40TH ANNUAL MEETING October 13 16, 2012 Pasadena, CA CTA Dose Reduction: Special Considerations in Children Jeffrey C. Hellinger, MD FACC New York Cardiovascular Institute Lenox Hill Radiology and Medical Imaging
40TH ANNUAL MEETING October 13 16, 2012 Pasadena, CA Disclosures Philips Healthcare TeraRecon Vital Images
Computed Tomographic Angiography Non-invasive High spatial resolution Robust, 3D and 4D imaging Fast, comprehensive cardiovascular imaging Ease of availability Ease of Patient Access Devices, stents, grafts
Computed Tomographic Angiography Radiation Exposure single multiple, cumulative Iodinated Contrast
Radiation Physics: Computed Tomography Image GENERATION: X-Ray beam attenuation within the body X-Ray beam REQUIRE sufficient Energy and Intensity Energy (voltage, kvp) determines the ability to penetrate and ionize tissues (e.g. deposit energy) Intensity (current, ma; exposure time; kvp) determines the number of photons in the beam (Signal Intensity vs Noise) Coverage TIME
Radiation Physics: CT Image Quality Number of X-Ray photons Signal intensity, direct relationship Noise, indirect relationship SNR N N N NOISE 1 N CNR = contrast to noise ratio (quantify image quality CNR = SHU 1 BgHU 2 N
Radiation Physics: CT Noise Determinants Number of Photons per voxel (indirect) Indirect relationships slice thickness (trade off for resolution) Field of view kvp mas Application: Increasing kvp, mas improves image quality, at the expense of increased radiation exposure
Core Radiation Reduction Strategies Appropriate indications Appropriate coverage Lowest possible kvp Lowest possible mas Fastest possible gantry rotation High-pitch spiral imaging
CTA: Appropriate Indications
Pediatric 64 channel single source MDCT ECG-Gated Cardic CTA: N=85 30 Histogram msv: 4.9 (with age weighting Factor) 25 20 Frequency 15 10 5 0 0 2.5 5 7.5 10 12.5 15 17.5 Arterial msv WITH Weighting Factor Hellinger et al, SPR 2010
18 Arterial msv WITH Weighting Factor 16 14 12 10 8 6 4 2 0 80 100 120 Kvp Hellinger et al, SPR 2010
Effective mas Direct impact on msv 800 700 Eff 1st pass mas 600 500 400 300 200 100 0 2 4 6 8 10 12 14 Arterial msv WO Weighting Factor Kvp 80 100 120 Hellinger et al, SPR 2010
Coverage (DLP) Direct impact on msv 700 600 1st Phase DLP 500 400 300 200 100 0 0 2 4 6 8 10 12 14 Arterial msv WO Weighting Factor Kvp 80 100 120 Hellinger et al, SPR 2010
10 y.o. Chest Pain msv=0.9
Congenital Lung CTA Low-dose CTA Chest CT P-value Male/Female 49/51 52/48 0.87 (%) Age at surgery 48 59 0.45 (days) CCAM/hybrid 68% 72% 0.59 Patients studied 114 103
Congenital Lung CTA Low-dose CTA Chest CT P-value Radiation dose range (msv) Number of sequestrations missed 0.25-0.5* 2-5 0.001 0/114 3/103
Pediatric CVCT: Four Year Experience 118 (8%) 294 (19%) 1070 66 (4%) Neonates 1-12months 12-24 Months >2 years
Pediatric CVCT: Neonates 40 35 30 25 20 15 10 5 0 Congenital Lung Pulmonary Artery Thoracic Aorta PHTN Pulmonary Vein LE Renal Biphasic Abd TA_Aorta SVC Whole Body Head_Neck PE UE_LE
Pediatric CVCT: Neonates Avg msv = 1.64 (0.7) 2007 msv = 3.2 2008 msv = 1.3 2009 msv = 0.95
2008 2009 2010 msv=3.2 msv=1.3 msv=0.5
msv = 0.77 (0.32)
msv = 0.28
msv = 0.21
Advanced Radiation Reduction Strategies Tube current modulation 70kV imaging Automated kv Increasing Detectors Leading to Volumetric Coverage Reduced mas Iterative Reconstruction Raw data domain Image domain Workstation image domain algorithms
Volumetric Whole Organ Imaging
Adenosine Rest-Stress CCTA
Adenosine Rest-Stress CCTA
Adenosine Rest-Stress CCTA
Volumetric Whole Organ Imaging msv = 3.5
Cardiovascular CTA Radiaton Exposure Acceptable Noise
Iterative Reconstruction
Iterative Reconstruction
Results SNR 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 FBP AIDR FBP AIDR FBP AIDR Original 50% 75%
Results CNR 4 3.5 3 2.5 2 1.5 1 0.5 0 FBP AIDR FBP AIDR FBP AIDR Original 50% 75%
Results Noise (SD) 700 600 500 400 300 200 100 0 FBP AIDR FBP AIDR FBP AIDR Original 50% 75%
Chest CTA 34mAs DLP 26.6 0.37mSv 0.5mm images Original FBP Original AIDR
Chest CTA 34mAs DLP 26.6 0.37mSv 0.5mm images 50% Dose FBP 50% Dose AIDR (17mAs)
Chest CTA 34mAs DLP 26.6 0.37mSv 0.5mm images 75% Dose FBP 75% Dose AIDR (8.5mAs)
Workstation Image Domain Algorithms Typical Smoothing filter Boundary of area is also smoothed and decreases high contrast resolution Denoising Software CT number is smoothed, but the edge is enhanced, CT number Structural preservation and enhancement Improves Low Contrast Resolution and High Contrast Resolution Scanner and workstation options
3D Structural Preservation and Enhancement noise reduction increased CNR
3D Structural Preservation and Enhancement
Enhancement 3D Structural Preservation and Enhancement 10 y.o HTN Renal CTA msv = 0.6 (0.47) CNR = 4.4 CNR = 14
Enhancement 3D Structural Preservation and Enhancement 10 y.o HTN Renal CTA msv = 0.6 (0.47) CNR = 4.4 CNR = 14
3D Structural Preservation and Enhancement
3D Structural Preservation and Enhancement
3D Structural Preservation and Enhancement
Summary: CTA Dose Reduction Core Imaging Strategies Appropriate indications Appropriate coverage Lowest possible kvp Lowest possible mas Fastest possible gantry rotation time High-pitch spiral imaging
Summary: CTA Dose Reduction Advanced Imaging Strategies Tube current modulation 70kV imaging Automated kv Increasing Detectors (Leading to Volumetric Coverage) Iterative Reconstruction Raw data domanin Image domain Workstation image domain algorithms
Summary: CTA Dose Reduction All healthcare providers and parents play a role Education, protocols, and QA are essential Consider Study goals vs expected image quality. Maximize image quality at the lowest possible msv Continued technological advancements will require continuous quality assessment to modify protocols
40TH ANNUAL MEETING Thank you for your attention! October 13 16, 2012 Pasadena, CA