Semester 2 physics exams Flashcards
If an x-ray imaging system is operated at 600 MA, 100 MS, the total MAS will be?
60mAs
Electron emission from a heated source
Thermionic emission
A radiographic technique calls for 800 MA, 1/20 s exposure what is the mAs
40
The difference between x-rays and gamma rays is
Their origin
Three main parts of the x-ray imaging system are the x-ray tube, _______, and ______
Operating console high-voltage generator
When considering the electromagnetic spectrum photons of a radio broadcast have relatively
Low energy and long wavelengths
Regarding the induction motor on the x-ray tube the only part to rotate is the
Rotor
Radio waves, light, and x-rays are all examples of ______ energy
Electromagnetic
Convert AC to DC
Rectifier
A diode allows electrons to flow _____
From cathode to anode
Which of the following principles of rectification produces the maximum efficiency of x-ray production
High frequency
As compared with particulate radiation, electromagnetic radiation Is
More penetrating
In modern imaging systems the components for rectification are
Solid state semi conductors
According to quantum mechanics the energy of an x-ray is
Inversely proportional to its wavelength
When a step up transformer is in use
The secondary voltage is greater than the primary voltage
The development of modern quantum mechanics is attributed to
Max Planck
Which of the following has a constant value for all electromagnetic radiation
Velocity
The mAs timer is usually set to give the ______ mA at the _____ time
Highest, shortest
Voltage across the x-ray tube is most constant with
High frequency generator’s
In AEC device can
Use an ionization chamber between the patient and the image receptor
The high-voltage generator contains a high-voltage transformer and the
Rectifiers
The difference in the waveform between the primary and secondary sides of the high-voltage transformer is the
Amplitude
When compared with visible light x-rays have shorter
Wavelength
Voltage across the x-ray tube is most constant with
High frequency generator’s
X-ray tube current is usually measured in which of the following
Amperes
Smallest quantity of any type of electromagnetic radiation is a
Photon
The four properties of photons are
Frequency, wavelength, velocity, amplitude
The principal purpose of the high-voltage transformer is to do which of the following
Increase voltage
Line compensation is
Required to stabilize voltage
X-ray transformers operate on the principle of
Mutual induction
The x-ray generator with the lowest power rating is the ______ imaging system
Single phase
Variations in power distribution do the x-ray machine Are corrected by The
Line voltage compensator
For any electromagnetic radiation and increase in frequency result in
An increase in energy
X-rays and gamma rays are both examples of electromagnetic radiation in addition they both have
No electrostatic charge
X-rays have ____ mass and _____ charge
No mass no charge
The most accurate type of timer is the
Electronic timer
A transformer operates on
AC NOT DC
What is the removal of an electron from an Atom called
Ionization
A single-phase waveform has a ______ ripple
100%
If an automatic exposure control device ____ is required
Back up timer
The energy of an x-ray photon is directly proportional to its
Frequency
Bone that absorbs x-radiation is called
Radiopaque
The inverse square law states that
Intensity is inversely proportional to the square of the distance
The auto transformer has _____ windings
1
The exposure timer on a three phase radiographic imaging system will
Be electronic
Which of the following is greater for a 30 KEV x-ray then a 60 KEV x-ray
Wavelength
In radiographs of bony structures in bedded in soft tissue the bone is
Radiopaque
The inverse square law involving distance could be applied to
All of the above
The automatic exposure control terminates the exposure when
Sufficient radiation reaches the image receptor
Thermionic emission at the filament determines the _______ across the x-ray tube during an exposure
Milliamperage
Approximately ______% of the kinetic energy of the projectile electrons is converted to x-rays at the target
1%
Characteristic x-rays are produced by
Released binding energy
Most of the x-rays produced at the target are
Bremsstrahlung
An increase in mAs would ______ the ______ of the emission spectrum
Increase, amplitude alone
When electrons bombard the target _____% Of their kinetic energy is converted to heat
99
What is produced when the project electron excites an outer shell electron
Heat
In a tungsten targeted x-ray tube operated at 90 KVP the most abundant x-ray would be a
30 kev Brem X-ray
Which of the following is an advantage of the rotating anode tube over the stationary anode tube
Higher heat capacity
The x-ray tube current is
Controlled by the filament current
How does added filtration affect the emission spectrum
Reduced amplitude and a shift to the right
To maintain exposure on a radiograph and increase of 15% in KVP must be accompanied by a _____ reduction in mAs
50%
At 55KVP ______ of the x-rays produced Are bremsstrahlung
100%
An increase in KVP would _______ the ______ of the emission spectrum
