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!