Head and Neck CT and Planning

Question 1

Signs and Symptoms of HN Cancer

Answer 1

Pain/soreness
Difficulty swallowing and eating
Neck mass
Voice changes

Question 2

Classic Presentation of HN Patients

Answer 2

Generally older males
Significant history of smoking and drinking

Question 3

Epidemiology of HN Cancer

Answer 3

Young patients now make up 75% of HN Cancer
Used to be primarily older individuals

Question 4

Aetiology of HN Cancer

Answer 4

HPPV (HPPV 16 strain is most common strain to cause HN)
Smoking
Mets

Question 5

Immobilisation devices for HN Cancer

Answer 5

Thermoplastic mask
Head rest
Custom head rest
Vac Loc Bags
Shoulder support/fixation
Hand grips
Mouthpieces and mouth bites

Question 6

Important aspects of immobilisation for a HN patient

Answer 6

Adequate neck support
Moulding of shell around important anatomical features (nose, ears, chin)
Chin position
Shoulder position
Shell integrity (e.g., inconsistent stretching)

Question 7

Issues to consider prior to performing CT Sim

Answer 7

Length of time elapsed after surgery (residual swelling, tenderness may be present)
Surgical deficits
Dentures and plates
Dental Extractions (if required)
Claustrophobia
Tracheostomy tube
Potential Shell Shrinkage

Question 8

How to overcome effects of shell shrinkage

Answer 8

Place shims below head rest when initially moulding shell

Remove shims throughout the course of treatment once it becomes tight

Question 9

What is the purpose of shoulder retractors and handgrips

Answer 9

Fixate where the shoulders are sitting

Question 10

Imaging modality options for HN

Answer 10

MRI
PET
Diagnostic CT

These modalities can be utilised to fuse with one another to gain an anatomical and functional understanding of the patient

Question 11

Common VMAT Fractionation for HN Cancer

Answer 11

70Gy in 35#
56GY in 35#
63 Gy in 35#

Delivered as a SIB VMAT plan

Question 12

Post Operative Fractionation for HN

Answer 12

66Gy in 33# to positive margin area

54-60Gy in 27-30# to operative bed

Question 13

Organs at RIsk HN Patients

Answer 13

Spinal Cord
Brain stem
Parotid Glands
Lenses
Optic Nerve
Optic Chiasm
Brachial Plexus

Question 14

Critical Structure Dose Tolerances

Answer 14

 Spinal cord – 45Gy
 Brainstem – 54Gy
 Parotids – 20-26Gy mean dose
 Lenses – 6-8Gy
 Optic nerves – 50.4Gy
 Optic chiasm – 54Gy

Question 15

3D CRT Techniques HN

Answer 15

• Small field larynx (opposing lateral field, generally with bolus)
• Unilateral volume (e.g. parotid) (wedge pair or 3 field arrangement)
• Bilateral volume (e.g., oropharyngeal) (multifield arrangement to spare parotid)
• Bilateral volume (e.g., face) (6-8 field - lats, ant obl, post obl, pos)

Question 16

IMRT vs VMAT for HN

Answer 16

IMRT
- gold standard for complex, radical HN cancer
- 7-9 beams is best (similar arrangement to 3DCRT)
- no opposing fields

VMAT
- enhanced flexibility in delivery through alternating dose rate, gantry speed
- improved treatment efficiency
- generally 2x 360 degree arcs used for full HN patients

Question 17

Tomotherapy

Answer 17

Combination of CT and Linac

Continuous rotation around the patient while the couch is moving into the gantry

Involves delivery of tens of thousands of pencil beams of radiation