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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!