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Advanced Imaging

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Diagnostic units operate between_____
25-150 kVp
The x-ray table must be
radiolucent and thickness
All systems have three major components. What are they?
1. operating console
2. x-ray tube
3. high voltage generator
THe operating console the ____and ____
tube current and voltage
When discussing the operating console, the controls are for the ______? "3"
major and minor kvp
mA settings
exposure time
the operating console is the _____
interpreter
Power companies cannot provide
precise voltage consistently
Input voltage can vary as much as ___
5%
____is used to provide consistent voltage to the autotransformer
Pensation
line compensation
The main circuits function is to
modify incoming voltage to produce x-rays
Filament circuit
produced required thermionic emission at the filament
THe filament circuit is _____always
AC
The main circuit is _____from the line compensator to the high voltage transformer, the it is _____to DC
AC; rectified
Main circuit components
line compensator, autotransformer, Kvp controls, high voltage transformer, rectifers, tube
components to the filament circuit
line compensator, autotransformer, mAs selector, filament transformer, filament
autotransformer is designed to do what?
provide precise voltage to the high voltage transformer
the most versatile of the transformers; can act as a step up or step down;
autotransformer
autotransformer law
Vs/Vp=Ns/Np
what has primary and secondary sides
autotransformer
Tube current is measured in ____
milliamperes
number of electrons crossing from cathode to anode is ____
tube current
tube current is determined by?
temp of filament
Filament temp is controlled by? As filament temp increases, thermionic emission ______?
by the filament current; increases
The x-ray tube current is controlled by the?
filament circuit
Ohm’s law states that
Voltage equals current times resistance.
Four types of exposure timers controlled by the technologist. List
– Mechanical timers
– Synchronous timers
– Electronic timers
– mAs timers
Automatic Exposure Control is compromised of ______
flat plate ionization chamber positioned between the patient and the film
What four things must the AEC have to be accurate?
-Must be radiolucent – not interfere with the collected subject data

-Must be calibrated

-Must have a back-up time or mAs set – prevent over exposure due to equipment malfunctions

-Minimum reaction time – how quickly the system can respond.
The High-Voltage Generator
Three main parts?
–High-voltage transformer
–The filament transformer
–The rectifiers
The high voltage generator is Usually?Serves as?
immersed in oil; insulator to prevent electric shock
and helps dissipate the heat
High-Voltage Transformer
Primary purpose?
is to step up Voltage to Kilovoltage

high voltage transformer is what kind of transformer?
A step-up transformer
The turns ratio for the high voltage transformer is usually?
between 500:1 or 1000:1
When discussing the high voltage transformer, The wave form from the secondary side will differ from the waveform of the primary side only in ?
amplitude
The process of converting AC to DC
Rectification
how are xrays produced?
cathode to anode
Electronic device which allows electrons to flow in only one direction is called
a rectifier
Rectification is usually accomplised with
diodes
Because the transformer has to have __ to function properly, and the tube requires DC to function properly, a system of rectifiers is used between the ____ and the ____.
AC; high voltage transformer and the tube
Diodes
Two principal types?
– Vacuum-tube
– Solid-state
Vacuum-tube Diode
 Cathode and anode
 Used thermionic emission
Solid-state
Diode
 Made of semicondudors
 N-type – loosly bound electrons
 P-type – spaces or holes for electrons to fill
 Form a P-N junction
The X-ray Tube
 External Components
X-ray tube support
Protective Housing
Glass or Metal envelope
X-ray tube support
 Ceiling Support System
 Floor to ceiling support system
 Floor support system
 C-arm Support system
Protective Housing
 X-rays are produced isotropically
 X-rays emitted through the window form the useful beam
 X-rays emitted from any other part of the protective housing is called leakage radiation
 The function of the protective housing is to protect against leakage radiation and prevent shock
X-rays are produced
isotropically
X-rays emitted through the window
form the useful beam
X-rays emitted from any other part of the protective housing is called
leakage radiation
The function of the protective housing is
to protect against leakage radiation and prevent shock
A properly designed tube housing must reduce the level of leakage radiation to
less than 100 mR/hr at 1 meter.
Glass or Metal Envelope
 Contains the actual tube and helps form the vacuum required for unimpeded electron travel.
 Glass envelopes are made of Pyrex glass
 Metal envelopes are designed to prevent “bronzing” and have longer useful lives
 The window is the area though which the useful beam exits the envelope
Glass or Metal Envelope
 Contains?
the actual tube and helps form the vacuum required for unimpeded electron travel.
Glass envelopes are made of
Pyrex glass
Metal envelopes are designed to prevent
“bronzing” and have longer useful lives
The ___ is the area though which the useful beam exits the envelope
window
Internal components
cathode and anode
 It consists of the filament and the focusing cup
cathode
is where the boiling off of electrons occurs – thermionic emission
The filament
what is the cathode made of? why?
They are usually made of thoriated tungsten because of the high melting point and the resistance to vaporization
The focusing cup
Houses?
the filament
 Is negatively charged and helps to confine the electron beam
focusing cup
– Controls thermionic emission
filament current
The filament current
– Controls thermionic emission
– Electrons boiled off form the “space charge”
– The “space charge effect” is a phenomenon of the “space charge”
– Saturation Current
ANODE Serves three functions?
– Conducts the electrons
– Provides mechanical support for the target
– Acts as a thermal radiator
Anodes are ____or ____
 Stationary or rotating
–Higher tube currents and shorter exposure times are possible with rotating anodes
The target is made of
tungsten rhenium
Boiling off /Separation of Electrons

