Meaghan Piretti X-ray Production/Equipment Flashcards
Incoming Power Supply
A/C supply
220 Volts
Master Power Switch
Single Throw Double Blade Switch
Big switch on wall
Fuses (circuit breaker) job/location:
Protects equipment from excessive current
Located on primary side
Line Voltage Meter (compensator) job/location
Primary or low circuit
Measuring incoming line voltage
Detects a surge or drop
Maintains 220 volts to auto transformer
Auto transformer job/location:
Operates on self induction
Works off A/C
Low voltage/primary circuit side
KV selection (not production)
Determines line voltage sent to step up transformer
MA selector (Rheostat) (variable resistor) job/location
Regulates amperage/regulates thermionic emission
Think thermostat
Think Dimmer on a light switch
Location:low voltage- filament circuit
Step up transformer job/location:
Mutual Induction (2 wires)
More turns on secondary side
Works off AC
Increases Volts to Kilovolts
We need high Volts to produce x-rays
Step-Down Transformer job/location:
Filament transformer
Mutual Induction
More turns on primary side
2 jobs!
1. Decreases Voltage
2. Increases Amperage
Rectifier job/location:
Changes AC to DC
Solid state semiconductor
4 diodes
Single phase voltage ripple:
100% (the worst)
3 phase, 6 pulse voltage ripple:
14% (old equipment bad)
3 phase, 12 pulse voltage ripple:
4% (not as bad but aril not the best)
High frequency voltage ripple:
Less than 1% or 1
(Best) (newest equipment)
Place the voltage ripple in order:
Half wave, full wave, three-phase six pulse, three phase twelve pulse, high frequency
What voltage ripple is preferred?
High frequency (1% or 1)
Heat Units Definition:
Calculation of the total heat produced during an x-ray exposure
Heat Units Calculation for High Frequency:
kVp x mA x s x 1.45 (1.44)
Falling Load Generator Definition:
Provides extremely short exposure times by taking advantage of tube heat loading potential
4 things needed to produce x-rays:
Source of free electrons
-thermionic emission-filament heats up-mA
-cathode side-negative
A means of accelerating electrons
-potential difference (EMF/Voltage) kVp
A way to focus the electrons
-focusing cup (focuses the electrons toward the anode)
-molybdenum or Nickle
A means to decelerate these electrons
-rapidly stopping sudden deceleration
Anode- positive side made of Tungsten Rhenium
What is the focusing cup made of?
Molybdenum or Nickel
Anode is made of?
Tungsten Rhenium
The cathode is what charge?
Negative
The anode is what charge?
Positive
Source of electrons is a _________ at the __________ side of the tube.
Filament; cathode end
The filament consists of a:
Small coil of tungsten wire
As it is heated up the increased energy enables electrons to be released from the filament through:
Thermionic emission
The __________ provides the electron source for x-ray production.
Electron cloud
If you _____________, you increase the ____________; which in turn ___________ this leads to more x-ray photons being created.
Increase the mA, Increase the filament current, increases the tube current
The free electrons must be accelerated through the x-ray tube from _______ to _______.
Cathode to Anode
__________ forces the electrons across the tube giving them kinetic energy.
Voltage, Kilovoltage Peak (kVp) (tube potential)
The higher the kVp the more/less energy the accelerating electrons will have?
More
A _________ houses the filament wires
Focusing cup
When the kVp is applied the electrons are focused in a ________ beam.
Narrow
The focusing cup holds the released electrons in a tiny cloud sound the filament wires called the:
Space Charge
Electrons are directed from the:
Cathode toward the anode to the area of the focal track
_____ of elections are absorbed as heat.
99%
____% of electrons are created into x-ray photons through target interactions
1
The electrons _______ when they strike the anode.
Decelerate
The anode is a Tungsten disk which has a:
High atomic number 74 and a high melting point
The Anode heel effect refers to:
The lower field intensity toward the anode in comparison to the cathode due to lower x_ray emissions from the target material at angles perpendicular to the x-ray beam
The anode surface is:
At an angle
Decreasing anode angle (smaller angle degree) =
Increased heel effect
Anode Angle and Anode Heel effect have a _________ relationship:
Inverse
Decreasing the anode heel effect (steeper)=
Increase anode heel effect
Decreasing SID: __________ anode heel effect
Increases anode heel effect (not as present at 72”)
Increasing the field size= _________ anode heel effect
Increases
Define Line focus Principle:
The relationship between the actual focal spot on the anode surface and the effective focal spot size
Actual focal spot size location:
Where electrons interact with the anode (target)
Effective focal spot size location:
Is what exits the tube and interacts with the patient
What size is the effective focal spot compares to the actual focal spot:
Smaller
What size is the actual focal spot size compared to the effective?
Larger
Decrease anode angle= ______ effective focal spot
Decrease
Increase anode angle= __________ effective focal spot
Increase
Two types of interactions that occur at the target (anode):
Bremsstrahlung and Characteristic
Target interactions both start with a _______ and end with a _________ that will exit the tube.
Electron, x-ray photon
90% of all production, (100% below 70 kVp):
Bremsstrahlung
The incident electron brakes before the nucleus and bends direction, the closer the nucleus the harder the break the higher energy of the photon
Bremsstrahlung
What is the K-Shell binding energy of tungsten?
69.5 keV or 70 keV
Can you identify the bremsstrahlung interaction on a video?
Yes or no
Can you identify the circuit in a picture?
