RADIOGRAPHIC TECHNIQUE Flashcards
What does mA control with a constant exposure time?
X-ray quantity and patient dose.
Does mA affect x-ray quality?
No, x-ray quality remains fixed with a change in mA
What is the purpose of radiographic technique?
To produce a high-quality image.
Name the four prime exposure factors.
kVp, mA, exposure time, and SID.
What is the primary control of x-ray beam quality?
kVp
How does higher kVp affect image contrast?
It reduces image contrast.
What does mA determine?
number of x-rays produced.
What happens when exposure time is decreased?
mA must increase to maintain x-ray intensity.
What formula is used to calculate mAs?
mA x exposure time (s).
What is the purpose of the falling-load generator?
To adjust exposure factors to the highest mA and shortest exposure time allowed.
How does distance (SID) affect optical density?
Changing SID affects the intensity of the x-ray beam, thus altering OD.
Does changing the focal spot affect x-ray quantity or quality?
No, it does not.
Name the three types of filtration.
Inherent, added, and compensating.
What is inherent filtration equivalent to in mm of aluminum?
0.5 mm Al.
What is total filtration in radiography?
Inherent filtration + added filtration, totaling 2.5 mm Al.
What is the purpose of a compensating filter?
To deliver a uniform exposure to the image receptor.
Define half-wave rectification.
X-rays are produced and emitted only half the time.
How does three-phase power affect x-ray quantity and quality?
It results in higher x-ray quantity and quality.
What type of generator is commonly used in mammography?
High-frequency generator.
Name three patient factors affecting radiographic technique.
Anatomical thickness, body composition, and image quality factors.
What is body habitus?
The general size and shape of a patient.
List the four body habitus types.
Sthenic, hyposthenic, hypersthenic, and asthenic.
What tool is used to measure patient thickness?
caliper
How is radiolucent tissue represented on an x-ray?
black
How is radiopaque tissue represented on an x-ray?
white
What is destructive pathology?
Pathology that makes tissue more radiolucent.
What is constructive pathology?
Pathology that makes tissue more radiopaque.
what kind of pathology is emphysema?
destructive/subtractive
what kind of pathology is pneumonia?
constructive/additive
What are the main image-quality factors?
Optical density (OD), contrast, detail, and distortion.
The degree of blackening in the radiograph.
optical density
Which factor primarily controls OD?
mAs
What is overexposure in radiography?
When the radiograph appears too dark due to excessive x-ray exposure.
What is underexposure in radiography?
When the radiograph appears too light due to insufficient x-ray exposure.
Define the Fifteen Percent Rule.
Increasing kVp by 15% is equivalent to doubling the mAs.
What is contrast in radiographic imaging?
The difference in OD between adjacent anatomical structures.
What produces a long scale of contrast?
High kVp.
What produces a short scale of contrast?
Low kVp.
Name an exposure factor that decreases contrast.
Increased kVp.
The sharpness of appearance of small structures on the radiograph.
detail
How is sharpness of image detail best measured?
By spatial resolution.
How is the visibility of image detail best measured?
By contrast resolution.
The misrepresentation of object size and shape on the radiograph.
distortion
What causes elongation in radiography?
Poor alignment of the IR or tube.
What causes foreshortening in radiography?
Poor alignment of the anatomical part.
What are the principal radiographic image quality factors?
OD, contrast, detail, and distortion.
What are radiographic technique charts used for?
To determine the technical factors for specific examinations.
What is the main benefit of using a technique chart?
Consistency in exposure quality across technologists.
What is a variable-kVp technique chart?
A chart using a fixed mAs and varying kVp based on part thickness.
Who developed the fixed-kVp technique chart?
Arthur Fuchs.
What is a high-kVp technique chart ideal for?
Barium work and routine chest radiography.
What does AEC stand for?
Automatic Exposure Control.
What does AEC control in an x-ray system?
It determines radiation exposure duration.
What must the radiologic technologist select in an AEC system?
kVp, mA, backup time, sensor, and OD.
What is the primary benefit of AEC systems?
Consistent exposure and reduced need for manual adjustments.
What does APR stand for in radiographic technique?
Automatically Programmed Radiography.
What is the function of APR?
Guides RTs with preset exposure factors based on body part and size.
Imaging a plane of interest while blurring structures on either side of that plane.
tomography
What is the principal advantage of tomography?
Improved contrast resolution.
What is the principal disadvantage of tomography?
Increased patient dose.
The pivot point around which the x-ray tube and image receptor move.
fulcrum
What is the object plane in tomography?
The plane where structures are in focus while others are blurred.
What happens to structures outside the fulcrum plane?
They exhibit increasing motion blur.
The simplest form of tomography, using linear movement of the tube and image receptor.
linear tomography
It determines the section thickness of the tomographic image.
tomographic angle
Thick-slice tomography with a small tomographic angle (less than 10 degrees).
zonography
Where is panoramic tomography commonly used?
In dental imaging for fast surveys of the head.
What is magnification radiography?
A technique that increases OID to magnify structures.
What type of focal spot is used in magnification radiography?
A small focal spot.
Why are grids not needed in magnification radiography?
Large OID naturally reduces scatter.
What formula calculates the magnification factor?
MF = SID / SOD.
How does increasing mA affect x-ray quantity?
It increases x-ray quantity.
What happens to x-ray quality when exposure time is adjusted?
X-ray quality remains unaffected.
How does distance (SID) impact patient dose?
Increased SID reduces patient dose.
What effect does focal-spot size have on x-ray production?
Larger focal spots produce more x-rays.
What type of filtration is permanently installed in x-ray machines?
Inherent filtration.
What is the purpose of compensating filtration?
To create a uniform exposure across varying tissue densities.
How does full-wave rectification affect exposure time?
eliminates dead time, reducing exposure time.
What is the effect of single-phase power on x-ray emission?
X-ray emission is less constant than with three-phase power.
What voltage ripple percentage is associated with high-frequency generators?
Less than 1%.
What determines the visibility of small anatomical details on an image?
The sharpness of image detail.
What factor controls geometric detail in radiography?
Focal-spot size, SID, and OID.
What positioning reduces distortion in radiographic imaging?
Proper alignment of the IR, tube, and anatomical part.
How does thickness of body part affect optical density?
Thicker parts decrease OD due to increased attenuation.
What should be adjusted when changing patient thickness?
kVp or mAs to maintain OD.
How does high kVp impact subject contrast?
High kVp reduces subject contrast.
What is the recommended SID for chest radiography?
180 cm (72 inches).
What is the result of using a microfocus tube in mammography?
Enhanced visualization of microcalcifications.
What factor must change by 30% to affect OD?
mAs.
How much must kVp change to produce a visible OD change?
Approximately 4%.
What is the five percent rule in radiography?
Increasing kVp by 5% allows a 30% reduction in mAs for the same OD.
How does grid ratio affect contrast?
Higher grid ratios increase contrast by absorbing scatter.
What is the purpose of collimation in radiography?
To limit the x-ray field size, reducing scatter and improving contrast.
How does beam restriction impact contrast?
Increased restriction improves contrast.
What is the result of grid misalignment?
Grid cutoff, reducing image quality.
What factor is essential to APR’s functioning?
Proper calibration and input for accurate exposures.
What kVp setting is ideal for routine chest radiography?
High kVp for enhanced tissue visualization.
How should a technique chart be calibrated?
Based on accurate exposure settings and equipment consistency.
What is a primary disadvantage of fixed-kVp technique charts?
Less flexibility for specific body part adjustments.
Why are filters used in radiographic systems?
To harden the beam and improve tissue penetration while minimizing soft x-rays.
