Radiology and X-ray Physics

X-ray History

• X-ray was developed by Wilhelm Roentgen in 1895 in Wurtzberg Germany.
• First dentist to use X-rays was Dr. Edmund Kells

X-ray Physics

•  In the x-ray tube we have an anode and cathode. To create electrons, heat the anode, boil off the electrons, using a step down transformer.
•  We concentrate the electrons with a molybdenum focusing cup.
•  To move the electrons we create an electron potential difference, using a step up transformer (going from 110V to 65,000+ kilovolts). This increases the KVP. The higher the KVP the more energy the photon is going to receive.
•  To create a photon we move the electrons from the anode to the cathode and 99.8% of them are going to turn into heat and .2% become photons.
•  A photon is a bundle of energy.
•  We call the transformation from electron to photon: Bremsstrahlung (or break energy).
•  Review: So we have the X-ray tube made of glass, in the X-ray tube we have an anode and cathode and molybdenum focusing cup, and a vacuum. In the vacuum we create the electron potential difference, and the photons come out through the window.
•  All of the photons coming out of the window are parallel with each other.
•  The x-rays are long and short wavelength energy (can use the short because it has more penetrating power).
•  We get rid of the long wavelength with filtration: either aluminum (added filtration) or the glass tube itself (inherent filtration).
•  Inside the X-ray tube the coil is made of tungsten because of its high melting point (1500 C).
•  X-rays come out of the tube and then travel in a straight line until it has an interaction with whatever 32 times.
•  Electromagnetic ray length is measured in angstroms (smallest measurable denominator of the meter).
•  Every tissue in our body has a different Z number (atomic number). In order to have a good picture you must follow the following rules:

1. Source of the X-ray needs to be as small as possible (comes out from a dot)
2. Source to object distance is as long as practical
3. Object to film distance is as short as practical
4. Object and film must be parallel with each other
5. Central beam and object and film should be producing a 90 degree angle in all (any) directions.
X-ray film

• X-ray film is housed in an emulsion which contains silver halide/bromide/iodide/chloride etc.
• The silver bromide crystal has the capability of having an area of exit being exposed, called a sensitivity spec. It creates from the central crystal a latent crystal which could be developed later on.
• We have lead inside the x-ray film so we don’t get scattered radiation.
• We use high speed film to reduce patient exposure. 
•  Ultraspeed D speed (slow), E speed (not so slow), F speed Insight (fastest). F speed film is the same speed as digital radiography sensors to reduce patient exposure.