How CT / MSCT worksHow CT / MSCT worksHow CT / MSCT worksHow CT / MSCT works

Imageaquisition:Imageaquisition:

How CT / MSCT worksHow CT / MSCT worksHow CT / MSCT worksHow CT / MSCT works

Gerätetechnik: Gerätetechnik: GenerationenGenerationen

Gerätetechnik: Gerätetechnik: GenerationenGenerationen

Single vs Multirow Single vs Multirow Single vs Multirow Single vs Multirow

4 Slices 4 Slices +??+??

1 Slice1 Slice

X-Ray tubeX-Ray tube

Multirow Detector CT:Multirow Detector CT:Multirow Detector CT:Multirow Detector CT: Fixed Matrix DetektorFixed Matrix Detektor

Multirow detector Multirow detector CT:CT:

Multirow detector Multirow detector CT:CT:

Adaptive Array DetectorAdaptive Array Detector

Multirow detector CT:Multirow detector CT:Multirow detector CT:Multirow detector CT:

Adaptive Array DetectorAdaptive Array Detector

Image Plane

DetectorSlice broadening by spiral interpolation

Collimation Slice Sensitivity Profile (SSP)

increasing pitch -> Wider slice profile

Single Detector CTSingle Detector CTSingle Detector CTSingle Detector CT

Provided by Siemens Erlangen

Pitch 2

Pitch 3 Pitch 5 Pitch 7

Pitch 1 Pitch 1.5

Blurring

Single vs MultirowSingle vs MultirowSingle vs MultirowSingle vs MultirowSingle-slice

scanner

Volume Zoom

SURE VIEWProvided by Siemens Erlangen

„„Magic Triangle“Magic Triangle“„„Magic Triangle“Magic Triangle“

Larger Volume

Shorter Scan Time

Isotropic Resolution

Provided by Siemens Erlangen

ResolutionResolutionResolutionResolution

Isotropic ImagingIsotropic Imaging

isotropic voxel

No isotropic

voxels

SpeedSpeedSpeedSpeed

64 slices /rotation64 slices /rotation Rotation times < 0.5s possible Rotation times < 0.5s possible

Dynamic studiesDynamic studies

CT -- BenchmarkingCT -- BenchmarkingCT -- BenchmarkingCT -- Benchmarking

Geometric Resolution:Geometric Resolution:- xy:xy: 0.3-0.5mm 0.3-0.5mm- z: z: 0.6mm 0.6mm

Radiometric Resolution:Radiometric Resolution:- 12bit data = 4096 shades of gray12bit data = 4096 shades of gray- Hounsefield Units (HU): Hounsefield Units (HU):

Minimum:Minimum: -1024 HU = air-1024 HU = air Zeropoint:Zeropoint: 0 HU = water0 HU = water Fat:Fat: -120 – 80 HU-120 – 80 HU Bones:Bones: > 200 HU> 200 HU

CT -- BenchmarkingCT -- BenchmarkingCT -- BenchmarkingCT -- Benchmarking

Time Resolution:Time Resolution:- Standard: Standard: 0.5s0.5s- Cardiac Mode: Cardiac Mode: 0.33s0.33s

Maximal Scanlength:Maximal Scanlength:- ca. 150cmca. 150cm

ResolutionResolutionResolutionResolutionThickness 5.0mmIncrement 2.5mm

Thickness 2.5mmIncrement 2.0mm

Thickness 1.25mmIncrement 1.0 mm

ResolutionResolutionResolutionResolutionThickness 5.0mmIncrement 2.5mm

Thickness 2.5mmIncrement 2.0mm

Thickness 1.25mmIncrement 1.0 mm

CT – New:CT – New:Dual Source CTDual Source CT

CT – New:CT – New:Dual Source CTDual Source CT

CT & RadiatenCT & RadiatenCT & RadiatenCT & Radiaten

CT ~ 10% of Xray ExaminationsCT ~ 10% of Xray Examinations CT CT source of ~50% medical source of ~50% medical

related radiationrelated radiation Incresases stochastic risk for Incresases stochastic risk for

cancer development:cancer development:- 1mSv Totalbody irradation 1mSv Totalbody irradation risk for risk for

lethal cancer is increased by 5%lethal cancer is increased by 5%- USA: maybe about 500 children dying a USA: maybe about 500 children dying a

year by cancer due to CTyear by cancer due to CT