Basics of xray

Nano

deci

pico

micro

kilo

mili

• A changing magnetic field produces a [...] 

• A changing electric field produces a [...] 

• transient electric field 

• transient magnetic field 

This is the principle of induction

A wire carrying current experiences a [...] 

magnetic field 

[...]

• If iron core placed in center of solenoid, magnetic field much more intense 

electromagnet

What is the purpose of this image?

• [...] 

• [...] 

• A change in current (+ or -) influence magnetic field 

• When the swith opens or closes, see bumps in magnetic field 

2  types of current

• [...]: flow of electrons in one direction

• [...]: flow in alternating opposite directions 

• Direct current

• Alternating current

2 types of electricity

• [...]: electric charges at rest
  

  • Units: Coulombs

• [...]: moving electric charges
  

  • Units: Amperes 

• Static

• Current

2 types of electricity

• Static: electric charges at rest
  

  • Units: [...]

• Current: moving electric charges
  

  • Units: [...] 

• Coulombs

• Amperes 

Alternating current: flow in alternating opposite directions

• Pulse
  

  • One pulse is from negative to positive (or vice versa)

  • [how many pulses are in an AC current?]

• AC goes in opposite directions so one cycle has 2 pulses

As wavelengths decrease, frequency [increase or decrease?] 

increase 

Atom

• Atomic number (Z) = [...]

• Atomic Mass = [...] 

• number of protons

• number of protons + number of neutrons 

Atom

• [...] = number of protons

• [...] = number of protons + number of neutrons 

• Atomic number (Z)

• Atomic Mass

Basic X-Ray Generation

1. [step 1?]

2. [step 2?]

3. High KE electrons interact with target atoms to produce photons in x-ray wavelength

4. Electrons are conducted away & complete the circuit
   

   • Current is flowing and since it is a high voltage area, current needs be low in mA 

1. Electrons thermionically “boil off” filament embedded in the cathode

2. Negatively charged electrons are shot at positive anode tungsten target by the strong potential difference

Basic X-Ray Generation

1. Electrons thermionically “boil off” filament embedded in the cathode

2. Negatively charged electrons are shot at positive anode tungsten target by the strong potential difference

3. High KE electrons interact with target atoms to produce photons in x-ray wavelength

4. Electrons are conducted away & complete the circuit
   

   • [What unit is it in?] 

1. Current is flowing and since it is a high voltage area, current needs be low in mA 

Binding Energy (BE): the amount of energy that electrons have in each shell

• [Higher or lower?] BE if closer to nucleus

• Higher the atomic number, the tighter the K shell electrons are bound

Higher

The higher the BE, the harder it is to separate the electron (freeing an electron requires equal or more energy than the BE)

Outer shells like O and P have a really low BE (so its easy to pry those electrons away) but inner shells (like K) have a high BE

Binding Energy (BE): the amount of energy that electrons have in each shell

• Higher BE if closer to nucleus

• [Higher or lower?] the atomic number, the tighter the K shell electrons are bound

Higher

The higher the BE, the harder it is to separate the electron (freeing an electron requires equal or more energy than the BE)

Outer shells like O and P have a really low BE (so its easy to pry those electrons away) but inner shells (like K) have a high BE

Current Rectification

• Diodes only allow flow in [how many directions?]

one direction

Describe the second law of transformers? 

• [...] 

• [...]

• If voltage is increased in primary, it is at the expense of current in the primary 

• power in the primary equals the power in the secondary

VI = P (watts) 

Explain why X-Rays can be dangerous, in terms of the ionizing radiation.

• [...] 

• Energy is always transferred to any material with which it interacts
  

  • Since high energy EM can ionize atoms (disrupt DNA), there are safety concerns

  • IF there is an interaction, energy is transferred (likely disrupting DNA)

  • But if the X-Ray passes through without interaction, there no energy transferred and everything is okay (no harm, no foul) 

Frequency: number of waves passing per second  

• SI unit: [...]

• 1 Hz = 1 cycle per second 

Hertz (Hz)

Full Wave Rectification

• Accomplished by [...] 

a diode bridge, formed by 4 diodes 

Full Wave Rectification

• Disadvantages
  

  • [...]

