CT and IGCT Norbert J. Pelc, Sc.D. Department of Radiology Stanford University

Outline We get the best toysWe get the best toys opportunities in MDCT And we make some toys tooAnd we make some toys too Inverse Geometry CT (IGCT)

CT Input/Output array of projection data CT Reconstruction Program distribution of 

Filtered-backprojection

Volumetric coverage Multi-slice helical requires fewer rotations source detector * Helical CT requires multiple rotations source detector *

The Continuing Evolution: MDCT Manufacturer gantry rotation detector rows electronics rows slices GE (Lightspeed VCT) 0.35 s 64 x /40mm Philips () (Brilliance CT 64) 0.4 s 64 x /40 mm Siemens (Sensation 64) 0.33 s 32 x x /20 mm 24/32 mm Toshiba (Aquilion 64) 0.4 s 64 x /32 mm

CT future directions CheaperCheaper lower cost multi-row detectors and electronics lower cost computer systems FasterFaster scan times < 100 ms BetterBetter

Multi-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 directions CheaperCheaper lower cost multi-row detectors and electronics lower cost computer systems FasterFaster scan times < 100 ms faster volumetric coverage “an organ in a rotation” “an organ in a rotation” BetterBetter

CT future directions CheaperCheaper lower cost multi-row detectors and electronics lower cost computer systems FasterFaster scan times < 100 ms faster volumetric coverage “an organ in a rotation” “an organ in a rotation” BetterBetter better contrast discrimination higher spatial resolution lower dose

CT future directions CheaperCheaper lower cost multi-row detectors and electronics lower cost computer systems FasterFaster scan times < 100 ms faster volumetric coverage “an organ in a rotation” “an organ in a rotation” BetterBetter better contrast discrimination higher spatial resolution lower dose

Volumetric CT approaches Multi-row helical requires multiple rotations source detector * * source detector Cone beam VCT Scan the volume in a single rotation, or step-and-shoot

VCT with flat panel detectors  GE CR&D  Siemens Axiom Artis

Cone beam artifacts Cone beam VCT system, stack of 9 disks 9  cone angle (10 cm 65 cm), Feldkamp reconstruction K. Sourbelle, et al,, RSNA 2003, #183

Cone beam artifacts

indistingushableobjects 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) system designs reconstruction methods simulations and experiments NexRay, Inc., Los Gatos, CA detector array

Inverse-Geometry VCT AxialSagittal

“Defrise” phantom No cone-beam artifacts! Cone-beam VCT IGCT

Cadaver inner ear conventionalIGCT

Conclusions MDCTMDCT cheaper, faster, better better spatial and temporal resolution lower radiation dose “Organ in a rotation” with outstanding image quality needs a different approach“Organ in a rotation” with outstanding image quality needs a different approach Cannot use a simple point x-ray source Inverse Geometry CT (IGCT) preliminary results are promising Hang on to your hat, the data will fly in!Hang on to your hat, the data will fly in!