Cộng ảnh với hệ thống CTCộng ảnh×Cộng ảnh với hệ thống CT×Chẩn đoán hình ảnh×bài giảng chẩn đoán hình ảnh×CT trong chẩn đoán đột quỵ não×
Dual Energy Radiography Dual Energy Imaging with Dual Source CT Systems Rainer Raupach, PhD Siemens Healthcare rainer.raupach@siemens.com Radiograph Bone image energies Tissue image materials Armato SG III Experimental Lung Research 2004;30 (suppl 1):72-77 kV Switching with SOMATOM DRH – in the 80s Calculation of material selective images: Calcium and soft tissue Principle of Dual Energy CT Data acquisition with different X-ray spectra: 80 kV / 140 kV Standard image Rapid kVp switching Mean Energy: Calcium image 56 kV 76 kV Basis material decomposition Low kVp Tube Soft tissue image Tube High kVp Attenuation profiles Different mean energies of the X-ray quanta W Kalender: Vertebral Bone Mineral Analysis, Radiology 164:419-423 (1987) SOMATOM Definition The World’s First Dual Source CT Principle of Dual Energy CT Many materials show different attenuation at different mean energies Faster than Every Beating Heart 1.0E+02 gated mode / same kV high temporal resolution (80ms) Cardiac imaging Iodine Bone Attenuation 56 kV 76 kV 1.0E+01 Large increase One-Stop Diagnosis in Acute Care non gated mode / same kV low temporal resolution Obese patients, low kV scanning 1.0E+00 Small increase 1.0E-01 10 30 50 70 90 Energy / keV 110 130 Beyond Visualization with Dual Energy 150 different kV (gated and non-gated) Reason: different attenuation mechanisms (Compton vs photo effect) “Contrast Enhanced Viewing” using Dual Energy Information in Addition to Simple Image Mixing Spectra of Dual Energy Applications Basic application: Enhanced viewing, contrast optimization Contrast enhanced studies: Iodine has much higher contrast at 80 kV Non-linear, attenuation-dependent blending of the images combines benefits of 80 kV (high contrast) and mixed data (low noise) Direct Angio Lung PBV Virtual Unenhanced Lung Vessels 140 kV Hardplaque Display Heart PBV Musculoskeletal Gout Calculi Characterization Lung Nodules* *510(k) approved 80 kV Blending Brain Hemorrhage Xenon* Courtesy of CIC Mayo Clinic Rochester, MN, USA syngo Dual Energy Direct subtraction of bone syngo Dual Energy Direct subtraction of bone Modified 2-material decomposition: Separation of two materials Assume mixture of blood + iodine (unknown density) and bone marrow + bone (unknown density) Separation line 600 Iodine pixels Bone 550 HU HU at 80 kV 500 400 Automatic bone removal without user interaction Clinical benefits in complicated anatomical situations: Base of the skull Carotid arteries Vertebral arteries Peripheral runoffs Bone pixels Blood+iodine 80kV Marrow+bone 300 Iodine 425 HU Modified 2-material decomposition: Separation of bone and Iodine 200 100 Soft tissue -100 -100 Bone 400 HU Blood Marrow Iodine 250 HU 140kV 100 200 300 HU at 140 kV 400 500 600 syngoDualEnergy Differentiation between hard plaques and contrast agent Courtesy of Prof Pasovic, University Hospital of Krakow, Poland Image Based Methods Modified 2-material decomposition: Characterization of kidney stones Urine + calcified stones / uric acid stones HU at 80 kV high Z low Z HU at 140 kV Courtesy of CCM Monaco, Monaco syngo Dual Energy Musculoskeletal Visualization of tendons syngo Dual Energy Visualization of Tendons: Tibialis posterior tendon rupture SOMATOM Definition World’s first DSCT Spatial Res 0.33 mm Rotation 0.5 sec Scan time: s Scan length: 133 mm 140/80 kV Eff mAs 80/150 Spiral Dual Energy Courtesy of University Medical Center Grosshadern / Munich, Germany Courtesy of University Medical Center Grosshadern / Munich, Germany Applications of Dual Energy CT Gout: Application Three material decomposition: quantification