Table of Contents
Multi-slice helical CT physics and technology
Introduction
Why CT?
CT scanner development 1972 ? 2002
Technological advances, 1985 - 2002
Basic principles of CT scanning
Construction of a CT scanner
Basic principles of CT scanning
Data acquisition
What are we measuring?
Projections
Basic principles of CT scanning
Filtered back projection
Filtered back projection
Filtered back projection
m to CT number
Slip rings – allow continuous gantry rotation
Helical scanning
Helical pitch
Image reconstruction in helical CT
360º linear interpolation
Advantages of helical scanners
Dual slice scanning
Dual slice capabilities
Sixteen slice scanners
Sixteen slice detectors
Flexible image reconstruction
Multi-slice helical reconstruction
Pitch in multi-slice
Advantages of multi-slice
Scan speed
Scan speed
Z-axis resolution
Isotropic imaging
Z-axis resolution
Larger scan volumes
Scan flexibility
Problems / difficulties with MSCT
Overbeaming in z-axis
Cone beam artefacts
Cone beam effects – axial scanning
Cone beam effects – helical scanning
Effect of AMPR (used by Siemens, modified ASSR)
Implications of multi-slice scanners
Dosimetry – CT dose descriptors
Dosimetry – measurements
Dosimetry – weighted CTDI
Dosimetry – CTDIvol
Dosimetry – dose length product (DLP)
Dosimetry – effective dose
Dosimetry – typical effective doses from CT
Population doses
Testing and QC
Image noise
Spatial resolution
Spatial resolution
Measuring CT number
Artefacts
Streaking - partial volume artefact
Minimizing partial volume artefacts
Streaking – photon starvation
Streaking - metal artefacts
Avoidance of metal artefacts
Metal Artefact Reduction
Motion artefact correction
Shading artefacts
Ring artefacts
CT and PET
PET / CT image registration
PET / CT image registration - couch
PET / CT attenuation correction
PET / CT attenuation correction
Conclusions
Finally
|