SRT

Question 1

Stereotactic definition

Answer 1

Precise positioning in a 3 Dimensional plane
Highly precise treatment
Small targets
High dose

Question 2

Principles of Stereotactic

Answer 2

Use of multiple non-coplanar beams or
arcs
•Achieves a steep dose gradient -
minimal dose to critical structures and
surrounding healthy tissue
•Achieves conformity

Question 3

SRS versus SRT

Answer 3

Radiosurgery (SRS)
- Single, high dose of radiation

•Radiotherapy (SRT)
- Treatment is delivered in more
than one fraction

Question 4

Indications for SRT/SRS

Answer 4

•Small tumour size
•Tumour location
•Pathology of the tumour
•The patient
•Tumour recurrence

Question 5

How does stereotactic work

Answer 5

Tumour reduction occurs at the rate of
normal growth for the specific tumour cell

Question 6

Side effects

Answer 6

ACUTE: Headache, nausea,
vomiting, visual
disturbances, swelling
(usually managed with
steroids)

•DELAYED: Facial weakness,
numbness, hearing loss

Question 7

Advantages of stereo over VMAT

Answer 7

Minimal damage to surrounding tissue
•Treat to higher doses
•Treatment can be given multiple times

Question 8

What clinical sites are treated

Answer 8

Malignant or benign
Acoustic neuroma
Meningioma
Cranial Mets
GBM

Question 9

Acoustic neuroma

Answer 9

Benign tumour of the 8th
cranial nerve
• Presentation: hearing loss, tinnitus & balance
disturbances
• SRS utilised when surgery risks damage to facial nerves and hearing • SRS12Gy/1#

Question 10

Meningioma

Answer 10

Usually benign tumour
arising from meningeal
tissue
•Stereotactic for inoperable
or small tumours
•SRS: 18-20Gy
•SRT: 50-60Gy @ 1.8-2Gy/#

Question 11

Brain Mets

Answer 11

Metastases in the
brain arise from a
variety of primary sites •Patients can present with 1 or many mets •Stereotactic dose of
16
-20Gy/1# per met

Question 12

GBM

Answer 12

Highly malignant and fast growing – average survival time 12 months •Symptoms of gliomas may include headaches, nausea, vomiting, seizures, memory loss, changes in speech or personality and walking difficulties •Stereotactic used at time of
recurrence
•SRS: 6
-16Gy/1#

Question 13

Planning to treatment workflow

Answer 13

MRI
CT Sim
Planning
QA
Treatment

Question 14

Why MRI

Answer 14

•Essential for all patients
•Provide excellent definition of tumour volume
and critical structures
•Request scans that will best show the target
volume

Question 15

Stereo mask

Answer 15

Mask made in 20 min
Ensure eyebrows, nose, forehead, cheeks visible
Laterally outer canthus to anterior of Tragus
Two parts - 1 under patients head and one over

Question 16

CT parameters

Answer 16

CT – 1mm slices
•Primary image set for planning

Question 17

Planning

Answer 17

• Importing of image data sets (MRI + CT)
• Fusion of data sets
• Contouring
• Dosimetry
• RO approval
• Export to treatment

Question 18

Image fusion

Answer 18

CT and MRI images are fused together
•CT is always the primary image
•Fusions are automatic, but must be
checked

Question 19

Hyperarc planning

Answer 19

Select your treatment targets
•Assign prescribed dose to each target – can have different doses in the same plan
•Isocentre positioned in the middle of single PTV or middle of multiple PTVs
•Set floor and gantry angles
•Floor - 0, 45, 315, 270
•Gantry 360deg or 180deg arcs
•Optimise collimator position

•Enter planning goals into optimiser for PTVs and OARs
•Avoid entry and exit on OARs or previously treated PTVs

Visualise beam/arc to ensure they’re not treating OARs or other PTVs

Reduces collision risks

Question 20

Dose export

Answer 20

Once the plan has been approved by the RO it is
exported into:
o MOSAIQ - the R&V system
o ExacTrac - the BrainLAB isocentre positioning
system – Buderim patients

Question 21

Patient pre-treatment prep

Answer 21

Single shot patients
• Observations taken
• Nurses tend to administer
Ativan (Lorazepam)
Dexamethasone

Question 22

Treatment times

Answer 22

20 - 90 mins

Question 23

What are primary sites for Mets

Answer 23

Kidney
Lung
Melanoma
Breast
Colorectal

Question 24

Symptoms of brain cancer

Answer 24

Headaches, seizures, dizziness, memory gait, verbal issue, confusion