Yes or no
The incident electron collides with a k shell electron crashing it out of orbit and causing a cascade of electrons to fall into each shell closer to the nucleus, each time the electron cascades it causes characteristic x-rays closer to the nucleus the higher the photon energy:
Cascading “hallmark”
Cascade Effect
Select three properties of x-rays off of a list:
Travel in straight lines
Electrically neutral (no mass)
Heterogenous
Travel at the speed of light (186,000 miles per second) (3 x 10^8 m/s)
Capable of ionizing matter
Cannot be focused by a lens
Each photon carries its own energy (poly energetic)
Refers to the x-rays being produced by the x-ray tube and strike the patient
Primary beam
The primary beam is made up of:
Bremsstrahlung or Characteristic or both
Remnant means:
Remaining
Define remnant beam or exit radiation:
The remaining beam after it exits/leaves the patient
What is the remnant beam made up of?
Primary or secondary radiation
The type of secondary radiation that occurs when the beam intercepts an object causing the x-ray beam to be scattered
Scatter Radiation
Quality, energy, penetrability of the x-ray photons
kVp
kVp determines the:
Quality of the x-ray beam
Refers to the number, quantity of the x-ray beam:
mAs
Refers to the number of waves:
Frequency
Higher kVp= _______ energy
Higher
Higher kVp= _______ frequency
Higher
The distance between two successive peaks:
Wavelength
The higher the energy of the x-ray the ______ frequency
Higher
The distance between tops of the waves
Wavelength
High kVp= ____________ wavelengths
Short
Low kVp= __________ wavelength= ________ energy.
Long, less
Decrease wavelength, _________ frequency, _________ wavelength
Increase, increase
Frequency and wavelength have what type of relationship?
Inverse
kVp controls:
Subject Contrast
Beam Quality
Beam energy
Beam Penetrability
Increasing kVp also _________ scattered photons reducing image quality
Increases
Increase kVp ______ electron energy, _______ x-ray energy
Increase, increase
The degree of density difference between two areas on a Radiograph
Subject Contrast
Short scale of Contrast (Short Gray Scale):
High Contrast
Low kVp
Long Scale of Contrast (Long Gray Scale)
Low Contrast
High kVp
Digital Image Contrast is controlled by the:
Look Up Table (LUT)
A processing algorithm built into the equipment that the technologist does not control:
LUT (Look up table)
NOT controlled by kVp
Lower kVp settings use:
A long wavelength
Lower Energy
Lower Penetrating ability
Less chance of scatter radiation
Considered high contrast
______ kVp examinations penetrate fewer thicknesses and only have a few steps in between black and white (50-70 kVp)
Lower
Demonstrates fine bone markings and fractures better
Low kVp (small focal spot)
Low kVp
Small focal spot
High contrast
Short scale
Long scale of contrast have _______ shades of grey in between black and white.
Many (multiple)
Penetrate more thicker dense areas of anatomy
High kVp
Used for contrast barium
110 kVp
Large Focal Spot
High kVp
High kVp settings use:
Long scale of contrast
A short wavelength
Higher energy
Higher chance of scatter radiation
Low contrast:
High kVp
Long scale of contrast:
Decreases image quality
Increases patient dose
Increases tech dose
Measurement of tube current
mAs
Increases the filament temperature which increases the electrons boiled off from thermionic emission
Increase mA
mA controls
Beam Quantity
Receptor Exposure
Patient Dose
What is the calculation for MA
mA x s = mAs
How many seconds are in each of the following milliseconds?
1,000
50
400
1,000 milliseconds = 1 second
50= 0.05 sec
400= .4 sec
Exposures made while the patient is breathing:
Orthostatic breathing techniques
If you don’t have enough mAs or have quantum mottle (Noise):
Double original mAs or increase by 30%
mAs will never have an effect on:
Contrast and Scatter
There are multiple ways to combine mA and seconds to equal the same mAs
mAs Reciprocity Law
The reciprocity law shows us that:
mA and time are inversely proportional
If seconds increases= ______ mAs
Decreased
If mA is doubled= _____ should be cut in half
Time
If mA is cut in half= _____ time
Double
An original exposure was made using 100 mA at .10 sec. A repeat exposure must be made using 200 mA while keeping the same receptor exposure. What is the new time required?
Original Exposure: 100 x .10= 10 mAs
New exposure= 200 x ? = 10 mAs
Double mA? Cut time in half! .05 seconds
200 mA x 0.5 seconds = 10 mAs
Most common beam retracting device used in radiography. It can be used for any field size
Variable-aperture collimator
Primary purpose of beam restriction is to:
Restrict the primary beam to the area of interest and decrease patient dose
The simplest type of beam restrict or, and is made up of lead-lined metal sheet attached to the x-ray tube head
Aperture diagram
These modifications are the aperture diagram. It had extended metal structure which produces a circular image
Cones and cylinders
Decrease collimation=
Light field is getting bigger
Increase beam restriction=
Increase collimation= decrease field of view= smaller light field
Increase Field of View=
Decrease collimation=larger light field
The size of your light field
Field of view
Light field that is limited to the IR placed in the Bucky tray
Positive Beam Limitation (PBL)
Increase in Patient Size=
Higher Absorption of the beam into the tissue
Used to control spatialize resolution:
Focal Spot Size
Produce less blurring and better visibility of detail (extremity work/ribs)
Small Focal Spot
Greater heat dissipating capacity
Large focal spot (chest and abdomen)
SOD equation
SID-OID
Increasing SID
Further away
Magnification of the part:
Size Distortion
For every _____ increase in OID a ______ increase in SOD should be used to compensate
1”, 7-8”
