Introduction Flashcards
Radiation
The transfer of energy as particles or electromagnetic (EM) waves
Ionizing radiation
Radiation with sufficient energy (>15eV) to cause3 an atom or molecule that it reacts with to lose an electron
Production of X-Ray
Occurs through the conversion of energy within particulate radiation (electrons) to electromagnetic energy (X-rays)
Focusing cup
Negatively charged, repels the electrons and “focuses” the electron cloud toward the anode
KeV
Kiloelectron volt
The measure of the energy of a photon or electromagnetic wave
KVp
Kilovoltage peak applied across the tube
Beam includes many other energy X rays
Average energy of the beam is 1/3 - 1/2 KVp
Photoelectric effect (PE)
Ion pair created
Photon totally absorbed and does not contribute to image formation
Compton scatter (CS)
Ion pair created
Only some of the photon (X-Ray) energy is absorbed, but still continues as a lower energy X-Ray photon in a new direction
Probability of interaction is proportional to physical density of the subject/ (Energy)
Increased kVp decreases likelihood of
Compton scatter
Increased KVP decreased likelihood of
Photoelectric effect
Increased atomic number
Increased likelihood of photoelectric effect
No effect on Compton
Thickness/density of object increases
Compton scatter
Latitude
Maximum difference in Radiographic density of anatomical structures that can be evacuees on a given radiograph
Inversely related to contrast with many shades of gray
High KVp, low mAS
Used to abdomen and thoracic evaluation
The ability of a film to record differences in density (recognizable differences in shades of gray
Increase KVp by 15%
One-half mAS
Contrast
Difference in the photo density between two adjacent anatomic stuctures Very short gra scale Low KVp, high mAS Used for musculoskeletal techniques Decrease KVp by 15% Done mAS
More scatter will be produced with increases in
KVp setting (beam energy) Field size (collimating on) Patient thickness
