CT applications Flashcards
what is the choice of modality dependent on
- clinical indications
- pathology diagnosed
- stage of disease
- pre/post treatment
- follow up patient management options
name the scanning parameters of CT
- mA
- kVp
- scan time
- slice thickness
- pitch
- RFOV
- tube rotation speed
- patient positioning
what does ‘pitch’ refer to
the ratio of table movement to slice thickness during single rotation of CT scanner
- the faster the table moves, the higher the pitch
when is a lower kVp used
soft tissue imaging
when is a higher kVp used
bone imaging
longer scan time results in …
more detailed images
increased exposure
what does thin slices do to an image
- higher spatial resolution
- more radiation
- more data to process
- sharper images (mA must also be increased to avoid grainy images)
what does a thicker slice require
more flattening
- this is because to create an image the system must flatten the scan thickness
what is windowing
allows to find right balance between contrast and brightness to see details of interest within a CT image
what is window level?
brightness control
- move it up and image becomes brighter
- move it down = darker
what is window width
contrast control
- increase window width and the range of grey shades become broader - broader range of tissues
- decreasing it narrows range - easier to focus on specific density range like blood vessels
3d reconstruction
turns 2d images to 3d
MPR
- multi-planar reconstruction
- allows you to view same structure from different angles
MIP
- maximum intensity projection
- highlights brightest areas in CT scan eg blood vessels with contrast
volume rendering
- creates 3D images that includes both internal and external surfaces of structures
- assigns opacities of colour/grey scale to different types of tissue
how is legislation of required doses kept in line with ALARP
- dose efficient equipment
- equipment QA programmes
- optimizing scans
- training
- diagnostic reference levels
positive oral contrast
- iodinated agents (gastrografin) but can obscure lesions
- water soluble iodinated agents safe if bowel pathology or perforation
negative oral contrasts
- water
- effective in depicting stomach lining and bowel
- will not obscure blood vessels
positive bowel contrast
- iodinated gastrograffin
- water soluble iodinated agents safe if bowel pathology or perforation
negative rectal contrast
- air/ co2 via foley catheter
aim of IV contrast agents
- label blood vessels and organs
- iodinated agents
factors affecting IV contrast
- age
- weight
- cardiovascular status
- rate, volume and concentration of contrast agents
- pump inject for reliability and reproducibility
what is triple phase
- no contrast
- arterial contrast
- venous contrast
difference between CTA and angio
CTA provides detailed cross-sectional images of blood vessels throughout the body using CT technology and contrast material, while angiography involves X-ray and fluoroscopy-guided imaging of specific vascular regions via direct injection of contrast agents for diagnostic and interventional purposes
