Brachytherapy

Question 1

Why has brachy changed?

Answer 1

• better technology allows improved tumour control and toxicity
• safer and more acceptable for patients
• safer for staff
• LDR no longer supported

Question 2

What are the levels of dose rate?

Answer 2

• LDR: 0.4-2Gy/hr
• MDR: 2-12 Gy/hr
• HDR: > 12 Gy/hr`

Question 3

What are the advantages of HDR?

Answer 3

• outpatient treatment
• dose optimisation and adaptive planning
• reduced radiaiton exposure to staff
• more stable positioning
• smaller applicators
• shorter treatment time

Question 4

What are the disadvantages of HDR?

Answer 4

• 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

Question 5

How does the source applicator work?

Answer 5

• hollow needle with 7mm dead space at end

- source moves through at different times making the dose distribution

Question 6

What is the definition for high risk CTV?

Answer 6

• residual macroscopic diease at time of brachytherapy

Question 7

What is the definition for intermediate risk CTV?

Answer 7

• intial macroscopic disease at time of diadnosis

Question 8

What is the definition for low risk CTV?

Answer 8

• potential microscopic tumour spread not treated with brachy

Question 9

When do you image?

Answer 9

• pre treatment
• during insertion
• post treatment

Question 10

Why image pre treatment?

Answer 10

• evaluate tumour
• determine treatment modality
• determine treatment volume and dose

Question 11

Why image during insertion?

Answer 11

• evaluate tumour response
• verification of applicator position
• define CTV and OAR
• adaptive RT

Question 12

Why image post treatment?

Answer 12

• evaluate tumour response and toxicity

Question 13

What is the impact of inter and intrafraction motion?

Answer 13

• 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

Question 14

How is dose presribed for brachy?

Answer 14

• point A
• rectum
• bladder

Question 15

What are the advantages for HDR prostate?

Answer 15

• image guided needle placement
• optimised dose distribution
• organ motion minimised
• radiobiological advantage
• remote afterloading
• singel reusable source

Question 16

What are the acute clinical issues for prostate HDR?

Answer 16

• 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