Introduction To CT Flashcards
What does the x-ray tube in CT do?
It spins around to produce cross sectional images through anatomy (it produces slices of the patient’s body)
What part of CT is this?
CT x-ray tube
What does CT stand for?
Computed Tomography
What are the advantages of CT?
(6)
The images are acquired in slices
We can see soft tissue
Blood vessels can be visualised
Large areas can be imaged in a short space of time
Functional information
It can indicate what type of lesions someone has by how the lesion interacts with the contrast
How was CT founded?
Godfrey Hounsfield discovered that if an x-ray beam was passed through an object from all directions and measurements were made, information about the internal structure of the body could be obtained
Label the CT scanning room:
What is the gantry?
Where the x-ray tube is
What is the injector pump?
It’s what we connect the patient to when injecting the contrast into them
What is found inside the gantry?
(2)
X-ray tube
Detectors
What part of the CT scanning room is this?
The gantry
Label the operator console in CT:
What are the principles of CT scanning?
(4)
The CT scanner is an x-ray tube with a collimation device
The tube emits a very narrow, flat fan beam
The beam is aligned to an array of detectors in the form of an arc
Each detector is equidistant (on a curve) to the focal spot
What happens to the patient during CT scanning?
(3)
The patient continually rotates around while the patient moves through the gantry
The x-ray beam is attenuated (absorbed) by the patient on the way to the detector (depending on their tissue, which affects how much is attenuated)
The detector will measure the amount of attenuation
Label the CT scanner:
Label the patient in the CT scanner:
The denser the tissue, the … attenuation will occur
More
In CT, do bones or fat attenuate more x-rays?
Bones
How do the detectors work?
(3)
The array of detectors divide the body into linear strips
Each detector measures the attenuation that has occurred within its own strip
This information is then digitised and fed into a computer
How is a computer used in CT?
(3)
The computer assigns a numerical value to the data from each detector
This value is based upon the amount of attenuation that has taken place.
This is how the image starts being produced
What has to be done to obtain enough data to reconstruct an image?
Throughout the examinations, many exposures are undertaken as the patient passes through the gantry
Where is the data needed to reconstruct an image stored?
(2)
In a matrix or
Data set
What is a pixel?
A single square within the matrix
What does each pixel correspond to?
The volume of tissue
What is the volume of tissue known as?
A voxel
What are hounsfield units?
The numerical value that each pixel is assigned based on the average attenuation value of the whole voxel