Increase, amplitude and position
The wavelength of an x-ray
Becomes longer as projectile electron kinetic energy is reduced
When distance is increased x-ray quantity at that distance
Decreases in proportion to the distance squared
If radiographic technique is 74 KVP and 80 mAs
Brem x-ray energy increases if the voltage is increased to 84 KVP
X-ray tube current is usually measured in which of the following
Milliamperes
An increase in KVP results in an increase in
Radiation quality
Bremsstrahlung x-rays are produced by ______ ______ at the target
Slowing electrons
The useful characteristic x-rays from tungsten targets are ______ xrays
K-shell
Bremsstrahlung radiation is produced by
Conversion of projectile electron kinetic energy to electromagnetic energy
The intensity of x-ray exposure is best represented by
The area under the emission spectrum
In an average radiographic technique is used
Most x-rays are bremsstrahlung
A 15% increase in KVP is equivalent to
Doubling the mAs
The _____ is the source of radiation in the x-ray tube
Focal spot
The formula for heat units HU In a single phase high voltage generator is
KVP x mA x s
If the distance from the S ID is reduced by half how is the x-ray intensity at the image affected
It is increased four times
How would the bremsstrahlung spectrum change of operation at 80 KVP 200 MA 100 ms or change to 64 KVP 200 MA and 100 ms
It would shift to the left and the amplitude would be lower
Which of the following factors principally accounts for the reduced x-ray intensity at low energy
Added filtration
The heel effect occurs because of
X-ray absorption in the anode
Which is the most appropriate measure of x-ray beam quality
HVL
Which characteristic is reduced as x-ray energy increases
X-ray wavelength
The number of x-rays in the useful beam defined x-ray
Quantity
Normally the x-ray emission spectrum contains
Both characteristic and bremsstrahlung x-rays
The x-ray intensity is lower on the anode side of the tube because of the
Heel affect
Thermionic emission refers to
Electron emission from a heated source
The amplitude of the bremsstrahlung x-ray emission spectrum has
Maximum value at energy approximately 1/3 of the KVP
As the x-ray tube ages the inside can become coated with tungsten which can cause ____ in the tube
Arcing
The primary purpose of the glass envelope of an x-ray tube is to
Provide a vacuum
Which of the following statements applies to the x-ray emission spectrum
The target material affects the amplitude of bremsstrahlung x-rays
When the mass is increased x-ray quantity
Increases proportionately
Electron interactions at the inner shell of the target Atoms produce ____ radiation
Characteristic
It is often stated that mAs Controls quantity and KVP controls
Quality
An x-ray beam that could pass through dense tissue would have high
Both A & B
However it should be clear that mAs controls quantity and kVP controls
Quality and quantity
High capacity to rotators revolve at
10,000 RPM
Characteristic k shell x-ray is having an effective energy of
69KEV
The penetrability of an x-ray beam is called x-ray
Quality
The external structure of the x-ray tube includes a support structure of the protective housing and the
Glass envelope
The output intensity of an x-ray tube
Is primarily due to Brem x-rays
In ______ there is complete absorption of the incident x-ray photon
Photoelectric interaction
In the x-ray department patients receive more exposure (tissue ionization) with _______ Than with other forms of radiation - tissue interaction
Photoelectric interaction
When creating a radiograph
Low KVP is necessary when imaging soft tissue because it leads to high photo electric effect
High KVP in chest radiography will
Reduce patient dose
In a Compton interaction the scattered x-ray usually has
Less energy than the incident x-ray
Interaction that does not cause ionization
Classical scattering
The reduction of the intensity of an x-ray beam after passing through tissues is called
Attenuation
A negative contrast agent example would be
Air
Do use of contrast agents increases the amount of
All of the above
Which interaction creates the most occupational exposure and diagnostic radiography
Compton scattering
Basically an x-ray image results from
A & c
The results of photoelectric interaction are
One electron and a characteristic x-ray
Differential absorption is dependent on the
All above
As KVP ______ The probability of photoelectric absorption ______
Increases, decreases
The photo electric effect is
Complete absorption of an x-ray with the subsequent emission of an electron
Which of the following interactions involves no energy exchange
Classical scattering
Which of the following has the highest mass density
Bone
The probability of an increase in photoelectric interaction will occur with
Increasing atomic Number absorbers
Only at energies above 10 MEV can ________ take place
Photo disintegration
The Compton effect result in
A scattered x-ray whose wavelength is greater than that of the incident x-ray
The incident x-ray interacts with an outer shell electron ejected and continues in an altered direction the interaction is
