What are two classifications of mobile x-ray machines?
Battery operated and capacitor discharge units
What are the ranges for kVp and mAs on a mobile x-ray machine?
Ranges for kVp is 40 to 130
Ranges for mAs is 0.04 to 320
What is the total unit of power for a mobile x-ray machine?
Total unit power is between 15 and 35 kW
Explain the various factors of the mobile machine as it relates to speed, incline, charge, recharging and number of exposures.
- 2 sets of batteries (10 to 16 12V batteries connected in a series
- 2.5 to 3 mph average walking speed
- Maximum incline of 7 degrees
- 10 to 15 exposures when fully charged
- 10 miles on level ground when fully charged
- 8 hours charging time if fully discharged
What are the advantages/disadvantages of the capacitor-discharge unit?
- Smaller size/easy to move/lighter in weight
- kVp drops constantly during length of exposure (kvp may start @ 100 but during the exposure drop to 80 by the end)
What are the three important technical factors for mobile imaging?
Grid, anode heel effect, SID
The incorrect use of a grid can result in loss of density across all or part of an image. Grid cut-off can result from 4 factors:
- off-center grid
- off-level grid
- off-focus grid
- upside-down grid
If a longitudinal grid tilts transversely such as when placing under a patient on a mattress, the CR forms an angle across the long axis of the grid resulting in:
A lost of image density or grid cutoff
The CR must be centered along the center axis of the grid. If the CR is off from the midline, grid cutoff can result. The more CR is off centered the _____ the grid cutoff.
Greater
What is the ratio and focal range for most focus type grids?
6:1 or 8:1 ratio
36 to 44” focal range
What is the grid ratio for portable and bucky grids?
Portable grids: 6:1 or 8:1
Bucky grids: 12:1
What is the concept of the anode heel effect?
- The intensity of radiation from the cathode end is greater than at the anode end.
- The heel effect causes a decrease in image density at anode end due to the greater absorption of x-rays.
A ____ body part at cathode end and a _____ part at anode end.
Thicker; thinner
_____ radiography produces some of the highest occupational radiation exposures for radiographers.
Mobile
Recommended minimal distance from mobile unit when making exposures is ______ or length of the cord.
6 feet
The single most effective means of radiation protection is ________.
Distance
SSD or _________ cannot be less than _______ according to the Federal Safety Regulation.
Source-to-skin distance; 12 inches
What is trauma?
- A sudden, unexpected dramatic event
- Incorporates a range of conditions
In trauma imaging, how does one approach the standard projection that are part of the routine protocol for imaging different body parts?
Adaption (to patient)
What are the differences among the four levels of hospitals?
- Level 1
- Level 2
- Level 3
- Level 4
What are the different types of forces associated with trauma imaging?
- Blunt trauma (MVA, collisions, falls and aggravated assault)
- Penetrating trauma (gun shot wounds, stab wounds, impalement injuries, foreign body ingestion and aspiration)
- Explosive trauma (pressure shock waves, high-velocity projectiles and burns)
What is Principle 1 for trauma imaging?
2 projections 90 degrees to each other with true CR-part-IR alignment
What is Principle 2 of trauma imaging?
Entire structure is included on image
- Selection of IR size
- Secondary fractures
- Joint nearest fracture site
What is Principle 3 of trauma imaging?
To maintain safety for patient, healthcare workers and the public
