homework review Flashcards
CT tube voltages typically range from:
80-140 kV
Using _______, the data acquired during a single scan can also be processed differently to display primarily soft tissue or bony anatomy.
computer algorithms
To date, there have been ____ major generations of CT equipment.
7
_______ refers to the way the x-ray beam is emitted from the tube housing, passes through the patient, and is acquired by the CT detectors.
beam geometry
The gantry houses:
x-ray tube
collimators
slip rings
all of the above
A high-kilovolt (kV) technique is necessary in CT imaging for all the following reasons except:
a. to reduce the contrast of bone relative to soft tissues.
b. to reduce the dependence of attenuation coefficients on photon energy.
c. to increase the probability of beam hardening.
d. to produce a high-radiation flux at the detector.
c. to increase the probability of beam hardening.
All the following apply to computed tomography (CT) except:
a. a computer is used to reconstruct cross-sectional images of the patient.
b. X-ray film is used as the detector.
c. special detectors are used to detect X-rays that have passed through the patient at multiple angles.
d. mathematical methods are used to reconstruct images.
b. X-ray film is used as the detector.
T/F:
CT is better at recording very small differences in tissue contrast compared to conventional tomography.
True
The range of CT numbers in an image is called the:
window width (WW)
What scanner allows for continuous rotation of the x-ray tube while the patient moves simultaneously through the gantry aperture?
spiral/helical scanner
When considering detector efficiency, the measure of how well the detectors gather incoming photons is called:
capture efficiency
When considering detector efficiency, the measure of how well captured photons are absorbed and converted to electrical signals is called:
absorption efficiency
When considering detector efficiency, the measure of how consistently the detectors respond to similar transmitted radiation events is called:
reproducibility
In multidetector CT systems, __________ determine(s) slice thickness.
Reconstruction algorithms
In single slice CT scanning, thin collimation results in:
better resolution
The development of helical and continuous acquisition scanning was made possible by:
slip ring technology
A typical scout length for an adult CT abdomen/pelvis scan is approximately:
550 mm
Which of the following is FALSE regarding helical scanning compared to conventional axial scanning?
helical scanning reduces the likelihood of patient motion
helical scanning allows for faster imaging
helical scanning requires more contrast material
helical scanning prevents stair-step artifacts
helical scanning requires more contrast material
Pixel size is equal to:
field of view / matrix size
Which of the following is FALSE regarding isotropic scanning?
it enhances 3D and multiplanar reconstructions
it reduces stair-step artifacts
it increases resolution
it is more effective with fewer detector rows
it is more effective with fewer detector rows
All of the following media forms can be used to store CT images except:
a. laser optical disks.
b. magnetic disks.
c. VHS tapes.
d. digital videotape.
VHS tapes
T/F: The number of bits per pixel is the bit formation.
false; this is called bit depth
The opening in the gantry in which the patient is positioned during scanning is called the:
gantry aperture
What room generally houses the gantry and patient couch and should be large enough to accommodate gurneys and emergency equipment?
scanning room
