Exposure Chapter 5 The X-Ray Tube Quiz and Workbook
The steepness of the anode angle will effect the amount of the: 1. Anode heel effect 2. Field coverage 3. Thermionic emission
A. 1 and 2 only
A reduction in the kilovoltage setting during the operation of an x-ray tube will most likely: 1. Reduce the speed of the electron stream 2. Increase the filament temperature 3. Decrease the space charge
A. 1 only
Which of the following events occur within the x-ray tube during the exposure (second) stage of the timer mechanism? 1. A high potential difference is developed 2. Filament heating begins 3. The movement of Bucky grid begins
A. 1 only
The tube housing has heat capacities ranging from ___ to ____ million heat units
A. 1, 1.5
Calculate the heat units produced by 70 kVp at 40 mAs for a single-phase generator.
A. 2,800 (70 x 40 x 1)
The speed and energy of the electron stream as it passes across an x-ray tube is primarily controlled by the:
A. Applied kilovoltage
The tube in fluoro is usually ____________ the table.
A. Below
The discovery of x-rays was made by Wilhelm Roentgen in 1895 while experimenting with a partially evacuated glass tube called a:
A. Crooke's tube
The angle on the anode of a x-ray tube helps to insure that more of the x-ray photons produced at the target are:
A. Directed toward the patient
What is a tube current?
A. Electrons traveling from the anode to the cathode
The negative electrode of an x-ray tube is commonly called the:
A. Filament
The amount of space charge created at the cathode is primarily controlled by the:
A. Impressed amperage
As mA increases, blooming of the focal tract results in a:
A. Increase in the size of the effective focal spot
The formation of the space charge in the filament of the x-ray tube is accomplished during the ______________ of the normal exposure cycle
A. Prep or boost
When a radiographer changes from a small to a large focal spot for an exposure, he/she is actually:
A. Selecting a larger filament
As the angle of the anode is decreases, the effective focal spot becomes ___.
A. Smaller
The collective repulsion of the electron cloud around the cathode that creates an equilibrium with the rate of electron emission by the filament is termed the:
A. Space charge effect
In a modern diagnostic x-ray tube, the majority of the heat that is produced during the x-ray production process is created and concentrated on the:
A. Surface of the focal tract
In a modern diagnostic x-ray tube, the vast majority of the energy of the electron stream striking the target of the anode is converted into:
A. Thermal energy (heat) at the surface of the anode
A rotating anode can tolerate more heat than a stationary anode.
A. True
The filament is made of _______________ .
A. Tungsten
The ______________ is a structure where the primary x-ray beam exits the envelope, which allows less absorption or scatter of photons.
A. Window
The thin, flattened surface of the x-ray tube envelope, which allows for the minimum absorption of x-rays is termed the:
A. X-ray window
The principle method by which the space charge can be increased in a modern tube is by employing a higher:
A. mA station
Which of the following factors will effect the size of the focal spot? 1. Angle of the anode 2. Speed of the rotation 3. Size of the filament
B. 1 and 3 only
The target of a modern rotating anode is beveled or inclined to an angle of between:
B. 10-12 degrees
The main function of the Pyrex glass that forms the protective envelope of the x-ray tube is: 1. The containment of the electron stream near the filament 2. The containment of the vacuum within the x-ray tube 3. The production of the static electrical field around the filament
B. 2 only
The measurement of the focal spot size in most diagnostic x-ray tubes is based on the computation of the: 1. Actual focal spot 2. Effective focal spot 3. Electronic focal spot
B. 2 only
The intensity of the xray beam can vary as much as _____% from the anode to cathode side at the receptor.
B. 45
______________ is a byproduct of the line focus principle.
B. Anode Heel Effect
The maximum radiographic technique should never be applied to a ______________ tube.
B. Cold
The filaments in most modern x-ray tubes are surrounded by metal collars which serve to:
B. Compress the electron stream
The target surface irregularities due to cracking, pitting or melting of the anode will result in __________ radiation output.
B. Decrease
In order to prevent movement of electrons from the anode to the cathode during the exposure cycle, the type of current employed for an x-ray tube is:
B. Direct current
Most common cause of cathode failure is ____________________.
B. Filament evaporation
The smaller the anode angle, the ______ the heel effect.
B. Greater
Thermal capacity of anode is measured in _________ .
B. Heat units
In a modern rotating anode, the motion of the rotating disk is accomplished by the use of a:
B. Induction motor
At 400 mA or higher, the ______________ focal spot needs to be used.
B. Larger
For larger body parts, the ___________ filament is required.
B. Larger
Focusing cups have a slightly ________ charge to help move electrons between the anode and filament.
B. Negative
The focusing cup is made of ___________. The focusing cup surrounds the ___________.
B. Nickel; filament
The x-ray tube envelope is composed of a heat resistant material called:
B. Pyrex glass
Which is the proper sequence of materials traversed by the x-ray beam after leaving the anode of the x-ray tube?
