Head and Neck Lec 2 Flashcards
How has the patient demographic changed?
- Now seeing patients who are from a better socioeconomic class who don’t drink or smoke as much, this is due to the HPV epidemic
What should you consider prior to RT for a H/N patient?
- length of time elapsed after surgery (because of wound healing, residual swelling and tenderness)
- dentures and plates
- dental extractions required should be done prior to CT
What are some problems with immobilisation
- anatomical/ surgical abnormalities
- claustrophobia
- potential shell shrinkage/swelling
- no teeth
- tracheostomy
What are the conventional dose fractionations for a H.N patient? (high risk & elective areas)
High risk: 70 in 35Gy
Elective: 50 in 25Gy
What are the dose fractionations for IMRT for H.N pts? (high risk and elective areas?)
high risk = 70 in 35 (same as conventional)
elective = 56 in 35y
What is a common protocol used for H.N and how does it work/ what is it?
DHANCA protocol
- 68 in 34
- Give 2 Gy boost once a week for the last 4 weeks of tx and deliver the remaining 5# straight after ph1.
- for IMRT treat bi-daily once a week for the last 4 weeks of treatment.
What type of fractionation works better for H/N patients and why?
- Hyperfractionation
- Bc both the time between fractions and the dose per fraction changes the response of tissues.
What are the tolerances for; the brainstem, spinal cord, optic nerves, optic chasm, lens & parotids?
Brainstem: 54Gy Spinal cord: 45Gy Optic Chiasm: 54Gy Optic nerves: 50.4Gy Parotids: 26-30Gy Lens: 6Gy
What does the planning technique for head and neck depend on?
depends on the area and volume marked
- unilateral/ bilateral
- size of the volume
- proximity to other structures.
How would you treat a small feild larynx patient with 3DCRT?
- use opposing lateral fields (assuming this is ok for the shoulders)
- generally have bolus on the anterior field
field placement considerations:
- collimation along the spinal cord
- position of the shoulders
What would be an example of a unilateral volume and how would you treat it?
- Parotids
- Generally include the neck so will require a junction field –> would need to consider the volume geometry and anatomical limitations.
- could use a wedged pair or a 3 field arrangement
What arrangement would you use for 3DCRT plan of an advanced laryngeal cancer?
- Use a multi-feild arrangement that uses a combination of anterior, anterior obliques and posterior obliques.
- Send most dose through the ant beams and use the oblique beams to try and achieve sp cord tolerance.
What is the parotid sparing technique?
- used in bilateral tumours
- Uses a multifeild arrangement of 6-8 beams (ant obliques, post obliques, laterals, split post)
- apply most weighting through the lateral beams
- use the post obliques and split posts to ‘come off’ the spinal cord.
What are some facts about IMRT for H/N planning (6)?
- Gold standard of tx
- 7-9 beams is optimal
- doesn’t have opposing fields
- similar beam arrangement to 3dcrt
- can be static ‘step and shoot’ or dynamic ‘sliding window’ – this is the mlcs.
- all phases delivered concurrently
What is the benefit of VMAT over IMRT?
- Efficiency + flexible dose delivery
