for the final Flashcards
sampling breaks an image into _____
pixels
a byte consists of ______ bits
8
bit depth determines the imaging systems _____
contrast resolution
as spatial frequency increases, spatial resolution _____
increases
as matrix size gets bigger, spatial resolution _____
increases
a 4-bit system would display ___ shades of gray?
16
digital fluoroscopy systems with hybrid capabilities use both _____
temporal and energy subtraction
the computed radiography image has
Wide exposure latitude and improved contrast resolution
the dynamic range determines the degree of _____ in the image.
contrast resolution
an increase in mAs
effect on x-ray energy: none
x-ray intensity: increased
an increase in kVp
effect on x-ray energy: increased
x-ray intensity: increased
an increase in distance
effect on x-ray energy: none
x-ray intensity: reduced
an increase in filtration
effect on x-ray energy: increased
x-ray intensity: reduced
the number of gray shades that an imaging system can reproduce is called its
dynamic range
each pixel of information in the CT image contains numerical information in ____ units
Hounsfield
the CT scanner must be calibrated so that the CT number for water is zero?
True
a pixel is
2-d image cell
as signal-to-noise increases, image quality
increases
if an image receptor has a high probability of interacting with the x-ray beam, then it
DQE - detective quantum efficiency
the ability to distinguish different shades of gray or brightness levels is called?
contrast resolution
as spatial resolution increases, lp/mm
increases
currently, the imaging modality with the highest spatial resolution
mammography
when doing soft tissue radiography, the differential absorption between _____ and _____
glandular;fat;muscle
Which has the lowest spatial resolution?
Nuclear Medicine or Sonography
image noise limits
contrast resolution
Which of the following is a high contrast modality.
C.
A. CT
B. MRI
C. radiography
D. All of the above
the highest occupational exposure of diagnostic x-ray personnel occurs during
fluoroscopy
In digital radiography images are made up of discrete picture elements called?
pixels
the greater the dynamic range, the better the contrast resolution.
True
computed tomography has better ______ resolution than radiography.
contrast
For the digital image, the grid of rows and columns is called
matrix
The process of creating a series of pixels is called?
sampling
increasing the sampling rate…
increases spatial resolution
In digital radiography, spatial resolution is improved with increased
matrix size
The larger the voxel the ___________ the spatial resolution.
voxel size doesn’t affect
Spatial frequency is used to describe the quality of spatial resolution in terms of _____________
line pairs
image detail is also called
spatial resolution
Of all radiographic imaging systems, _____________ has the best contrast resolution
CT
has the best contrast resolution of all x-ray imaging systems because of x-ray beam collimation and the resultant reduction in scatter radiation
The image intensifier improved fluoroscopy by increasing
image brightness
The _______ in the retina are stimulated by _______ light; the _______ are stimulated by _______ light.
rods, low; cones, bright
The principal drawback of the first-generation CT scanner was the _______________
long scanning time
The third generation of CT scanners allowed for further reduction in _____________
scanning time and scattered radiation
CT imaging has excellent ______________ because of the narrow beam collimation
contrast resolution
Each sweep of the source-detector around the body during CT is called a __________
translation
As discussed in class, an advantage of digital fluoroscopy is it ________________ patient radiation dose
decreases
Noise can affect image quality in what way?
decreased contrast resolution
As image noise decreases, contrast resolution…….
increases
Quantization is the same as sampling.
False
As DQE is increased, the amount of radiation necessary to produce an image ______________
decreases
Bit depth determines the imaging systems ……
contrast resolution
DF have faster image acquisition and _______ to enhance image contrast.
post processing
The higher the spatial frequency, the ______ the spatial resolution
HIGHER
Select all of the following which can image in ‘realtime’?
fluoroscopy and sonography
An imaging system bit depth determines what aspect of image quality?
contrast resolution
Perfusion is associated with which imaging modality?
SPECT
A gamma camera records…
gamma rays
The only difference between x-rays and gamma rays is their ____.
origin
Which modality utilizes rectangular pixels?
MRI
Perfusion imaging is typically done by which modality?
SPECT
Of the following, which is the dominant radioisotope used in NM?
technicium
Today, new MR scanners are typically
3.0 Tesla
Which of these are contrast materials/media for radiography and CT?
barium and iodine
more shades of gray is
better contrast resolution
Requires the highest spatial resolution of ALL imaging modalities
Mammography
____ resolution image loses detail; _____ resolution image shows detail
low; high
