Intro To Radtech. X-ray Production Flashcards
What are x-rays?
A group or rays belonging to the electromagnetic spectrum
Electromagnetic spectrum measures in…
Wavelengths and light
What is radioactivity?
Radioactivity is the process of decay.
Everything around us is radioactive
Sine waves travel at what speed
The speed of light
What is the speed of light?
186,000 miles per second
3x10^8 meters per second
3x10^10 centimeters per second
C=constant
EM wavelengths are measured in
The distance between two successive crests in a wave
Lamda
EM Frequency is measure in
The time between each crest
Nu
Wavelength and frequency of Em waves are
Inversely proportional
Speed of light = wavelength x frequency
What is the crest of a wave?
The highest point in the wave
What is the trough of a wave
The lowest point
The wavelength of a wave
Crest to crest or trough to trough or center to center.
Distance between
What is the wave height?
Distance between the crest and its neighboring trough
What is amplitude?
The amount that the wave has been displaced from its median position.
Half of the wave height
What is the undisturbed surface of a wave
The middle line of the wavelength
What is frequency?
The number of crests or troughs that pass through during a specific time interval.
Inverse of period
What is period?
.the length of time it takes to complete one cycle
X-Ray beams are
Heterogenous
Meaning different energies
Average- very short wavelength
Useful range is 0.1A through 0.5A
What are the two theories on properties of x-rays?
Wave concept
Particle concept
What is the wave concept on properties of x-rays
It explains how they move through space. And yet travel in a vacuum
What is the particle concept on properties of x-rays?
Explains how they can interact with matter as though they were particles.
Define mathematical constant
- constant: a non-varying value
- variable: changing value
- constant, in a formula, usually denoted by a letter, such as c for the speed of light
- or planck’s constant: the letter h
Is there a relationship between photon energy and frequency?
- energy = plancks constant x frequency
- plancks constant = 6.63x10^-34 joule-seconds
Symbol is h
As frequency increases, photon energy increases
Who discovered x-rays?
Wilhelm Conrad Roentgen
November 8, 1895
Discovered by accident
Observed by 12 other scientists previously
Roentgen identified all of the properties of x-rays less than a month after his discovery
Part of university of wurzburg
What is the first known medical radiograph?
A wrist x-ray performed on February 3, 1896 at Dartmouth college
What conditions are needed for x-ray production?
- separation of electrons
- high-speed electrons
- sudden stopping of electrons
- concentration(focusing) of electrons
Separation of electrons
Thermionic emission
Heating of the tungsten filament
Creates electron cloud aka space charge
All x-Ray tubes are…
Dual focus
Two filaments used one at a time
One wired with high voltage and one with low
Space charge
“Electron cloud”
Space charge effect
Limits the number of electrons present in the space charge
Due to the negative charge on the focusing cup, forcing the electrons together
In spite of the electrostatic repulsion the electrons have for each other
How fast do electron move?
Half of the speed of light
Speed of light = 186,000 mi/sec
What is the focal spot?
The actual area on the anode that is struck by electrons
The smaller the focal spot, the greater the spatial resolution on the resulting images
What is the line-focus principle?
Actual focal spot size is larger than the effective focal spot
Bremsstrahlung Radiation
Means braking radiation
Also known as general radiation
Brems makes up 100% of the primary beam
If under 70 kVp and ~85% if over 70 kVp is used
Caused by deceleration of “cathode rays” when they are near the nucleus of a tungsten atom of the target
What moves electrons?
Kinetic energy
What is characteristic radiation?
Up to 15% of the primary beam (if over 70 kVp)
A direct hit between cathode rays and tungsten atoms
Energy of radiation is characteristic of the energy shell of the tungsten atom it interacted with
Cathode
The negative electrode
Made of two parts
- tungsten filaments
- nickel focusing cup (or molybdenum)
Filament is heated by a separate low-voltage circuit
Anode
Positive electrode
Made of a tungsten-rhenium alloy (some have layers of molybdenum and graphite)
Circular, it rotates to dissipate heat
- 3600 to 10,000 RPM
What are the properties of x-rays?
