1. Radiological imaging of the
orbit, PNS and petrous bone.
Dr/ ABD ALLAH NAZEER. MD.

2. The orbit is a feature of the face and contains the globe.
Gross anatomy
In the adult human, the orbit has a volume of approximately 30ml, of which the
globe occupies 6.5ml. It has a roof, floor, medial and lateral wall. The orbit is open
anteriorly where it is bound by the orbital septum, which also contributes to the
eyelids. Posteriorly the orbit angles inward, such that their apices communicate
with the intracranial compartment via the optic canal and superior orbital fissure.
Contents:
globe , extraocular muscles, cranial nerves, optic nerve (CN II), branches of the
oculomotor nerve (CN III), trochlear nerve (CN IV), ophthalmic division of the
trigeminal nerve (CN Va)
abducents nerve (CN VI), autonomic nerves and ganglia.
ciliary ganglion
sympathetic root to the ciliary ganglion (parasympathetic root travels in the
oculomotor nerve)
Arteries:
ophthalmic artery
Veins:
superior and ophthalmic vein
Fat:
lacrimal gland, fascia bulbi (Tenon's capsule)

3. Bony margins:
The orbit's bony margins are made up of seven bones:
pars orbitalis of the frontal bone
lacrimal bone
lamina papyracea of the ethmoid bone
orbital process of the zygomatic bone
orbital surface of the maxillary bone
orbital process of the palatine bone
greater and lesser wings of the sphenoid bone
Communications:
The orbit communicates posteriorly with the intracranial cavity via the optic canal,
through which the optic nerve and ophthalmic artery is transmitted. Immediately
inferolateral to the optic canal is the superior orbital fissur, through which most
neurovascular structures pass. The infratemporal fossa is accessed via the inferior
orbital fissure, which is in direct continuation with the infraorbital foramen, through
which the infraorbital nerve exits to supply the skin below the eye (and where it is
often damaged by a blow-out fracture).
Medially small communications with the paranasal sinuses are via the anterior
ethmoid foramen and posterior ethmoidal foramen.
Anteriorly the supraorbital notch is closed inferiorly by the orbital septum forming a
fibrous supraorbital foramen. The nasolacrimal duct drains the nasolacrimal sac via
the nasolacrimal foramen.

4. Normal orbit measurements.

5. Orbital anatomy.

7. Gross anatomy.

9. Schematic showing positioning for a Waters projection. (CM, canthomeatal
line; CR, central ray) B. Radiograph of a Waters projection. The petrous ridge
lies below the maxillary sinus. (a, frontal sinus; b, medial orbital wall; c,
innominate line; d, inferior orbital rim; e, orbital floor; f, maxillary antrum; g,
superior orbital fissure; h, zygomatic-frontal suture; i, zygomatic arch)

10. Schematic showing positioning for a Caldwell projection. (CM, canthomeatal line; CR,
central ray) B. Radiograph of a Caldwell projection. The petrous ridge is positioned at the
orbital floor. Detail of the orbital floor and maxillary sinus is blocked. C. The radiograph is
taken at a steeper angle so the petrous ridge is now positioned lower within the maxillary
antrum. (a, frontal sinus; b, innominate line; c, inferior orbital rim; d, posterior orbital
floor; e, superior orbital fissure; f, greater wing of sphenoid;g, ethmoid sinus; h, medial
orbital wall; i, petrous ridge; j, zygomatic-frontal suture; k, foramen rotundum)

11. Schematic showing positioning for a lateral projection. (CR, central ray) B.
Radiograph of a lateral projection. (a, orbital roof; b, frontal sinus; c, ethmoid
sinus; d, anterior clinoid process; e, sella turcica; f, planum sphenoidale)