B. Pyrex glass, oil, aluminum
The point at which a further increase in kVp will not result in higher mA because all available electrons have been used is called __________________.
B. Saturation current
The reduction of effective focal spot size from about 2 mm to 1 mm can be accomplished by:
B. Selecting the smaller of the two filaments
What is the phenomenon called that limits thermionic emission of additional electrons by the filament.
B. Space charge effect
The temperature of the filament in a modern x-ray tube is most closely related to:
B. The amount of current impressed on the filament
When electrons are separated from the filament, it is called _____________.
B. Thermionic Emission
The process by which heating of the filament results in the liberation of electrons in the x-ray tube, is called:
B. Thermionic emission
The first modern digital radiographic tube having a heated filament was originally developed in the early 1900s by:
B. William Coolidge
The anode of a modern rotating anode tube is generally composed of a combination of tungsten and: 1. Copper 2. Rhenium 3. Molybdenum
C 2 and 3 only
Small focal spot sizes usually measure ___ to ___ mm.
C. 0.5, 1.0
Large focal spot sizes are usually _____ to _____ mm.
C. 1, 2
The space charge effect limits routine x-ray tubes to a maximum ____ to ____ mA ranges.
C. 1,000-2,000
The anode angles range from 7-17 degrees, the most common is _____ degrees.
C. 12
A modern dual focus x-ray tube contains: 1. One filament 2. Two filaments 3. One anode
C. 2 and 3 only
Vibration of the x-ray tube, during a digital radiographic exposure, will most likely result in: 1. An increase in gray scale range 2. A decrease in digital radiographic contrast 3. An increase in the amount of focal spot blur
C. 2 and 3 only
Off focus radiation may contribute to as much as _____% of the primary beam?
C. 25-30
The rotor revolves at ____to____RPM? What about a high speed rotor used in Cath Labs?
C. 3,200-3,600; 10,000
The rotation speed of an anode in most single phase x-ray units is about:
C. 3000 rpm
The average filament lasts _______________ hours and _______________ exposures.
C. 6-9; 10,000-20,000
The atomic # of tungsten is ______.
C. 74
In a modern x-ray tube, the positively-charged electrode that serves as the target for the electron stream is the:
C. Anode disk
As tungsten vaporization increases in the x-ray tube, which tube failure is more likely to occur?
C. Arching
The most common cause of tube failure is _____________.
C. Arcing
In a rotating anode, the molybdenum stem is a poor conductor of heat. This material helps in preventing:
C. Bearing damage of the induction motor
The anode has a ___ edge.
C. Beveled
Protective housing guards against _____________________. A. Excessive radiation exposure B. Electric shock C. Both A and B
C. Both A and B
In a stationary anode tube, the target is imbedded in an anode made of:
C. Copper
The size of the electron stream is determined by _________________.
C. Filament size
The ____________________ is the shallow depression in the cathode assembly designed to house the filament.
C. Focusing cup
The general formula that is used to determine the anode heat units created with a fully rectified x-ray tube is:
C. HU= mA x kVp x Time
Rotating anode allows ______ tube currents and _______exposure times
C. Higher; shorter
________________shows time required for tube housing to cool.
C. Housing Cooling Chart
If the mA is increased, heat production will ______. If the KV is increased, the heat production will _______.
C. Increase; Increase
All x-rays that exit the tube housing other than through the tube window are called __________________.
C. Leakage radiation
When x-ray is produced anywhere other than the focal spot, it is called ________________.
C. Off-focus radiation
The majority of heat in a modern rotating anode tube is dissipated through the:
C. Passage of radiant heat to the tube envelope
The ball bearings which aid in the rotation of the induction motor require a special low vaporizing lubricating material called:
C. Powdered silver
The amount of heat storage capacity of a rotating anode is not dependent upon which of the following:
C. Prep (boost) time
The entire cathode and anode assembly is housed within this metal structure called a__________________.
C. Protective housing
The glass enclosure of the x-ray tube is made of ________________.
C. Pyrex glass
When the target angle is made smaller, the effective focal spot becomes________
C. Smaller
Why is tungsten the material of choice for the target?
C. Thermal conductivity
The target is usually made of __________________ alloy
C. Tungsten, rhenium
In a stationary anode the target consists of ___________ embedded in ____________.
C. Tungten alloy; copper
X-rays that exit through the tube window are called ____________________.
C. Useful Beam
If the angle on a x-ray tube anode is decreased from 12 degrees to 7 degrees, it will result in a decrease in: 1. Size of the focal spot 2. Loading capacity of the tube 3. Field coverage
D. 1, 2, and 3
The maximum anode heat storage capacity of a digital radiographic tube is related to the type and size of the: 1. Anode disk 2. Cooling fan 3. External housing
D. 1, 2, and 3
Tungsten is the principle material used in the formation of the: 1. Surface of the target of a rotating anode 2. Surface of the target of a stationary anode 3. Wire used in the helix of the x-ray tube filament
D. 1, 2, and 3
Digital radiographic examinations requiring large tube currents or serial exposures, will often employ high speed rotating anodes with rotational speeds of about:
D. 10,000 rpm
Leakage radiation at 1 meter from the x-ray housing can not exceed _____ mR per hour.
