Rad Review Questions Worksheet Flashcards
The formula for determining the heat units for a 3-phase, 6-pulse x-ray generator is
kV x Time x mA x 1.35
The voltmeter, which reads the kVp selected, is located where in the radiographic circuit?
between the auto xfmr. & step-up xfmr.
How many rectifiers are required for a full-wave, 3-phase, 12-pulse x-ray generator?
twelve
During fluoroscopy, what is the range of mA used in the x-ray tube?
0.5-5 mA
An exposure is taken with a spinning top on a single-phase, fully rectified x-ray generator at an exposure time of 1/30 sec. If the timer circuit is working properly, the radiograph should yield
4 dots
Why is it important for the x-ray tube to have a vacuum inside it?
this allows electrons to flow without any impedance
A tube rating chart is used to
provide a safe range of exposure factors that may be utilized
Which of the following methods are used to regulate the amount of thermionic emission that occurs at the filament?
variable resistor
How long does it take for the completion of one sine wave representing 60 hertz of current?
1/60 second
According to the law of conservation of energy, voltage and amperage have which type of relationship across a transformer?
inversely proportional to each other
In the image intensifier, the anode serves to
accelerate the electrons across the tube
What component in the image intensifier allows images to be magnified?
electrostatic focusing lens
The inverse square law relationship between intensity and distance from a source is based upon
divergence
Photomultipliers, thyratrons, and ionization chambers are devices used in
automatic exposure devices
The size of an object is 7”. The SID is 40”. The OID is 9”. What is the resultant size of the image?
9.03”
When electrons approach the positive electrostatic field of the target, they are abruptly decelerated and lose energy. This energy is converted to
Bremsstrahlung radiation
In the usual diagnostic KV range, insofar as energy absorption from the beam is concerned, which type of interaction between radiation and matter predominates?
photoelectric effect
In the x-ray circuit, the current flowing between the rectifier and the tube is
pulsating DC
As radiation enters the body, two effects can occur: it can be attenuated or it can penetrate completely through. Which of the following is not a factor affecting attenuation?
X-rays are electrically neutral
Which of the following statements is/are correct regarding the anode?
I. It is the positive pole
II. The electron cloud forms here
III. It may be stationary or rotating
I and III
Minification gain occurs when
electrons from the photocathode converge on the output screen
A radiographic unit that requires an oscilloscope to detect voltage waveform irregularities would be
a 3-phase, 12-pulse unit
The thickness of the tomographic section is determined by
exposure angle
The compton effect is characterized by
. part transfer of energy upon collision
Gamma and x-radiation are the same in every way except
both have the same origin
The basic reward of the air-gap technique, improved contrast, relies on the following principle
due to increased OID, the angle of the scatter will miss the film
The M shell orbit in atomic formation is able to contain a maximum of
18 electrons
X-rays produced from the movement of electrons from an outer shell to an inner shell is termed
characteristic radiation
What is the efficiency of x-ray production, using a tungsten anode, at 90 KVp?
0.675%
Faraday’s Law is also referred to as the
Law of Electromagnetic Induction
During a fluoroscopic procedure, the radiologist selects a smaller field-of-view, resulting in a magnified image on the TV monitor. How does this affect the amount of radiation that the patient receives?
it increases the amount of radiation the patient receives
The incident photon gives up all its energy to cause excitation; a new photon of the same energy is given off in a random direction
Unmodified Scatter
Produces an ion pair.
Photoelectric and Compton Scatter
Is responsible for true absorption.
Photoelectric Effect
Is responsible for scattered radiation causing fogged film
Compton Scatter
Causes ionization in tissue
Photoelectric Effect and Compton Scatter
Incident photon with KeV greater than but close to the binding energy of inner shell electron. Atomic # is high to increase probability
Photoelectric Effect
Incident photon with KeV considerably greater than the binding energy of outer shell electrons.
Compton Scatter
Results in true secondary radiation and energies characteristic of the binding energies of the shells involved
Photoelectric Effect
