H+N contour and QUANTEC

Question 1

Contouring guidelines to follow

Answer 1

DAHANCA, EORTC, GORTEC, NCRI, TROG

Question 2

Brainstem contouring

Answer 2

Should be heart shaped superiorly and then tube shaped inferiorly. Ends at dens (ant bit sticking in c2)

Question 3

Thecal sac contour

Answer 3

extends from the top of the dens (vertebral body of C1/Atlas) to the second sacral vertebrae

Question 4

Parotid gland position

Answer 4

Each gland lies behind the mandibular ramus and in front of the mastoid process of the temporal bone.

Question 5

Parotid gland parts

Answer 5

The gland has four surfaces — superficial or lateral, superior, anteromedial, and posteromedial. Includes the carotid artery and retromandibular vein
The parotid gland has two ends- superior end in the from of small superior surface and an inferior end or apex

Question 5

Inter-observer variability

Answer 5

Due to poor image delineation of CT scans, contours of same anatomical structures may vary from person to person

Question 6

Inner ear parts

Answer 6

Tympanic membrane separates inner and outer ear
Inner ear contains Cochlea and vestibular apparatus (shaped like V)

Question 7

Consequence of irradiating inner ear

Answer 7

Radiation induced hearing loss: conductive or sensorineural
Alteration of endothelium causes sensorinural hearing loss
Causes atrophy of sensory structures and fibrosis and ossification of fluid spaces in few weeks or months after
Inflammation and odema may compress cochlear nerve in the ear canal and cause damage

Question 8

How to ensure accuracy of cochlea contouring:

Answer 8

Use bone window
Width -2000HU
Level- 400HU

Question 9

Pharyngeal constrictor muscles

Answer 9

One single OAR- for efficiency and reproducibility
Thickness of 3mm assumed

Question 10

Hippocampus

Answer 10

Needs to be preserved for QOL- Centre for cognitive function
Recurrence often occurs near this due to highly proliferative cells
VMAT avoids hippocampus

Question 11

Spinal cord tolerance and toxicity endpoint

Answer 11

Max dose <48Gy Myelopathy

Question 12

Brain stem tolerance and toxicity endpoint

Answer 12

Max dose <54Gy <5% Necrosis

Question 13

Parotid tolerance and toxicity endpoint

Answer 13

Mean <24Gy <20% Long term salivary function loss

Question 14

Rectum tolerance and toxicity endpoint

Answer 14

V50<50%, V60<35%, V65 <25% <10% Grade 3+ toxicity

Question 15

Bladder tolerance and toxicity endpoint

Answer 15

Max dose <65Gy <6% Grade 3+ toxicity, V65<50% Grade 3+ toxicity

Question 16

Penile bulb tolerance and toxicity endpoint

Answer 16

Mean dose 50Gy , severe erectile dysfunction

Question 17

Mandible tolerance and toxicity endpoint

Answer 17

V70Gy <10% Osteoradionecrosis

Question 18

Larynx tolerance and toxicity endpoint

Answer 18

Mean <45Gy <20% Grade 2 Edema

Question 19

Lens tolerance and toxicity endpoint

Answer 19

Max dose 6Gy Blindness

Question 20

Cochlea tolerance and toxicity endpoint

Answer 20

mean dose <45Gy Hearing Loss