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- Noise Reduction Techniques for CT
- ASIR (GE healthcare)
- SAFIRE (Siemens)
- IRIS (Siemens)
- AIDR (Toshiba)
- iDose (Phillips Healthcare) - “ The purpose of applying noise reduction methods is to make low-dose images appear similar to higher dose images in terms of image noise levels. This provides an opportunity to significantly reduce CT radiation dose while maintaining image quality.”
Reducing Radiation Dose in CT Enterography
Del Gaizo AJ et al
RadioGraphics 2013; 33:1109-1124
- “ The use of adaptive iterative dose reduction using 3D processing resulted in greater consistency of emphysema quantification by low-dose CT, with quantification by standard dose CT.”
Emphysema Quantification by Low-Dose CT: Potential Impact of Adaptive Iterative Dose Reduction Using 3D Processing
Nishio M et al.
AJR 2012; 199:595-601 - “ The alliance looks forward to its next 5 years of collaboration with parents, the manufacturing community, government agencies, other regulatory and advisory organizations, and allied health groups to achieve the goals critical to better care for children.”
Image Gently 5 Years Later: What Goals Remain to Be Accomplished in Radiation Protection for Children
Gosse MJ et al
AJR 199; 477-478, 2012
Joint Commission Alert August 2011
- “ The prototype iterative reconstruction algorithm studied significantly reduces image noise and improves qualitative and quantitative measures of image quality in low-dose pediatric CT datasets, compared with standard wFBP.”
Assessment of an iterative reconstruction algorithm (SAFIRE) on image quality in pediatric cardiac CT datasets
Han BK et al.
J Cardiovasc Comput Tomogr (2012) 6, 200-204 - “There was a 34% decrease in noise, a 41% increase in contrast to noise ratio, and a 56% increase in signal to noise ratio in the prototype iterative reconstruction, compared with wFBP.”
Assessment of an iterative reconstruction algorithm (SAFIRE) on image quality in pediatric cardiac CT datasets
Han BK et al.
J Cardiovasc Comput Tomogr (2012) 6, 200-204
- “ We conclude that iDose is an important tool in the reduction of radiation dose in CT. However, continuous efforts to reduce radiation dose should be pursued.”
Initial Performance Characterization of a Clinical Noise Suppressing Reconstruction Algorithm for MDCT
Noel PB et al.
AJR 2011; 197:1404-1409 - “ iDose is a hybrid iterative reconstruction algorithm that provides reduced image noise compared with the conventional filtered back projection.”
Initial Performance Characterization of a Clinical Noise Suppressing Reconstruction Algorithm for MDCT
Noel PB et al.
AJR 2011; 197:1404-1409 - “ The HU values remain stable while employing iDose. With iDose, the noise is significantly reduced. This is reflected by an improvement in the contrast to noise ration and in the noise power spectrum compared with standard reconstruction. The measurements of the modulation transfer function confirm that, with iDose, there is no decline in spatial resolution.”
Initial Performance Characterization of a Clinical Noise Suppressing Reconstruction Algorithm for MDCT
Noel PB et al.
AJR 2011; 197:1404-1409
- SAFIRE
- Sinogram Affirmed Iterative Reconstruction
- Iterative reconstruction that is specific to the Siemens scanner - SAFIRE
- Creates 5 different images with varying noise levels and you select the best one (1 has most noise and 5 has least noise)
- Allows for dose reduction by improving image quality by decreasing noise
- Better than previous techniques in imaging and better than FBP or IRIS
- Dose reduction in the 60% range (FDA Approved) - Image Reconstruction: FBP vs IR
- FBP is classic reconstruction technique for CT (filtered back projection)
- Statistical iterative reconstruction technique (IR) works by focusing on image noise and attempting to decrease it
- New IR techniques include MBIR and SAFIRE
- Bottom line: may decrease dose 60-90% while maintaining image quality
- “ Use of hybrid iterative reconstruction technique, such as ASIR, enables substantial radiation dose reduction for pediatric CT when compared with FBP and maintains image quality and diagnostic confidence.”
Radiation Dose Reduction with Hybrid Iterative Reconstruction for Pediatric CT
Singh S et al.
Radiology 2012; 263:537-546 - “ Adaptive statistical iterative reconstruction (ASIR) enables 46.4% (3.7 vs 6.9 mGy) and 38.2% (5.0 vs 8.1 mGy) radiation dose reduction for pediatric chest and abdomen CT, respectively, when compared with filtered back projection (FBP).”
