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)