VETN 205B: X-Rays - History, Physics, Machines

Who invented x-rays for medical purpose and when?

Roentgen in 1895

What is radioactivity?

When excited/unstable atoms decay and release particles and energy in order to become stable

What is ionization?

The loss of electrons and to become more positively charged → Ion

• Leads to electron production for x rays

In the electromagnetic spectrum, what do shorter wavelengths represent?

Higher energy and higher frequency

• Ex: x-rays, UV, gamma rays

In the electromagnetic spectrum, what do longer wavelengths represent?

Lower energy and lower frequencies

• Ex: Infrared rays, microwave, TV

What is energy movement measured in?

1. Waves

2. Particles - photons

When it comes to frequency, the higher the frequency…

The higher the penetration/strength AND the smaller/narrow the wavelength (and vice versa)

When it comes to photon energy, the smaller wavelength…

The higher the energy

What is the main property of x-rays?

They obey all the laws of light or they behave just like light

What are the special properties of x-rays?

• Penetration

• Elicit fluorescence

• Produce image on film

• Excite/ionize

• Biologic changes

• Produce scatter

What are the things involved when it comes to generating x-rays?

Electrons repel same charges and will attract opposite charges (protons)

What are the parts of the x-ray tube?

Cathode - negative

Anode - positive

What are the results/products of generation of x-rays?

<1% energy = x-rays

>99% energy = heat

What are the types of x-ray machines?

1. Portable

2. Mobile

3. Stationary

What is the only type of x-ray machine that has some preset settings?

Portable - has a fixed mA

What settings can you change on the different types of x-ray machines?

• mA

• kVp

• Time

What are the parts of an x-ray tube?

1. Controlled beam of x-ray photons

2. Cathode - electron source (negative)

3. Anode - target, positive charge → attracts electrons

4. Glass envelope → creates a vacuum = no air

What is kVp?

Kilovoltage peak - Electron acceleration or high electrical potential

The higher the kVp…

The higher the energy and the smaller the wavelength

What are the parts of a cathode?

• Filaments - used to heat up electrons

• Focusing cup - directs electrons

What is mA?

Miilliamperage - the energy needed to heat up the filament

The higher the mA…

The higher the temperature → The more # of electrons

What are some parts of the anode?

• Beveled up - at 10-20 degrees → creates focal spot

• Target - made up of Tungsten

What are the two types of anodes?

1. Stationary - small → used for dental and portable x-ray machines

   1. Rotating - has a focal track instead → helps to dissipate heat

What are the characteristics of the anode?

Heat production - creates >99% and >2200C (HOT)

Dissipates heat via:

• Conducting metal like copper

• Rotation - rotating anode

• Oil - exchanges heat

What is a focal spot?

When electrons hit the anode at the target area is the focal spot

What is the line-focus principle?

Using the target angle effect, when electrons hit the target