It is heating the ___ to a “white” hot temp. which causes electrons to be “boiled” off.
The controlling factor is __ (milliamperes)
Filament;mA
Increasing mA on the control panel increases the heat in the filament, which increases the number of electrons boiled off.
This will increase the ____ (darkness) on the film


density
Thermionic Emission
_____of _______
Ultimately, This determines the ___ of photons produced in the X-Ray Tube and the amount of blackness / density on the radiograph.
-Space-charge effect
Separation of Electrons; NUMBER
Four Conditions Necessary for the Production of X-Ray
Production of High Speed Electrons
–______ Controlling factor
–Increase kVp
Increase speed of projectile electrons
Increases projectile electron kinetic energy
Increases
Kvp;
Concentration of Electrons
–____does this...how?
Focusing Cup; Cup has a negative charge which concentrates the electrons onto the target (area bombarded by electrons) of the anode
Sudden Slowing or Stoppage of Electrons
_____ controls this
Transfer of kinetic energy to heat and x-ray
Over 99% goes to heat
Less than 1% goes to x-ray production
Target/Anode;
Flow of Electrons
The flow of electrons is from Cathode (-) to anode (+).
_____ on the secondary side of the high voltage transformer
Constitutes the_____




Rectifiers;tube current
Remnant Radiation
A beam of____ – exit beam
-_____-____ x-rays
-The information must be transferred to a readable medium – Image Receptors (IR)
– Film
– Fluoroscopic II
– Television monitor
– Laser Imaging system
– S
varied intensity;Image forming
Electromagnetic Spectrum
Continuum of electromagnetic energy
 3 Regions:
– Visible Light
– Radio Frequency
– X-Radiation
kVp
 Increasing kVp
–Increases the speed of ____ traveling from the (-) to the (+)
–Increases –
Increases- the
-of the Projectile electron?
-the kinetic energy of the electron
-strength of the x-ray photon created
-the symbol of wavelength?
-Unit of wavelength is the?
- Wavelength is
The longer the wavelength the weaker the photon
Lambda:Angstrom
the distance between the crests of a wave.
Minimum Wavelength
l min
Refers to the strongest photon in the beam of radiation.
Wave - Particle Duality Phenomena
 A photon (pure energy) acts as _____
 Ex: ?
if it has the characteristics of matter.

An X-Ray photon dislodging an orbital electron from an atom.



12 Properties of X-Rays
1. They are invisible
2. They diverge in a straight line from a point source.3. They are unaffected by electrical or magnetic fields. They are electrically neutral.
 4. Travels at the speed of light.
– 186,000 miles / sec
Created at the speed of light, exists at the speed of light, or does not exist at all.

5. Affect photographic film; They affect PSP plates
6. They are Highly Penetrating.
7. They are Heterogeneous
8. They can ionize atoms
9. They can cause certain crystals to fluores.
10. They can not be focused by a lens.
11. They can produce chemical and biological changes.
12. They can produce Secondary and Scattered Radiation.
Types of generators
ï‚¡ Single-Phase
ï‚¡ Three-Phase
 6-Pulse
 12-Pulse
ï‚¡ High Frequency
ï‚¡ Capacitor Discharge
ï‚¡ Battery Powered Generators
ï‚¡ Falling load generator
Single phase Results in a ____
Results in a pulsating x-ray beam
Single phase is ___pulses per seconde for half wave; ___pulses per seconde for full-wave; THe ripple effect is ______.
ï‚¡ 60 Pulses per second for half wave rectification
ï‚¡ 120 pulses per second for full-wave rectification
ï‚¡ Ripple effect is 100%
Three Phase

______are superimposed over one another. THe result is ____.
ï‚¡ Multiple voltage waveforms are superimposed on one another
ï‚¡ The result is a more constant voltage
Three Phase

There are ____or ___times the number of pulses per second.

The result is ____in ripple.
THe machine is ______ ____.




ï‚¡ There are three or six times the number of pulses per second
ï‚¡ The result is a reduction in ripple
ï‚¡ The machine is more efficient
High Frequency

____ _____ ____ circuits are converted to high frequency

Increase from ___hertz to ___ to ___HZ.



