Chapter 28 (Module 1) Flashcards
Spatial resolution is
a. the degree of geometric sharpness.
b. definition.
c. the accuracy of the structural lines actually recorded in the radiographic image.
d. all of the above.
All of the above
The traditional unit of resolution measurement typically used in film/screen imaging is
a. dots per millimeter.
b. line pairs per millimeter.
c. pixel size.
d. the DEL size.
line pairs per millimeter
Poor spatial resolution is caused by unacceptable levels of
a. IR exposure.
b. umbra.
c. penumbra.
d. contrast.
Penumbra
Which can negatively impact recorded detail?
a. using small focal spot
b. longer SID
c. involuntary motion
d. minimal OID
involuntary motion
Factors affecting recorded detail include
a. kVp and filtration.
b. radiographic grids and collimation.
c. mAs and grid ratio.
d. focal spot size and patient thickness.
focal spot size and patient thickness
Spatial resolution is improved when
a. OID increases.
b. OID decreases.
c. SID decreases.
d. the x-ray tube is angled.
OID decreases
Spatial resolution is improved when
a. OID increases.
b. SID increases.
c. SID decreases.
d. the receptor is angled.
SID increases
Spatial resolution in digital imaging is determined by the
a. bit depth.
b. matrix size.
c. pixel size.
d. all of the above.
all of the above
Which radiograph below exhibits the best recorded detail?
a. a PA chest radiograph for evaluation of the heart at 40 in.
b. a PA chest radiograph for evaluation of the heart at 72 in.
c. a lordotic projection of the chest at 72”.
d. an AP chest radiograph for evaluation of the heart at 72 in.
a PA chest radiograph for evaluation of the heart at 72 inches
As focal spot size decreases,
a. umbra is improved.
b. penumbra decreases.
c. spatial resolution increases.
d. all of the above.
all of the above
Penumbra decreases as
a. focal spot decreases.
b. OID decreases.
c. SID increases.
d. all of the above.
all of the above
When switching from a 400 RS film screen combination to a 200 RS system, one should expect
a. an increase in spatial resolution.
b. to use a longer exposure time.
c. a decrease in patient dose.
d. a decrease in spatial resolution.
an increase in spatial resolution
In order to improve the temporal resolution on an image,
a. a longer SID should be used
b. a smaller x-ray beam angle should be used
c. a shorter exposure time should be used
d. the 15% rule should be considered
a shorter exposure time should be used
The best method for controlling motion when the patient is unable to cooperate is to
a. decrease the focal spot size.
b. maintain mAs, while decreasing time.
c. maintain mAs, while decreasing mA.
d. decrease kVp.
maintain mAs, while decreasing time
As a last resort, which human immobilizer is used to hold a patient in position?
a. the radiography student
b. the radiologic technologist
c. the ER nurse
d. the male relative
the male relative
The ____ represents a depth to the information in the digital image.
a. z axis
b. y-x grid matrix
c. y axis
d. x-y grid matrix
z axis
The composite measure of image accuracy compared to the original object, on a scale of 0 to 1 is referred to as?
a. line spread function
b. modulation transfer function
c. point spread function
d. noise reduction function
modulation transfer function
All of the following affect visibility of detail EXCEPT
a. 15% rule.
b. filtration.
c. radiographic grids.
d. SID.
SID
As object spatial frequencies increase
a. MTF increases
b. MTF decreases
c. Nyquist is not a factor
d. MTF is unaffected
MTF is unaffected
A pixel bit depth of 216 will demonstrate _______ shades of gray
a. 32
b. 256
c. 4096
d. none of the above
none of the above
As the spatial frequency of objects increases,
a. MTF increases proportionally.
b. MTF decreases.
c. MTF values approach 1.
d. MTF computes to a value of 1.
