mahoney 3

Question 1

Measurement = Air Kerma (roentgen) (R)

Answer 1

Quantity of exposure

• exposure = amount of ionization that is produced when radiation passes through matter

Question 2

Measurement: rad or Gray (gy)

Answer 2

quanitity of absorbed dose

• absored dose = amount of energy absorbed by matter when radiation passes through it

Question 3

Rem (r) or Sievert (Sv)

Answer 3

quantity of effective dose equivalent received by radiation works

• Dose equivalent = measure of bilogical damage caused by radiation

Question 4

Curie or becquerel

Answer 4

quantity of radioactivity

Question 5

what are some dose equivalents (Gy –> rad and Sv –> rem)

Answer 5

• 1 Gy = 100 rads
• 1 Sv = 100 rem

Question 6

Attenuation

Answer 6

• Attenuation = x-ray are partially absorbed by matter
  
  • results in different shades of gray on film
  • Matter that absorbs X-ray appear WHITE are are RADIOPAQUE
  • Matter that allows TOTAL PENETRATION on X-rays appear BLACK and are Radiolucent

Question 7

Inverse square law

Answer 7

• light intensity from a souce is inversely proportional to the square of the distance between the object and the source

Question 8

kVp (kilovoltage peak)**

Answer 8

• energy of the x-ray beam
• 50-70 kVp’s
• manipulates primarily the energy of quality of x-rays and to be lesser extent the quantitiy of x-ray
• INCREASING kVp increases both QUALITY AND QUANTITY
  
  • Governs PENETRATING POWER OF ELECTRONS
    
    • low kVP produces high contrast
    • high kVP produces low contrast
    • 15% increase in kVP will cause same change as doubling mA (make image look darker
      *

Question 9

mA (miliamperage)**

Answer 9

• 10-30mA’s
• manipulates quantiity of x-rays
  
  • how many photons reach patient and film
• INCREASING mA’s INCREASES QUANITITY BUT NOT QUALITY

Question 10

Timer**

Answer 10

• controls length of exposure
• 1/60th to 1/100th of a second
• manipulates quanitity of x-ray
  
  • primarily!!!

Question 11

What affects QUANTIITY of the x-ray

Answer 11

• X-ray quantity (output intensity, X-ray intensity, x-ray exposure) is the NUMBER of X-ray

Question 12

what affects Quality of an x-ray?

Answer 12

• X-ray quality is the penetrability of the x-ray or how much ENERGY it has
• FILTRATION DECREASES QUANTITY, INCREASES QUALITY

Question 13

X-ray interaction with matter

Answer 13

• coherent scattering
• compton scattering
• photoelectric effect

Question 14

Coherent scattering

Answer 14

• as X-ray photons excite the target atom, a secondary photon of eual energy is released in different direction which is abosrbed by the patient but does nto contribute to diagnostic image

Question 15

Compton scattering

Answer 15

• Occurs when x-ray photon interacting with matter ejects the out-shell electon causing ionization
• CREATES FOG that impairs the image quality by reducing its contrast
• high kVP facors COMPTOM SCATTERING (more radiation makes its way to the x-ray film)

Question 16

Photoelectric effect**

Answer 16

• Process causes beam attenuation and image formation
• contributes to patient absorbed dose
• Low kVP facors photoelectric effect, but increases dose of radiation

Question 17

resolution*

Answer 17

• Ability to separate the distinguish between two separate objects (detal)
  
  • TYPES
    
    • Spatial = image sharpness = ability to distinguish between two objects when are side by side and have different contrasts
    • Contrast = ability to distinguish between differences in density or intesnity

Question 18

radiographic density

Answer 18

• amount of darkening in the radiograph
• along with contrast , are required to give visibility to the structural detals
• mA’s is the PRIMARY CONTROLLING FACTOR
  
  • as mA’s increase, the IMAGE BECOMES DARKER
• other factors:
  
  • kilovoltage (kVp)
  • Distance (SID) = alter number of photons striking film (too far –> makes image lighter)
  • Film/Screen combinations (higher the speed, the less radiation is needed)
  • compensation filter
  • film processing

Question 19

kVP roles in contrast

Answer 19

• kVP is PRIMARY FACTOR IN CONTROLLING CONTRAST
  
  • higher kVp’s produce low contrast and vice versa
  • to produce shorted contrast, increase mAs by 2 and decrease kVP by 15%
  • to produce lengthed contrast, decrease mA’s by 1/2 and increase kVP by 15%

Question 20

2 scales of contrast

Answer 20

• Short contrast
  
  • used in foot and ankle imaging
  • distinguishes bone margins froma dajacent soft tissues
• Long contrast
  
  • used in abdomen
  • visualize different soft tissue structures that have more similar densities