Exam 1 (Selective, Compensatory filtration, and Tube failure) Flashcards
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Function of selective/compensating filtration
Improves film quality by compensating for the patients varied thickness’ to produce a better image
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
How does selective/compensating filtration improve the film quality?
Attenuates part of the beam to lessen intensity to the thinner parts (and reduces radiation before it strikes the patient)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
______ are placed on the front of the beam limiting device and are usually made of aluminum or copper
Portal filters
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F Selective filters are not necessary with spinal radiography
FALSE
Selective filters are necessary for full spine films and most A-P & lateral thoracic films
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F Selective filters can be used when X-raying feet to filter toes. It does produce a line between filtered and unfiltered parts (unless the line is tapered)
TRUE
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
_________ have a gradual decrease in thickness that produces no line of demarcation between filtered and unfiltered areas
Wedge Filter Taper (part of Wedge Filter System)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
What is the Nolan Filter System?
A system of variable filters that use multiple pieces of aluminum and copper of different thicknesses to create more versatile selective filters
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Refers to the use of beam attenuation after the beam intensity has passed through the patient, therefore, adding unneeded exposure
Underpart filters
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Underpart filters and mostly used in the form of _________ and often used for ___________ films
Split screens Full spine
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
What can cause the anode to melt?
Failure of the tube leading to wearing down the ball bearings in the anode causing the surface to melt
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
How to prevent the anode from melting
Limit the time that you hold the rotor button down to prevent increased thermionic emission (excessive exposures cause anode pitting)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Charts that come with all X-ray machines
Tube rating chart
Tube cooling chart
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Unit used for some calculations of the tube rating or tube cooling chart
Heat Units (HU)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
How to calculate HU
mA * time * kV = HU Ex: 100 mA 0.5 sec 50 kV
100 * 0.5 * 50 = HU
HU = 2500
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
If the tube hasn’t been used for a number of hours, a tube _______ is recommended before making a large exposure
Warm up
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Function of the warm up
Prevents thermal shock to the anode which can cause your anode to crack or more likely the anode stem to crack and break off
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
If you need to increase the mAs, do it with either the _______ or _______
mA station or time
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
A ____ mA setting will lessen tube stress
Lower
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
A ______ time will allow less patient motion
Shorter
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F Most all machines will automatically prevent harmful exposures or if the exposure would overload the tube
TRUE
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Transformers and rectifiers found in generators require ____ volts and ___ amps
220 volts
100 amps
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Part of a generator that changes the incoming current from volts to kilovolts
Transformer
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Alternate names for the high voltage transformer of a generator
Step up transformer
High voltage circuit
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Converts amps to milliamps
Filament circuit
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F 1/10 of an amp is a milliamp
FALSE
1/1000th of an amp = 1 milliamp
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
What is the mA and kV usually used for an office setting?
40-125 kV
50-300 mA
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Alternate names for the filament circuit
Filament transformer
Low voltage circuit
Step down transformer
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Changes the current from AC to DC
Rectifiers
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Current where electrons are moving forward and backward directions
Alternating current (AC)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F AC is used for the tube
FALSE.
AC would send electrons toward the cathode and destroy it. Therefore DC is needed for the tube
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Process of changing AC to DC as done by rectifiers
Rectification
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
How do rectifiers work?
Rectifiers are diodes that eliminate the lower negative pulse of the cycle protecting the filament. Causes a half wave rectification
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Rectifiers that change the negative charge to a positive charge and allowing 2 positive waves away from the cathode making it more efficient than half wave rectification
Full wave rectification
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
The high point of the wave
Peak
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
The desired kV that is set in the rectifier is called this
Kilovolt peak (kVp)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
The variable of the kV below the peak that make up some of the exposure
Ripple
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F The more ripple, the better
FALSE.
The less ripple, the better
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Has 1 line sources and creates maximum ripple
Single phase generators
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Has 3 separate but intertwined lines that allows for more peaks and less dips (less ripple)
3 phase generators
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
3 phase generators eliminates most _____ and maintains most of the _____. While more efficient, it is not practical due to its ______
Ripple
kVp
Expense
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Generators that have virtually no ripple, are more accurate, produces greater photon energy, has fewer soft rays, gives the patient less exposure, and is more affordable than a single or 3 phase generator
High Frequency Generators
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Controls the length of the exposure.
Timer circuit
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
T/F The longer the timer circuit, the more electrons that bombard the anode which increases the number of x-rays
True
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Range of exposure time. Why is the shortest time preferred?
1/120th of a second to a few seconds Reduces the chance for patient motion
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Types of timer circuits
Synchronous
Electronic
mAs
Automatic Exposure Control (AEC)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Timer circuit in widest use
Electronic timers
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Combine mA and seconds in 1 control. Pretty popular timer circuit. Calculated to use the lowest time and safest mA
mAs timers
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Circuit timer that uses photocells in front of a film
Automatic Exposure Control (AEC)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Found on older machines. Protects against voltage drops and surges
Line voltage compensator
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
Selector options usually found on a low voltage circuit (mA) or filament circuit
-50, 100, 200, 300 mA
-Small or Large focal spot sizes (automatic)
Ex: 50S, 100S, 100L, 200L, and 300L
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
High voltage circuit (kVp) that adjusts settings in increments of 10 kVp
Major
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
High voltage circuit that adjusts settings by increments of 1 kVp
Minor
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
When activated (pressed) it rotates the anode and activates the filament circuit causing thermionic emission
Rotor control (Prep button)
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
When depressed, send shooting electrons to the anode to create the exposure. Must remain depressed for the entire exposure.
Exposure button
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
What happens to the film if the finger slips off before the full exposure?
Film will be too light from lack of full exposure
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
When the finger slips off the exposure button, in this case its called the __________, the film will be underexposed
Deadman switch
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
What systems utilize a part selection button on their equipment?
Anatomical programming systems
Exam 1 (Selective/Compensatory Filtration, and Tube Failure)
4 primary factors concerning X-ray exposure
1) Kilovoltage peak (kVp)
2) Milliamperage (mA)
3) Time of exposure
4) Distance of the tube from the receptor
What controls the speed of electrons, the beam energy, the penetrating power, the quality of the x-ray beam, and the film contrast?
Kilovolts (kV)
T/F Increasing kVp will darken the film (decreasing contrast)
True
What controls the tube current, quantity of electrons, and quantity of X-rays independent of time?
Milliamperage (mA)
T/F Increasing mA lightens the film
FALSE.
Increasing mA darkens the film
What controls the tube current, quantity of electrons, and quantity of X-rays dependent on time?
Length of time of exposure (in seconds = mAs)
Controls the quality of the x-ray reaching the patient and the film. Beam intensity does decrease as we increase this.
Distance of the tube from the receptor(film)
a.k.a. Tube distance
T/F Increasing the tube distance will lighten the film
True
T/F The image size increases with tube distance
False
Size decreases due to less divergence
Inverse square law
States that photons striking the film are inversely proportional to the square of the distance.
2 standard tube distances
40 inches
72 inches
What is the difference in the mAs required for shotting X-ray at 40 inches and 72 inches?
about 3x or 1/3, depending on the conversion
72” to 40” = 1/3 mAs
40” to 72” = 3x mAs
Secondary factors the effect the X-ray exposure
1) Field size
2) Compensating filtration
The more collimation, the ____ the secondary radiation, causing the film to _______
Less
Darken
T/F Increasing compensating filtration darkens the film
FALSE.
It lightens the film