N.U.H ORGAN AT RISK CONTOURING TEMPLATE FOR
HEAD AND NECK PLANNING
Literature search on pubmed indicates:
 There is no literature on the appropriate contouring of organs at risk structures
for the head and neck region – we assume that on the job training allows for
adequate accuracy and consistency in organs at risk contouring
 There is no literature in the use of a contouring template to see if it improves the
accuracy and consistency between all staff (therapists & oncologists) in terms of
organs at risk contouring
Optimal is CT with contrast simulation scan with MRI fusion if available
TO BE CONTOURED IN THE BRAIN WINDOW
Temporal Lobes
Inferior:
bounded by bony cranium boundaries.
Superior:
extends to the effacement of the sylvan fissure
Posterior:
dividing the cranium into half in the coronal plane - looking at the
posterior half,
extends to the boundary between the anterior and posterior quarters
Anterior:
bounded by the bony cranium
Medial:
bounded inferiorly by the bony cranium, however bounder must include
medial temporal including the hippocampus and move laterally thereafter
to not volume basal ganglia
Lateral:
bounded by the bony cranium.
Brainstem
Inferior:
Superior:
Posterior:
Anterior:
Medial:
Lateral:
level of C2 odontoid process
one slice below level of cerebral peduncles or bifurcation of Basilar artery
into Posterior Communicating Artery
unremarkable
up to the Basilar Artery
NA
unremarkable
TO BE CONTOURED IN THE SOFT TISSUE WINDOW
Optic Chiasm
Mid-line middle cranial fossa structure located anteriorly and superiorly (by one slice) to
the pituitary gland and stalk
Optic Nerves
Clearly identifiable – ensure it is contoured all the way to the posterior eye and optic
foramen where visible. Do not visualize a nerve on a slice where it might be
Lens & Eyes
Unremarkable
Parotid Gland
This wedge shaped organ has contains the external carotid artery and some of its contents
identifiable on a contrast simulation scan. These vessels should not be considered the
medial border of the parotid gland but should be include in the contour. MRI fusion is of
significant help. Even in the context of poor matching, it allows identification of medial
and superior extent and organ shape, which can be visually match to the simulation scan.
Superior border is often obscured by artifact from the reference markers placed at the
mastoid process.
Inferior:
variable but does not extend beyond the angle of the mandible
Superior:
zeugmatic arch
Posterior:
skin and superiorly by the external auditory canal and mastoid process
Anterior:
rami of the mandible and variable over the masseter muscle
Medial:
extends deeply into the neck medial to the glenoid fossa (temporal bone)
of the TMJ and medial to the styloid process beneath the mastoid process
Lateral:
to subcutaneous tissue
Thyroid
Easy to identify and contour, especially with a contrast scan, from a radiology point of
view.
Pituitary
Attempt to identify this soft-tissue density ensuring all countours do not extend beyond
the bony pituitary fossa.
TO BE CONTOURED IN THE BONE WINDOW
Inner Ear
This includes:
1. Vestibule
2. Cochlea and
3. Semi-circular canals
4. Bony part of Cranial Nerve 8
The vestibule is the common junction of the cochlea and semi-circular canals and
receives fibers from cranial nerve 8. Due to the close proximity of cranial nerve 8 and its
clinical importance, it is not practical to attempt to exclude it from being contoured. Its
soft-tissue - bony interface provides a consistent contouring landmark. All contours must
remain within the Piteous part of the Temporal Bone.
TMJ
The whole joint will not be visualized on any one slice due to angulation of the neck at
simulation +/- jaw opening. The joint space is convex from anterior to posterior and right
to left with the joint space extending more posteriorly than anteriorly. It is for this reason
that the joint space appears more prominent posteriorly rather than anteriorly (Grey’s
anatomy)
Inferior:
one slice superior to the appearance of the sigmoid notch connecting to the
coronoid process
Superior:
appearance of joint cavity
Posterior:
include glenoid cavity of temporal bone
Anterior:
include condyloid process of mandible
Medial:
joint cavity and inferiorly condyloid process
Lateral:
condyloid process of mandible
ORGAN
CHALLENGES
TEMPORAL LOBES
Posterior/superior extent
1) Sylvan fissure
2) Posterior/middle third boundary
BRAINSTEM
Superior extent
1) Bifurcation of Basilar Artery
2) 1 Slice below bifurcation of cerebral
peduncles
1) Contour posterior eye to orbital
foramen
1) CT-MRI fusion
2) 2 slices in width
3) sup/ant to pituitary
1) Attempt to contour pituitary, not
fossa
1) Contour in CT with bone windows
OPTIC NERVES
OPTIC CHIASM
Location
PITUITARY
Exact pituitary
INNER EAR
Bony demarcation
TMJ
Contour of glenoid cavity & inferior extent
PAROTID
Medial/superior border
METHODS TO OVERCOME
1)
2)
1)
2)
3)
Contour in CT with bone windows
Only until sigmoid notch
CT-MRI fusion
Parotid can have deep medial margin
Contour gland beneath external
auditory meatus
N.U.H ORGAN AT RISK CONTOURING TEMPLATE FOR
HEAD AND NECK PLANNING
Optimal is CT with contrast simulation scan with MRI fusion if available
TO BE CONTOURED IN THE BRAIN WINDOW
Temporal Lobes
Inferior:
bounded by bony cranium boundaries.
Superior:
extends to the effacement of the sylvan fissure
Posterior:
dividing the cranium into half in the coronal plane - looking at the
posterior half,
extends to the boundary between the anterior and posterior quarters
Anterior:
bounded by the bony cranium
Medial:
bounded inferiorly by the bony cranium, however bounder must include
medial temporal including the hippocampus and move laterally thereafter
to not volume basal ganglia
Lateral:
bounded by the bony cranium.