Medical Imaging Technologies an der TU München

Radiography: 2-D image

CT: Cross sectional views and 3D images

20-140 keV

The tube converts electric energy into x-rays and heat.

Because of the high temperature of the filament, the binding energy of the electrons is lower --> electrons emitted.

The cathode provides the electrons and the anode is used an target.

The x-rays get emitted downwards.

For higher power by better heat distribution

Acceleration voltage of the tube

Flux only

1. Bremsstrahlung:
   Negative acceleration of an electron in the Coulomb field of the atom nucleus.
   
   
2. Characteristic Emission:
   Electron transition in the inner shells lead to the emission of characteristic X-ray energies

An accelerated electron ejects an electron from one of the inner atomic shells (accelerated electron kicks out inner shell electron)

This state of the atom is now very unstable --> An electron of the outer shell retakes the place of the inner shell electron, which has been ejected.

By jumping from one of the outer shells to the inner shell a photon of a characteristic energy is emitted.

We can generate a high intensity with low photon energy --> dose reduction 

Is also called Thomson or Rayleigh scattering .
The non relativistic moving electron is accelerated by the electric field of the incident wave.
The electron will move into the same direction as the oscillating  electric field, resulting in emission of the electromagnetic radiation.

Learning Outcomes in the beginning 

Advantages :

• High sensitivity
• Quantitativ

Disadvantages:

• Radiation
• Requires cyclotron
• low spatial resolution