12. Ultrasound anatomy
At the anterior pole of the eyeball, the eyelids and the conjunctiva abutting
the cornea produce a moderate echogenic structure which outlines the ventral
part of the anterior chamber. With high resolution transducers, the cornea
appears as a convex echofree thin line bounded posteriorly by an echogenic
interface. The anterior chamber is echofree and is delineated posteriorly by
the strong reflecting line of the iris. The pupil appears as a translucent
disruption of iris continuity. Posterior to it lies the anechoic lens. The anterior
margin of the lens is not apparent, and neither is the posterior chamber,
which is too thin to be visible. The lens diameter is 10 mm with a maximal
thickness of 3-4 mm. The posterior margin of variable spatial relationship
with the ultrasonic beam, is only partly apparent. The ciliary body produces a
focal thickening of the eye wall, next to the margins of the lens.
The vitreous humor is echofree, homogenous and occupies more than two
thirds of the eyeball volume. Since it only adheres to the posterior wall in a
few points, movement of the vitreous humor relative to the wall can be
observed during real time scanning. The posterior wall of the eyeball is
echogenic, often with no inner layers. With high frequency transducers and
lowering of distal gain compensation, the choroid appears less echogenic than
neighboring retina or sclera.

13. Behind the eyeball, the intraconal fat pad is hyperechoic, mainly due to
acoustic enhancement in the vitreous humor. The optic nerve appears as a
sagittal hypoechoic structure, 4, 5 – 5 mm thick, than runs from the outer
part of the eyeball to the tip of the orbit. The length of the optic nerve is
approximately 2, 5 cm. The extrinsic muscles that form the intraorbital
muscular cone appear as hypoechoic bands with typical longitudinal
striations. The oblique muscles are almost never seen, due to their close
relation to the rectus muscles and thin belly. The rectus muscles can
always be assessed, especially if trapezoid emission of ultrasound at the
surface of the transducer is used. They are oriented in a sagittal plane and
occupy the four cardinal points in the orbit (superior, inferior, medial and
lateral). The medial rectus muscle, which is best seem, has the maximal
thickness of 4 mm. The inferior rectus muscle is the most difficult to assess.
Normal orbital vessels (ophthalmic, ciliary, and retinal) are not seen on grayscale
scans. Color or power Doppler adjusted for low flow is the method of choice for
vessel detection while spectral display is used to analyze flow velocity and
patterns. Typically, central retinal and ciliary arteries display low resistance flow.
The lachrymal glands occupy the upper outer angle of the anterior orbit. They are
almond shaped, echogenic with the long axis below 1 cm. Quite often, they cannot
be differentiated from neighboring fatty tissue.

14. The anterior pole of the eye. C = cornea; P = pupil; I =
iris; CB = ciliary body; L = lens; VH = vitreous humor.

15. The retroocular space. ON = optic nerve; VH = vitreous humor

16. Extrinsic eye muscles. LRM = lateral rectus muscle; MRM = medial rectus muscle

17. Eyeball vessels. CR = central retinal vessels; ChB = choroid blush

18. The lachrymal gland (LG).

23. T2W axial section,with fat suppression, through midorbit, showing LR- lateral rectus, MR-medial
rectus, V-vitreous, A -aqueous, arrow - optic nerve, arrow head-lens, E-ethmoid
sinus

24. T2W axial section through the superior orbit showing the superior ophthalmic vein (arrow
head), superior rectus (double arrows). In the same section, lacrimal glands (single arrows)
are well seen

25. T2W axial section through the inferior orbit showing the inferior rectus (arrow head),
inferior portion of the globe (G), ethmoid air cells (E), sphenoid sinus (S), cavernous sinus
(white outlines 1 and 2) and flow void of internal carotid artery (arrow)

26. T2W coronal section through the anterior orbit showing the globe (single arrow), lens
(arrow head) and the inferior obique (double arrow)

27. T2W coronal section through the globe showing the vitreous (V), lacrimal gland (L), medial
rectus (arrow head), inferior rectus (single arrow) and superior rectus (double arrow)

28. T2W coronal section posterior to the globe showing the intraconal space (within the
circle1), optic nerve (*), inferior rectus (short single arrow), medial rectus (arrow head),
superior oblique (double arrow heads), superior rectus (double arrow), superior
ophthalmic vein (long white arrow), lateral rectus (LR), T-turbinates and sinuses (E-ethmoid,
M-maxillary)

41. IO, inferior
oblique muscle;
IRGL, global layer
of inferior rectus
muscle; IROL,
orbital layer of
inferior rectus
muscle.

