40. GLOTTIC
LARYNX
T2: If supragltc xtnsn take higher
T2: if subglottic xtnsn drop lower
SUP: Top thyroid cartilage
INF: Bottom cricoid
ANT: 1cm flash
POST: Ant edge VB
46. Sup: BOS ant & 2 cm sup to mastoid tip
Post: include jx & RP LN
Inferior: 1–2 cm below cricoid or lower,
depending upon inf dz extent
Anterior
Pharyngeal wall tumors: exclude ant third
of glottis (broken line)
Pyriform sinus tumors: 1 cm post to ant
skin edge (solid line)
Posterior: post aspect of C2 spinous
process to include posterior cervical nodes
53. Sup Ant
T1–2 & early T3: split pituitary fossa & include
sphenoid sinus and BOS w/2 cm mrgn
Adv T3 & T4 involving BOS & CNs: include entire pit
fossa, base of brain in suprasellar region, adjacent
middle cranial fossa, and post ant cranial fossa
Sup Post: 2 cm sup to mastoid tip
Inf: thyroid notch
Ant: try to spare some oral cavity
Ant Sup: include posterior 2 cm of NC & Max sinus
& post ¼ orbit
Ant Inf: 2 cm post to mentus to include the
submandibular nodes
Post: 2 cm post to post aspect of the SCM mm to
include jx & posterior cervical LN
63. 2-3 : 1
ORBITAL INVSN MIN ORBIT INVSN NO ORBIT
3-FIELD TECHNIQUE (AP & OPP LATS)
- 1 anterior portal and 2 posteriorly tilted lat portals (w/wedges) used
- Beams are weighted 2 – 3:1 in favor of the anterior portal
- Lateral portals often do not encompass all dz b/c ant tumor extnsn cannot be treated
w/lateral portals w/out also exposing both eyes
- Lateral portals tilted posteriorly ~ 5o to avoid exit dose thru c/l eye
64. Single Anterior Portal
Superior: include cribriform plate and all/part of frontal sinus
Inferior: lip commissure to include the maxillary antrum
-for maxillary tumors extending into OC, inf border may be lowered to encompass
gross dz
Medial: 2 cm across midline to include entire NC, ethmoid-sphenoid complex, and
medial c/l orbit
Lateral: entire ipsi orbit should never be completely blocked b/c doing so would
also block posteroinferior ethmoid cells and a portion of the maxillary antrum
- for no radiographic orbital invsn and min ethmoid dz (C): portal transects ipsi eye
just medial to the limbus to preserve lacrimal and retinal function
- for no radiographic orbital invsn but extnsv ethmoid dz (not diagramed below):
50% of the orbit included in initial tx field to 4500 cGy
- portal is then reduced to transect the ipsi eye just medial to limbus to preserve
lacrimal and retinal fcn
- for min radiographic orbital invsn (B): orbit included in initial tx field except major
lacrimal gland and lateral upper eyelid may be blocked
- for clinical orbital invasion (A): entire orbit is included in the initial treatment field
65. Opposed Lateral Portals (D)
Superior
1 cm superior to the roof of the ethmoid sinuses
border is extended 2 – 3 cm superior to the roof of the ethmoid sinuses for
intracranial invasion
Inferior
lip commissure
for maxillary tumors extending into the oral cavity, inferior border may be
lowered to encompass gross disease
Anterior: lateral bony canthus
Posterior: split VB to avoid dose to brain stem and spinal cord
68. NASAL VESTIBULE
Tx volume if >1.5cm or poorly diff
-B/l facial lymphatics (moustache)
-Submandib & subdigastric
69. NASAL VESTIBULE
Opposed lateral technique
portals angled post to ensure adequate post coverage; wedges
added to compensate for angulation
Advantage: Avoid exposure of underlying structures (i.e., brain)
Disadvantage: Full skin reaction occurs b/c wax bolus over
entire nose is required to ensure homogenous dose distribution
70. NASAL VESTIBULE
Anterior portal
consists of electrons alone or photon-electron mixed beam
bolus is not applied to the tip of the nose unless it is involved by tumor
Advantage: ease of setup
Disadvantage: exposure of underlying structures
71.
72. WEDGED PAIR PHOTON FIELD
Use technique only w/ CT-based planning to define tumor bed, LN groups,
and perineural pathways
- rec if tx perineural pathways and BOS
- max neck xtnsn important to min exit dose thru c/l orbit
- if neck xtnsn not eliminatng dose thru c/l orbit, then couch rotated to
angulate beams inf
73.
74. HOMOLATERAL MIXED BEAM FIELD
OF PRIMARY & UPPER NECK
PHOTON FIELD
Superior: 2 cm sup to zygomatic arch
Inferior: thyroid notch
Anterior: ant border masseter mm (level of
2nd upper molar where Stensen’s duct
drains)
Posterior: 2 cm post to mastoid
ELECTRON FIELD
1 cm larger than photon portal to
accommodate constriction of electron
isodose lines at depth
• Not rec for pts tX to perineural pathways and BOS
• Sim film taken at 100 SSD, which is std for e-
• 12–16 MeV e- combined w/ 60Co or 4–6 MV phtns with
80% of the dose given w/ e-
• Dose prescibed to depth of deep lobe; ~ 4–5 cm
• To reduce dose to cord, place either a wedge in photon field
with the heel toward the cord or an electron compensator in
e-field to reduce beam depth
