Dual Energy CT (DECT) Dual Energy CT (DECT) – – Technology Approaches and Technology Approaches and Scan Modes Scan Modes Marc Marc Kachelrie Kachelrie ß ß Institute of Institute of Medical Medical Physics Physics (IMP) (IMP) Friedrich Friedrich - - Alexander Alexander - - University University Erlangen Erlangen - - N N ü ü rnberg rnberg SCCT 2010 www.imp.uni www.imp.uni - - erlangen.de erlangen.de
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Dual Energy CT - Technology and Scan Modes Energy CT - Technology and... · Dual Energy CT (DECT) – Technology ... HA400 80 kV 140 kV. Measurement Results Bone material density
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Dual Energy CT (DECT) Dual Energy CT (DECT)
––
Technology Approaches and Technology Approaches and
Scan ModesScan Modes
MarcMarc KachelrieKachelrießß
Institute ofInstitute of MedicalMedical PhysicsPhysics (IMP) (IMP)
• I have the following financial relationships to disclose
– Consultant to CT Imaging GmbH
– Managing director of RayConStruct GmbH
– Grant supports from AiF, DFG, Intel, Siemens, Varian, Ziehm
• I will discuss the following off-label use in my presentation
– Exact Material Decomposition from Inconsistent Rays
Standard CT image
Calcium density image Soft tissue density image
Kalender WA et al. Radiology 164:419-423, 1987
1980ies: The First Clinical DECT 1980ies: The First Clinical DECT Product ImplementationProduct Implementation
DECT (ImageDECT (Image––based)based)
C/W=0/500 HU
2500 HU
1700 HU
E0
High energyspectrum 140 kV
Low energy spectrum 80 kV
80 keV 140 keV
wj
µ–images
Aluminum densityWater density 70 keV image
DECT ApplicationsDECT Applications• Selective display of body substances with high atomic number:
Quantification of calcium, iron or iodine concentrations, bone mineral density etc.
• Separate displays of bones and soft tissue: Material-selective projection radiography of the chest, the skeleton etc., and image segmentation
• Distinction between iodine and calcium: Differentiation between contrast medium in blood and calcified plaque or bone for CT angiography
• Selective display of contrast media and other injected tracers:Concentration measurement of injected substances such as iodine or gadolinium
• Exact quantification of contrast media: Perfusion measurement
• CT numbers for hypothetical monoenergetic sources: Attenuation correction for PET/CT (at 511 keV) and for SPECT/CT
• Electron density: Planning of radiation therapy with protons, electrons or high-energy x-rays
• …
Dual Energy whole body CTA: 100/140 Sn kV @ 0.6mm
Courtesy of Friedrich-Alexander University Erlangen-Nuremberg - Institute of Medical Physics / Erlangen, Germany
Single DECT
Scan
DE bone removal
Virtual non-contrastand Iodine image
Examples(Slide Courtesy of Siemens Healthcare)
Technology ApproachesTechnology Approaches• Multiple scans at different spectra
• Dual source CT
• Fast tube voltage switching
• Slow tube voltage modulation
• Dual layer detectors (sandwich detectors)
• Split detector (different prefiltration)
• Photon counting detectors (two or more energy bins)
DemandsDemands
• Simultaneous acquisition to avoid motion artifacts
• Independent tube current curves for both spectra– Select tube currents
– Select anatomy-dependent tube current curves1
• Free and application-dependent choice of spectra– Select prefiltration
– Select tube voltages
• Achieve good angular sampling
• Avoid scatter and cone-beam artifacts
• Acquire consistent rays– Each ray should be measured twice
– or reconstruction should correctly handle inconsistencies2
1 Stenner, Kachelrieß. Dual energy exposure control (DEEC) for computed tomography. Med. Phys. 35(11):5054-5060, November 2008. 2 Maaß, Meyer, Kachelrieß. Exact dual energy material decomposition from inconsistent rays (MDIR). Med. Phys 37:under consideration, 2010.