42. Radiology of Nasal Cavity
and Paranasal Sinuses.
Imaging modalities:
X-RAY.
CT.
MRI.

43. Paranasal sinuses:
The paranasal sinuses consists of, usually,
four paired air-filled spaces, named for the
facial bones in which they are located:
maxillary sinus
sphenoid sinus
ethmoid sinus
frontal sinus
Osteomeatal complex.
Nose and nasal cavity.

44. Occipito-Mental (OM) view - Normal

45. Occipito-Mental 30º (OM30) view - Normal

47. Computed tomography (CT) of the para-nasal sinuses (PNS)
has nowadays become the investigation of choice for the radiological
diagnosis of nasal and sinus diseases. Unlike plain radiography, sinus
CT shows an excellent anatomical soft tissue and bony details, helps in
the diagnosis, and gives detail of sinonasal anatomy for safe surgery.
Endoscopic sinus surgery (ESS) is a common procedure which requires
a meticulous assessment of patient and a detailed radiological
description of the anatomy and its anatomical variations in nose and
PNS. Although the role of anatomical variations of osteomeatal
complex in the etiology of sinonasal disease is controversial3 but
knowledge of these variations in every patient is important before
surgery is planned to avoid damage to surrounding vital structures like
the orbit and the brain. The frequency of these variations may differ
among the different ethnic groups.4 In review of literature, there is no
data on anatomical variations of nose and PNS in our population. The
aim of this study was to report the frequency of these variations in
patients with sinonasal symptoms who underwent CT scan in the
hospital.

48. Frontal Sinus:

50. Ethmoid Sinus:

53. Maxillary Sinus:

55. Sphenoid Sinus:

78. Petrous part of temporal bone.
The petrous temporal bone (PTB) has a pyramidal shape with an apex and a base
as well as three surfaces and angles:
apex
direct medially; articulates with posterior aspect of the greater wing of
sphenoid and basilar occiput
forms internal border of the carotid canal and the posterolateral boundary of
the foramen lacerum
base
directed laterally and fuses with the internal surface of squama temporalis
and mastoid
The PTB has three surfaces - anterior, posterior and inferior.
The anterior surface forms the posterior part of the middle cranial fossa. It is
continuous with the inner surface of the squamous part united by the
petrosquamous suture. Near its center lies the arcuate eminence, which indicates
the location of the superior semicircular canal. Lateral to the arcuate eminence is
a depression which indicates the position of middle ear cavity. A shallow groove
directed posterolaterally to open into the hiatus of the facial canal. Lateral to this
hiatus a smaller hiatus for the lesser petrosal nerve. At the apex the termination
of carotid canal is present.

79. The posterior surface forms the anterior part of posterior cranial fossa. It fuses
with the inner surface of mastoid. Near the center of the posterior surface is
the internal acoustic meatus. Posteriorly to the internal acoustic meatus is a
small slit, leading to the canal of the vestibular aqueduct.
The inferior surface forms part of the exterior of the base of the skull. There
are a number of foramina including the inferior opening of the carotid canal
and posteriorly the jugular foramen and in between a small inferior tympanic
canaliculus, through which the tympanic branch of the glossopharyngeal
nerve passes. The stylomastoid foramen is situated on the inferior surface. It
provides attachment to the levator veli palatini and the cartilaginous portion
of the auditory tube.
The petrous temporal bone has three angles:
superior angle - attachment of tentorium cerebelli, its medial arm lodges
the trigeminal nerve and the superior petrosal sinus lodges in the groove of
the angle. posterior angle - contains a sulcus that lodges the inferior
petrosal sinus medially and jugular notch of occipital bone forms the jugular
foramen laterally. anterior angle - medial half articulates with the spinous
process of the sphenoid and lateral half fuses with the squamous part by the
petrosquamous suture.

