1
Q
Why has brachy changed?
A
- better technology allows improved tumour control and toxicity
- safer and more acceptable for patients
- safer for staff
- LDR no longer supported
2
Q
What are the levels of dose rate?
A
- LDR: 0.4-2Gy/hr
- MDR: 2-12 Gy/hr
- HDR: > 12 Gy/hr`
3
Q
What are the advantages of HDR?
A
- outpatient treatment
- dose optimisation and adaptive planning
- reduced radiaiton exposure to staff
- more stable positioning
- smaller applicators
- shorter treatment time
4
Q
What are the disadvantages of HDR?
A
- more complex planning and treatment
- compressed time frame for planning
- greater potential for error
- potential for high radiation exposure to staff and patient if source error
5
Q
How does the source applicator work?
A
- hollow needle with 7mm dead space at end
- source moves through at different times making the dose distribution
6
Q
What is the definition for high risk CTV?
A
- residual macroscopic diease at time of brachytherapy
7
Q
What is the definition for intermediate risk CTV?
A
- intial macroscopic disease at time of diadnosis
8
Q
What is the definition for low risk CTV?
A
- potential microscopic tumour spread not treated with brachy
9
Q
When do you image?
A
- pre treatment
- during insertion
- post treatment
10
Q
Why image pre treatment?
A
- evaluate tumour
- determine treatment modality
- determine treatment volume and dose
11
Q
Why image during insertion?
A
- evaluate tumour response
- verification of applicator position
- define CTV and OAR
- adaptive RT
12
Q
Why image post treatment?
A
- evaluate tumour response and toxicity
13
Q
What is the impact of inter and intrafraction motion?
A
- more significant for HDR as less fractions
- steep dose gradient around applicator
- tumour shrinkage and normal tissue fibrosis may occure over total lenght of time
14
Q
How is dose presribed for brachy?
A
- point A
- rectum
- bladder
15
Q
What are the advantages for HDR prostate?
A
- image guided needle placement
- optimised dose distribution
- organ motion minimised
- radiobiological advantage
- remote afterloading
- singel reusable source
16
Q
What are the acute clinical issues for prostate HDR?
A
- template/catheter movement: minimise movement of patient/bed rest
- haematuria/clot retention: contionus bladder irrigation
- perineal discomfort and back discomfort: analgesics
- infection risk: prohylactic antibiotics
- DVT prophylaxis: stockings/heparin
- defaecation: low residue diet prior to and during admission
Planning
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