Chapter 20 Flashcards
Digital radiographic systems are divided into two classes. They are
a. storage phosphor and photostimulable plate technology.
b. direct and indirect conversion.
c. laser digitizers and selenium plates.
d. computed radiography and storage phosphor technology.
direct and indirect conversion
Computers operate using a(n) ____ language.
a. monosyllabic source language
b. binary machine
c. logarithmic machine
d. alphanumeric source language
binary machine
Each binary number is called a
a. pixel.
b. bit.
c. byte.
d. voxel.
bit
An eight-bit word is called a
a. byte.
b. RAM.
c. bit.
d. kernel.
byte
Analog to digital conversion involves two steps. They are quantification and ___________.
a. rescaling
b. sampling
c. pixelization
d. toning
sampling
A voxel is different than a pixel in that a voxel
a. has only two dimensions
b. controls the volume of audio
c. possesses a third dimension
d. controls the pixel dimensions
possess a third dimension
A graphical analysis of signal values from minimum to maximum values in a data set is termed a
a. look-up table.
b. histogram.
c. pixel spread.
d. exposure index.
histogram
The shape and distribution of values on an x-ray exposure histogram is specific to selected anatomy and the exposure used for the exam. In the histogram, the data is analyzed to identify the __________.
a. line spread function
b. point spread function
c. values of interest (VOI)
d. modulation transfer function (MTF)
values of interest
The window level controls image
a. resolution.
b. contrast.
c. speed.
d. brightness.
brightness
The window width controls
a. darkness.
b. contrast.
c. speed.
d. resolution.
contrast
Spatial resolution is controlled by
a. bit depth.
b. pixel size.
c. matrix size.
d. byte size.
pixel size
Computerized digital images consist of a ________ of picture elements, each with a video display value or gray shade.
a. row
b. matrix
c. column
d. pixel
matrix
Each pixel in a digital display matrix is located according to its
a. electronic address.
b. voxel position.
c. DICOM address.
d. field of view.
electronic address
A matrix of size 2048 × 1536 would have _______ pixels.
a. 512
b. 3584
c. 3,145,728
d. 2048
3,145,728
In digital imaging, the limiting factor in spatial resolution is the
a. pixel depth.
b. pixel size.
c. bit depth.
d. pixel pitch.
pixel size
A pixel that has an eight-bit depth displays _______ shades of gray.
a. 126
b. 256
c. 512
d. 1024
256
Which of the choices below would produce the highest spatial frequency and contrast?
a. gall bladder
b. Contrast-filled urinary bladder
c. 3-mm renal calculi (stone)
d. contrast-filled appendix
3-mm renal calculi (stone)
All of the following are related except one. Select the choice that is NOT RELATED to the others.
a. local processing
b. manual processing
c. point processing
d. geometric processing
manual processing
In digital image processing, the digital data set is arranged into a histogram distribution in order to determine the
a. display matrix.
b. exposure index.
c. values of interest (VOI).
d. both b and c.
both b and c
In digital image processing, an overexposed or underexposed image can be modified to achieve an acceptable “look” through a histogram analysis. This is the result of the digital processing technique of
a. spatial frequency processing.
b. point processing.
c. rescaling.
d. look-up table application.
rescaling
The purpose of an LUT is to
a. determine the exposure index.
b. create the histogram.
c. apply a predetermined scale of contrast to the digital data set.
d. perform geometric processing in order to reorient the image on display.
apply a predetermined scale of contrast to the digital data set
If the radiographer applied an ankle LUT to a chest radiograph data set, the image would demonstrate
a. high contrast.
b. low contrast.
c. very high resolution.
d. low resolution.
high contrast
All of the following are true of local area processing EXCEPT:
a. It relies on the application of kernels to pixels.
b. Kernels are ultimately applied to the entire pixel data set.
c. Spatial filtering is an example of local area processing.
d. Electronic magnification of the image is an example of local area processing.
electronic magnification of the image is an example of local area processing
The relationship between digital image resolution
a. is direct with matrix size.
b. is indirect with pixel size.
c. is direct with pixel bit depth.
d. both a and b.
both a and b
When matrix size is increased and pixel size goes down,
a. spatial resolution decreases.
b. spatial resolution increases.
c. contrast increases.
d. both a and c.
spatial resolution increases
Noise on a digital image is the summation of inherent electron system noise and quantum mottle noise. Of these two, the radiographer can improve the quantum noise on an image by
a. decreasing the exposure intensity of the x-ray beam.
b. increasing the exposure technique.
c. turning off any electronic devices during exposures.
d. all of the above.
increasing the exposure technique
- When the quality of a digital detector is inspected for purchase, the preferred detector for purchase would have a
a. DQE of 65 percent and MTF of 0.55.
b. DQE of 40 percent and MTF of 0.80.
c. DQE of 68 percent and MTF of 0.80.
d. DQE of 55 percent and MTF of 0.35.
DQE of 68 % and MTF of 0.80
The deviation index (DI)
a. compares entrance dose to the detector to an established department target dose.
b. compares entrance dose to the patient to a reference industry-standard target dose.
c. compares exit dose to the detector to an established department target dose.
d. compares DQE and MTF with a reference value.
compares entrance dose to the detector to an established department target dose
All of the following impact digital image spatial resolution EXCEPT
a. pixel pitch.
b. bits/pixel.
c. DEL dimension.
d. sampling frequency.
bits/pixel
Exposure indicators used in digital radiography
a. represent exposure to a digital detector.
b. may be direct or indirect with regard to exposure and the number calculated.
c. can be used to assess image quality.
d. all of the above.
all of the above
Fuji Medical System’s exposure indicator system uses an S# as the measure of exposure to its digital detector. From the choices below, select the item that is NOT TRUE of Fuji’s system.
a. An S# of 200 represents approximately 1 mR of exposure
b. S#s change directly with exposure, in a linear fashion
c. Proper exposures should range between 150 and 250 in terms of S# values
d. The S# is inversely proportional to exposure
S#’s change directly with exposure, in a linear fashion
In a radiology department that is consistent with ALARA guidelines
a. EI#s and DI#s cannot be used interchangeably.
b. Target EI#s for all exams will be established.
c. EI#s and DI#s are used as benchmarks of image quality.
d. all of the above.
all of the above
To reduce the visual appearance of noise on a digital radiographic image, what postprocessing technique can be used to suppress the noise?
a. image magnification
b. low-pass filtering
c. high-pas filtering
d. rescaling
low-pass filtering
