreased lesion conspicuity and image contrast. The purpose of our double-blinded study was to evaluate the effect of a new adaptive non-linear image post-processing filter on image quality of abdominal CT acquired at low radiation dose.
METHOD AND MATERIALS: 31 subjects (mean age=72, M:F 15:16 ) underwent abdominal CT on a four-row MDCT. After standard of care CT, two series of images were acquired immediately at an identical z-position with standard (160-220mAs) and with 50% reduced (80-110mAs) radiation dose, with remaining parameters held constant. DICOM images were exported to adaptive filter software (SharpView CT) for improving quality of low dose CT images with applications of two levels of noise reduction. Resulting two sets of post processed images were randomized with original standard and reduced dose images (n=124 image series) and presented to two radiologists for independent assessment of image noise, contrast, conspicuity of small soft tissue structures less than 5 mm in size, diagnostic acceptability and presence of artifacts on a five point scale (1=excellent; 5=unacceptable). ROIs were drawn in liver to measure CT numbers and quantitative image noise. Statistical analysis was performed with Wilcoxon signed rank test.
RESULTS: There was a strong interobserver agreement between the two radiologists (kappa=.8; p<.01). Post processed low dose images had significantly lower image noise and superior visibility of small structures greater (p<.001). Of the 24 CT examinations graded as unacceptable or with suboptimal noise on low dose CT images, adaptive filtration resulted in acceptable noise in 21 CT, with no significant change in image contrast or image artifacts (p>.5). There was no significant change in HU numbers with the use of adaptive filters (p>.8), but mean quantitative image noise improved from 21.5 for low dose CT to 17.1 and 14.9 respectively, with adaptive filtering at two strengths (p=.02- .006).
CONCLUSION: Contrary to previously reported studies of prior versions, new adaptive non-linear filters can help reduce abdominal CT radiation dose by up to 50% without compromising image contrast or conspicuity of small structures.
CLINICAL RELEVANCE/APPLICATION: Radiation dose reduction by as much as 50% is possible for abdominal CT examinations with application of adaptive non-linear filters to low radiation dose DICOM image datasets.
ARRS 09, Boston; 04/2009
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ABSTRACT: PURPOSE
Raw data based noise projection techniques have been reported for creating low radiation dose CT images. The purpose of our study was to assess if DICOM image based noise projection software can help to generate simulated low radiation dose from higher radiation dose CT images.
METHOD AND MATERIALS
An anthropomorphic chest phantom measuring 30x20x15 cm was scanned on a 16-slice multidetector-row CT using automatic exposure control (auto mA, GE Healthcare) with different noise indices (5, 10, 15, 20, 25, 30, 35) and slice thicknesses (1.25, 2.5 and 5 mm) to obtain original images at different radiation doses. A new DICOM image based noise projection software (GE Healthcare) was used to obtain simulated low radiation dose images (with 10-95% dose reduction compared to routinely used radiation dose) from higher dose CT images. The original (n= 21 series) and simulated low dose (n= 54 image series) images were de-identified and randomized. Five radiologists unaware of image types performed a pair wise comparison on a standard PACS workstation for image noise and beam hardening artifacts. Objective image noise and CT numbers were recorded using spherical region of interests. Data were analyzed using linear and logistic regression tests.
RESULTS
There was strong correlation for quantitative image noise (0.97-0.98, p<0.0001) between original and simulated low dose images. None of the radiologists could differentiate image noise or beam hardening artifacts between original low radiation dose and corresponding simulated low dose images. Simulated low dose images were rated as having either identical (75-90%) or slightly lower noise (10-25%) compared to the corresponding original low dose images (p<0.01).
CONCLUSION
DICOM based noise projection offers a quick, reliable and alternative way to raw data based noise projection to obtain simulated low dose CT images for research and teaching purposes.
CLINICAL RELEVANCE/APPLICATION
DICOM based noise projection offers a quick, reliable and alternative way to raw data based noise projection to obtain simulated low dose CT images for research and teaching purposes.
QUESTIONS ABOUT THIS EVENT EMAIL:
ssingh6@partners.org
RSNA 08, chicago; 12/2008
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[show abstract]
[hide abstract]
ABSTRACT: PURPOSE/AIM
Studies have shown that commercially available adaptive non-linear post processing image filters can be used to reduce the radiation dose associated with CT. The purpose of our educational exhibit is to describe the technical aspects of adaptive filters, along with their practical applications, radiation dose reduction potential, and limitations.
CONTENT ORGANIZATION
Overview of image post processing techniques for CT radiation dose reduction
Rationale for use of image filters for CT dose reduction
Technical aspects of adaptive non-linear filters for noise reduction
Practical applications of adaptive filters in different body regions and patients of different sizes with illustrations and examples from phantom and patient studies: How much dose reduction is possible?
Limitations of adaptive image filters
Integration of adaptive filters in CT workflow.
SUMMARY
Image post processing filters have become available for improving the image quality of CT scanning performed at lower radiation dose. This education exhibit highlights specific aspects of these adaptive filters with practical and easy to use methods of reducing radiation dose. Appropriate examples from patient and phantom studies are used to illustrate how much dose reduction is possible with adaptive filters and to highlight their main limitations regarding CT radiation dose reduction.
QUESTIONS ABOUT THIS EVENT EMAIL:
ssingh6@partners.org
RSNA 08, chicago; 12/2008
