Radiography: Image Acquisition and Evaluation Flashcards
What radiography imaging system feature measures and automatically terminates exposure when a preset amount of radiation is detected?
Automatic exposure control
Would imaging a patient with a small bowel obstruction require an increase or decrease in radiographic technique to maintain receptor exposure?
A decrease
Would imaging a patient with ascites require an increase or decrease in exposure factors?
An increase
Misrepresentation of the true size or shape of an imaged part is known as ___________________
distortion
Loss of detail in a radiographic image will occur if the object-to-image distance is increased or decreased?
Increased
Will elongation or foreshortening occur if there’s an increase in X-ray tube angulation?
Elongation
If an insufficient number of X-ray photons reach the detector, what will the resulting image demonstrate?
Quantum noise (or quantum mottle)
Standard radiographic X-ray tubes typically have focal spot sizes in what size ranges, from small focus to large focus?
0.6 mm for small focus to 1.2 mm for large focus
What are the 3 factors that keep a radiographic image from losing detail and becoming unsharp?
**Source size/Source-to-image-receptor distance (SID), source-to-object distance (SOD), and object-to-image-receptor distance (OID) **
A grid ratio is defined as the relationship between the height of the lead strips and the _________________ .
distance between the lead strips
Which grid has lead strips angled to coincide with the divergence of the X-ray beam?
A focused grid
The number of grid lines per inch or centimeter is called the __________________ .
**grid frequency **
The absorption of the useful beam with resulting loss of exposure across the image receptor is called _______________________
grid cutoff
Which grid ration will absorb the most scatter radiation: 8:1, 10:1, 12:1, or 16:1?
**16:1 **
What range of grid ratios is most often used for general-purpose X-ray imaging systems?
Between 10:1 and 12:1
Grids should be used when the thickness of the anatomy being radiographed exceeds ________________.
Approximately 3.93 inches (10 cm)
What technical factor must be increased when using a grid to compensate for absorbed X-ray photons?
mAs
When mAs adjustments are not possible, image receptor exposure can be doubled or halved by employing what rule?
The 15% Rule
_______________________ technique charts provide the lowest amount of patient radiation exposure.
Variable kV (or kVp)
What specific technique setting must be adjusted when imaging a patient undergoing a barium enema?
kVp
What type of technique chart uses a fixed mA value and a kVp that varies according to the thickness of the anatomy being imaged?
A variable-kVp radiographic technique chart
Is the resulting image contrast higher or lower when using a variable kVp technique chart versus using a fixed kVp technique chart?
**Higher **
In digital radiography, _________________ and ___________________are determined by computer software and monitor controls.
brightness and contrast
In digital radiography, the _________________________ provides critical exposure feedback that the correct imaging settings have been received by the phosphors in the imaging plate, which are usually proprietary.
exposure indicator/index (EI) or deviation indicator/index (DI)
The ability to distinctly image small objects next to each other, with high contrast, is referred to as ________________.
spatial resolution
_____________________ is the ratio of an image to the object as a function of spatial frequency.
The modulation transfer function
___________________ is the measurement of how efficiently a detector converts incident X-ray photons into useful image signals (relative to noise).
Detective quantum efficiency
Scatter radiation produced by extra tissue in the X-ray field from improper collimation or lack of shielding, that degrades image quality, results in what effect?
**The “fogging” effect **
In digital radiography, _____________________ is the range of X-ray intensities, or shades of gray, that a digital system can reproduce.
the dynamic range
______________________ is an interference pattern/artifact caused by the coincidence of grid lines and a scanning laser in a computed radiography system.
A moiré pattern
The inadvertent use of more radiation dose to overcome the noise effect of underexposure is commonly known as ________________.
**dose creep **
In a standard radiographic table, how many sensors (cells) are typically contained within an automatic exposure control device?
3
In radiography, ____________________ is proportional to the amount of image contrast and the square root of the number of photons that are transmitted.
the signal-to-noise ratio
The range of exposure value to the receptor that produce an optimal diagnostic image is known as _______________ .
**exposure latitude **
In computed radiography, this is comprised of europium-doped barium fluorohalide.
A photostimulable phosphor plate
The spatial resolution in a flat-panel digital radiography receptor is primarily controlled by the size of the ___________________ .
detector elements
If an image is produced with a low number of X-rays, will the quantum mottle be higher or lower than if the image was formed with a high number of X-rays?
Higher
TRUE or FALSE: Information about exposure techniques involving adding X-ray beam filtration is NOT needed on a radiographic exposure technique chart.
True
Radiographic contrast is the product of which 2 factors?
Image receptor contrast and subject contrast
What law states that regardless of whether a radiograph is made with short exposure time or long exposure time, the receptor exposure will be the same if the mA value is constant?
The reciprocity law