  • [...] 

• Tube pulsates and anode receives rapidly varying amounts of energy

• Intensity of x-ray beam varies. Consequently, quality of beam varies over each half cycle 

increased patient dose via "soft radiation"

Full Wave Rectification

• [What parts of the alternative voltage] are used to produce x-rays
  

  • Converts alternate current to direct current

Both halves of the alternative voltage

Generally no more than [...] electrons in the outermost shell 

8

How does additional phases affect ripple factors? 

• [...]

Additional phases results in low ripple factors which means better image quality but also more expensive

How does the secondary coil recieve current?

• [...] 

• Rapidly changing electric fields in the primary coil induce rapidly changing magnetic fields
  

• The rapidly changing magnetic fields in turn induce rapidly changing electric fields in the secondary coil 

Induced EMF's

• Current flow thru one coil can cause [...] in a 2nd coil wrapped around the same iron core or rod 

mutual inductance

Basis of the transformer

Induced EMF's

• EMF= 􏰉[...] x [...]

• Number of wires x Change in flux per unit time

Ionizing Radiation: X-Ray electromagnetic radiation energy range

• Can penetrate matter

• Causes some material to [...]

• Reacts with [...] of film 

• fluoresce

• silver halide

X-Rays have enough energy to cause atoms to ionize (gain or lose electrons) 

Ripple Factor

• Half-wave
  

  • Unfiltered – [...]%

  • Filtered – [...]%

• Full-wave
  

  • Unfiltered – [...]%

  • Filtered – [...]% 

• 100%

• 20%

• 100%

• 9%

Secondary Coil

• If there are more coils in the secondary coil, then it is a [step up or step down] 

• If there are less coils in the secondary coil, then it is a [step up or step down] 

• step up transformer 

• step down transformer 

Sinusoidal (in the form of the sine curve) electric and magnetic fields are [...] to each other 

perpendicular

Step down transformer

• Has less coils in the secondary coils than the primary coil

• [Function?] 

• Used to heat filament 

Step up transformers

• Has more coils in the secondary coil than the primary coil

• [Where is it used?] 

• Used in the electron accelerating part of the x-ray tube 

Tungsten

• Atomic number = [...] (so number of protons is also [...])

• Atomic mass = [...] (so 110 neutrons) 

• 74

• 74

• 184

Wave-Particle Duality

• EM radiation has wavelike properties and particle properties
  

  • Particles are called [...]

• Energy of a photon can be calculated via following equation
  

  • Energy = h x frequency where h = Planck’s constant 

photons

Wave-Particle Duality

• EM radiation has wavelike properties and particle properties
  

  • Particles are called photons

• Energy of a photon can be calculated via following equation
  

  • Energy = [...] x [...] where h = Planck’s constant 

h x frequency

What is the first law of transformers?

• [...] 

• Ratio of number of turns is equivalent to the ratio of voltage in the circuits 

What's the difference between half-wave rectification & full-wave rectification? 

• [...]

Why can AC current not be used with X-Rays? 

• [...]
  

  • Not safe & produces poor images 

• AC cannot be used in an X-Ray tube bc its pulsating

Why can't direct currents be used in a transformer? 

• [...]

A rapidly changing electric field is required to induce a magnetic field

X-Ray Generator

• Function
  

  • [...]

    • Accomplished by a transformer

  • [...]

    • Rectified by diodes 

• Must transform voltage from 115 to that 40 – 150 kVp that is required

• Must convert alternating current (from the wall plug) into direct current

X-Ray Generator

• Function
  

  • Must transform voltage from 115 to that 40 – 150 kVp that is required

    • Accomplished by a [...]

  • Must convert alternating current (from the wall plug) into direct current

    • Rectified by [...] 

• transformer

• diodes 

X-ray imaging is between [...] and [...] energy (eV)

• This range is called the ionizing radiation (the high energy EM can ionize matter) 

10⁴ and 10⁵

X-Ray Machine 3 basic components

1. [...]

2. [...]

3. [...] 

