Computed Tomography Flashcards
What is computed tomography?
A CT scan uses X-rays and a computer to create detailed images of the insides of the body. CT scans are sometimes referred to as CAT scans or computed tomography scans.
What are some current trends/uses of CT scanning?
Diagnosis - fractures, cancers, blockages etc
Monitoring - disease progression, cancer, infection, healing processes
Pre-op planning - complex anatomical structures mapped out
Image Guidance - deep brain stimulation etc…
What are two different types of CT scanners?
Industrial CT scanners
Spiral CT scanners
What are some uses of an industrial CT scanner?
Used for the internal inspection of components, no dose limitations
Flaw detection
Failure analysis
Assembly analysis
Reverse engineering
What are some benefits of spiral CT scanning?
Fast Large volume of data No partial volume artefact No step artefact Enhanced 3D rendering
Which is faster CT or MRI?
CT within 5 mins
MRI between 30 and 45 mins
What different images do CT and MRIs pick up on?
CT - Bone, organs, lungs, chest
MRI - Tendons, ligaments, brain, spinal column
Which scanning technique uses radiation?
CT
How does MRI scanning work?
Strong magnetic field causes hydrogen molecules to give off RF signal which is translated into image data
What are the 2 different methods of computation for CT scanning?
Back projection - produces transaxial blurred images
Filtered back projection - data is filtered before reconstruction, specific filters for different diagnostic purposes
What is the difference between a pixel, axial and voxel?
Pixel
Axial is a 2D slice
Voxel is a 3D image
What are houndsfield units?
A linear attenuation coefficient is assigned to each tissue density, this is represented by a CT number of Houndsfield unit. Each pixel has a HU assigned to it and is demonstrated by a different shade of grey. Shades of grey being displayed can be limited depending on the type of tissue we want to see most clearly
What are 3 different types of scan output from CT scans?
Low dose scans
Plain scans
Contrast enhanced scans
Why reconstruct CT data?
To view information not clearly demonstrated in axial plane
Convey CT information in a format more easily understood e.g. to simulate other examinations
To replace these sometimes riskier examinations as CT is non-evasive
Why are multiplanar reconstructions used in CT scanning?
Most common method used in routine scans
Data volume reconstructed to be shown in any plane
Fast method
Set up pro-actively to scan being performed
Aid to traditional axial viewing of data