Full wave rectified circuits are converted to high frequency

Increase from 60 hertz to 500 to 25,000 Hz
High Frequency

Inverters are used to do what?

They are smaller cheaper and more efficient?
Inverters are used to “chop” the DC current into smaller square pulses

They are smaller, cheaper, and more efficient
Capacitor Dischargers are used in _____.

Silicon controlled rectifiers are used to create what?

Used in portables mostly

Silicon controlled rectifiers are used to create high voltage that is stored in capacitors
Capacitor Discharge

During exposure, what happens?

What is one problem?
During exposure, the kVp falls and the capacitors discharge the stored voltage

One problem is that x-ray is produced until the discharge is complete
Battery Powered Generators use ____batteries

Sends _____ to a rotary inverter.

Use nickel cadmium batteries

Sends direct current (non pulsating) to a rotary inverter
Battery Charged Generator provides AC of ____or ____

is ____and ______
Provides AC of 3 phase 12 pulse or greater

Is mobile and rechargeable
Falling Load Generator

Maximizes the tube ____ ____.

why does it use the highest mA setting?
ï‚¡ Maximizes the tube loading potential
ï‚¡ Uses the highest mA setting for decrease in time
falling load generator

___-are a must
Not selected by radiographer

AECs are a must
Eliminates signals outside of collimation margins

If margin not detected, extraneous data included in the histogram
⬢ Automatic exposure field edge detection
• Histogram Analysis
– Uses the shape of the signal distribution to determine:
⬢Relevant information in the exposure field
⬢Exposure Index
– Mapping grayscale to “pixel values of Interest” to achieve specific display levels
– Provides images that have uniform brightness over a wide exposure range


⬢ Automatic Rescaling
what are the three parts of Initial Image Processing?
Automatic Exposure Field Recognition

Histogram Analysis

Automatic Rescaling
Two major types of Histogram Analysis?
A priori

Neural
Histogram Analysis determines what?
regions of interest to be processed for optimal visibility of anatomical structures
Extremity Model (Type 1)

Describe.

needs direct exposure

source of "do not collimate"
General Model (Type 2)
does not need direct exposure
Metal Model
allows for metal in beam
If type 2 is used with barium what happens?
VOImin would seek lowest exposure, include low data; exposure index misdetermined; wrong automatic rescaling
Neural Histograms

Describe.

learn exposure patterns

When histogram shape changes:
Positioning
Non uniform beams

Determines VOImax and VOImin
Automatic rescaling will fail if....
histogram analysis is flawed
Histogram analysis maybe flawed if
Exposure fields edges not detected

large over and under exposure

unexpected material in data set
Grayscale deals with
Level (density and brightness) and window (contrast)
Frequency is associated with
Unsharp masking

edge enhancement

smoothing
equalization is combo of ____ and ____
grayscale and frequency processing
increased contrast along an edge. elaborate software function;
edge enhancement
edge enhancement increase _____what along the edge?
contrast
Edge enhancement causes an ____effect
halo
Improves display range; weighted processing; enhance local contrast; alter local density ; low exposed areas- light so displays darker adn vice versa
equalization
Mottle is considered high frequency variation, post processing modification of high spatial frequencies can reduce noise...1)
2)
Also reduces small clinical features.

Does not change SDNR and edge still degraded
Unsharp masking

Multifrequency processing

Smoothing
Noise suppression software; reduces visibility of mottle;
smoothing
Quality images are achieved when the tech has:
part position

beam alignment

exposure field recogniztion

proper receptor exposure
Classification of Artifacts
Image Receptor Artifacts

Software Artifacts

Object Artifacts
Digital Image Receptor Artifacts
Dust or Dirt

Scratches

Ghost Images
Where can dust be?
on CR receptor

anywhere in path
Scratches
on any pixel damage requires replacement of IR
Ghost Images
incomplete erasure

constantly over exposure
WHat QC should be performed on each IP?
Image Frequency

Imaging Performance

Physical Condition
Software Artifacts

Digital Images are obtained as ______.

The data is ready for ____.
For processing Images are manipulated into ____.
Raw data sets

Pre processing

For presentation
Software Artifacts

Preprocessing

2 terms: Dead Pixels
Flatfielding
1. not reacting to x-ray
2. computer function (heel effect)
lossless
reduces data by 50 %
lossy
can greatly reduce size; but some data loss;
Object Artifacts can be caused by Two things:
1. Tech error
2. Backscatter
Object Artifacts from tech errors: examples....
1. positioning
2. collimation
3. histogram selection
Collimation/Partition

2 things:

Exposure Field Recognition Errors
Multifield imaging
patitioning
2 or 4 fields

clear margins and distinct edges
BOLD
BOLD
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