2ND YEAR IMAEQMA Flashcards
What refers to the quality of image?
kvp
where does the kvp, mAs, and the autotransformer belong to
Operating console, control console, or low voltage section
What is the formula of kVp?
kVp= BT (cm) x 2 + machine constant
What is the machine constant of non digital and digital machine?
Non digital: 30
Digital: 40
What is the other unit for kVp
Half Value Layer
It refers to the penetrability of the x-ray beam
kVp specifically, Quality
It adjusts the kvp, mas, and the focal spot size and controls x-ray tube current and voltage
Operating console
What is the formula of mAs
mAs= mA x time (s)
Refers to the quantity of x-ray photons and intensity of x-ray beam
mAs
Other unit for mAs
MR (Milliroentgen)
Controls voltage to 110v - 220v
Autotransformer
Receives voltage from power source
Autotransformer
Provides precise voltage to the x-ray tube
Line compensator
What winding does the line compensator belong to
Primary winding
What is the winding of the Major and Minor kVp?
Secondary winding
It is the 2 separate connections on the autotransformer that selects the kvp
Major & minor kVp
Allows the monitoring or measurement of voltage before exposure
Pre-reading voltmeter
Controls voltage to heat x-ray tube
High Voltage Generator Section
3 Parts of the High Voltage Generator
High Voltage Transformer
Filament transformer
Rectifier
Function of rectifier
Converts AC to dc
Provides high voltage to x-ray tube
High voltage transformer
Increases current & intensity for heating filament
Filament transformer
Increases current & intensity for heating filament
Filament transformer
It is where the production of x-ray happens
X-ray tube
What type of device is the x-ray tube
Electrical device
Amount of voltage needed to operate x-ray tube
220v
Length and diameter of x-ray tube
Length: 30-50cm
Diameter: 20 cm
What is thermionic emission?
Process of heating filament to release electrons
Heat needed by filament to produce/release electrons
2200*c
X-ray tube consists of :
Cathode
Anode
Which is the negative and positive part of the x-ray tube
Cathode negative
Anode positive
Parts of cathode
Focusing cup
Filament
Designed to condense and repel electron beam to a small area on focal track
Focusing cup
What is the focusing cup made of
Nickel
Where is the filament embedded
Focusing cup
Produces high speed electrons
Filament
Filament is a small coil made up of_
Thoriated tungsten
Why is thoriated tungsten used for filament?
high thermionic emission
better thermal conductivity
high melting point
How many x-ray tubes do modern x-ray have
2
Length and diameter of filament
Length: 1 - 2 cm
Diameter: 2mm
Factors that determine the effectiveness of focusing cup
Size & shape
Charge
Filament size and shape
Position of filament
What is space charge effect
Electrostatic Repulsion of space charge
What happens to space charge when it boils
The charge becomes more negative
It attracts the electrons produced by cathode
anode
_ % heat _ % x-ray
99%
1%
Other functions of anode
Mechanical support for target
Electrical conductor
2 types of anode
Rotating
Stationary
Anode used for general radiography
Rotating
Why is the rotating anode used for general radiography
High exposure
short time production of high intensity x-ray beams
Why does the rotating anode provide greater exposure than stationary
larger target area
larger heat dissipation
Where is stationary used
Dental radiography
What is stationary anode made up of
Tungsten target embedded in large copper bar
Parts of anode
Target
Focal spot
Area of anode struck by projectile electrons
Target
What is target made up of
Tungsten
Rhenium
Actual source of radiation and releases it
Focal spot
Material of focal spot
Graphite
Copper
Molybdenum
2 sizes of focal spot and their measurement
Large: 0.4mm-1.2mm
Small: 0.1mm- 0.5mm
Size for focal spot that is used for technical factors that produce high heat
Large
Pros and Cons of large focal spot
Pros: good heat dissipation ; thick body part; short exposure time
Cons: large effective FS
Size of focal spot used for better spatial resolutions
Small
Pros and cons of small focal spot
Pros: thin body part; small effective focal spot
Cons: poor heat dissipation
Incorporated to the x-ray tube allowing large area for heating while maintaining small focal spot
Line focus Principle
What happens when you angle the target?
Smaller target effective area than electron interaction
Electron bombarded by cathode travelling to anode
Incident electron beam
Electron bombarded by cathode travelling to anode
Incident electron beam
Physical area of anode when bombarded by electron beam that emits x-ray
Actual focal spot
Area projected to patient
Effective focal spot
Pros and Cons of smaller anode angle
Po: small effective FS (increased spatial resolution)
Con: limits usable field size
Type of timer that has simple clock system
Mechanical timer
Where is the mechanical timer used
Portable dental units
Precision device driving the shaft at _ rps
Synchronous timer
60 rps
Why should the synchronous timer not be used for rapid exposure
Needs to reset after exposure
Minimum exposure of synchronous timer
1/17 msec
Most accurate, complicated, and sophisticated timer
Electronic timer
What timer is used for rapid serial exposure
Electronic timer
Determines intensity or number of x-ray
mAs timer
Terminated exposure time when desired mAs is attained
mAs timer
Measure quantity of radiation reaching the image receptor
Phototimer
Other name for phototimer
Automatic Exposure control
Terminates exposure when desired density is attained
Phototimer
What is a critical component of phototimer
Photomultiplier sensing device
What are the 3 STRUCTURES of x-ray tube
Support structure
Protective housing
Glass envelope
A support structure that is frequently used
Ceiling support
A support structure that has 2 rails mounted to the ceiling directly over the radiographic table
Ceiling support
A support structure that has a single column with rollers attached at each end
Floor to ceiling support
An alternative to column mount
Floor mount system
It is mounted underneath the radiographic table
Fluoroscopy
Used in hospitals for patients with critical conditions
Portable/mobile machine
Term for patients that are unable to walk without assistance
Non-ambulatory
C-shaped structure that provides flexible x-ray tube positioning and live imaging
C-ARM SUPPORT system
Support system used in fluoroscopy
C-ARM SUPPORT system
Protects radtech against electric shock
Protective housing
Mechanical support for x-ray tube
Protective housing
What is the purpose of oil in protective housing
Electrical insulator and thermal cushion
X-ray that escapes the protective housing that is unnecessary for diagnostic imaging
Leakage radiation
X-ray that is emitted through the window that emits isotropically
Useful beam / primary beam
What is glass envelope made up of
Pyrex glass
What does isotropically mean
Emit equal intensity in all directions
Why is Pyrex glass used for glass envelope
Withstands extreme heat
A portion of envelope that allows useful x-ray beam output from tube
Window
A part of the glass envelope that minimizes radiation absorption
Window
Why does the glass envelope contain a vacuum/ empty space inside?
Efficient x-ray production
Longer tube life