CT Principle 2 Flashcards
(61 cards)
factors involved in data acquisition
- pitch
- kVp
- mAs
- time
- beam width
- scan type
- SFOV
factors involved in image reconstruction
- slice thickness
- FOV
- matrix
- filter
factors involved in display control
- window width
- window length
- zoom
SFOV
scan field of view
SFOV is the area where ___
raw data is collected within gantry
DFOV is the area which ___
determines how much of SFOV is reconstructed into an image
How does manipulating the pitch in CT scanning affect the quality of the images and the radiation
dose to the patient?
Lower pitch results in better image quality and higher radiation dose; Higher pitch results in lower image quality and lower radiation dose
Which of the following scenarios would benefit from using a pitch value of less than 1? Select all that apply
a) Rapid whole-body scans.
b) Low-dose lung cancer screening.
c) High-detail imaging requirements.
d) Imaging small structures like the internal auditory canal
c & d
What are the possible reasons for adjusting the display field of view (DFOV) post-acquisition? Select all that apply.
a) To exclude unnecessary areas from the image.
b) To focus on a specific anatomical region.
c) To reduce the radiation dose.
d) To include more anatomical information in the image.
a & b
In which clinical situations would a high pitch value be preferred? Select all that apply
a) Imaging of small detailed structures.
b) Low-dose lung cancer screening.
c) CT angiography.
d) Imaging of the internal auditory canal
b & c
What is the significance of scan field of view (SFOV) in CT imaging? Select all that apply
a) It determines the total area from which data is acquired..
b) It limits the maximum possible display field of view (DFOV).
c) It can be adjusted after the scan to display a different area.
d) It affects the initial data acquisition during scanning.
a, b & d
kVp used in CT
constant at 120 / 130 kVp
what does a lower kVp result in
- more contrast by exploiting k-edge
- more noise (countered by higher mAs)
CT dose is proportional ____ of kVp
to square
kVp
The peak voltage applied to the X-ray tube, influencing the maximum energy of the X-ray photons produced.
keV
The energy of individual X-ray photons
average keV
The mean energy of the X-ray photons in the beam, impacting overall image contrast and quality
max keV
The highest energy level of X-ray photons, determined by the kVp setting, indicating the most penetrating photons
iodine attenuation ___ at ___ kVp due to decreased compton scatter & greater photoelectric effect as photon energy approaches k-edge of iodine
increases; decreased
What is the primary role of kVp in a CT scan?
To measure the beam intensity or ability to penetrate anatomy
what is the r/s between slice thickness and noise & contrast & spatial resolution
thicker slices = less noise & better contrast & spatial res for soft tissues
what happens during image reconstruction
3D raw / helical data converted to 2D image data
what happens before reconstruction
interpolation; raw data is interpolated into series of 2D images before FBP
how is interpolation achieved
weighted average of helical data from either side of reconstruction plane
