Physics Test part 6 Flashcards
Reaches on ½ of preset value
rectifier malfunction
Excessive Fluctuation
– loss of tube vacuum
Spiking of meter
indicates a short circuit in the filament circuit of a blown high voltage cable and can be accompanied by smoke and/or the odor of burning rubber.
. Filament Transformer
A step-down transformer to decrease voltage to the filament of the x-ray tube (4 – 12 volts).
Rectifiers
Found in all equipment except for self-rectified.
They are located between the step-up transformer and the x-ray tube.
diode, valve tube, or kenotron tube
Found on older single-phase units.
These are similar in construction to an x-ray tube in that they have a cathode and anode.
Solid state
Found in all newer equipment.
These are made up of silicon crystals with various impurities that can make an N-type or P-type semiconductor.
Valve Tube Transformers
Step-down transformers for the filaments of valve tubes and only used with valve tube rectifiers
High Voltage Cables
Connects the high voltage section to the x-ray tube.
POWER RATINGS FOR HIGH VOLTAGE SECTION
This measures the maximum power that this section can deliver to the x-ray tube during x-ray production during a 0.1 second exposure.
. Fixed mA
A fixed mA is maintained by the circuitry during x-ray production.
Falling Load
Used for all high frequency units and many 3-phase as well.
It is used whenever AEC and mAs timers are utilized.
Advantages of falling load
Shorter exposure times in heavy load situations
* Simpler operation
Disadvantages of falling load
Will not work with tomography
* Can shorten x-ray tube life due to higher mA.
Shared Generators
Two separate exposure rooms share the same high voltage section.
Each room will have its own x-ray tube and control panel but will share a common high voltage section.
Advantages of shared generators
- Lower capital cost versus buying two separate units
Disadvantages of shared generators
Only one room at a time can make an exposure
* If high voltage section malfunctions, two rooms are down.
X-ray Tube Supports
Must possess these characteristics in order to meet FDA guidelines:
a) Strong and sturdy – to support the weight of the x-ray tube, tube housing, and collimator.
b) Support must be counterbalanced
c) Must allow adequate range of motion in order to perform x-ray exams.
Must have SID indicator
e) Immobilization locks need to be incorporated in the support
) Floor Mounted or Vertical Tube Stand
Oldest design for mounting the x-ray tube.
Advantages:
* Low Cost
* Simple installation
* High voltage cables can be relatively short and out of the way.
Disadvantages:
* Not as sturdy as other options
* Track is unhygienic
* Transverse and horizontal movements are restricted, making this option undesirable for a trauma room or for patients on carts or in wheelchairs.
Floor to Ceiling Stand
A second track is mounted on the ceiling, directly above the track on the floor, making for a sturdier installation.
Overhead or Ceiling Suspended System
The tracks are mounted on the ceiling only, with nothing on the floor.
Integrated Tube Stand
The tube mount is integrated or part of the patient table.
C or U Arm
The x-ray tube is mounted on one end of a large metal frame that is in the shape of the letter “C” or “U”.
. Filtration
Material added immediately beneath the x-ray tube window to remove low energy or “soft” x-rays from the beam.
The amount of total filtration can be expressed in two different ways:
Thickness of material
Measured in millimeters and is the most common method.
Half Value Layer (HVL)
The thickness of material that will reduce the intensity of the x-ray beam to ½ of its original intensity.
. Collimator
This is mounted beneath the added filter and consists of a series of lead shutters at right angles to one another that move in opposing pairs.
Patient Table
Place where patient is placed for most exams (except for upright, wheelchair or cart exams), and also contains the image receptor
Upright Bucky
Upright Bucky
