Dr. Korvatko's Radiation Physics: X-ray Production & Emission

___________ emission results with the cloud of electrons emitted from the cathode:

Thermionic

True or False: Characteristic Radiation can occur at K through P shells of an atom. However in diagnostic x-rays only K-characteristic x-ray emission is important

True

True or False: Characteristic x-rays have precisely fixed (discrete) energies and form a discrete emission spectrum.

True

True or False: For Characteristic Radiation This interaction is very specific when an x-ray photon has the specific energy equal to the difference in binding energies of the orbital electrons:

True

True or False: The intensity of bremsstrahlung radiation is proportional to the square of the atomic number of the target (Z)

True

How are x-rays produced?

X-rays are produced due to sudden deceleration of fast moving electrons when they collide and interact with the target anode. In this process of deceleration more than 99% of the electron energy is converted into heat and less than 1% of energy is converted into X-rays

Bremstrahlung radiation-German for what?

breaking or slowed-down radiation

The x-photon production increases with increase in ____

kVp

At 60 kVp-only __% are-x-photons. 100 kVp aprox __% are x-photons

0.5, 1

As the E-cloud approaches the anode, what 3-main events are occurring?

1) The cathode's-E-lose their kinetic energy 2) 99% interactions of the electrons at target will result in heat production 3) The remainder will produce: Bremsstrahlung and Characteristic radiation

What are the 4-principal factors influencing the shape of an x-ray spectrum?

1. Electrons traveling across the tube do not all have the peak kinetic energy. Some e- have very low energies when they strike the anode target. Heat and low energy x-rays are produced. 2. Throughout the x-rays production, many of the Bremsstrahlung x-rays emitted are the result of multiple projectile e- interactions. For each successive interaction, a projectile e- has less energy. Thus lowering the x-photons energy. 3. Low energy x-rays are absorbed in the target. 4.External filtration is always added to selectively remove low energy x-rays from the x-rays beam. This will manifest with higher quality x-ray beam and reduction in patient's radiation dose

Bremstrahlung x-rays form a continuous spectrum with "peak" of the spectrum typically at approx what % of E-max?>

1/3

In diagnostic x-rays the greatest number of x-rays emitted are approximately _____% of the maximum energy.

33% or 1/3

What is a Cathode?

A Cathode is the negative terminal of the x ray tube made of tungsten filament and when current is flown through it, the filament gets heated and starts emitting its surface electrons through thermionic emission

What is an Anode? and what 2 x-ray types are produced?

Anode is the positive terminal of the tube. It is made of tungsten disc. Fast moving electrons interact with anode in following ways: •interaction with K-shell electron produces Characteristic radiation •Interaction and deflection of the projectile electrons with the nucleus causes Bremsstrahlung radiation that forms the majority of x-rays in the spectrum

What is Bremstrahlung radiation?

As electrons emitted from the cathode bombard the anode's target containing high atomic number (Z), strong nucleic field created by positively charged protons begin to influence the projectile electrons. Some projectile electrons then change their course or deflect with some or all of their original kinetic energy being lost and resulting energy released as x-ray photons known as

What is Characteristic Radiation called "characteristic"?

Because each element on the periodic table has its characteristic electron binding energies the energy of characteristic x-rays is also different and The effective energy of characteristic x-rays is directly related to the atomic number (Z). of a particular element.

What is Characteristic Radiation?

Characteristic x-rays are produced when a projectile electrons interact with inner-K-shell atomic electrons. More precisely when projectile electron's energy is exceeding binding energy of K-shell electron, the K-electron is removed from its orbit. Outer or L-shell electron then, fills the void with resultant energy released as x-photon or Characteristic radiation.

True or False: Bremsstrahlung x-rays have a spectrum of production which varies between zero to 1/3 of the energy peak of each photon or individual photon energy.

False: Bremsstrahlung x-rays have a spectrum of production which varies between zero to highest energy peak of each photon (e.g. 0-150 keV) or individual photon energy

True or False: Light particles such as electrons bombarding targets of low atomic number (i.e. anode's focal spot) are more efficient producers of bremsstrahlung radiation

False: Light particles such as electrons bombarding targets of high atomic number (i.e. anode's focal spot) are more efficient producers of bremsstrahlung radiation