Radiation Dose Reduction with Hybrid Iterative Reconstruction for Pediatric CT
Singh S et al.
Radiology 2012; 263:537-546 - “ Radiation dose used with ASIR was lower than that used with FBP; however, subjective image quality with ASIR was equal to or better than that with FBP.”
Radiation Dose Reduction with Hybrid Iterative Reconstruction for Pediatric CT
Singh S et al.
Radiology 2012; 263:537-546 - “ In conclusion, ASIR-enabled and indication-based protocols reduce image noise in lower radiation dose pediatric chest and abdomen CT examinations compared with FBP.”
Radiation Dose Reduction with Hybrid Iterative Reconstruction for Pediatric CT
Singh S et al.
Radiology 2012; 263:537-546
- “These somewhat contradictory findings indicate that the diagnostic efficacy and accuracy of
CTE for evaluating inflammatory activity of the bowel in Crohn disease may not directly
correlate with image quality. That is, although there is likely a point at which the deterioration in
image quality would have a negative effect on diagnostic efficacy and accuracy, some decrease
in image quality may not affect the ability to diagnose the bowel abnormalities.”
A Prospective Comparison of Standard-Dose CT Enterography and 50% Reduced-Dose CT
Enterography With and Without Noise Reduction for Evaluating Crohn Disease
Lee SJ et al.
AJR 2011; 197:50-57 - “ Contrary to these results, the subjective image quality of both low-dose FBP and low dose
IRIS CTE was significantly lower than that of standard dose CTE.”
A Prospective Comparison of Standard-Dose CT Enterography and 50% Reduced-Dose CT
Enterography With and Without Noise Reduction for Evaluating Crohn Disease
Lee SJ et al.
AJR 2011; 197:50-57 - “ Contrary to these results, the subjective image quality of both low-dose FBP and low dose
IRIS CTE was significantly lower than that of standard dose CTE. These somewhat
contradictory findings indicate that the diagnostic efficacy and accuracy of CTE for evaluating
inflammatory activity of the bowel in Crohn disease may not directly correlate with image
quality.”
A Prospective Comparison of Standard-Dose CT Enterography and 50% Reduced-Dose CT
Enterography With and Without Noise Reduction for Evaluating Crohn Disease
Lee SJ et al.
AJR 2011; 197:50-57 - “ Low-dose CT Enterography using 50% reduced dose performed similarly to standard-dose
CTE in identifying findings of enteric inflammation of Crohn disease.”
A Prospective Comparison of Standard-Dose CT Enterography and 50% Reduced-Dose CT
Enterography With and Without Noise Reduction for Evaluating Crohn Disease
Lee SJ et al.
AJR 2011; 197:50-57 - “ Low-dose CT Enterography using 50% reduced dose performed similarly to standard-dose
CTE in identifying findings of enteric inflammation of Crohn disease. Although a noise
reduction method markedly reduced image noise in half-dose examinations, its effect on image
quality was not as great and was reader dependent.”
A Prospective Comparison of Standard-Dose CT Enterography and 50% Reduced-Dose CT
Enterography With and Without Noise Reduction for Evaluating Crohn Disease
Lee SJ et al.
AJR 2011; 197:50-57 - “ It remains to be determined whether noise reduction techniques will allow significant radiation dose reduction while preserving diagnostic accuracy in clinical practice.”
Body CT: Technical Advances for Improving Safety
Marin D et al.
AJR 2011; 197:33-41 - Noise Reduction Techniques and Iterative Algorithms
- Noise reduction techniques from the image data alone (IRIS, Siemens Healthcare)
- Noise reduction techniques performed from both the projection and image data (ASIR, GE Healthcare; Safire, Siemens Healthcare; iDose, Philips Healthcare)
- Iterative reduction techniques performed from projection data alone (MBIR or Veo, GE Healthcare) - “ CT radiation dose reduction to 3.5 mGy is achievable for ASIR-enabled chest CT while maintaining acceptable image noise and diagnostic confidence.”
Adaptive Statistical Iterative Reconstruction Technique for Radiation Dose Reduction in Chest CT: A Pilot Study
Singh S et al.
Radiology 2011; 259:565-573 - “ Acceptable image quality can be obtained for chest CT images acquired at 40 mAs by using ASIR wihout any substantial artifacts affecting diagnostic confidence.”
