CT and IGCT Norbert J. Pelc, Sc.D. Department of Radiology Stanford University.
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Transcript of CT and IGCT Norbert J. Pelc, Sc.D. Department of Radiology Stanford University.
CT and IGCTCT and IGCT
Norbert J. Pelc, Sc.D.Norbert J. Pelc, Sc.D.Department of RadiologyDepartment of Radiology
Stanford UniversityStanford University
OutlineOutline
• We get the best toysWe get the best toysopportunities in MDCTopportunities in MDCT
• And we make some toys tooAnd we make some toys tooInverse Geometry CT (IGCT)Inverse Geometry CT (IGCT)
CT Input/Output
array of projection
data
CTReconstruction
Program
distributionof
Filtered-backprojectionFiltered-backprojection
QuickTime™ and aCinepak decompressor
are needed to see this picture.
Volumetric coverageVolumetric coverage
Multi-slice helicalMulti-slice helicalrequires fewer rotationsrequires fewer rotations
source
detector
*
Helical CTHelical CTrequires multiple rotationsrequires multiple rotations
source
detector
*
The Continuing Evolution: MDCTThe Continuing Evolution: MDCT
ManufacturerManufacturergantry gantry
rotationrotationdetector detector
rowsrowselectronics electronics
rowsrowsslicesslices
GEGE(Lightspeed VCT)(Lightspeed VCT)
0.35 s0.35 s 64 x 0.62564 x 0.625 6464 64/40mm64/40mm
PhilipsPhilips((Brilliance CT 64))
0.4 s0.4 s 64 x 0.62564 x 0.625 6464 64/40 mm64/40 mm
SiemensSiemens(Sensation 64)(Sensation 64)
0.33 s0.33 s32 x 0.632 x 0.6+ 8 x 1.2+ 8 x 1.2
323264/20 mm64/20 mm24/32 mm24/32 mm
ToshibaToshiba(Aquilion 64)(Aquilion 64)
0.4 s0.4 s 64 x 0.564 x 0.5 6464 64/32 mm64/32 mm
CT future directionsCT future directions
• CheaperCheaperlower cost multi-row detectors and electronicslower cost multi-row detectors and electronicslower cost computer systemslower cost computer systems
• FasterFasterscan times < 100 msscan times < 100 ms
• BetterBetter QuickTime™ and aCinepak decompressor
are needed to see this picture.
Multi-source systemsMulti-source systems
Berninger et al, US Patent 4,196,352, filed 1978
• reduced minimum gantry rotation
• significant increase in scan speed and cost
• could have major application impact
CT future directionsCT future directions
• CheaperCheaperlower cost multi-row detectors and electronicslower cost multi-row detectors and electronicslower cost computer systemslower cost computer systems
• FasterFasterscan times < 100 msscan times < 100 msfaster volumetric coveragefaster volumetric coverage “ “an organ in a rotation”an organ in a rotation”
• BetterBetter
CT future directionsCT future directions
• CheaperCheaperlower cost multi-row detectors and electronicslower cost multi-row detectors and electronicslower cost computer systemslower cost computer systems
• FasterFasterscan times < 100 msscan times < 100 msfaster volumetric coveragefaster volumetric coverage “ “an organ in a rotation”an organ in a rotation”
• BetterBetterbetter contrast discriminationbetter contrast discriminationhigher spatial resolutionhigher spatial resolutionlower doselower dose
CT future directionsCT future directions
• CheaperCheaperlower cost multi-row detectors and electronicslower cost multi-row detectors and electronicslower cost computer systemslower cost computer systems
• FasterFasterscan times < 100 msscan times < 100 msfaster volumetric coveragefaster volumetric coverage “ “an organ in a rotation”an organ in a rotation”
• BetterBetterbetter contrast discriminationbetter contrast discriminationhigher spatial resolutionhigher spatial resolutionlower doselower dose
Volumetric CT approachesVolumetric CT approaches
Multi-row helicalMulti-row helicalrequires multiple rotationsrequires multiple rotations
source
detector
*
*source
detector
Cone beam VCTCone beam VCT
Scan the volume in a single rotation, or step-and-shoot
VCT with flat panel detectorsVCT with flat panel detectors
GE CR&DGE CR&D
Siemens Axiom ArtisSiemens Axiom Artis
Cone beam artifactsCone beam artifacts
Cone beam VCT system, stack of 9 disks9 cone angle (10 cm z-FOV @ 65 cm), Feldkamp reconstruction
K. Sourbelle, et al, , RSNA 2003, #183
Cone beam artifactsCone beam artifacts
Cone beam artifactsCone beam artifacts
indistingushableindistingushableobjectsobjects
fundamental problem, no correction exists
2D scanned anode x-ray source
detector array
source and detector have the same axial extent
Inverse-Geometry CT (IGCT)Inverse-Geometry CT (IGCT)
• system designs
• reconstruction methods
• simulations and experiments
NexRay, Inc., Los Gatos, CA
detector array
Inverse-Geometry VCTInverse-Geometry VCT
AxialAxial SagittalSagittal
““Defrise” phantomDefrise” phantom
No cone-beam artifacts!No cone-beam artifacts!
Cone-beam VCTCone-beam VCT IGCTIGCT
Cadaver inner earCadaver inner ear
conventional IGCT
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
ConclusionsConclusions
• MDCTMDCTcheaper, faster, bettercheaper, faster, better
better spatial and temporal resolutionbetter spatial and temporal resolutionlower radiation doselower radiation dose
• ““Organ in a rotation” with outstanding Organ in a rotation” with outstanding image quality needs a different approachimage quality needs a different approach
Cannot use a simple point x-ray sourceCannot use a simple point x-ray sourceInverse Geometry CT (IGCT)Inverse Geometry CT (IGCT)
preliminary results are promisingpreliminary results are promising
• Hang on to your hat, the data will fly in!Hang on to your hat, the data will fly in!