1. X-Ray Generator

2. X-Ray Tube

3. Control Panel 

X-Ray production

• Cathode is a [step up or step down] transformer that generates electrons

• Anode is a [step up or step down] transformer that accelerates electrons
  

  • Responsible for potential difference between cathode & anode?? 

• step down

• step up

X-Ray production

• [...] is a step down transformer that generates electrons

• [...] is a step up transformer that accelerates electrons
  

  • Responsible for potential difference between cathode & anode?? 

• Cathode

• Anode

X-Ray Tube Head

• [Positive or negative?] charged tungsten cathode
  

  • Coiled filament within the cathode

• [Positive or negative?] charged copper anode
  

  • With embedded tungsten target 

• Negatively

• Positively

X-Ray Tube Head

• Negatively charged [which element] cathode
  

  • Coiled filament within the cathode

• Positively charged [which element] anode
  

  • With embedded tungsten target 

• tungsten

• copper

X-Ray Tube Head

• Negatively charged tungsten cathode
  

  • [what's found within it?]

• Positively charged copper anode
  

  • [what's found within it?] 

• Coiled filament within the cathode

• With embedded tungsten target 

[...]: the amount of energy that electrons have in each shell 

Binding Energy (BE)

[...]

• Way to store energy

• Builds up energy when the circuit is closed

• Quickly discharges when it senses dropping voltage in the tubes 

Capacitors

[...] anytime electric charges are made to accelerate 

EM radiation

[...]: process whereby atom gains or loses electrons (typically from outer shell)

• Positive ions = cations

• Negative ions = anions 

Ionization

X-Rays have enough energy to cause atoms to ionize (gain or lose electrons) 

Ionization: process whereby atom gains or loses electrons (typically from outer shell)

• Positive ions = [...]

• Negative ions = [...] 

• cations

• Anions

X-Rays have enough energy to cause atoms to ionize (gain or lose electrons) 

[...]: X-Ray electromagnetic radiation energy range 

Ionizing Radiation

[Primary or secondary] Coil = whatever is plugged into the wall or battery

Primary

[...]

• Atom & molecules can only exist in certain energy states & changing states requires energy

• Ionized – when an atom or molecule changes its state (requires energy) 

Quantum Theory

[...]: variation in the voltage across the x-ray tube, expressed as a percentage of its maximum value 

Ripple Factor

[...]

• Coils generate heat, forming an electron cloud and a positive and a large negative at the other end

• Electrons move in a clockwise fashion and electricity flows through the current & converts it to a direct current

Simple Vacuum Diode System

[...]

• current in coil of wire creates weak magnetic field 

solenoid

[...] x [...] = velocity (c) 

• Changing = wavelength & frequency

• Constant = speed is the speed of light (constant for EM waves)
  

  • C = 3e8 m/s

Wavelength x Frequency

Wavelength x Frequency = velocity (c) 

• Changing = [...]

• Constant = [...]
  

  • C = 3e8 m/s

• wavelength & frequency

• speed is the speed of light (constant for EM waves)

[...]

• Supplies electric power to the x-ray tube

• Begins with wall plug (115 V)

• Filament heating requires ~10 V

X-Ray Generator

X-Ray Generator

• Supplies electric power to the x-ray tube

• Begins with wall plug (115 V)

• [...] requires ~10 V

Filament heating

• Electrons all acquire the same KE or velocity (half the speed of light) --> [...]
  

  • Travels a very short distance (b/w cathode & anode): 1 to 3 cm

• Photons are comprised of varied energies (different wavelengths) --> [...]  

• monochromatic

• polyenergetic  

• [...] --> monochromatic
  

  • Travels a very short distance (b/w cathode & anode): 1 to 3 cm

• [...] --> polyenergetic  

• Electrons all acquire the same KE or velocity (half the speed of light)

• Photons are comprised of varied energies (different wavelengths)

• Electrons all acquire the same KE or velocity (half the speed of light) --> monochromatic
  

  • Travels a very short distance (b/w cathode & anode): [what's the distance?]

• Photons are comprised of varied energies (different wavelengths) --> polyenergetic  

1 to 3 cm