model based iterative reconstruction, asir, and fbp … adaptive... · asir, and fbp in the same...
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![Page 1: Model Based Iterative Reconstruction, ASIR, and FBP … Adaptive... · ASIR, and FBP in the Same Patient: Impact on Image Noise and Image Quality William P. Shuman MD, FACR University](https://reader031.vdocuments.mx/reader031/viewer/2022020205/5bbe805509d3f2911c8c9a02/html5/thumbnails/1.jpg)
Model Based Iterative Reconstruction, ASIR, and FBP in the Same Patient:
Impact on Image Noise and Image Quality
William P. Shuman MD, FACRUniversity of Washington
SCBTMR Annual Course Washington DC, Oct. 23-26, 2011
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Conflict of Interest Statement
• I administer a grant from GE Healthcare which supports clinical investigations in body CT
• No support for equipment or salaries
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Generations of CT Reconstruction
Filtered back Projection (FBP)– Assumes “perfect” model
1st Generation
Image Filters & Kernels– Image space approach– Filter noise, Application specific
2nd Generation
Statistical Iterative Reconstruction– Raw Date Recon Approach– Models noise (Photon & Electronic)
3rd Generation
4th GenerationFull Iterative Recon - Model Based– Models CT system geometry – Reconstruct more accurate imagesIQ
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510(k) pending at FDA. Not available for sale in the U.S.
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“Idealized” Optics to Real Optics
Filtered Back-Projection
pencil beam
point source
Assumes perfect noise sample
point detector
real source
Real measurementnoise
real detector
Model-Based Iterative Reconstruction
point voxel real 3D voxel
510(k) pending at FDA. Not available for sale in the U.S.
fan beam
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Optimize algorithm to run faster on multi-core
processorsMaximize performance
density: more computing powerBlade Center
High-performanceProcessor Technology
Enterprise class blade center with efficient architecture
Proprietary optical modeling algorithm
MBIR Reconstruction
510(k) pending at FDA. Not available for sale in the U.S.
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Raw data
SYSTEM NOISE STATISTICS
REAL 3D SYSTEM OPTICS
noise vs. detail low dose, detail lower dose and better detail
SYSTEM NOISE
STATISTICS
Statistical Model-based
Rapid Rapid 30+ mins
510(k) pending at FDA. Not available for sale in the U.S.
Evolution of Image Reconstruction
FBPDirect Reconstruction
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FBP ASIR MBIR
120 kVp, variable mAs (NI=36), 1.375 pitch. 0.625/0.8 mm slice: Width = 400, Level = 40 HU, BMI=33Kinahan et al
Soft Tissue ConspicuityIncreased noise Increased conspicuity
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Three-phase liver
FBP
MBIR
Arterial Venous 5 min delay
120 kVp, variable mAs (NI=36), 1.375 pitch. 0.8 mm slice: Width = 400, Level = 40 HU, BMI=25
Kinahan et al
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Liver: FBP vs ASIR vs MBIR
• 36 cirrhosis patients with known liver lesions• Scanned with low-dose ATCM (NI = 36)
• Clinically optimized for 40% ASIR• kVp 120, BMI up to 35
• Raw data from late-arterial phase reconstructed with FBP, 40% ASIR, MBIR
• Images shown to 2 independent readers• Identify lesions• Characterize as hyperdense, hypodense, mixed• Score lesion conspicuity
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Liver: FBP vs ASIR vs MBIR
• Lesion, liver HU density measured
• Noise measured in liver, air, fat, aorta
• Three separate “Truth Readers”• Unblinded – looked at all reconstructions, EMR,
comparison studies• Established lesion number, character, location
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MBIR ASIR FBP
Arterial
Delayed
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MBIR ASIR FBP
Arterial
Delayed
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Liver: FBP vs ASIR vs MBIR
• Preliminary Results:
• Apparent equal lesion detection among the reconstruction types (51 lesions)
• Apparent equal lesion characterization among the reconstruction types
• Subjective lesion conspicuity appears slightly better on MBIR
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Liver: FBP vs ASIR vs MBIR
• Preliminary Results:
• Background noise in air for MBIR was one quarter that of ASIR and one fifth of FBP
• Contrast-to-noise ration for MBIR was five times greater than ASIR and six times greater than FBP
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Conclusion :
• When CT scanning factors are optimized for 40% ASIR:• Recon of the same raw data set with MBIR,
ASIR and FBP results in subjectively comparable liver lesion detectability, lesion characterization, and lesion conspicuity
• Measured image noise is dramatically lower with MBIR and measured lesion CNR is much greater
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Conclusion :
• Suggests that when CT scanning factors are optimized for MBIR, patient radiation dose can be much lower (~ 80 to 90% lower)
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MBIR FBPASIR
100 kVp, 25-38 mA, 0.4 sec
Images courtesy of Pr Maher, Cork University Hospital, Ireland 510(k) pending at FDA Not available for sale in the U.S.
Low Dose abdomen + pelvis - 0.6 mSv
39 cm