Compton scattering
Mass density is
Best described in B and C
During photoelectric interaction
An electron is emitted from the atom
Which x-ray interaction involves the ejection of the K shell electron
Photoelectric absorption
Which of the following occurs in Compton interaction
And Atom is ionized
Two primary forms of x-ray interaction in the diagnostic range are
Compton scattering and photoelectric absorption
When very high energy x-rays escape interaction with electrons and the nuclear electrostatic field
All of the above
Compton scatter is directed at _____ angle from the incident beam
Any
The photo electric affect is principally associated with which of the following
Absorption of an x-ray
The scattered x-ray from a constant interaction has a _______ wavelength than the incident photon
Longer
In which of the following tissues does differential absorption most depend on differences of mass density
Lung and bone
Differential absorption although a complicated process is basically the result of differences between
Photo electric affect and transmission
Increasing KVP an x-ray imaging well
Reduce skin dose
Which of the following is not one of the five basic x-ray interactions with matter
Bremsstrahlung
Occurs only at the very high energy is used in radiation therapy in nuclear medicine PET imaging
Pair production
The Compton effect is characterized by
Partial transfer of energy upon collision
To optimize x-ray mammography
Low KVP is necessary to take advantage of the photo electric affect
Attenuation is caused by
Both a and B
As x-ray energy increases there is reduced
Reduced absolute photo electric effect
X-rays transmitted without interaction contribute to
The radiographic image
At low energy is the majority of x-ray interactions are
Photo electric
Total absorption of the energy of the incident incoming photon occurs in
Photoelectric interaction
Which of the following interactions contributes to Image noise
Compton
The energy of a Compton scattered x-ray is equal to
The difference between the energy of the incident x-ray and the energy of the ejected electron
Compton interactions photo electric absorption and transmitted x-rays all contribute to
Differential absorption
Barium is a good contrast agent because of its
High atomic number
When the mass density of the absorber is ______ it results in ______ Compton scatter
Increased, increased
Anatomic structures that readily transmit x-rays
Are radio Lucent
The photo electric affect
A & C are true
Feeling the fluoroscopic image in magnification mode increases
All of the above
Magnifying the viewed area on the patient by decreasing the image intensifier field size will do what your skin dose
Increase
The maximum allowed absorbed equivalent dose for radiographers is
5 rem
For those units where possible increasing the kilovoltage (penetrating power) of the beam will do what to patient dose
Decrease
A medical physicist will remeasure typical dose rates for each fluoroscopy unit every
Year
Nationwide the most common operator error for the C-arm units that unnecessarily increase patient dose is
Having the image intensifier too close to the skin
After a lead apron the most effective device for reducing the radiation risk to an individual is
Thyroid shield
The fluoroscope was invented by
Thomas Edison
Compared with a radiographic exam the purpose of fluoroscopy PE exams are to visualize
Dynamic images
Automatic brightness stabilization (ABS) is designed to compensate for changes in which of the following
Patient composition
Where are the rods located in the eye
Cornea
What is the function of the iris
Control the light level
The cones in the eye are
Photo optic vision
Rods are used principally for which of the following
Dim lighting
In general during fluoro exams as compared to radiography use
Lower ma
Which of the following describes the fluoroscopy system used to maintain constant image intensity
ABS
Emission of electrons from an illuminated source
Photo electric emission
At what stage of the image intensified fluoro is the number of image forming photons the lowest
Entering input phosphor
Image intensifier brightness gain increases with increasing
Flux gain
When an image intensifier receives x-rays at the input phosphor what is admitted at the output phosphor
Visible light
Which of the following is the input phosphor of the image intensifier
Cesium iodide
Which of the following is the output phosphor of the image intensifiers
Zinc cadmium sulfide
The photocathode converts
Visible light into electrons
Which of the following is a component of the image intensifier responsible for focusing the electron beam
Electrostatic lens
The ability of an image intensifier to enhance image illumination is called
Brightness gain
An image that displays vignetting
Dim around the periphery
What is the camera tube most used in television fluoroscopy
Vidacon
What is the principal disadvantage of the couple in TV camera to the image intensifier with the use of fiber optics
Photo spot camera can’t be used
What is the most important component of a television monitor
Cathode x-ray tube
What is the electron beam of the television camera tube
Modulated