Adaptive Statistical Iterative Reconstruction Technique for Radiation Dose Reduction in Chest CT: A Pilot Study
Singh S et al.
Radiology 2011; 259:565-573 "After adjustment for scan settings, ASIR was associated with a 27% reduction in radiation dose compared to to FBP (95% CI,21-32%). Despite the reduced current ASIR was not associated with a difference in adjusted signal, noise, or signal-to-noise ratio. No differences existed between FBP and ASIR for interpretability per coronary artery or per patient."
Estimated Radiation Dose Reduction Using Adaptive Statistical Iterative Reconstruction in Coronary CT Angiography: The ERASIR Study
Leipsic J et al.
AJR 2010;195: 655-660"ASIR enabled reduced tube current and lower radiation dose in comparison with FBP, with preserved signal, noise, and study interpretability, in a large multicenter cohort. ASIR represents a new technique to reduce radiation dose in coronary CT studies."
Estimated Radiation Dose Reduction Using Adaptive Statistical Iterative Reconstruction in Coronary CT Angiography: The ERASIR Study
Leipsic J et al.
AJR 2010;195: 655-660"ASIR lowers noise and improves diagnostic conspicuity of subtle abdominal lesions at 8.4 mGy when images are reconstructed with 30% ASIR blending and 4.2 mGy in patients weighing 90 kg or less when images are reconstructed with 50% or 70% ASIR blending." "Although quantitative image noise did increase with both FBP and ASIR with a decrease in dose and an increase in patient size, quantitative image noise with ASIR remained remained lower than with FBP for all dose levels in all patients, regardless of their weight or transverse diameter."
Abdominal CT: Comparison of Adaptive Statistical Iterative and Filtered Back Projection Reconstruction Techniques
Singh A et al.
Radiology 2010;257:373-383- ASIR: What is it and why is it important?
- Although ASIR techniques have been used since the dawn of CT, filtered back projection techniques became more popular due to their faster image reconstruction times and ease of implementation.
- Interactive reconstruction techniques produce higher resolution images with less issues with artifacts at the cost of longer reconstruction times and usually more expensive comouter hardware
- ASIR uses a forward reconstruction model and a more precise modeling of scanner geometry and the underlying physics.
- Potential for quality CT scans with less artifact especially at lower radiation doses
- Potential for substantial radiation dose reduction in all patients but especially in smaller patients including pediatric patients "After adjustment for scan settings, ASIR was associated with a 27% reduction in radiation dose compared to to FBP (95% CI,21-32%). Despite the reduced current ASIR was not associated with a difference in adjusted signal, noise, or signal-to-noise ratio. No differences existed between FBP and ASIR for interpretability per coronary artery or per patient.” “ASIR enabled reduced tube current and lower radiation dose in comparison with FBP, with preserved signal, noise, and study interpretability, in a large multicenter cohort. ASIR represents a new technique to reduce radiation dose in coronary CT studies."
Estimated Radiation Dose Reduction Using Adaptive Statistical Iterative Reconstruction in Coronary CT Angiography: The ERASIR Study
Leipsic J et al.
AJR 2010;195: 655-660"ASIR lowers noise and improves diagnostic conspicuity of subtle abdominal lesions at 8.4 mGy when images are reconstructed with 30% ASIR blending and 4.2 mGy in patients weighing 90 kg or less when images are reconstructed with 50% or 70% ASIR blending." "Although quantitative image noise did increase with both FBP and ASIR with a decrease in dose and an increase in patient size, quantitative image noise with ASIR remained remained lower than with FBP for all dose levels in all patients, regardless of their weight or transverse diameter."
Abdominal CT: Comparison of Adaptive Statistical Iterative and Filtered Back Projection Reconstruction Techniques
Singh A et al.
Radiology 2010;257:373-383- ASIR: What is it and why is it important?
- Although ASIR techniques have been used since the dawn of CT, filtered back projection techniques became more popular due to their faster image reconstruction times and ease of implementation.
- Interative reconstruction techniques produce higher resolution images with less issues with artifacts at the cost of longer reconstruction times and usually more expensive comouter hardware
- ASIR uses a forward reconstruction model and a more precise modeling of scanner geometry and the underlying physics.
- Potential for quality CT scans with less artifact especially at lower radiation doses
- Potential for substantial radiation dose reduction in all patients but especially in smaller patients including pediatric patients