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Flashcards in Mobile Imaging Review Deck (16):
1

What are the two classifications of mobile x-ray machines?

-Battery operated units
-Capacitor discharge units

2

(T) What are the ranges for kVp and mAs on a mobile x-ray machine?

-Range for kVp is 40 to 130
-Range for mAs is 0.04 to 320

3

What is the total unit of power for a mobile x-ray machine?

Total unit power is between 15 and 25 kW

4

(T) 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 12 volt 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

5

(T) What are the advantages/disadvantage 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

6

(T) What are the three important technical factors for mobile imaging?

-Grid
-Anode heel effect
-SID

7

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:

1. off-center grid
2. off-level grid
3. off-focus grid
4. upside-down grid

8

(T) 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 greater the grid cutoff.

9

What is the ratio and focal range for most focus type grids?

-6:1 or 8:1 ratio
-36 to 44” focal range

10

(T) What is the grid ratio for portable and bucky grids?

-Portable grids: 6:1 or 8:1
-Bucky grids: 12:1

11

(T) 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 @ anode end due to the greater absorption of x-rays.

12

(T) Anode heel effect:

A thicker body part @ cathode end and a thinner part @ anode end.

13

(T) Mobile radiography produces:

the highest occupational radiation exposures for radiographers.

14

(T) Recommended minimal distance from mobile unit when making exposure is:

6 feet or length of the cord.

15

(T) The single most effective means of radiation protection is :

Distance

16

(T) according to the Federal Safety Regulation. SSD or source-to-skin distance cannot be :

less than 12 inches