SRS and SRT

Question 1

What defines sterotactic?

Answer 1

• high precision
• small targets
• high dose

Question 2

What does SRS allow?

Answer 2

• steep dose gradient and thus minial dose to OAR

- increased conforminty

Question 3

How is conformity achieved?

Answer 3

• use of multiple non-coplanar beams

Question 4

What is SRS?

Answer 4

• single high dose of radiation

Question 5

What is SRT?

Answer 5

• treatment is delivered in more than one fraction

Question 6

What are the indications for SRS/SRT?

Answer 6

• small tumour size
• tumour location
• pathology of tumour
• the patient
• tumour recurrance

Question 7

What are the acute side effects of SRS?

Answer 7

• headache
• nausea/vomitting
• visual disturbances
• swelling

Question 8

What are the late side effects of SRS?

Answer 8

• facial weakness
• numbness
• hearing loss

Question 9

What are the advantages of stereo over VMAT?

Answer 9

• minimal damage to surrounding tissue
• treat to higher doses
• treatment can be given mutliple times

Question 10

What are the most common sites for SRS?

Answer 10

• acoustic neuroma
• meningioma
• cranial mets
• AVM (arteriovenous malformation)
• GBM (glioblastoma multiforme)

Question 11

What is acoustic neuroma?

Answer 11

• benign tumour of the 8th cranial nerve

Question 12

What are the presentation symptoms or acoustic neuromas?

Answer 12

• hearing loss
• tinnitus
• balance disturbances

Question 13

When is SRS used for acoustic neuromas?

Answer 13

• when surgery risks damage to facial nerves and hearing

- 12Gy in 1#

Question 14

What is meningioma?

Answer 14

• benign tumour arsiing from meningeal tissue

Question 15

When is SRS used for meningioma?

Answer 15

• inoperable or small tuours
• SRS: 18-20Gy in 1#
• SRT: 50-60Gy in 25-30#

Question 16

When is SRS used for mets?

Answer 16

• can treat up to 5 in one session

- 16-20Gy in 1#

Question 17

What is AVM?

Answer 17

• vascular abnormality

Question 18

What are the presentation of AVM?

Answer 18

• intracranial bleed
• seizures
• problems with movement speech or vision

Question 19

When is SRS used for AVM?

Answer 19

• where surgery or embolisation is high risk of failed

- 15-20Gy in 1#

Question 20

What is a GBM?

Answer 20

• highly malignant and fast growing tumour

Question 21

What are the presentations of GBM?

Answer 21

• headache
• nausea/vomitting
• seizures
• memory loss
• changes in speech or personality
• walking difficulties

Question 22

When is SRS used for GBM?

Answer 22

• reccurence

- 6-16Gy in 1#

Question 23

Why is MRI used?

Answer 23

• excellent definition of tumour volume

and critical structures

Question 24

What occurs in sim for SRS patients?

Answer 24

• in treatment position lying on brainlab couch overlay

- cranial array positioned over patient to ensure head fits in

Question 25

What are the advantages of brainlab mask?

Answer 25

- suitable for SRS and SRT - non-invasive - forehead, nose and mouth re-enforcement for extra stability - re-usable

Question 26

What are the dosimetric considerations for SRS?

Answer 26

- beam vs arc depends on tumout size and location - numer of beams and floor angles dictates length of treatment and need to consider patient tolerance - achieve most optimal plan

Question 27

What are stero plans presribed to achieve?

Answer 27

- 80% iso line covering PTV

Question 28

What are the patient pre-treatment preparations?

Answer 28

- obs taken | - nurse administer lorazepam

Question 29

How does exactrac work once the patient is on bed?

Answer 29

- patient moved to iso defined from sim - x-rays taken and infr-red detector moves patient bed position adjusted - once in tolerance treatment starts - imaging is repeated every time floor angle is changed

Question 30

What are the imaging tolerances?

Answer 30

- >3Gy: 0.5mm - <3Gy: 0.9mm - VMAT: 3mm

Question 31

What do the patients do after SRS treatment?

Answer 31

- wheeled out in wheelchair - obs repeated by nurses and monitored for 30 mins - not to drive home