Wk 11 Proton Therapy

Question 1

Radiation cause damages to DNA through __________ and _______________.

Answer 1

Direct action and indirect actions

Question 2

DNA damages include ________________ and ___________________

Answer 2

Single strand break (SSB) and double strand break (DSB)

Question 3

DNA damages that cannot be paired caused ______________.

Answer 3

Cell death

Question 4

What is therapeutic ratio?

Answer 4

The ratio of radiation damages to cancer cells vs to normal cells

Question 5

What forms the Bragg peak?

Answer 5

Energy loss via ionisation and atomic excitation

Question 6

What do a proton therapy system consist?

Answer 6

1. Accelerator (cyclotron or synchrotron)
2. Energy selection and beam transport system
3. Beam delivery system (fixed beam or gantry)

Question 7

What is the function of a cyclotron or synchrotron?

Answer 7

Produce and accelerate protons suitable for cancer treatment (230MeV, 66% of light speed)

Question 8

What is the function of energy selection system in proton therapy system?

Answer 8

It changes the beam energy to that needed for tumour depth in patient.

Question 9

What is the function of the beam transport system in the proton therapy system?

Answer 9

-focuses beam
- maintain protons in beam to uniform energy (discrepancy <1%)
- transport beam to individual treatment rooms

Question 10

What is the weight, diameter and degree of rotation of proton gantries?

Answer 10

Weight >100 tons
Diameter >10m
Rotation >360 degrees

Question 11

What do a proton therapy treatment room consist?

Answer 11

1. 360 rotating gantry
2. Nozzle (treatment head)
3. Orthogonal X-ray and CBCT imaging panels
4. 6D rotating robotic couch

Question 12

What are the particle beam delivery techniques?

Answer 12

3D conformal proton therapy technique
- double scattering beam
- single scattering beam
- uniform scanning beam

IMPT technique
- pencil beam scanning (PBS)

Question 13

What consist in the universal nozzle?

Answer 13

• 1st scatterer
• range modulator and focusing magnets
• scanning magnets
• 2nd scatterer
• variable collimators
• monitor chambers

Question 14

What equipment is used to conforming dose to target laterally?

Answer 14

Metal apertures
Made of brass or low-melting point alloys

Question 15

What equipment is used to conform dose to target distally?

Answer 15

Range compensators

Question 16

Why adaptive proton therapy plan is needed?

Answer 16

Plan revision is required due to tumour shrank and target changed due to patient weight loss

Question 17

How is offline plan adaptive performed?

Answer 17

Repeat CT scan after the start of treatment —> image registration and contouring —> dose calculation and evaluation —> revision required? If yes, conduct plan revision and QA, then use the revised plan

Question 18

What are the advantages of proton therapy?

Answer 18

1. Volumes of patient body receiving low dose is significantly reduced, reduced early and late complication of treatment
2. For shallower tumours, the nearby critical organs are better protected