digital imaging unit 2 test
which imaging system has a higher DQE
DR
images having higher spatial resolution are composed of
a greater number of pixels
a bit depth of _____ bits produces an image with the greatest contrast resolution
higher like 16
a high signal to noise ratio SNR provides an image with
higher spatial resolution
which of the following would improve digital image quality
large matrix and increased pixel density
which one of the following is used to extract the latent image from the photostimuable phosphor plate
laser light
when comparing DR to CR, DR produces
lower pt dose and less spatial resolution
the arrangement of pixels in rows and columns is known as
matrix size
the process of assigning a numeric value to each pixel to represent a gray tone is called
quantization
which of the following is not a step that is required to transform an analog image into a digital image
ranging
the purpose of a capacitor, such as those used in DR flat panel detectors are used to
store electric charges (electrons)
the image on a photostimuable phosphor plate is not permanent and will fade at a rate of about
25% within 8 hours of the exposure
if the desired spatial resolution for an image is 20lp/mm what must the sampling frequency be
40 lp/mm
this converts xrays to electrons in a direct conversion flat panel detector
amorphous selenium
a fill factor of 80% in direct or indirect digital radiography means that
20% of the pixel area is occupied by the detector electronics with 80% representing the sensing area
the greatest modulation transfer function number is
1
when the CR casette is placed in the reader, arrange the following in the proper sequence of processing the latent image
1. the phosphor plate is scanned with a laser light 2. light guide collects light 3. photomultiplier tube produces an analog signal 4. ADC convers the analog signal to digital signal 5. erase the imaging plate
which one of the following matrix sizes will be able to display the highest spatial resolution
1024x 1024
the analog signal is changed into a digital signal in the
ADC
an image receptor with a high detective quantum efficiency compared to an image receptor with a low DQE would result in
a lower pt dose
the purpose of a "scintillator" in a flat panel receptor is to
absorb xray photons and emit light photons
the gray scale value in the pixels is closely related to the
attenuation properties of the amount and density of the tissue
in CR what is the name of the photostimuable phosphor in the imaging plate
barium fluorohalide
contrast resolution of a CR/DR image is determined by the ______ of the system
bit depth
the number of visible shades of gray in a digital image is determined by _______
bit depth
the xray scintillator layer used in indriect flat panel digital detectors is usually either _____ or ______
cesium iodide, gadolinium oxysulfide
which of the following are found in the detector element of a flat panel detector
charge collection area, capacitor, thin film resistor
the type of image receptor that uses a photostimulable phosphor to acquire the latent image
computed radiography
the smallest exposure change or signal difference that can be detected is a definition for
contrast resolution
At the end of an image extraction cycle, the photostimulable phosphor plate (PSP) is erased by exposing it to intense: a. red light b. laser beam energy c. x-ray energy d. white light
d. white light
which of the following measures the efficiency of a system to convert the xray input signal into a useful output signal
detective quantum efficiency
spatial resolution in a flat panel receptor primarily is controlled by the size of the
detector element (DEL)
the flat panel detector matrix is made up of rows and columns of
detector elements (DELs)
an image formed by recording discrete signals is known as _______ signal
digital
when a greater number of samples are taken from the image receptor signal, this indicates that the
digital data more closely resembles the original signal
which one of the following is defined as the range of exposures that may be captured by a detector
dynamic range
what represents the latent image in a photostimuable phosphor CR system
electrons trapped in conduction band
What is the rule for erasing the fog, caused by the background radiation, from the imaging plate
erase the imaging plate if it has been unused for more than 48 hours
what directly influences the number of electrons collected in a detector element (DEL) of a flat panel detector
exposure to image receptor
to reduce the appearance of grid lines and the moire artifact, grids used in digital imaging should have a high
grid frequency
the principle effect of the use of an insufficient amount of radiation when performing any type of digital radiographic examination is a/an
increase in the amount of quantum mottle (noise) on the image
as the fill factor in the DEL decreases in size, patient dose will need to be
increased
a major advantage of digital receptors over analog receptors is
increased contrast resolution
which of the following will improve the quality (spatial resolution) of the digital image
increased sampling frequency and decreased sampling pitch
thin film transistors are found in which type of digital imaging system
indirect and direct flat panel detectors
with DR image receptors, CCD and complementary metal oxide semiconductors are used in
indirect conversion flat panel detectors
__________ is a measurement of the ability to transfer contrast at a particular resolution from the object to the image receptor
modulation transfer function
as SNR decreases
noise in the form of graininess increases
the highest spatial resolution that can be recorded, and is controlled by pixel pitch, is known as
nyquist frequency
To prevent a moire pattern in your CR digital image, it is best to have the grid lines running _______ to the direction of the laser beam.
perpendicular
the layers of a CR imaging plate include
phosphor, reflective, protective
a device contained within CR, readers that functions to collect, amplify, and convert light released by the photostimuable phosphor into electrical energy is called a
photomultiplier tube
pixel is a shortened term for
picture element
the smallest area represented in a digital image is the
pixel
________ is defined as the number of pixels/mm
pixel density
_______ is defined as the measurement from the center of one pixel to the center of the adjacent pixel
pixel pitch
__________ is the measurement from side to side of the pixel
pixel size
in CR imaging, the sampling frequency of an imaging system determines the
pixel size
contrast resolution is a digital systems ability to
show small differences in gray levels
_______ is defined as the sharpness of the structural edges recorded in the image
spatial resolution
digital imaging systems have a wide dynamic range
true
the higher the contrast to noise ratio, the higher the contrast resolution
true
within the histogram the area that is used to locate the minimum and maximum values of the pixels for the body part is called the
value of interest
a larger image matrix
will increase digital image resolution
a smaller pixel size
will increase digital image resolution
a smaller pixel pitch
will increase the digital image resolution