MTF decreases
For general radiography, an MTF value of 1 is
a. average.
b. suboptimum.
c. theoretically impossible.
d. a function of mAs.
theoretically impossible
Imaging noise is different from quantum noise in that imaging noise
a. is a function of mAs.
b. is dependent upon kVp.
c. is inherent in the imaging system.
d. cannot be filtered out.
is inherent in the imaging system
In general radiography, quantum noise is
a. filtered out of images.
b. a function of mAs and kVp.
c. designed into the receptor specifications.
d. a recorded detail parameter.
a function of mAs and kVp
The Nyquist frequency is
a. important in analog imaging.
b. sampling a minimum of twice per cycle.
c. unique to radiography.
d. related to involuntary motion.
sampling a minimum of twice per cycle
In digital imaging systems, increasing sampling frequency of the data
a. increases dose.
b. increases image fidelity.
c. decreases MTF.
d. decreases dose.
increases image fidelity
When the sampling frequency is less than the Nyquist value,
a. aliasing is eliminated.
b. the Moire effect can occur.
c. patient dose must increase.
d. the Nyquist value must be altered.
the Moire effect can occur
The overall general shape of human anatomical structures are
a. round or oval.
b. linear.
c. cuboid.
d. curvilinear.
round or oval
A digital detector with a high fill factor
a. will produce poor resolution.
b. will require longer processing time.
c. will produce high resolution.
d. requires more radiation exposure.
will produce high resolution
You have completed a chest radiograph on a 2-month-old infant using a restraining device at a 72” SID. Because of the design of the device, your OID is suboptimum. The image reveals good resolution of the bony anatomy but the pulmonary vasculature is blurred. The EI value is 2040 and the target EI value is 2000. In an effort to improve the quality of the repeat image, the competent radiographer would
a. raise the mA and decrease the exposure time.
b. decrease the SID and maintain the same mAs.
c. switch to small focal spot.
d. ask for mild sedation of the infant to decease respiration.
raise the mA and decrease the exposure time
On a PA projection of the wrist, you notice what appears to be a soft tissue mass superimposed over the bony anatomy. When you inspect the patient, you notice the presence of a large linear scar from a previous injury. The visualization of this scar is primarily due to what characteristic of digital detectors?
a. temporal resolution
b. low contrast resolution
c. high contrast resolution
d. the DEL fill factor
low contrast resolution
Quantum noise impacts radiographic image quality by
a. decreasing geometric unsharpness.
b. increasing temporal resolution.
c. diminishing the visibility of recorded detail.
d. adding artifacts to the image.
diminishing the visibility of recorded detail
From the choices below, select the FALSE statement regarding Contrast-Noise-Ratio(CNR)
a. It is the ratio of the signal difference between areas of interest
b. It is affected by SNR
c. A high CNR is only possible with a low SNR
d. If image noise is high, the CNR will be low
A high CNR is only possible with a low SNR
A convenient and easy patient immobilization method an experienced radiographer will use is
a. a high mA and short exposure time
b. a high kVp and low mA
c. a piece of tape wrapped around the patient’s anatomy
d. a tissue bolus material to hold the body part in position
a piece of tape wrapped around the patient’s anatomy
Of the choices given below, which one would yield the highest image quality?
a. 600 mA, 85 kVp, .70 sec. exp time, 1.2 mm fs, 1.5 mm Al filtration, 4 lp/mm, MTF= 40%
b. 300 mA, 97 kVp, .35 sec exp time 1.2 mm fs, 1.5 mm Al filtration, 3 lp/mm, MTF= 25%
c. 600 mA, 85 kVp, .70 sec exp time 0.6 mm fs, 1.0 mm Al filtration, 1.5 lp/mm, MTF= 60%
d. 200 mA, 110 kVp, .25 sec exp time, 2.0 mm fs 1.2 mm Al filtration 2 lp/mm, MTF = 30%
600 mA, 85 kVp, .70 sec. exp time, 1.2 mm fs, 1.5 mm Al filtration, 4 lp/mm, MTF = 40%