A. Can penetrate matter of any kind
B. Electrically neutral ( not deflected by magnetic or electric field)
C. They occur in a wide range of wavelengths (0.04 A to 1000 A)
D. X-ray beams are heterogenous
E. x-rays travel in straight lines
F. Travel at the speed of light in a vacuum
G. Capable of ionizing gases
H. Cause fluorescence in certain crystals
I. Cannot be focused by a lens
J. Affect photographic film
K. Produce chemical and biological changes
L. Produce secondary and scattered radiation
Exposure rate is altered by…
Milliamerage
Kilovoltage
Distance
Filtration
Milliamperage (mA)
Determines quantity of radiation
Settings on panel go from 25 mA - 1500mA
Increases tube current, so increases number of x-rays produced
Exposure rate is directly proportional to the mA
What is mAs?
Milliamperage x time(in seconds) = mAs
Milliampere-second
Kilovoltage(kV)
Determines the quality of radiation
Quality is the penetrating ability of the beam. (Denotes energy of beam)
• kV increases speed of electrons from cathode to anode
More kinetic energy of the electrons traveling from cathode to anode results in…
More x-ray energy when those electrons hot the anode
The 15% rule
Increasing the kVp by 15% will have the same effect (on density/brightness) as reducing the mAs to 50%
Formula: kVp x 1.15; then mAs/2
KVp x 0.85; then mAs x 2
Inverse square law
a law stating that the intensity of an effect such as illumination or gravitational force changes in inverse proportion to the square of the distance from the source.
Beam quality
The penetrating ability of the beam
Longer wavelengths are low kV
Crookes x-ray tubes (col cathode tubes) were used until
About 1920
What year did eastman introduce radiographic film?
1918
What year was the society of radiographers formed?
1920
When did Siegbahn receive the nobel prize in physics for x-ray spectroscopy
1924
What is an x-ray beam?
A group of rays belonging to the electromagnetic spectrum
Wavelength is?
The distance between to successive crests
Wave frequency is
The number of crests per second
Speed of light =
Wavelength x frequency
What is radiation
The transfer of energy in the form of particles or waves
Or
A relatively high-energy photon having a wavelength in the approximate range from 0.01 to 10 nanometers
What is an angstrom
Measurement of wavelength
1A= .1 nanometer
1 electron
What is a photon
The smallest amount of any type of electromagnetic radiation
Also considered a bundle of energy called a quantum
Travels at the speed of light, in waves in a straight path
Types of photons
X-radiation Gamma Light Radio Etc
Maximum E in a photon beam is expressed in
KVp
The wave equation
Wavelength= velocity/frequency
Characteristics of x-rays
- are invisible
- are electrically neutral
- have no mass
- travel at the speed of light in a vacuum
- cannot be optically focused
- form a polyenergetic or heterogeneous
- can be produced in a range of energies
- travel in straight lines
- can cause some substances to fluoresce
- causes chemical changes in radiographic and photographic film
- can penetrate the human body
- can be absorbed or scattered in the human body
- can produce secondary radiation
- can cause damage to living tissue
In what year where x-rays discovered?
A. 1892
B. 1895
C. 1898
D. 1901
B. 1895
In what year were some of the biologically damaging effects of x-rays discovered?
A. 1892
B. 1895
C. 1898
D. 1901
C. 1898
X-rays were discovered in experiments dealing with electricity and___________?
A. Ionization
B. Magnetism
C. Atomic structure
D. Vacuum tubes
D. Vacuum tubes
X-rays were discovered when they caused a barium platinocyanide-coated plate to ____________?
A. Fluoresce
B. Phosphoresce
C. Vibrate
D. Vacuum tubes
A. Fluoresce
X-radiation is classified in which spectrum?
A. Radiation
B. Energy
C. Atomic
D. Electromagnetic
D. Electromagnetic
X-rays have a duel nature, which means that they behave like both _________________
A. Atoms and molecules
B. Photons and quanta
C. Waves and particles
D. Charged and uncharged particles
C. Waves and particles
The wavelength and frequency of x-rays are_______________related
A. Directly
B. Inversely
C. Partially
D. Not
B. Inversely
X-rays have____________electrical charge
A. A positive
B. A negative
C. An alternately positive and negative
D. No
D. No
X-rays have__________
A. No mass
B. The same mass as electrons
C. The same mass as protons
D. The same mass as neutrons
A. No mass
The x-ray beam used in diagnostic radiography can be described as being________________
A. Homogenous
B. Monoenergetic
C. Polyenergetic
D. Scattered
C. Polyenergetic
The unit that measures the transfer of radiation energy into tissue is known as the____________
A. Roentgen
B. REM
C. Gray
D. Sievert
C. Gray
Which of the following will minimize radiation exposure to the patient?
A. Beam restriction
B. Gonadal shielding
C. Screening for pregnancy
D. All of the above
D. All of the above
