KV Radiation Equipment

Question 1

KV PDD (2)

Answer 1

-d-max at skin surface
- not penetrating

Question 2

KV Treatments (2)

Answer 2

• Good for skin treatments
• High superficial dose

Question 3

KV Scatter

Answer 3

low and medium energy x-rays readily scatter in air

Question 4

Applicators (3)

Answer 4

• used to achieve sharp penumbras and delineate treatment fields
• solid walls, not thick due to x-rays hitting at an oblique angle
  -applicators extend to patient surface

Question 5

Lead cut outs (4)

Answer 5

• minimizes normal tissue irradiation
• customized for patient lesion
• lead thickness dependent on x-ray energy
• must be slightly larger than applicator (clinical margin)

Question 6

Anode angle

Answer 6

• the angle at which electrons hit the target
• effects focal spot size
• large angle = larger focal spot
• small angle = smaller focal spot

Question 7

Heel effect

Answer 7

• a loss in intensity on the anode side of the x-ray field caused by the attenuation of the x-ray beam by the anode
• refers to the variation in intensity across beam and to the cut off in the shadow behind the anode

Question 8

Imaging anode angle (4)

Answer 8

• want to avoid a blurry image = small focal spot required (reducing object to film distance also helps)
• area electrons hit on target must be small
• steep angle must be used to achieve this
• smaller anode angle (17 degrees)

Question 9

Imaging target type (4)

Answer 9

• imagine needs to be as fast as possible
• target exposed to large amount of electrons in a short period of time
• enormous amount of heat will occur on a very small area of target (very bad)
• target/anode must rotate so heat can be better distributed (very good)

Question 10

Therapy anode angle (4)

Answer 10

• we want a homogenous field = larger focal spot required (don’t need a clear image)
• area electrons hit on target must be larger
• flatter angle must be used to achieve this
• larger anode angle (45 degrees)

Question 11

Therapy target type (4)

Answer 11

• therapy can be delivered over longer periods of time (stabilizing set up)
• target exposed to large amount of electrons over a longer period of time
• heat is better distributed over target
• target/anode is stationary

Question 12

Anode cooling (3)

Answer 12

• x-ray tube requires time between uses to cool down
• amount of time it takes to set patient up is usually enough time
• x-ray tube also has protective mechanisms such as overload protection and water cooling which prevent damage