D. 100
The temperature at which thermionic emission occurs is approximately:
D. 2200 degrees C
The melting point of tungsten is__________________o C.
D. 3,370
The major reason that tungsten is the material chosen for the electrodes of a modern x-ray tube is its high melting point of about:
D. 3400 degrees Celsius (this is the workbook answer the one you should learn is 3370 from the powerpoint)
At what angle, would the line focus principle relationship change?
D. 45 degrees
What percentage of energy of the projectile electrons is converted to heat?
D. 99.8%
Which of the following is not an advantage of a rotating type anode tube?
D. A reduction in the amount of low energy photons produced during an exposure
An radiologic technologist can protect anode bearings by: A. Not moving tube while anode is rotating B. Not pressing exposure button more than needed C. Not starting rotor more often than necessary D. All of the above
D. All of the above
Damage to anode can be prevented by: A. Using warm up procedures B. Using higher KVp and lower MAs C. Not clustering exposures in short time D. All of the above
D. All of the above
Elements needed for x-ray production include: A. Source of electrons B. Vacuum environment to make electrons travel straight C. Target for electrons to hit D. All of the above
D. All of the above
How are high speed electrons able to produce x-rays at the anode? A. Potential difference offered by kV applied during exposure. B. High amount of amperage supplied to filament C. Potential difference offered by cathode having a negative charge and anode having a positive charge D. All of the Above
D. All of the above
Major components of tube that can be damaged are _________________. A. Cathode B. Anode C. Glass envelope D. All of the above
D. All of the above
The Anode Heel Effect is known for ________________________. A. Variation in intensity of beam emitted from x-ray tube B. Intensity is weaker towards anode side due to absorption of x-ray by anode & target material C. Most apparent with LG FILM, LOW KVP, SHORT SID D. All of the above
D. All of the above
The area of the target that projectile electrons hit is called _________________. A. Target B. Focal track C. Focal spot D. All of the above
D. All of the above
The kvp set at console determines _____________________. A. Kilovoltage peak B. Maximum voltage applied across tube C. Penetration power of rays (QUALITY) D. All of the above
D. All of the above
The target area at the anode is called a _________________. A. Focal point B. Focal spot C. Focal track D. All of the above
D. All of the above
The unit of power, the watt, is derived from the product of:
D. Amperage x voltage
A type of tube that quickly regulates the flow of electrons, producing x-ray photons is called ______________. A. Grid-controlled B. Grid-biased C. Space charge effect D. Both A and B
D. Both A and B
The ______________________ provides a guide regarding the most common technical factor combinations that can be used without overloading the tube. A. Radiographic tube rating chart B. Tube rating chart C. Housing cooling chart D. Both A and B
D. Both A and B
The components on the anode side of the x-ray tube include _______________. A. Anode B. Stator C. Filament D. Both A and B
D. Both A and B
The part of the x-ray tube that works on the concept of electromagnetic induction is ______________. A. stator B. rotor C. focusing cup D. Both A and B
D. Both A and B
What type of tube failure can occur when the stator does not work properly?: A. Pitting B. Melting C. Arcing D. Both A and B
D. Both A and B
What are the 2 types of anodes?
D. Both A and B (Rotating and Stationary)
The mAs set at the console determines __________________. A. Number of electrons produced at the filament B. Quantity of x-rays to be produced at the anode C. Penetrating power of the x-rays D. Both A and B only
D. Both A and B only
What purpose does the oil layer between tube and housing serve? A. Electrical insulation B. Thermal conduction C. Lubrication D. Both A and B only
D. Both A and B only
The main reason tungsten is employed as filament material in an x-ray tube is its:
D. High melting point
Newer improved tubes replaced the glass housing with ________________.
D. Metal
The line-focus principle concerns the effect of target angulation and focal spot size. Which is a true statement of this principle? A. The actual focal spot is larger than the effective focal spot B. As tube angulation decreases, the effective focal spot increases C. Radiation intensity is greatest on the cathode side of the tube D. More than one but not all the above
D. More than one but not all the above
The material often added to a rotating anode disk to reduce surface defects and cracks is called:
D. Rhenium
Which of the following portions of the induction motor and anode disc assembly of a rotating anode is not normally contained within the vacuum of the tube?
D. Stator windings
The principle disadvantage using a smaller focal spot during a digital radiographic exposure is:
D. The limitation of the amount of mAs that can be applied to the anode
The durability and efficiency of the tungsten filament is often improved by the addition of the metal:
D. Thorium
The cathode has a _________ charge.
negative
The anode has a _______ charge.
positive