80. Radiograph of the lateral
view of temporal bone.
1. posteroinferior limit of
the middle cranial fossa.
2. anterior limit of the
posterior cranial fossi.
3. internal auditory meatus.
4. external auditory meatus.
5. condylar neck.
6. roof of glenoid fossa.
7. articular tubercle.
8. sigmoid notch of mandible.
9. mastoid process .
10. styloid process.
11. atlas.

81. Internal auditory meatus X-Ray.

105. RADIO-IMAGING ANATOMY at 3T:
The internal auditory canal:
- Has three parts: the internal acoustic meatus (medial opening), the
canal (an average of 8 mm) and the fundus, of irregular shape
(modulates the passage of the VII and VIII cranial nerves).
- Nervous contents: the facial nerve (the largest in size) and the
cochleo-vestibular nerve that divides into the cochlear nerve and the
vestibular nerve which further divides itself into the superior
(innervates the utricle and the ampulla of the superior and lateral
SCC), and the inferior branches (innervates the saccule and the
ampulla of the posterior SCC).
The singular nerve (or the posterior ampullary nerve) has its proper
canal, the singular canal, in the postero-inferior quadrant of the
fundus that can be often be observed with 3T imaging.
- Vascular content: arterial by the labyrinthine artery and venous
with three drainage pathways (internal auditory vein, vein of
cochlear aqueduct and vein of vestibular aqueduct)

106. Axial section through the inner auditory canal (IAC) and the
labyrinthe with visualization of the cochlear and inferior vestibular
nerves. The utricular macula is also well depicted.

107. Anterior coronal section through the IAC. Outline of the facial nerve in its
complete cisternal course, the cohlear nerve is only partially viewed.

108. Posterior coronal section through the IAC. Vestibular nerve
division and vestibular ganglion (of Scarpa) are visualized.

109. Appearance variant of the vestibular nerve with inferior vestibular division
into the saccular nerve (that innerves the saccule) and the posterior
ampullary nerve (for the ampulla of the posterior semicircular canal).

110. Sagittal seriate sections of the IAC from medial (left), showing the pontocerebellar
cistern, to lateral (right), showing the fundus and inner ear structures.

111. Cochlear nerve at the fundus of the IAC and its passage via
the modiolus to the cochlea in an oblique sagittal section

112. Heavily T2 coronal section respective to the IAC. Vestibular and cochlear
structures are seen, note the utricular macula and spiral lamina.

113. Sagittal section respective to the IAC through the inner ear in a 3D
Heavily T2 sequence. This section is also orthogonal to the macula
of the utricle and unfolds partially the cochlea.

114. Oblique coronal section through the anterior labyrinth
and fundus of the IAC, 3D Heavily T2 sequence.

115. FLAIR sequence in the axial plane four hours after Gd intravenous
injection, the saccule and part of the utricle are visualized

116. Axial FLAIR Gd sequence through the utricle, the saccule is partially visualized.

117. Heavily T2 in the plane of the lateral semicircular canal (oblique
axial). The ampulla and its ampullary crest (low signal) are seen.

118. FLAIR Gd sequence section in the lateral SCC plane, passing through the utricle.

119. Section in the plane of the superior semicircular canal (plane of
Pöschl, sagittal to the petrous bone), with heavily T2 sequence.

120. Section in the same plane (as Fig.14) of the superior
semicircular canal with FLAIR Gd sequence.

121. T2 sequence in the plane of the posterior SCC (plane of Stenver,
coronal to the petrous bone). Notice the common part of the
superior and posterior semicircular canals, i.e. the common crus.

122. FLAIR and Heavily T2 sequences, sections in the coronal plane. Notice the
position of the utricular macula (T2 sequence) relative to the utricle (FLAIR).

125. Thank You.