gamma knife

Question 1

stereotactic

Answer 1

the 3D localisation of a point in space by a unique set of coordinates that relate to a fixed external reference frame

Question 2

what is stereotactic radiosurgery

Answer 2

​- DOES NOT involve any surgical procedure.​

• Narrow beams of radiation precisely focused on a small target.​
• Tends to be single fraction but can have up to 5#’s.​
• Normally delivered usingGammaknife™orCyberknife™.​
• Can be delivered using a linear accelerator.​

Question 3

aims of SRS

Answer 3

• Highly conformal radiotherapy - used to achieve an extremely high concentration of absorbed dose to a small spherical target.
• Can only be used for limited tumour volume size < 3.5cm diameter.
• Extremely rapid dose fall-off to normal surrounding tissue = high therapeutic ratio.

Question 4

advantages of SRS

Answer 4

• Reduced toxicity to normal tissue.
• More precise treatment.
• Reduction in acute side effects.
• Fewer appointments required.

Question 5

what is gamma knife

Answer 5

• Array of Cobalt 60 sources (varies from 201 – 192)
• Aligned using a collimation system
• sources are focused on the target area and sources can be turned on or off to achieve the best dose to the target.
• Sources are evenly distributed over the surface of the hemispherical source core.
• Each beam is directed at a common focal spot at the centre.
• Enables high doses to be delivered to the abnormal tissues whilst sparing the adjacent healthy tissue.