of iodine – iodine image HU at 80 kV Iodine Iodine content 65 Tissue -100 Fat -90 60 HU at 140 kV Vancouver General Hospital, Canada Removal of iodine from the image: virtual non-contrast image Image Based Methods Applications of Dual Energy CT Most promising application: 3-material decomposition Calculation of a virtual non-contrast image, Iodine quantification Virtual non-contrast image and iodine image: Characterization of liver / kidney / lung tumors Solve ambiguity: low fat content or iodine-uptake Quantify iodine-uptake in the tumor and at the tumor surface Differentiation benign - malignant Monitoring of therapy response Mixed image Mixed image 80kV+140kV Virtual unenhanced image VNC image Iodine image Iodine overlay image + Courtesy of University Hospital of Munich - Grosshadern / Munich, Germany SOMATOM Definition Flash Latest Generation of Dual Energy CT Applications of Dual Energy CT Quantification of iodine to visualize perfusion defects in the lung Avoids registration problems of non-dual energy subtraction methods 80/140kV Mixed Image Iodine Image Mixed image + iodine overlay System Design Two X-ray tubes at 95°, each with 100 kW 33 cm Two 128-slice detectors, each with 64x0.6mm collimation and z-flying focal spot Embolus SFOV A/B-detector: 50/33 cm 0.28 s gantry rotation time 75 ms temporal resolution Courtesy of Prof J and M Remy, Hopital Calmette, Lille, France Dual Energy Imaging with Tin Filtration ‘Definition’ vs ‘Definition Flash’: Improved DE Signal SOMATOM Definition Flash Single dose Dual Energy Mixed Images 80 kV 140 kV overlap VNC Iodine DE Images Definition Conventional DE DSCT Dual Energy DE with Selective Photon Shield 80 kV 140 kV with SPS overlap Tissue characterization Improved DE contrast Dose-neutral compared to a single 120 kV scan Definition Flash DE with Selective Photon Shield SD and dose: equal SD: -25% Images acquired and processed in collaboration with CIC Mayo Clinic Rochester, USA SOMATOM Definition Flash Impact of the Selective Photon Shield SOMATOM Definition Flash Image Dual Energy Whole Body CTA: 100/140Sn kV @ 0.6mm Dose neutral DE: comparison of 120 kV and 100 kV/140 kV+0.4 mm Sn Single DE CT Scan 120kV, 500mA 100/140Sn kV, 500mA noise: 14.1 HU noise: 13.9 HU iodine: 329.0 HU iodine: 330.0 HU bone: 334.8 HU bone: 335.3 HU Courtesy of Friedrich-Alexander University Erlangen-Nuremberg - Institute of Medical Physics / Erlangen, Germany Dual Energy CT New Application Classes Are there alternative approaches? 40 keV Sequential acquisition at 80 kV and 140 kV with single source CT Registration problems (heart/lung motion, varying contrast density) Fast kVp-switching during the scan with single source CT Inadequate power at low kV Unequal noise for low and high kV data Measurement of Lung Nodule enhancement courtesy of ASAN Medical Center, Seoul, Korea Measurement of Xenon Concentration 190 keV Spectral sensitive „sandwich“ detectors Inferior spectral separation courtesy of ASAN Medical Center, Seoul, Korea Mono-energetic imaging courtesy of Klinikum Großhadern, Munich, Germany Dual Energy CT Evaluation of alternative approaches Quantum counting Paralysis at high flux rate Spectral overlap by fluorescence and pile-up Dual Energy CT Evaluation of alternative approaches dual−source (tin filter) dual−source (std filter) sequential kVp dual−layer (GOS) dual−layer (CsI) dual−layer (ZnSe) quantum counting (CZT) 1.6 1.4 DE Performance @ equal dose relative DEC² 1.2 0.8 0.6 0.4 Dose 0.2 15 20 25 30 35 phantom diameter [cm] 40 45 S Kappler et al., Dual-energy performance of dual-kVp in comparison to dual-layer and quantum-counting CT system concepts, Proceedings of the SPIE Medical Imaging Conference, Volume 7258, pp 725842 (2009) Thank you!